Photo by Dave Allen

Pat Welsh says that locally the pest that most troubles tomatoes is tomato hornworm, a large caterpillar that can grow as long as four inches,

The ripe round red tomato sitting on the kitchen table is alive and busy. While we are asking, “How shall I eat it?” the tomato is huffing and puffing, sending signals throughout its meat and juices that cue color, texture, and flavor changes. The tomato, if it could talk, would tell us it doesn’t give a damn how we eat it. It only wants to get its seeds out into soil and make more of itself. It’s dying, it would say, to do that.

Vince Lazaneo, the county extension horticulturist, tries a dozen varieties every year in his Mira Mesa home, including Celebrity, San Diego Hybrid, Better Boy, Big Pick, Carmelo, Whopper, and Sweet 100.

Photo by Dave Allen

As you and I consider gustatory possibilities (sliced into thick slabs and topped with fresh basil?), out in the garden, the tomato plant has gone into red alert. On the scratchy vine, messages stream from the wound our picking left behind. One set of messages instructs the plant to make a scab so liquids can’t flow out and bacteria and viruses can’t get in. Another set of messages, more a memo, really, advises the plant, “There’s one less mouth to feed. Send his food and water to the other fruits.”

Joyce Gimel, who teaches vegetable gardening and grows tomatoes at her Chula Vista home: “White fly can’t stand wind. So white fly can be overcome in a back yard by spacing out plants not too close together

Photo by Dave Allen

If animals seem smarter than plants, it’s only because a plant’s activities go on at cellular levels, literally beneath our notice. An animal, when you give it trouble, can eat you up or run away. A plant's rooted down, stuck in dirt. It has to take whatever gets dished out. So plants, to survive, have developed complicated defense mechanisms. Some researchers even describe plants as “slow animals,” forced by immobility to respond in subtler ways.

Colin Wyatt, who developed Celebrity tomatoes at Petoseed: "We emasculate those plants that will bear the tomato, pinching off male parts, using either a fingernail, if you have long nails, or tweezers."

Photo by Dave Allen

With the thought of that huffing, puffing tomato on the table, I considered the plant’s progress from seed to ripe fruit. What did that plant do? It popped out of the ground, put out leaves, grew taller, put out more leaves, then yellow blossoms and, finally, green tomatoes that ripened and turned red. That was all I knew.

Paul Thomas, who developed Better Boy: “One advantage of San Diego is that it is so early down there that I could go see which experimental hybrids performed best."

Photo by Dave Allen

I have in hand Pat Welsh’s two-pound paperback Pat Welsh's Southern California Gardening while by telephone she and I talk about tomatoes. Born into a gardening family in what she describes as “a great, beautiful garden in Yorkshire, England,” Welsh spent her teen years on a farm in Pennsylvania. In 1945 she came west with her family, eventually marrying and settling in San Diego. Welsh was San Diego Home/Garden's first garden editor and was for five years “Resident Gardener” on San Diego’s NBC television affiliate.

Bernarr Hall, UC farm advisor for San Diego County. “Hall was instrumental in getting drip tapes going."

Photo by Dave Allen

Welsh plants Early Girl tomatoes for a June crop, then for August, Celebrity and Better Boy. “I always grow Better Boy,” she says. “That’s the one I like best. For a smaller, cherry type, I grow Sweet 100. Close to the ocean, I just don’t think you can do better than Better Boy and Early Girl and Celebrity. But Better Boy grows just everywhere.

“The most important thing about tomatoes, no matter where you live in the county, is sun. I’ve had people call me and say, ‘My tomatoes have no blossom and no fruit.’ And I say, ‘Did you plant them in shade?’ and inevitably they answer yes.

Al Steindorff “works on the premise of feeding the soil rather than feeding the plant.”

Photo by Dave Allen

“In the interior, grow a heat-resistant variety. Ace Hybrid or San Diego Hybrid. And if you live in the interior, do not prune leaves off your tomatoes. If you do, your fruit will get sunburned.

“People shouldn’t plant Patio in the ground, and a lot of people don’t realize that. They look at it in the nursery and think it looks so healthy, so sturdy, the stem is so thick, and so they buy it not realizing it doesn’t have any of the protection for growing in the soil. It’s not resistant to certain soil-borne diseases, because it was built to grow in a container with potting soil, and potting soil has none of those ‘baddies.’”

I ask Welsh what is the best tomato she’s ever eaten, and she answers quickly. “The best I ever ate in my life was in England in my grandfather’s greenhouse, and I don’t think I could ever eat such a tomato here.”

Does she recall what variety her grandfather’s tomato was?

“No. And I don’t think it made much difference what variety it was. It was that it was grown in a moist, warm greenhouse and tasted so good picked off the vine with this magnificent aroma. I always remember that tomato. But once in a while, picking a tomato off the vine in my own garden, smelling that warm, bright, marvelous smell, and eating it right then and there, I’ve tasted that same flavor and had that same feeling.”

Tim Hartz is a state agricultural extension specialist, with offices at the University of California at Davis. Hartz tells me that California produces 90 percent of the nation’s tomatoes. UC Davis, he says, is the leader in research in basic physiology, biochemistry, and genetics of tomatoes. “If you include entomologists and pathologists and molecular geneticists,” Hartz says, “at least two dozen people on the Davis campus are working primarily on tomatoes.”

Critics of the commercially grown fruit speak of UC Davis as the “Treblinka of the tomato.” Researchers there developed the mechanical tomato picker in the early ’60s. Then their breeders created tough-skinned, square processing tomatoes, able to bear up under rough-handling mechanical harvest.

Some facts: Tomatoes are part of the cuisine on four of the five continents. After potatoes, tomatoes are America’s most important commercial vegetable. We eat about 80 pounds of tomatoes per year per person, a figure that includes fruit used to make tomato paste and sauce, salsa, catsup, and juice. Tomatoes are the most frequently canned vegetable in the U.S.

Tomato professionals (breeders, plant physiologists and biochemists, growers, county extension agents) speak of the tomato as three different crops: processing, fresh market, and home garden.

The processing tomato is meaty, with a high pectin content that gives pastes, sauces, and catsups a thick consistency. It is bred to be harvested, bush and all, by machine and shipped long distances.

Fresh market tomatoes, sold in supermarkets and used by restaurants, are bred to taste good and be round, red, and smoothskinned. In 1992, according to USDA statistics, the fresh market tomato commanded $5 billion in retail sales.

Home garden tomatoes are those we buy as seed or transplants. Most home garden tomatoes are hybrids, plants developed from two genetically unlike parents.

Tomato people say tomatoes have “no legs,” by which they mean tomatoes don’t ship well. The fresh market tomato we buy in supermarkets is picked before it’s fully red and is shipped in refrigerated cars. Produce Stockers in Lucky and Vons say that customers complain regularly about the poor flavor and softball hardness of these so-called “vine ripened” tomatoes.

According to a USA Today survey, 85 percent of home gardeners grow tomatoes. (Peppers are a distant second at 58 percent.) We can choose from more than 1000 tomato varieties, 300 of which are grown widely.

When we think “tomato,” we think “red.” But tomatoes are also yellow, orange, pink, white, purple and black. Some are striped green and yellow or red and yellow. Garden Peach and Red Peach tomatoes have fuzzy skin. Fruit size ranges from mini-cherry tomatoes weighing less than an ounce to beefsteak monsters of more than two pounds.

