A place in the sun

Plants can tell the difference between the shade of an inanimate object and the shade of another plant. When a plant detects competition from neighboring plants, it initiates a set... Click here for more information.

LA JOLLA, CA — Those spindly plants that desperately try to reach for a break in the canopy formed by larger plants all suffer from the same affliction: Shade avoidance syndrome or SAS. Now, the molecular details of SAS have been brought to light by researchers at the Salk Institute for Biological Studies.

To step out of their neighbors’ shade, plants switch on a natural chemical factory for the synthesis of the plant growth hormone auxin that lets a plant grow and ultimately stretch toward the sun, the Salk researchers report in an article published in the April 4, 2008 issue of the journal Cell. Understanding this response at a molecular level will allow scientists to naturally manipulate this response to increase yield in crops ranging from rice to wheat.

“Plants compete with each other for light, and shade avoidance syndrome has a big ecological and economic impact, especially in the high density plantings typical of modern agriculture,” says Howard Hughes Medical Institute investigator Joanne Chory, Ph.D., a professor in the Plant Biology, who led the study. “Suppressing the shade avoidance reaction in crops may allow us to increase biomass and seed yield.”

Plants can sense and respond to the presence of other plants in their neighborhood by the relative increase in incoming far-red light resulting from absorption of red light by canopy leaves and reflection of far-red light from neighboring plants.