Plants fight for a place in the sun

April 4th, 2008 - 3:16 pm ICT by admin  


Washington, April 4 (IANS) Plants can sense the difference between the shade of an inanimate object and that of another plant; it comes in handy while reaching out for sunlight. They accordingly cease their efforts when a building comes in the way, knowing that it would be in vain. But when it is a question of competing with another of their species, they go into overdrive.

For example, spindly plants requiring sunlight desperately try to break through the overhead canopy formed by larger plants, in what is known as ’shade avoidance syndrome’ or SAS.

To step out of their neighbours’ shade, plants switch on a natural chemical factory for synthesising auxin, a hormone that enables them to grow and stretch towards the sun, according to a study.

Findings of the study have been published in the latest issue of the journal Cell.

“Plants compete with each other for light and SAS has a big ecological and economic impact, especially in the high density plantings typical of modern agriculture,” said Joanne Chory of Howard Hughes Medical Institute, who led the study.

To secure their place in the sun, plants direct their growth resources toward stem elongation and away from bulking up harvestable portions such as leaves and seeds.

“If all else fails, the plants put out what I like to call a premature ‘desperation flower’ to produce at least a couple of seeds that might find better growing conditions during the next season,” explains Chory.

In an earlier study, Chory had confirmed the existence of a separate molecular pathway that plants use to adjust their growth and flowering time to shade. But the molecular events linking the detection of changes in light quality to changes in growth patterns were still poorly understood.

To identify genes that are involved in SAS, co-author of the study Yi Tao identified a handful of genes that play a role in the shade response, one of which encoded an enzyme similar to alliinase, that produces the characteristic flavour of onion, garlic and other members of the Alliaceae plant family.

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