Tomatoes are rich in vitamins A and C. For adults, a one-third-pound fresh tomato can supply about 20 percent of recommended daily allowances of vitamin A and 40 percent of vitamin C.

What the white rat is to animal research, the tomato is to plant studies. A UC Davis plant biochemist explains that what makes tomato particularly appealing to plant scientists is more than the money tomato growers and packers provide to agriculture and research. The tomato, he says, is exceptionally well endowed for genetic and cellular research. In part this is because the tomato is a self-pollinator, with male and female in the same flower. “Therefore,” he said, “all plants within a given lot will be identical. So if you want to understand a phenomenon and you’re not interested in genetic influence, you’ve got plants that are all the same, which is very nice.”

The wild tomato, parent of tomatoes we eat today, grew first along the Andes’ northern arm, in Peru, Ecuador, Bolivia, Chile, and Colombia. They still grow there today, like weeds, and look like cherry tomatoes.

The tomato spread north into Central America and Mexico. From Mexico, after Spain’s conquest of the Aztecs (circa 1520), the tomato went to Europe. Aztecs cultivated a yellow-fruited tomato, and its first common European name translated as “golden apple.” In Italy they still call it that: pomodoro.

Taxonomically, the tomato belongs to the Nightshade family. Among edible Nightshades are eggplant, Irish potato, and pepper. Petunia and tobacco are Nightshades, as are poisonous black henbane, belladonna, mandrake, and jimson weed. Toxic alkaloids are present in many Nightshades, including the Irish potato and in tomato stems and leaves. The cultivated tomato’s scientific name indicates something of Western Europe’s initial fear of it: Lycopersicon esculentum, Latin for “edible wolf peach.” Europeans long regarded the fruit as poisonous, as did the Colonists who brought tomatoes back to the New World in the 17th Century.

Botanically, tomato is a fruit, the ripened ovary of a seed plant. Legally, for purposes of trade and tariffs, the U.S. Supreme Court in 1893 ruled that tomato is a vegetable.

Thomas Jefferson planted tomatoes in his garden at Montkello. But the tomato was not widely consumed in the U.S. until French-Creole cooks in Louisiana began adding them to gumbos. In the late 19th and early 20th centuries, Italian immigrants arrived in America, bringing recipes for salsa di pomodoro. By 1929 Americans, annually, were eating 36 pounds of tomatoes per capita.

Tomato seeds, properly stored, could last 100 years without losing much viability. Normally, though, hybrid tomato seeds packed for planting in 1993 would have been produced in 1992 or, at latest, 1991.

When you spread tomato seeds onto a piece of paper, you see tiny beige oval specks. They do not appear alive but are. All along, in the seed packet, they have been steadily breathing.

Beneath the seed coat are the embryo (carrying all the genetic potential to produce a tomato plant), two foodstoring cotyledons, and a second food-storage structure, the endosperm, the green plant’s version of the mammal’s placental tissue. To germinate, the seed needs sufficient water, proper temperature (70 degrees is considered optimum), and soil.

Local county extension farm agent Wayne Schrader likes to plant tomato seeds in orange rinds. “You take half an orange, eat it, then put a little dampened soil in the rind, plant your seed, and put the orange rind in the windowsill. When you get the plant up to size, you tear off the orange rind and put out your plant.”

Let’s say that at 10:00 on a Monday morning we place a tomato seed in soil under greenhouse conditions and give it water. Almost immediately, water molecules enter the seed coat and make their way between dry cell walls and into the dry cellular materials.

The cell is the smallest independently alive unit from which plants and animals are constructed. To get an idea of what a typical plant cell is like and what it can do, I know no clearer explanation than in Brian Capon’s Botany for Gardeners (Timber Press, Portland, Oregon). Capon writes,

Imagine the cell as a large factory, capable of manufacturing thousands of different and elaborate products from simple raw materials — water, air and soil. The factory uses sunlight rather than electricity or oil as an energy source. It is designed to exert considerable autonomous control over what goes on within its boundaries and, whenever increased productivity is called for, it simply builds an exact copy of its entire physical structure — within a day or two. Now, mentally squeeze this factory into a box, each side approximately 1/2,000 of an inch. That is a cell.

As plant cells mature, they follow genetic instructions and assume different forms adapted to specific functions. If differentiation did not occur, the result would be not a tomato plant, but a shapeless blob with no distinct tissues.

Back in our greenhouse, by 10:00 Monday night, water has reached the embryo. Respiration rate increases. Enzymes are activated, catalysts that speed up chemical reactions. These enzymes trigger conversion of the seed’s food reserves into energy that fuels cell growth.

By Tuesday morning at 10:00, water uptake is expanding the material within the seed. The seed coat splits, allowing more water into the seed and opening paths to oxygen in the soil.

By 10:00 Wednesday night, cells at root and stem tips are elongating, dividing, and elongating again at growth points called apical meristems. By Saturday morning, the tomato’s tap root has penetrated an inch into the soil. The stem tip has expanded, forced open the seed coat, and is pushing through the soil toward the surface. As it grows, the stem must produce enough of what is called emergence force to overcome the soil’s resistance.

All this must be accomplished before endosperm food reserves are exhausted. A seed’s food supply is so carefully calculated that if the seed is set, for instance, too far underground, it will use up those reserves before it can emerge from soil and will die.

Monday morning, the stem tip pokes out of dirt. “Once the apex of that stem hits light,” says Lawrence Rappaport, retired head of plant genetics at UC Davis, “it begins to photosynthesize. It’s a dramatic, flags-flying moment.” In animal terms, like a newborn’s first breath.

Photosynthesis is the process by which plants capture the energy in the sun’s rays and use that to create food from carbon dioxide and water. During the day, our tomato plant’s leaves absorb carbon dioxide from air, break it up and reassemble it as sugars in photosynthesis, and then dispose of the waste, oxygen, back through the leaf. At night, this is reversed, the plant takes in oxygen and releases carbon dioxide. This exchange is part of the process called respiration, in which sugar molecules are broken down to release energy to fuel plant activity. (Respiration also takes place during daylight but is masked by the greater gas exchange arising from photosynthesis.)

For the next six to eight weeks, roots and shoots and stems and leaves will grow. How, I ask, does the root know to go down and the stem know to go up?

Tropisms are growth responses to external stimuli. It is geotropism, growth in response to gravity, that in part causes the shoot to grow up and root to grow down. The top of the plant grows against the force of gravity and roots grow with it.

And how do food and water move through the plant? “Plumbing,” Rappaport says, “it’s all plumbing.” Products of photosynthesis, principally sucrose, move out of the leaves through food-conducting tissue called phloem. Water and minerals pass into the root and upward through tissues called xylem.

During a hot spell, a tomato plant might transpire (give off water vapor) ten times its own weight in a 24-hour period. Without water replacement, cells shrink and become flaccid, and the plant wilts and droops.

Local county extension horticulturist Vince Lazaneo, whose gardening columns can be read in the San Diego Union-Tribune, lives in Mira Mesa and grows his home garden tomatoes in raised beds in native soil amended with compost. He tries a dozen varieties every year. He often includes Celebrity, San Diego Hybrid, Better Boy, Big Pick, Carmelo, Whopper, and Sweet 100.

What should we look for when we buy our jiffy pack transplants at a nursery?

According to Lazaneo, “Young, sturdy plants with healthy green leaves. Avoid plants that are rootbound or that have yellowed foliage or immature fruit.”

