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Why hot plants resort to fetal position.

Why hot plants resort to fetal position

Leave a plant too long in the blazing sun and you'll notice a typical botanical reaction: The leaves curl up. In grasses and other plants, leaf rolling is a common response to stress, but botanists have remained unsure how much protection it actually provides.

At the University of Illinois in Urbana, Scott A. Heckathorn and Evan H. DeLucia have now measured the effects of leaf rolling on leaf temperature, gas exchange and water-vapor loss in the wetlands grass Spartinia pectinata. Leaf rolling's major benefit, they conclude, is that it reduces the surface area exposed to sunlight, lowering leaf temperature by more than 5[degrees]C.

Other researchers experimenting with the desert resurrection plant, Selaginella lepidophylla, report that the curling response significantly reduces damage to the plant's photosynthetic enzyme system. Jefferson G. Lebkuecher and William G. Eickmeier of Vanderbilt University in Nashville held plants' leaves flat with a device resembling a tennis racket, then exposed the plants to indoor lighting equivalent to full sunshine. Compared with unrestrained plants under the same lights, the test plants showed marked destruction of chlorophyll and decreased activity within the electron transport system that converts sunlight into energy for the plant. "Curling reduces high-irradiance damage that would otherwise occur during dessication," they conclude.
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Title Annotation:why leaves curl when plants are stressed
Author:Weiss, Rick
Publication:Science News
Date:Aug 11, 1990
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