Tag Archives: vegetables

Circadian Rhythm in Vegetables

The vegetables you eat may be better for you based on how and when they are exposed to light. Just as animals adhere to circadian rhythms, research shows that some plants may generate different levels of healthy nutritional metabolites based the light cycle as well.

From ars technica:

When you buy vegetables at the grocery store, they are usually still alive. When you lock your cabbage and carrots in the dark recess of the refrigerator vegetable drawer, they are still alive. They continue to metabolize while we wait to cook them.

Why should we care? Well, plants that are alive adjust to the conditions surrounding them. Researchers at Rice University have shown that some plants have circadian rhythms, adjusting their production of certain chemicals based on their exposure to light and dark cycles. Understanding and exploiting these rhythms could help us maximize the nutritional value of the vegetables we eat.

According to Janet Braam, a professor of biochemistry at Rice, her team’s initial research looked at how Arabidopsis, a common plant model for scientists, responded to light cycles. “It adjusts its defense hormones before the time of day when insects attack,” Braam said. Arabidopsis is in the same plant family as the cruciforous vegetables—broccoli, cabbage, and kale—so Braam and her colleagues decided to look for a similar light response in our foods.

They bought some grocery store cabbage and brought it back to the lab so they could subject the cabbage to the same tests they gave their model plant, which involved offering up living, leafy vegetables to a horde of hungry caterpillars. First, half the cabbages were exposed to a normal light and dark cycle, the same schedule as the caterpillars, while the other half were exposed to the opposite light cycle.

The caterpillars tend to feed in the late afternoon, according to Braam, so the light signals the plants to increase production of glucosinolates, a chemical that the insects don’t like. The study found that cabbages that adjusted to the normal light cycle had far less insect damage than the jet-lagged cabbages.

While it’s cool to know that cabbages are still metabolizing away and responding to light stimulus days after harvest, Braam said that this process could affect the nutritional value of the cabbage. “We eat cabbage, in part, because these glucosinolates are anti-cancer compounds,” Braam said.

Glucosinolates are only found in the cruciform vegetable family, but the Rice team wanted to see if other vegetables demonstrated similar circadian rhythms. They tested spinach, lettuce, zucchini, blueberries, carrots, and sweet potatoes. “Luckily, our caterpillar isn’t picky,” Braam said. “It’ll eat just about anything.”

Just like with the cabbage, the caterpillars ate far less of the vegetables trained on the normal light schedule. Even the fruits and roots increased production of some kind of anti-insect compound in response to light stimulus.

Metabolites affected by circadian rhythms could include vitamins and antioxidants. The Rice team is planning follow-up research to begin exploring how the cycling phenomenon affects known nutrients and if the magnitude of the shifts are large enough to have an impact on our diets. “We’ve uncovered some very basic stimuli, but we haven’t yet figured out how to amplify that for human nutrition,” Braam said.

Read the entire article here.

MondayMap: The Double Edge of Climate Change

So the changing global climate will imperil our coasts, flood low-lying lands, fuel more droughts, increase weather extremes, and generally make the planet more toasty. But, a new study — for the first time — links increasing levels of CO2 to an increase in global vegetation. Perhaps this portends our eventual fate — ceding the Earth back to the plants — unless humans make some drastic behavioral changes.

From the New Scientist:

The planet is getting lusher, and we are responsible. Carbon dioxide generated by human activity is stimulating photosynthesis and causing a beneficial greening of the Earth’s surface.

For the first time, researchers claim to have shown that the increase in plant cover is due to this “CO2 fertilisation effect” rather than other causes. However, it remains unclear whether the effect can counter any negative consequences of global warming, such as the spread of deserts.

Recent satellite studies have shown that the planet is harbouring more vegetation overall, but pinning down the cause has been difficult. Factors such as higher temperatures, extra rainfall, and an increase in atmospheric CO2 – which helps plants use water more efficiently – could all be boosting vegetation.

To home in on the effect of CO2, Randall Donohue of Australia’s national research institute, the CSIRO in Canberra, monitored vegetation at the edges of deserts in Australia, southern Africa, the US Southwest, North Africa, the Middle East and central Asia. These are regions where there is ample warmth and sunlight, but only just enough rainfall for vegetation to grow, so any change in plant cover must be the result of a change in rainfall patterns or CO2 levels, or both.

If CO2 levels were constant, then the amount of vegetation per unit of rainfall ought to be constant, too. However, the team found that this figure rose by 11 per cent in these areas between 1982 and 2010, mirroring the rise in CO2 (Geophysical Research Letters, doi.org/mqx). Donohue says this lends “strong support” to the idea that CO2 fertilisation drove the greening.

Climate change studies have predicted that many dry areas will get drier and that some deserts will expand. Donohue’s findings make this less certain.

However, the greening effect may not apply to the world’s driest regions. Beth Newingham of the University of Idaho, Moscow, recently published the result of a 10-year experiment involving a greenhouse set up in the Mojave desert of Nevada. She found “no sustained increase in biomass” when extra CO2 was pumped into the greenhouse. “You cannot assume that all these deserts respond the same,” she says. “Enough water needs to be present for the plants to respond at all.”

The extra plant growth could have knock-on effects on climate, Donohue says, by increasing rainfall, affecting river flows and changing the likelihood of wildfires. It will also absorb more CO2 from the air, potentially damping down global warming but also limiting the CO2 fertilisation effect itself.

Read the entire article here.

Image: Global vegetation mapped: Normalized Difference Vegetation Index (NDVI) from Nov. 1, 2007, to Dec. 1, 2007, during autumn in the Northern Hemisphere. This monthly average is based on observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite. The greenness values depict vegetation density; higher values (dark greens) show land areas with plenty of leafy green vegetation, such as the Amazon Rainforest. Lower values (beige to white) show areas with little or no vegetation, including sand seas and Arctic areas. Areas with moderate amounts of vegetation are pale green. Land areas with no data appear gray, and water appears blue. Courtesy of NASA.

When to Eat Your Fruit and Veg

It’s time to jettison the $1.99 hyper-burger and super-sized fires and try some real fruits and vegetables. You know — the kind of product that comes directly from the soil. But, when is the best time to suck on a juicy peach or chomp some crispy radicchio?

A great chart, below, summarizes which fruits and vegetables are generally in season for the Northern Hemisphere.

[div class=attrib]Infographic courtesy of Visual News, designed by Column Five.[end-div]