Even before we bring home Celebrity or Better Boy or the San Diego Hybrid, we are likely to have given consideration to soil into which our plants will go.

Walking across the garden, the average person tends to think of that soil as an undifferentiated solid, as “dirt,” compact beneath his feet. But in fact the first six inches or so mix weathered rock and minerals with decomposing plants and animals and living creatures. Take up a handful of sod into your palm and you may be holding millions of microscopic soil mites and some 5 billion one-celled bacteria— about as many bacteria as there are men, women and children on Earth. So small are many soil components that when you turn over your garden dirt, you could inhale a kingdom of mites, bacteria, and spores.

When we get our transplant home and take it out of its container, the roots tend to be balled and the taproot no longer intact. Tim Hartz, the Davis-based extension agent, talks about what happens to roots when you bring home a tomato plant and stick it into soil.

“After you plant, there will be a period of four days’ to two weeks’ transplant shock. No real advance of root happens. The roots draw water, but basically they sit there.

“It takes a while for the interface of root ball and soil to get a good capillary lock so that water and oxygen can equilibrate across that barrier. And the root itself will take several days to begin to generate new growth that goes off and explores into soil.”

Let’s say it’s perfect late-spring tomato weather, with few cloudy days and temperatures never below 55 at night. Our tomato plant has been in garden soil for two weeks. Although the plant will appear to be just sitting there, looking as if it never worked a day in its life, activities of incredible complexity are taking place.

Animals, including ourselves, produce hormones, or gland secretions, that initiate and regulate various body functions. (“Hormone” comes from the Greek word meaning “to excite.”) Animal hormones are produced in glands specialized for this purpose — the pancreas produces insulin, the thyroid produces thyroxin.

Plants produce chemicals similar to hormones in animals. Plant hormones, however, are produced in cells of general rather than specific organs — stems, leaves, roots, and flowers.

Each plant hormone delivers messages regulating plant growth and functions. From planting to harvest, these hormones regulate the plant’s life.

The Big Five of plant hormones so far identified are auxin, abscisic acid, cytokinin, ethylene, and gibberellin. Each has more than one function. Auxin, for instance, sparks the rate of cell elongation, signals shoots to grow up and roots to grow down, and curbs lateral shoot growth. Synthesized auxin is an ingredient in the contact herbicide 2,4-D, that kills broad-leaved weeds like dandelion, by speeding up plant metabolism to such a rapid pace that the plant kills itself. Synthesized auxin is also an ingredient in Agent Orange defoliant.

Rubbing fingertips across plant leaves or along a stem, we will feel minuscule hairs, trichomes. Tomato plants have at least 24 different kinds. These structures perform a multitude of tasks: heat protection, ¬¬defense against insects, water-loss prevention, and scenting our hands with that familiar bittersweet, skunky green-tomato smell.

An insect walking through the forest of trichomes would find some of these hairs as sharp as knives; they scrape against it and cut its shell. An insect can bleed to death while walking across sharp, spiny hairs.

UC Davis entomologist Sean Duffey says that some wild tomato varieties growing in the Andes “are particularly hirsute, just thick with hairs. They also have a very sticky surface. Any insect who lands on these is basically doomed.”

Duffey explains that some trichomes have at their ends a structure that seen through a microscope would look like four basketballs lashed together. “The basketball-like structures contain volatile oils that turn to gas at very low temperatures. Since they volatize, they are a useful place to hide poisons and allergens. Should you brush against these trichomes, you might well find your skin beginning to redden and itch.”

Our plant has been in the garden about four weeks. Roots soak up water and nutrients. New shoots and new leaves appear. From now until the plant reaches mature height of, say, six feet, it will grow an inch a day. “Nothing,” says Tim Hartz, “compared to melons. They’ll put out three, four, even five inches of vine a day, but you don’t notice because the vine’s running along the ground.”

Joyce Gimel teaches basic vegetable gardening at Foothills Adult Education Center in El Cajon. Her students are male and female, young people and retirees. Almost all want to learn to grow tomatoes.

Gimel was raised during the Depression. Her father gardened and her mother canned his produce. “We had a large garden,” she says, “plus chickens. Like all kids, I didn’t pay much attention to what my father did in the garden and now I wish I had. I got a terrible attitude as a kid about garden chores because I had to pick off those damned tomato worms. I got a rash from tomato vines so I had to wear long cotton stockings on my arms.

“When I got married and got a home of my own, then I began to garden. I canned and froze what I grew—did the whole thing.”

Gimel gardens now at her home in Chula Vista. I ask about her tricks for growing tomatoes.

“I use row covers,” she says, ‘‘when plants are small. Row covers accelerate growth. There will not be that big variation between day and night temperature. I use it on hoops and keep it on the plants day and night until they get up to the top of the tunnel, about 24 inches. By that time plants are pretty well established and beginning to bloom.”

How does Gimel get rid of white fly, a tiny insect that sucks sap from tomato leaves’ undersides?

“White fly,” she says, “can’t stand wind. So that white fly can be overcome in a back yard by spacing out plants not too close together so that they get good air circulation. You also can go out with a vacuum cleaner, just put a piece of nylon-hose over the tube, and suck them up and squash them.”

Gimel sometimes visits her students’ home gardens. “New people get discouraged if things don’t work. It sounds so easy if you hear about it or read a book. You just put these little things in the ground and they pop right up and then you go out and pick fruit. They don’t realize the work that goes into maintaining it for four months.

“Most are disappointed when they have disease or insect problems or they haven’t prepared in advance for keeping tomatoes upright by putting in stakes or poles. As soon as plants get heavy with fruit, they fall over and get sunburned, and you can lose about 90 percent of your crop.

“Other than that,” Gimel says with a laugh, “most people don’t have too much trouble with tomatoes.”

Pat Welsh says that locally the pest that most troubles tomatoes is tomato hornworm, a large caterpillar that can grow as long as four inches. Welsh says, “It really chomps a lot,” leaves, stems, and fruit.

A high-tech bright green with diagonal white stripes, fitted out with a black horn, tomato hornworms are the larvae of hawk moths, which lay pale, beady green eggs on foliage undersides.

The home gardener isn’t defenseless against hornworm. They can be picked off the plant. Or Trichogrammas, tiny wasps that parasitize the hornworm, can be bought at nurseries and by mail order. Row covers help, and there is always Dipel or Thuricide or Bacillus thuringiensis (Bt).

Even left to its own devices, the tomato plant is not entirely vulnerable to hornworms. All plants produce at least two types of defensive chemicals. The first, like alkaloids in leaves and stems (which have been known to kill cattle that ate them as forage), is a normal constituent of the plant, present whether or not the plant is under attack. The second is an inducible defense, a genetically programmed response to attack.

Washington State University’s Clarence “Bud” Ryan was the first plant biochemist to demonstrate that when the hornworm bites into a tomato leaf, the plant doesn’t sit in abject surrender. In 1972 Ryan demonstrated that only a few hours after a beetle chewed a tomato leaf s edge, the plant began producing defensive chemicals. By 1982 Ryan had confirmed that tomato plants produce chemicals that deprive insects of nutrients and retard growth.

I telephone Dr. Ryan in Pullman, Washington, and ask if he’d describe what happens when a hornworm starts snacking on a tomato leaf.

