Picked fruits and vegetables continue to respond to light as if they were still growing, scientists have shown.
The discovery has implications for grocery storage and its effect on the health benefits of plant foods.
Lead researcher Professor Janet Braam, from Rice University in Texas, US, said: “Vegetables and fruits, even after harvest, can respond to light signals and consequently change their biology in ways that may affect health value and insect resistance.
“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.”
Plants respond to changing light conditions by altering levels of chemicals that protect them against insects.
Some of these phytochemicals, evolved to make plants distasteful to herbivores, are believed to have anti-cancer properties.
Prof Braam’s team found that even after being harvested, vegetables and fruits remained sensitive to light and kept their biological clocks ticking.
The researchers, whose findings are published in the journal Current Biology, first made the discovery in cabbages.
They then went on to show similar responses in lettuce, spinach, courgettes, sweet potatoes, carrots and blueberries.
Picked items subjected to light and dark at the right times suffered less damage when exposed to caterpillars of a plant-eating moth.
“It may be of interest to harvest crops and freeze or otherwise preserve them at specific times of day, when nutrients and valuable phytochemicals are at their peak,” Prof Braam said.