(Inside Science TV) -- Fruits and vegetables may seem to be merely passive pieces of food sitting on your kitchen counter, but new research shows that there's more to them than meets the eye.
Janet Braam, a biologist at Rice University in Houston, Texas, found that produce can "tell time" in a way.
"All organisms have a biological clock that enables them to keep track of 24 hours," said Braam.
In a first-of-its-kind study, scientists showed that plants use their "biological clock" to prepare for insect attacks. At the time of day when caterpillars were most likely to strike, the plants released chemicals to ward off the pests.
Braam said, "If they do attack, the plants are already ready."
Plant geneticists also observed the biological clocks of spinach, zucchini, sweet potatoes, carrots, squash, blueberries and cabbage by exposing the already picked veggies and fruits to normal light and dark cycles that they would be exposed to if they were still growing in the ground.
"When you pick a cabbage from the field, the cells, the tissues of a cabbage, don't immediately die," said Braam.
Braam found that under the light and dark cycles simulated in the lab, the plants released more phytochemicals -- chemical compounds that plants use for self-defense, among other functions -- during certain times of the day.
"We know that these phytochemicals are among the most potent natural anti-cancer chemicals known," said Braam.
The findings suggest that eating vegetables at a specific time, or exposing them to light and dark might make a difference in how many nutrients are present.
Braam said, "There may be an advantage to keeping post-harvest fruits and vegetables under light-dark cycles to keep their clocks running. It would make them more resistant to pests, and it may also influence their levels of phytonutrients and phytochemicals."
Braam says more research is needed to determine exactly what times of day are best to consume the fruits and vegetables she studied. She and her team have already begun follow-up research -- funded by the Bill and Melinda Gates Foundation -- to test whether light or other stimuli may be used to enhance the pest resistance qualities of food crops in developing countries.