When the hornworm bites into a leaf, Ryan explains, cells are crushed and lose water and tension. Signals are released at the wound site that send out a chemical warning scream. These chemicals move through the vascular fluid, shuttling from leaf cell to leaf cell, alerting the entire plant to the danger. (At about the same rate it takes the plant to make this “scream” heard, it would take half an hour for you to register you’d stubbed your toe.) The “scream” chemical is a polypeptide (the principal molecular structure making up proteins) that Ryan and fellow WSU researchers call systemin.

Systemin switches on genes in plant cells that trigger production of protein-digestion blockers called proteinase inhibitors. These inhibitors, says Ryan, are “anti-nutrient proteins” that curtail pests’ ability to break down proteins in plant foliage.

Two to three hours after the hornworm takes his first bite on the leaf, proteinase inhibitor floods the plant. As the hornworm dines on the greenery, says Ryan, “the proteinase inhibitor acts in the hornworm’s intestine by deranging digestive enzymes, thus making it difficult or even impossible for the hornworm to get the nutrition it needs. The hornworm responds by making more and more digestive enzymes.

“And then, at the same time, the hornworm continues chewing and making new wound sites. This causes release of more and more systemin. This triggers gene cues that further amplify signals and increase proteinase inhibitor production.”

While all this goes on, says Ryan, “a message goes to the hornworm’s brain that slows down appetite. Bit by bit, this process slowly kills him.”

Although earlier studies showed that the tomato produced natural insecticide, Ryan says his research team was first to pinpoint a polypeptide that could send signals within a plant.

By 1985 Ryan and fellow WSU researchers had identified the gene that causes tomato to produce proteinase inhibitors. Now Ryan and his team have identified the gene that codes for the chemical “scream.” Identifying that gene made way for the team’s making an anti-sense gene and inserting that into plants. An antisense gene reverses the effect of the original gene, canceling out its messages. “This,” says Ryan, “shuts down production of the polypeptide, and when we do this, the plants can’t respond anymore. We have a paper going out now that shows that tomato plants having these anti-sense genes can’t defend themselves against hornworms, and hornworms go ahead and demolish the plant.”

If I go into the garden and give my tomato plant a good kick in the stem, would it feel it?

“You betcha.”

Would this affect plant growth?

“Not much. Even if the plant has to give over one or two percent of its growth to making inhibitors during the attack, that will not affect productivity that much. Now if you kept kicking the plant every few minutes for a week then you might see some affect. That’s of course why we want to get rid of insects, because when they constantly chew, plant productivity goes down.”

All day, out in the garden in its place in the sun, the eight-week-old tomato’s leaves intercept light, taking in carbon dioxide and releasing oxygen through small pores, stomata, in the leaf surface. These stomata open and shut, controlling passage of gasses and water. As water evaporates from an opened stoma, more water is pulled up along a vein that stretches down to a root. Underground, roots travel farther out and farther down into soil, drawing in ever more water and minerals. Some of this water will be used to transport sugars from leaves back down to the roots.

Were you to set a camera in front of the tomato plant and take time-lapse photographs, you would see, looking at the film, that all day, plant leaves wave and move and twist.

With proper recording devices, you might hear the plant grow. Lawrence Rappaport reminded me that even without technological aid, you can sometimes, when walking through a corn field, hear com grow. “You can hear cracking. The plant is growing rapidly; it takes up water at enormous rates. Terrific tension is created as it twists and turns.”

We begin to get our hopes up for tomato fruit when we notice yellow flowers. The plant is able to flower only when it is large enough to support blossoms and fruit and has sufficient food reserves to supply reproductive organs. When the plant reaches that size and when day-length and temperature remain optimal for several days in a row, the plant switches to flower production.

A favorite tomato of Pat Welsh and Vince Lazaneo is Celebrity VFNT, a 1983 choice of All-America Selections (an AAS award is the plant world’s equivalent of an Oscar). Celebrity had its early field trials in San Diego during the late 70s and produces dependably in each of San Diego County’s microclimates.

Celebrity was bred by Colin Wyatt of the Petoseed Company, one of the top five seed developers in the world. Wyatt is also responsible for the “Husky” Series of tomatoes, named a 1993 AAS winner.

About tomato breeding, Wyatt says, “Farmers had always selected and saved seeds from superior specimens, gradually breeding out objectionable qualities and breeding in the desirable. Until the turn of the century, most improvement came by way of selection.

“And then in the 1940s we got into manipulation of sexual reproduction of the plant, where you took the male of one plant and put it onto the female of the other. We called this plant breeding.”

Wyatt explains that the tomato has 12 chromosomes with varying numbers of genes on each chromosome. Plant scientists have isolated many of the particular characteristics of the tomato and mapped the location of the gene or genes responsible for that characteristic on individual chromosomes. Among these characteristics would be color, earliness, extra-large fruits, skin resistant to cracking, tall vine or short vine, resistances, flavor.

A tomato like Wyatt’s Celebrity is a hybrid. A hybrid is a plant developed from two genetically unlike parents. What plant breeders hope to accomplish by hybridizing is to create plants with qualities better than those of either the original parent plants. They describe such a combination as hybrid vigor.

Many generations of tomato plants will be planted and harvested for seed before arriving at the final two parents. Breeders speak of these ancestors as background material.

Self-pollinators often suffer from inbreeding depression, in which genes that would be hidden by cross-pollination are expressed. It’s a situation comparable to that of inbred pedigreed dogs. Modem row crops often lose resistance to disease. Crossbreeding with wild cultivars can create a new variety endowed with disease resistance.

Tomato breeding, said Wyatt, is as much (or more) art as it is science. When Bill Moyers filmed his PBS series on creativity, he went to Petoseed and interviewed Wyatt and tomato breeder Paul Thomas (whose accomplishments include the 1964 Better Boy, one of the best-selling tomatoes during the past quarter-century).

“Developing a new tomato,” Wyatt said, “I get an idea. I say to myself, ‘I might as well try and do something with this thing.’ Then I get a few more ideas. Then I’m started.

“The first place I work is on my desk in my office. I develop crossing plans. I doodle. I don’t work on it all the time.

You have to have quiet and reflect on what you’re doing and figure what will happen when you do this or do that.

“The steps come slowly. Building up my background material can take 10 or 15 years from the first cross to commercial introduction. The one desirable trait you’re looking for may come with half a dozen genes acting together, rather than one. So, it can get complicated.

“You go in the direction [in which] you get favorable responses. If things are working pretty good, you go after it. If I run up against a stone wall, then I say to myself, ’Forget it. Maybe I better do something different.’”

Tomato flowers have both male (stamen) and female (pistil) in the same flower. Normally, the tomato flower’s fruit-setting ovary (a part of the pistil) would be fertilized by pollen from the flower’s own pollen-producing anther (a part of the stamen). The tomato flower does not need insects for pollination.

Hybrid pollination, in which pollen from one parent will be placed on the stigma of another, requires interference. In order to guarantee hybrid seed, plants must be prevented from fertilizing themselves. “It would work this way,” said Wyatt. “In fields where plants are reared for breeding, Parent X, the male line, and Parent Y, the female line, would be grown at a distance of about one mile apart.

“In the tomato flower, the anther,” Wyatt continued, “forms an anther cone. It comes over and covers up the female parts. Before the blossom opens up and male parts have matured, we go to plants that form our female line — the plants that will bear the actual tomato fruit— and we emasculate those plants, pinching off male parts, using either a fingernail, if you have long nails, or tweezers. Once you remove this anther cone, then the female part is totally exposed.

