Rice biologist Janet Braam, the lead researcher of the current study published in Current Biology, said “Vegetables and fruits don’t die the moment they are harvested. 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.”
The researchers simulated day-night cycles of light and dark to control the internal clocks of vegetables and fruit like blueberries, carrots, squash, and cabbage.
This study is a follow-up to a previous one by the same researchers on how plants use their internal circadian clocks in order to ward off hungry insects. They found that Arabidopsis thaliana – a model organism used in plant studies – starts triggering production of insect fighting chemicals a short time before sunrise, this is when insects start to feed.
Arabidopsis thaliana has given an important view into genetics, cell division, and light sensing – which drive 24-hour behavioral cycles.
The investigators in the current study started their research by trying to entrain the clocks of cabbage in the same method they had with Arabidopsis.
Entrainment is similar to what happens when international travelers recover from “jet lag“. After flying to a far off destination, travelers frequently have difficulty sleeping until their internal circadian clock restarts itself to the day-night cycle in the new time zone.
By using controlled lighting in a closed off chamber, the authors found that they could entrain the circadian clocks of post harvest cabbage just as they had done with the Adabidopsis in the 2012 study. After they successfully controlled the cabbage, they examined spinach, lettuce, blueberries, sweet potatoes, zucchini, and carrots.
Study lead author Danielle Goodspeed said, “We were able to entrain each of them, even the root vegetables.”
The authors suggest that storing vegetables and fruits in dark trucks, refrigerators, and boxes may decrease their ability to stay with daily rhythms.
“We cannot yet say whether all-dark or all-light conditions shorten the shelf life of fruits and vegetables. What we have shown is that keeping the internal clock ticking is advantageous with respect to insect resistance and could also yield health benefits.”
The investigators were able to alter cabbage leaves to up their production of anti-insect metabolites at different times of the day. One metabolite known as glucoraphanin, or 4-MSO, is a previously known anti-cancer compound that has been examined before in broccoli and other vegetables.
Follow-up studies have already begun and are supported by the Bill and Melinda Gates Foundation. They will explore whether light and other stimuli, such as touch, could be used to improve pest resistance of food crops in developing nations.
Goodspeed said, “It’s exciting to think that we may be able to boost the health benefits of our produce simply by changing the way we store it.”
Written by Kelly Fitzgerald