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The Healthy Benefits of a Stressed Out Plant

The biological principle of xenohormesis suggests that organic farming advocates might very well be pampering their plants into nutritional laziness.
(Photo: sripfoto/Shutterstock)

(Photo: sripfoto/Shutterstock)

Any organic farmer worth his salt knows that he’s primarily a cultivator of soil. Humus is the agro-ecological king; carbon density the driving obsession. More than any other factor defining the organic mission, soil quality roots the movement in a unique ideological substrate, one that touts the connection between healthy soil and healthy food—food for which consumers are willing to pay a hefty premium.

But the connection between soil health and plant health—one of the most touted benefits of organic agriculture—has come under fire in recent years. “The published literature lacks strong evidence that organic foods are significantly more nutritious than conventional foods,” concluded a much-publicized 2012 study. Rebuttals to this finding were weak. Most follow up reports reacted as the Washington Post did, identifying “no significant nutritional difference between organic and conventional produce.”

How could healthier soil not lead to healthier food? From the perspective of agriculture—specifically, the noble soil farmer investing in nutritive health through time-honored methods—the question certainly merits some head scratching. After all, you embed the soil with nutrient wealth, that wealth transfers to the plant, and the result is an especially delicious and healthful product. What could be more basic to agricultural logic? Hence Sir Albert Howard, the father of organic agriculture, who opened his 1943 manifesto, An Agricultural Testament, with the credo that “the maintenance of the fertility of the soil is the first condition of any permanent system of agriculture.” Simple.

Xenohomesis demands that, when it comes to growing nutritious food, we must humble ourselves to the mysteries of a plant-animal relationship that long precedes the relatively recent evolution of our frontal lobes.

But it’s not so simple. Taking a non-agricultural perspective—namely, that of plant stress and the evolutionary benefits it confers—places the question of soil health and a plant’s nutritive value in a more interesting (and, for farmers, humbling) light. Central to this perspective is a biological principle known as xenohormesis.

Xenohormesis explains how plants undergoing ecological stress—such as drought-wracked or over-salinated soil—produce “extranutritional constituents” that confer survival advantages upon the animals who eat them. “Animals,” according to Philip Hooper et. al., “can piggyback off products of plants' sophisticated stress response which has evolved as a result of their stationary lifestyle.”

From the perspective of agriculture, xenohormesis is a counterintuitive notion. Whereas one might logically assume stressed plants to be withered organisms lacking nutrient density, xenohormesis proposes exactly the opposite scenario: Floral struggle under environmental stress can make a plant healthier (and, in some cases, tastier) to eat. The reason involves evolution. Billions of years of sedentary existence required some plants to endure harsh conditions by absorbing more nutrients from drier and saltier soils. Animals who consumed this scrappy vegetation—these Horatio Algers of the plant world—were rewarded with healthier food and greater longevity. This form of mutualism ensured the persistence of plants that worked harder under more difficult circumstances to take more from less.

The result of this evolutionary legacy is evident today in a wide range of plants—including cucumbers, mustard seeds, wheat-rye hybrids, grapes, lettuce, soybeans, black currants, and chokeberries. These are just a few of the agricultural products capable of producing what one study calls “higher yields of potentially therapeutic bioactive compounds” under stressful circumstances.

Xenohemosis is a cunning little concept. It enters the turbulent world of agricultural discourse—a world stubbornly intolerant of ambiguity—and, insisting on a broader evolutionary focus, sends everyone’s farming philosophy into a tailspin. Organic advocates might very well be pampering their plants into nutritional laziness with finely calibrated and moisture-absorbent soil; conventional agribusiness, with its relentless emphasis on yield increase and chemical control, is certainly eliminating critters that might reward the tougher and more nutritious plants. Those who are absolutely assured that colony collapse disorder (of honeybees) is exclusively linked to “the smoking gun” of neonicotinoid insecticides will now have to consider the possibility that bees might be feasting on fewer and fewer nutrient dense plants. And so on.

In essence, Xenohomesis demands that, when it comes to growing nutritious food, we must humble ourselves to the mysteries of a plant-animal relationship that long precedes the relatively recent evolution of our frontal lobes. The concept offers a sobering corrective for agricultural advocates who think that farming should replicate natural processes to achieve healthier food. It reminds us that natural processes honed over billions of years cannot be effectively approximated by anyone, much less conventional farmers, organic growers, agricultural scientists, or biodynamic-loving hippies.

The very recent human process of taming the wild to coax food from the soil is an endeavor that, over the last 10,000 years, we’ve undertaken very poorly. Xenohomesis ultimately suggests that any future where the food we eat is more nutritious is a future in which agriculture as we know it is history.