“When flowers begin pollen production, then we go to the plants that produce our male line and gather that pollen. We shake the flower and collect pollen in a tube.

We then take the tube to the field where the female plants are growing. The anthers, remember, have been removed and the stigma at the end of the female’s pistil is exposed. You dust or sprinkle the pollen onto the stigma with a small stick or your fingernail.

“This, if all goes well, results in fertilization and a fruit whose seeds carry all the characteristics of both male and female parents, at least for the first generation.”

Hybridizing is time consuming, labor intensive, and expensive. A single non-cherry-type tomato produces only 50 to 100 seeds. Seeds for newer tomato hybrids, bred at one of the company’s farms in Mexico, Taiwan, China, Thailand, japan, or Indonesia, can cost as much as $1000 per pound. On average, there will be 150,000 tomato seeds in a pound.

The hybrid cross must be made each year to generate seed for the next year. When the home gardener buys hybrid seed. Celebrity, for instance, and plants them, grows tomatoes, and harvests their seed, he cannot plant these seeds the next season and expect Celebrity. Plants will revert to their panoply of ancestors and yield five or six varieties.

I ask Wyatt how Celebrity came by its name. “Simple,” he said, “at Petoseed we have a naming committee. The committee tries to find a really appealing name for its new seeds, a name that will have a ring and consumer appeal. Celebrity has that ring.”

Mornings, when we walk into the garden, oxygen will be spraying out from stomata, and solar panels in leaves will be gearing up for light capture. Some yellow blossoms may have dried up and dropped off, leaving behind no green tomato. This indicates that pollination was not completed. Temperatures may have been too high and humidity too low, as when Santa Ana winds blow across the county. This dry heat will cause pollen to desiccate and lose ability to fertilize.

Pat Welsh says, about blossom drop, “You have to pollinate the tomato to have fruit. People who don’t know this and who grow tomatoes in a still and protected place may have few tomatoes or may not even have any. So you must jiggle your blossom and produce the effect of wind.” In Welsh’s Southern California Gardening, she suggests that pollination can be improved by “rapping with a hammer on tomato stakes or cages in the middle of the day, when the weather’s warm and dry.” To ensure pollination, commercial producers of greenhouse tomatoes use what they call an electric bee to vibrate tomato plants. Home growers of greenhouse tomatoes often use an electric toothbrush.

Although pollen is mature and ready for transfer when the tomato flower opens, the stigma at the female pistil’s end is receptive for only six days — two days before the flower opens and four days after.

Pollen is shed most abundantly on bright, sunny days between ten in the morning and four in the afternoon. Let’s say that we go out to the garden one Saturday at noon. Following Welsh’s suggestion, we rap the plant stake with a hammer. Pollen grains land on the stigma, sticky and ready for pollination. By 1:00 each pollen grain begins to put out a pollen tube. During the next 12 hours this tube grows down through the pistil into the ovary to the ovules. Pollen from, say, a zinnia, wouldn’t have any luck with the tomato. A flower obtains clues to pollen’s compatibility from the grain’s shape and chemical composition. Six hours after reaching the ovule, at 6:00 Sunday morning, the ovule is pollinated and a zygote, the union of sperm and egg, forms.

An aside. Walking out in your garden you inhale pollen grains (along with mites, bacteria and spores). The pollen grain ends up in your nose. A sticky protein is spread on the grain’s surface, as an aid to fertilization. These pollen grains, in your nose or on a plant’s stigma, want only to mate. That is their function. They will try to mate with the mucous membranes that line your nasal cavities (as desirable in their own way as the tomato plant’s sticky, ready-to-breed stigma). If you are among those people who suffer from pollen allergies, you may start sneezing. It is the pollen’s gummy protein that stimulates your histamine response.

Colin Wyatt suggests I talk with his colleague at Petoseed, Paul Thomas. Thomas is best known as breeder of gardeners’ now 30-year-old favorite, Better Boy. He also developed the tomato marketed locally as the San Diego Hybrid.

How, I ask Thomas, did he happen on the San Diego Hybrid? In the late ’50s, Thomas said, Petoseed wanted to get into the San Diego market and sell tomato seed to local commercial growers. Thomas laughed. “So, basically, I went to Bernarr Hall.” Up in North County’s tomato fields, growers still talk fondly of the late Bernarr Hall, who served 40-plus years as University of California Cooperative Extension Service farm adviser for San Diego County. In 1987, when Hall died, the San Diego Union bannered his obituary, “B.J. Hall, 75; A Help to Farmers.”

A native San Diegan who made his home in La Mesa, Hall joined the extension service in 1941. As one among his duties, Hall supervised field trials for seeds developed by universities and seed companies.

When Thomas telephoned Hall to inquire about Petoseed’s selling seed to local farmers, Hall suggested that what county commercial growers most needed were tomatoes with disease resistance. “So,” recalled Thomas, “we put some hybrids together that had F and V resistance.”

New gardeners wonder when they study seed packets what the letters V, F, N, and T mean. These letters, following | the name of a tomato hybrid, indicate that resistance to I verticillium wilt, fusarium wilt, tobacco mosaic and nematodes is bred into the tomato.

In Petoseed’s first years, Paul Thomas lived and worked in Ventura. “During growing season,” he said, “I would get I up at 4:00 and drive down to San Diego two or three days a week.”

What Thomas came to check were Hall’s vegetable crop field trials, in which Petoseed would enter hybrids. “Bernarr was always good about trialing material. He’d plant plots down in the south end of the county, almost to Chula Vista, and then on up to Oceanside, and then in a third location. He would be able to look at this tomato in three different sections of San Diego County.

“I always put early stuff in San Diego in spring trials. I would send it [his seeds] to Bernarr, and he would put it in growers’ trials, which included seeds from all companies.

“One advantage of San Diego is that it is so early down there that I could go see which experimental hybrids performed best so that when we planted our material in Ventura County, we could concentrate on those that performed best in San Diego.”

What would become the San Diego Hybrid had its start in work done by tomato geneticist Charles Rick, whose Tomato Genetics Stock Center at UC Davis stores some 3000 variants of the tomato, many of which Rick collected in the Andes.

“Charlie Rick in the late ’40s,” says Thomas, “put together a combination that turned out not to be a bad tomato, the H11. Unfortunately, H11 for fresh market growers, had no disease resistance. So the effort was to come up with something comparable to Ricks H11 that was disease resistant.”

The San Diego Hybrid is also known as 7718. Each seed company has its own system for coding breeders’ experiments. Thomas explained that in Petoseed’s old system, 7718 would indicate a tomato plant that was the result of Petoseed’s 18th hybridizing cross made in 1977.

One morning in the late ’60s, a call came to Thomas at his Ventura office. It was Hall. “You need to get on down here,” Hall said, “there’s trouble in the tomato fields.”

Thomas drove to San Diego and met Hall at the edge of a North County field where plants from Thomas’s seeds were growing. “A devastating disease had struck some ten acres of commercial growers’ fields. It looked like a tomato graveyard. It was like you hit the tomato fields with a blow torch. Ten or more acres of tomato vines appeared dead.”

North County tomato grower Al Steindorff remembered the event this way. “The plants were all dead with fruit still hanging on them that wasn’t developed completely. It looked like a Biblical curse had fallen on the fields.”

