Friday, April 04, 2014

Natural fluorescence by chlorophyll as seen by satellite

Wired Magazine shows a cool satellite image showing chlorophyll-dependent fluorescence over the United States, based on an article which appeared in the March 25 issue of PNAS. Basically, light energy hitting the chloroplast can be successfully harvested to drive energy production; can be lost as heat; or can be reemitted as fluorescence. Chlorophyll dependent fluorescence in healthy plants
Chlorophyll-dependent fluorescence over North America.
Most of the signal is attributed to cornfields. 
accounts for 1-2% of the energy absorbed, and its intensity is thus is an indirect measure of photosynthesis. Sunlight-induced chlorophyll fluorescence is most prominent in the red and infrared portion of the spectrum.
The strong signals shown in the figure can be attributed to massive photosynthesis in North American cornfields, which exceeds that of the Amazon basin during the North American growing season.
Fluorescence by chlorophyll increases when plants are under stressed, and can be used on a laboratory scale to monitor response to drought or pathogens. Back at the satellite level, this phenomenon is also used to phytoplankton blooms in oceans.