【英语时差8,16】遮荫避综合症

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Don: What's wrong with these plants, Ya?l? They've grown all long and spindly, and just  have a few small leaves!

Ya?l: Hmm. It could be SAS, Don.

D: SAS?

Y: Plants that grow tall and spindly trying to reach the sunlight are usually "suffering"   from Shade Avoidance Syndrome¹, or SAS. Now scientists have identified the  molecular process that controls the onset² of SAS. When a plant that requires bright  sunlight detects shade from another plant, it will switch into SAS mode and try to  quickly grow taller, up into sunlight again.

D: That's a clever strategy.

Y: Yep. To figure out how SAS worked, researchers at the Salk Institute in California   searched through a large collection of mutated plant seedlings³ for individual plants  that didn't turn on shade responses even when in their neighbor's shadow. From  these plants, the researchers were able to identify genes⁴ involved in the shade      response. They found that one of the genes produces an enzyme⁵ that speeds up  production of a plant growth hormone⁶ called Auxin when the plant is shaded.

D: Growth hormone, eh? So that's why the plants get taller and taller when light-   depived?

Y: Right. The plants have receptors in their cells that are sensitive to light. When these   photo-receptors detect the presence of neighboring plants, it triggers the Auxin-      producing pathway, which triggers the stem to start growing rapidly.

D: I suppose growing taller diverts the plant's resources away from reproductive efforts  like making flowers, fruits and seeds.

Y: That's one reason that understanding SAS has such exciting potential. Crop breeders  and farmers could eventually use these new discoveries to maximize the yield of   grains or fruits in their fields.   

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