Earth and Sky科普英語：Sunscreened Plants 遮光植物

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A NASA researcher is finding that alfalfa plants grow more poorly when exposed to UVB -- ultraviolet B radiation from the sun. Learn more about sunscreened plants -- today on Earth and Sky.

JB: This is Earth and Sky. Earth's ozone layer protects us from the sun's ultraviolet -- or UV, radiation. Ozone depletion has been blamed for an increase in skin cancers in human beings.

DB: And this radiation seems to have a negative effect on plants as well. Jay Skiles is a scientist at NASA's Ames Research Center in Mountain View, California.

Jay Skiles: ... and what we found is that the ozone depletion is not only in the southern hemisphere over the poles but we're actually getting increased ultraviolet light here, at about 38 degrees north latittude ...

JB: For the past six years, Skiles has been growing alfalfa in three ways -- in the open air -- and under two kinds of filters. One set of filters block harmful UVB, or ultraviolet B radiation. The other filters let pass all light from the sun. Filtering UVB more or less simulates conditions that existed under an intact ozone shield -- before ozone depletion.

Jay Skiles: And we're finding that plants that are grown without UV ... are actually doing better -- they're producing more above-ground biomass. Their morphology is better, they're more vigorous, more chlorophyll . . . and they actually survive longer.

DB: . . . more evidence that Earth's ozone layer must remain protected and intact. For more, come to today's show at earthsky.org. Special thanks today to NASA's Earth Science Enterprise. We're Block and Byrd for Earth and Sky.