A UC Riverside pathologist misidentified the disease as seed borne fusarium crown rot. That he called the disease seedborne caused problems for Petoseed, said Thomas. “The finger of guilt pointed directly at us.”

Thomas telephoned UC Davis’s veg crop department and asked for help. The department head called a meeting of seed companies and university plant pathologists. “A fellow at Davis and his assistants identified the disease as alternaria stem canker.” Though they pinpointed the alternaria, they couldn’t find its origin. “We still don’t know,” says Thomas, “exactly where it came in from. Probably out of the soil. In San Diego at that time, farmers pinched out growing shoots near the bottom of the plant. It seemed as if the organism would go in on holes in the plant stem where pruning took place. The stem would be girdled, cutting off the flow of food. Plants would turn brown right above ground and soon the tops would die.”

Not all the field was infected. One spot in the tomato graveyard continued lush and green. It was a stand of Petoseed tomatoes — 6718VF — bred by Thomas to give local growers verticillium and fusarium resistance.

“We did not know it at the time,” said Thomas, “but one of 6718’s parents was resistant. After the alternaria was identified, we assayed our breeding material to see what was susceptible to this altenaria and what was resistant. Everything we have now is resistant to it.

“In 1977 we replaced 6718 with 7718. They were similar except for a change in one parent that made 7718 a smoother fruit.”

Thomas agrees with Colin Wyatt’s assessment that breeding is as much an art as a science. “I will wake up at three in the morning,” he says, “because an idea hits me. Sometimes they look pretty dumb when you get up and look at them.”

Thomas doesn’t work with a computer. “The new young people,” he says, “seem to have them attached to their feet.” He adds that 40 years ago, when he was one among the new young people, most plant breeders weren’t, as they are now, PhDs. “Our graduate school was the field. We didn’t even have offices. We went out in the fields with the plants.

“The computer is a useful tool, but it doesn’t tell you everything because much of what we do is not measurable. You go by feel. When you are trying to test firmness of a tomato, a lot of this is in how you squeeze fruit, how it comes off the plant. How do you find out these things? You find them out by doing them.

“Living in Ventura and trialing in San Diego gave me a chance to see material all through production season. You like to look at plants when they first start coming into production, see the first fruit, how it starts to set, if it comes in with a good yield.

“As the season progresses, you want to see later settings, to make sure you are able to maintain fruit size up on top of the plant. Being able to watch material allows you to see if you are going to get a continuous set or a concentrated set for one big pick and then a big gap before the next pick. Commercial growers and home gardeners like to have continuous harvest.

“And you want an opportunity to see what happens when the plant goes through stress — temperatures that are too low or too high, too little water, too much.”

Of the three tomato types — home garden, processing, and fresh market — home garden is the smallest part of the market. “And,” says Thomas, “the most fun. That’s where you can let your creativity go crazy. You don’t have to meet the standard of a packing box or picking machine. You don’t have to worry about whether it peels easy or has good color, whether it has high solids or high viscosity. In home garden, if you find something unusual and different, you can go with it.”

Did Thomas ever stroll through nurseries and look at plants grown from his Better Boy seeds?

“I sure do,” he said. “It’s a thrill, to be honest with you, that they’ve done what they’ve done.”

Our tomato plant, put into the ground in May, by late June will stand five, six, even seven feet high. Leaves suck to their work of photosynthesis, producing sugar and allocating that sugar to each truss of fruit. (It takes about 13 leaves to furnish one tomato fruit enough food to bring it to a one-pound weight.) Roots stick to their work, drawing up water and minerals.

If pollination has occurred, chemical messengers set off activities responsible for making fruit. One of the most important triggers in tomato fruiting is ethylene.

Ethylene, one of the Big Five plant hormones, is better known as a raw material in production of petrochemicals. Ethylene is also a naturally occurring gas emitted by fruits and vegetables. Apples, tomatoes, bananas, and melons give off the most ethylene.

It is to ethylene that we owe the adage, “One bad apple can spoil the barrel.” A bruised apple or a tomato with broken skin discharges more ethylene than an unblemished or unbroken fruit. Increased ethylene discharge in turn causes a respiration increase; with this increase comes faster-than-normal decay. This increase spurs nearby unbroken fruits to generate more ethylene and respire more rapidly and decay sooner. Hence, the bad apple that spoils the barrel.

Most plant cells make ethylene all the time. But ethylene does not just sit in the tomato waiting to act, it has to be synthesized from basic elements in the fruit.

UC Davis’s Joseph Ahrens, in the veg crop department, is by training a cell wall chemist. He is considered an expert on post harvest physiology — what happens to fruits and vegetables after they’re picked. I ask Ahrens if he can explain what ethylene does in tomato ripening.

“Ethylene,” he says, “acts as a switch. It initiates a cascade effect, turning on one after another enzymes. And in a feedback effect, it induces its own synthesis.”

Ovules in the ovary of our tomato plant fertilized on Sunday morning, by Tuesday afternoon will be dividing, creating an embryo, around which is endosperm. The ovule is attached to the columella — the “meat” at the center of the tomato — by the funiculus, the plant’s umbilical cord. Sucrose and nitrogen pass from fruit through funiculus into the ovule.

During the next eight weeks, the ovary, weighing 10 mg (a drop of water weighs 10 mg) will grow to a tomato fruit that may weigh as much as two pounds — “bragging weight.” This eight-week period can be divided roughly into two parts. During the first four weeks, cell division takes place. During the last four weeks there is cell enlargement, due in part to water uptake.

Nutrients are diverted into fruiting. Two days after pollination, import of sugars and water and minerals to the ovary of our tomato plant increased substantially. “Sugars,” says Ahrens, “come into the fruit and are assembled temporarily into starch for storage. The tomato takes two sugar units and slams them together into starch. It’s like knitting wool together: you make chains of starch, which are just ways to store sugar. The tomato also stores sugar in the vacuoles, big storage areas in the cell.”

Daily dry matter accumulation rate in the green tomato increases from 30 mg (the weight of 30 drops of water) to 150 mg by the end of the first two weeks after pollination. Green tomatoes no bigger than your pinkie’s end will begin to show under the leaf canopy.

During weeks three to five of the eight-week fruiting period, growth in the ovary is rapid and due almost entirely to cell enlargement. By the end of this period the tomato reaches what is described as its mature-green stage and looks like a full-sized, hard, green tomato fruit. The mature-green fruit, if torn from its vine, could ripen and produce viable seed.

If the tomato has not quite reached mature-green, says Ahrens, and “if you wound that tomato, if something takes a big bite out of it, or the stem gets broken and stopped giving nutrients to the tomato, it will detect that. It will go into a stress which the fruit perceives as an imbalance of nutrients inside it, and it will start to produce ethylenes and try to hurry up and ripen. It will force itself to ripen in order to make a last-ditch effort to make some seeds. It’s quite amazing.”

Tomato acreage in San Diego County, once the largest fresh market tomato producer in the state, fell from 6600 acres in 1981 to 3426 acres in 1992, according to statistics gathered by county farm agents. Fresh market tomatoes that used to be grown primarily in North County and sold to the L.A. and East Coast markets are grown now in Baja and in the state’s central valley.

County farm adviser Vince Lazaneo explained the decline in local fresh market tomato acreage this way. “Not only are land costs higher here than they are in Baja or the central valley, so are labor and water costs. A lot of local growers helped that move to Mexico by going into partnership with growers in Mexico.” Why?

