Can humans measure photosynthesis on a global scale?
Since plants consume CO2 during photosynthesis, one way is to measure the relative amount of atmospheric carbon dioxide (CO2) using satellites (click on photo at left for more info).
But plants also release CO2 as a product of respiration. This has confounded efforts to accurately measure photosynthesis at ecosystem levels.
The answer may come from measuring another gas consumed by plants, namely, carbonyl sulfide.
A recent report has shown that measuring relative levels of carbonyl sulfide may give scientists a way to more accurately gauge the Earth’s carbon-cycle on an ecosystem scale. A very important aspect of climate research, indeed.
How a gas emitted by hot plants may disrupt some plant’s insect defenses.
“It surprises most people to learn that plants emit much more hydrocarbon into the atmosphere than that coming from human activities, especially during extended warm weather…” from a recent review in the Annals of Botany
The hydrocarbon in this case is isoprene. Most scientific evidence supports the hypothesis that isoprene is synthesized by many plants because it helps photosynthesis recover from short high-temperature episodes.
Indeed, the summertime haze over places such as the Great Smokey Mountains (see right) may be due primarily to isoprene emissions from the trees. (photo credit)
However, isoprene may interfere with some plant defenses.
Recent research suggests that isoprene may interfere with other volatile compounds emitted by plants that attract beneficial insects, such as wasps that parasitize insect herbivores.
How a parasitic plant may “sniff out” its victims.
Speaking of parasites… dodder (genus Cuscuta) is a parasitic plant on other plants. But how does this plant find its host?
Apparently, dodder seedlings locate potential hosts by using volatile compounds emitted by plants. These compounds may serve as chemo-attractants. A dodder seedling can presumably sense these chemicals and adjust its development in order to grow toward its host.
Listen to report on NPR about this subject
View Quicktime movie of dodder in action
More recent news about dodder suggests that this parasitic plant may also tap into chemical signals traveling in the host’s vascular system. (more on this later)
Bottom line: Plants emit an array of volatile compounds that serve many functions – from thermotolerance to plant defense against herbivores – but that also betray a plant’s location.
