The Secret Life Of Vegetables: Your Salad Might Have Jet Lag

 @rpalmerscience
on June 21 2013 1:56 PM
salad
Even after harvest, light-dark cycles can still affect produce in terms of insect resistance and nutrient storage. Flickr via Creative Commons/cookbookman17

Even vegetarians have had the experience of sinking their teeth into a still-living thing -- though the produce you buy at the grocery store doesn’t have a brain or consciousness, it is still, in some sense, alive.

"Vegetables and fruits don't die the moment they are harvested," Rice biologist Janet Braam said in a statement Thursday. "Even after harvest, [they] can respond to light signals and consequently change their biology in ways that may affect health value and insect resistance."

Even in the grocery store, parts of the plant are still alive and functioning independently. Now, in a new paper appearing in the journal Current Biology, Braam and her colleagues from Rice and the University of California, Davis found that the vegetables and fruits you buy at the grocery store may benefit from being kept on a proper schedule.

"They respond to their environment for days, and we found we could use light to coax them to make more cancer-fighting antioxidants at certain times of day," Braam said.

The researchers had already shown that the model organism Arabidopsis thaliana, or wild thale cress, uses its sense of daylight to build up stores of defensive, anti-insect chemicals during the night, to prepare for bug onslaughts the next day. In the current paper, they experimented first with a close relative of thale cress, the humble cabbage. In the tests, the cabbage was pitted against its natural enemy, the cabbage looper – a small moth larva.

Half of the store-bought cabbage was stored under a controlled 24-hour cycle, with 12 hours of light and 12 hours of darkness. The cabbage loopers were kept on the same schedule. But the rest of the cabbage was placed on an opposite 24-hour cycle from the larvae – their “night” was the insects’ “day,” and vice-versa.

As expected, the unsynchronized cabbages proved much less resistant to the attacks from the cabbage loopers. The out-of-sync vegetables were, in a sense, “jet-lagged,” struggling to adapt to conditions that were running on a different time schedule.

When the researchers repeated the experiment with a host of other produce – blueberries, zucchini, spinach, among others – the same results arose. The fruits and vegetables whose light-dark cycles matched up with the bugs’ suffered significantly less damage. The effect showed up even in root vegetables like sweet potatoes and carrots.

“These results suggest that new postharvest storage practices for vegetables and fruits that include clock entrainment may profoundly impact diverse metabolite accumulation in many crops and thereby [affect] overall edible crop health value,” the authors wrote.

In plainer English, that means that treating our produce like a still-responsive thing and not a crunchy corpse could pay off on the plate. For instance, freezing or preserving fruits and vegetables at certain times of day could capture nutrients at their peak.

"Perhaps we should be storing our vegetables and fruits under light-dark cycles and timing when to cook and eat them to enhance their health value," Braam said.

SOURCE: Goodspeed et al. “Postharvest Circadian Entrainment Enhances Crop Pest Resistance and Phytochemical Cycling.” Current Biology 23, 8 July 2013.

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