“The bottom line is, can you make a profit?”

As for the exodus of tomato acreage to the Central Valley, Lazaneo explains that most local tomato growers plant stake or pole tomatoes, which go into fields as transplants and must be hand-tied to stakes and pruned. Fruit is hand-picked off vines six to seven times per season On the other hand, central valley farmers plant a bush tomato that grows close to the ground and requires no staking, tying, or pruning and can be mechanically harvested. Mechanical harvesters separate fruit from vines and sort it with electric eyes according to color.

I want to see some local fresh market tomatoes.

I telephone Andrea Peterson of Peterson Specialty Produce in Fallbrook, who grows cherry and pear tomatoes for the gourmet market. Peterson suggests I go see Al Steindorff s organically grown tomatoes. Steindorff, she says, isn’t “a real chatty person,” but he was “very knowledgeable and had been doing it forever.” She added that compared to Steindorff, “the rest of us [local organic-tomato growers] are just abject newcomers.”

I meet Steindorff on acreage he leases from Palomar Airport. The land lies directly beneath the airport’s flight path. A big man, dressed in blue work shirt, blue jeans, and sneakers, Steindorff initially proved as taciturn as Peterson hinted he might. In the ten-acre patch, at whose edge we stood, Steindorff raises celery, cucumbers, and tomatoes. He had been farming this patch for ten years and grows eight acres of tomatoes here and in another location. He sells tomatoes “to customers back East and up North and in Seattle, and Eugene, Oregon, San Francisco and L.A.” He points toward a jet whose wings and belly shade us for a moment and whose roar drowns out our talk. He says (and I have to read his lips to understand him), “You get used to the planes after a while.”

Steindorff leads me to a section he planted two weeks earlier with six-week-old transplants called Bingo, a variety whose high yield of firm fruit and ability to ship without damage makes it a favorite for fresh market growers. Rank upon rank, two-foot-high, vividly green tomato plants grow in straight rows. Black plastic has been rolled out the length of each row. Each tomato grows through holes in the plastic, which acts as a synthetic mulch, smothering weeds and holding moisture in the soil. A wooden stake stands next to each plant. White string ties each plant stem to its stake at a point six inches from the ground.

We sit on our heels while Steindorff shows me drip tapes that run alongside the black plastic. “Bernarr Hall,” he says, “years ago, was instrumental in getting drip tapes going. It used to be when we were doing furrow irrigating, you would have to turn on water and direct it down the ditch, and then you would have to move it and do it again. Now I just open the valve and it waters the whole field all at the same time.”

Steindorff brightens as he talks about Hall. “He was a great guy, very knowledgeable about plants. We used to kid him. We’d ask him, ‘Since you are so smart about plants, how come you aren’t a grower?’ He’d say, ‘Well, it takes a certain kind of person to be a grower. You have to be a natural-born gambler.’ He was right about that.”

We walk toward a second acre of tomatoes planted in late January and grown, after some three and one-half months, to heights ranging between three and four feet. Tennis ball-size green tomatoes hang in trusses off stocky plants, and yellow blossoms lift from stem ends.

Most of the fruit is still hard and bright green, but we can see, toward the bottom of plants, fruit turning paler green. “When these are picked,” Steindorff says, “they will be almost ripe and will weigh six to eight ounces. They will taste like a tomato, unlike what you get at the store.”

Steindorffs tomatoes are “vine ripes.” They will not be ripened in ripening rooms, but they are not picked red ripe as they would be in a home garden. According to USDA standards, a tomato is “vine ripe” when it has acquired ten percent color, with a hint of palest pink showing through green.

Steindorff grew up in Montana, where his father grew sugar beets and raised cattle. “I thought being a farmer was the last thing I wanted to do, but after I got away from it, I knew there was something missing in my life. So I came out here in the ’60s and went to work for a flower grower. Then I started a place of my own in Encinitas, growing cucumbers.”

Steindorff became an organic grower, he says, “for the challenge. Farming without chemicals, he adds, “gets in your blood and you get addicted to it.”

He uses fish fertilizer and compost he makes from horse, chicken, and steer manure. He doesn’t “spray with anything detrimental to people” and depends for insect control on lady bugs, lacewings, and parasitic wasps.

An organic farmer, Steindorff says, “works on the premise of feeding the soil rather than feeding the plant.” In the decade he’s grown vegetables under Palomar’s incoming jets, Steindorff says he has significantly improved the soil. “When I began, it was hard and compacted.

It would go from being wet to dry in a few days. Over time. I’ve incorporated organic matter that holds on to water.”

His current crops, he says, are pretty good. “If you look at a successful crop, it makes you feel good, and if you look at a devastated field, it’s depressing. It’s like your children who are doing real well and you’re happy, and if one gets in trouble with the law, you feel very sad. You ask yourself, ‘Where did I go wrong?’ It’s the same way with plants. You ask yourself, ‘Where did I go wrong?’ ”

Early on in my attempt to figure out tomatoes. I’d ordered from the UC Davis bookstore a book Colin Wyatt recommended as essential: the 665-page, $165 The Tomato Crop. When the book arrived and I began to read, much of the text might as well have been written in German, a language I’d studied for one semester in high school and in which 30 years later I could recognize not much more than simple nouns. In The Tomato Crop, I’d been reading Grierson and Kader’s article “Fruit Ripening and Quality,” in which the authors mention the “respiratory climacteric.”

I asked Dr. Ahrens to explain this “respiratory climacteric.”

“Some fruits ripen after harvest and some don’t. Apples, tomatoes, bananas keep on ripening after you pick them. Strawberries and pineapple and oranges won’t. If you pick an orange when it’s green, it stays green. Those that do ripen after picking go through what we call a respiratory climacteric.”

Whether or not the tomato has been picked, said Ahrens, it goes through the climacteric. “When you first notice that bit of pink on the bottom of a green tomato, the fruit will have started breathing more rapidly. As ripening continues, the fruit breathes faster and faster until about the time it gets half pink and half red. At that point the tomato is at climax, which is what we speak of as the respiratory climacteric.”

After reminding me that in respiration, sugar molecules are broken down to release energy to fuel plant activity, Ahrens said that at Davis they gauged tomato respiration by “putting tomatoes inside a chamber and measuring how much carbon dioxide they produce.” They also measured banana, avocado, and apple. Apple respires more slowly than tomato; banana and avocado respire faster.

Weeks seven and eight of ripening are a second period of slow growth during which there is little gain in fruit weight. Now, intensive metabolic change takes place. Starch molecules break down, turning into fructose and glucose. Acids in the locular gel mellow. Enzymes send messages to soften rigid cell walls and pectin that glues them together.

Softening occurs in two general phases. There is the initial cell wall softening associated with cell growth. A second stage of softening that breaks down the pectin in cell walls occurs in these last few weeks.

Calgene’s FLAVR SAVR tomato, under development in Davis since 1984 and promised for supermarket shelves before year’s end, addresses this last-stage softening. The gene that controls the enzyme polygalacturonase, or PC, that breaks down pectin, has been taken out, turned around, and put back in reverse order. The anti-sense gene stops PC production and delays final softening.

At the same time that softening occurs, other enzymes signal for color change. Green chlorophyll breaks down and is replaced, successively, by yellow, orange and finally, red pigments.

