RUI: Adaptive Significance of Circadian Rhythms in StomatalFunction and Photosynthesis

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Practically all organisms-from human beings to bean plants- exhibit "circadian rhythms," rhythmic fluctuations in all kinds functions that have a period of about twenty-four hours. Plants have such rhythms, too. Bean plants, for example, hold their leaves horizontally during the day (in a position to catch the sun), but hold them vertically along the stem at night, and they will continue this rhythmic movement even if plants are kept in constant light, with no clues as to what time of day it is. No one knows whether this rhythmic leaf movement does the plant any good, but that is partly because no one knows what benefit the plant might get from having its leaves folded along the stem, whether rhythmically or not. The investigators will examine the possible benefit to the plant of a rhythmic movement, but in a process whose function is much better understood than leaf movements. Leaves are connected to the air by small pores called stomata, and these pores can open and close. It is well known that the stomata open when the plants can photosynthesize (during the day, for example), and that they close when photosynthesis is unlikely to take place (at night, for example). In addition to responses like these to environmental changes, stomata also open and close according to an internal clock with a period of about twenty-four hours: they have circadian rhythms. Until now, no one has tried systematically to understand how circadian rhythms affect stomata. This question is important to basic science for two major reasons. First, understanding of stomatal responses cannot be really complete without an understanding of the rhythmic element. Second, several laboratories are concerned with understanding the basic working of the clock that drives circadian rhythms in organisms ranging from humans to single-celled plants, and any circadian research has some promise for shedding light on this extremely important and elusive basic question. There are also potential practical benefits, because research on stomata always has potential for agricultural applications. Stomata control the rate at which plants use water, and water use is an extremely important characteristic of any crop, particularly in an era of global change when breeding and selecting of plants that can survive a changed environment take on immense importance. Finally, the research will be done at an undergraduate institution and will involve undergraduate students extensively, providing a valuable opportunity to educate and inspire them for the career in science.