At Dr. Ahrens’s suggestion I call Adel Kader, author of “Fruit Ripening and Quality.” Kader, says Ahrens, is a “great expert" on ripening color change. I find Dr. Kader in Davis’s department of pomology. Kader explains that although he had done his doctoral dissertation on irradiation’s effect on tomatoes, he is now in pomology, “working on peaches and pears and strawberries and some on apricots.”

Depending on temperature, Kader says, “it takes about ten days to go from fully green to fully red tomato.”

What makes green tomato green, he says, is chlorophyll. As the fruit ripens, the chlorophyll is degraded and carotenoids synthesized. Among the carotenoids are beta carotene, which gives carrot its color, and lycopene, which gives red tomato its red flesh.

“The carotenoid biosynthetic pathway,” says Kader, “is a very lengthy pathway, and it has very many enzymes involved and many branching points. These chemical changes are all under genetic control, so there is a gene for every one of those steps. And that’s why it is possible, genetically speaking, to produce a tomato that is orange, one that is yellow, or one that is red or combinations thereof. That is all based on which genes conclude the steps in the carotenoid pathway.

“There are anatomical changes coupled with the biochemical changes. There’s more and more gel-like liquid forming in the locules. This is important. If the tomato does not have that kind of juice, it is not good in terms of eating."

For eating raw, Kader prefers cherry tomatoes. “Cherry tomatoes always come on top, because of the high sugar and high acid.” Early Girl he likes and grows in his back yard. The flavor of Early Girl, he says, is closest to that of cherry tomatoes.

If we put our tomato in garden soil in May, by the middle of July we might find, under the canopy of spicy-scented leaves, our first ripe red tomato. We may also find tomato pests. Once tomato fruits turn mature-green and begin to ripen, the plant no longer directs as much energy to repelling predators. UC Davis entomologist Sean Duffey explains, “Genetic information (that would tell the plant to produce chemical defense against insects is not programmed to respond anymore. In ripening, what happens to fruit has become irrelevant, because the seeds are already formed. All the plant wants is to have its seeds disseminated. And from the plant’s point of view, it doesn’t matter what happens to the fruit after that point.” Marita Cantwell, a professor in the UC Davis veg crop department, is an expert in post-harvest physiology. Cantwell explained that the end for which the tomato was genetically determined was to stay on the vine and prepare seeds for dispersal and reproduction. “But we have distorted that evolutionary purpose somewhat,” she said, “to meet our consumer needs.”

I ask Dr. Cantwell what happens to the red ripe fruit when I pull it off the vine.

“During the first few seconds after the tomato is picked from the vine,” she says, “we don’t know precisely what happens. We do know we’ve cut the fruit off from its water supply. It begins losing moisture through its stem scar rather than taking up water. It will no longer be able to accumulate sugars from photosynthesis. It is now on its own. It must use its own sugar reserves to continue ripening and softening. But it’s not dead. It continues to take in oxygen and give off carbon dioxide. It will do this until it rots.” In the ripened ovary, picked from the vine, the seed remains attached to the fruit. The picked fruit continues the ripening process of softening, coloring, sweetening. And it will continue this process right up until the moment of consumption.

Senescence, or aging, acts differently in plants than in animals, Ahrens explains. “In plants there is a programmed senescence, a programmed death. The idea is to make itself attractive and get the seeds dispersed.”

Why does the supermarket tomato taste so bad and the homegrown vine-ripe tomato taste so good?

Tomato flavor, tomato experts all say, depends upon a combination of sugars, acids, and aroma volatiles, or readily vaporizing compounds. “And,” Adel Kader emphasizes, “it has to be a proper balance."

Tomatoes bred to have more meat and less locular jelly, because their acid content will be lower, will tend to taste bland, says Ahrens. Tomatoes picked before they are mature-green will taste bitter, in part because starches will not have entirely turned to sugar. And an underripe tomato is very acidic. As it ripens, acids decrease.

Tomato is a tropical fruit. Cold, temperatures below 55 degrees, is the great enemy of tomato flavor. When a fresh market tomato is picked as mature-green and shipped cross-country in refrigerated trucks and held in a cooled storeroom, development of the fruit’s volatile chemicals stops.

Cold is as much an enemy to the genuinely red vine-ripe tomato as to the mature-green. Toss your red vine ripe into the refrigerator, says Ahrens, and the chill will destroy the proteins that carry the fruit’s volatile chemicals.

Breeders Paul Thomas and Colin Wyatt agree that part of the problem in breeding for flavor is that people experience taste differently. Joyce Gimel illustrated this point. Gimel recalled that early in the ’80s, the local master gardeners’ class did taste-testing in connection with a tomato-growing project at Cuyamaca College. “We bought 12 varieties of tomato at local nurseries and raised three tons of tomatoes. When we came to tasting, everyone agreed that certain tomatoes were better. But it was surprising how much difference there was in how people felt about flavor. It is very subjective. One person would like a mild tomato, and another liked one with a little zing to it.”

To ask more about tomato flavor, I telephone chemist Ronald Buttery at the USDA’s Western Regional Research Center in Albany, California. He studies the tomato’s volatile compounds. Buttery explains that only when the tomato is cut open and chewed does the fruit yield its final bouquet. “When you hold an uncut tomato in your hand and smell it, the fruit has very little odor. But cut it open and you get the aroma. That’s the moment when the enzyme system in the tomato breaks down the fatty acids and releases the volatiles.

“What people call taste is actually aroma. When you eat a tomato, bite down on a chunk of it and start chewing, volatiles are released. The volatiles go way up in the nose, close to the brain. As you chew, enzymes are released that break down fatty acid and convert it to an aromatic compound known as (Z)-9-hexenal. Within seconds, this hexenal mixes with other tomato aromas to make up the conglomerate of scents that the nose takes in as ‘tomato.’ ”

Buttery echos other tomato experts. Cold is flavor’s foe. “Do not,” he says, “put tomatoes in the refrigerator.” He adds, “Do not cut a cold tomato. If you slice open the tomato when it’s cold, the cold will have turned off the enzymes and they will not be available to start the chemical reaction that produces the volatiles and thus the aroma.”

Buttery hopes that his team will be able to piece together the chemistry of what makes a tomato taste good or bad and then, from that knowledge, build a tomato that doesn’t lose flavor when it is refrigerated.

One day in early June I talk a second time with Pat Welsh. She has just come in from the garden, where she’s been tying up her Early Girls, Celebritys, and Better Boys. She declares herself immensely pleased. “The plants,” she says, “are not unblemished. They have some worm holes in them. Today, gardeners point with pride to the few worm holes. We are not looking for a plant that doesn’t have a blemish on it. What we want to see is a very sturdy stem, the bottom leaves not curled, and plenty of good, healthy leaves so the tomatoes won’t become sunburned. I was looking at my tomatoes with pleasure this morning because the plants look strong and healthy, the fruit is coming along, not ripening yet, but looking promising. And I brushed up against hem and set off that marvelous aroma that just seems to have in it the whole promise of summer.”

I want to tell Pat Welsh about my father. He collapsed and died on an October morning six years ago. Several hours earlier, he’d put up seven pints of chili sauce made from tomatoes he’d grown in his garden. He loved to eat a tomato picked right off the vine for breakfast. He’d stand shirtless and barefoot in the garden, his massive freckled chest streaked yellow with tomato pollen, and pick a ripe fruit off a plant grown tall as he was (six feet plus). Eating a tomato,” he would say, as juice dribbled down his chin, ‘is, by God, like biting into summer.”