Response to Crowding and Vegetation Shade in Impatiens capensis: Genetic Variation and Fitness Consequences

小行星9708114施密特 许多植物物种对拥挤和植被遮荫表现出特有的形态反应，如茎伸长和分枝减少。 这种“避荫反应”是由绿色植物透射或反射的光中红色与远红色波长（R：FR）的比率降低引起的;这种R：FR信号被称为光敏色素的光传感分子感知。 据推测，光敏色素介导的阴影， 回避反应通过使植物能够预期和避免在密集林分中对光的竞争而对植物有益。该项目最近的结果有力地支持了这一假设。 在田间试验中，茎伸长增加了繁殖的常见的一年生凤仙花在密集的看台上，但植物诱导显示避荫反应在低密度遭受健身相对nonelongated植物，显然是由于不可测量的生理成本。拟议的研究的目标是研究避荫反应的遗传基础和潜在的机制，在现场选择的反应，并测试生理，生态和遗传成本的反应。 复制的近交系不同的大小的形态反应R：FR将种植到一个自然群体在操纵的密度和组的组成，以研究水平的选择作用于避荫性状。 伸长的和非伸长的幼苗将在不同水平的水和养分下生长，以确定生长条件。 这些避荫特性可能是昂贵的。 本研究将整合遗传学、生理学和种群生物学方法，研究光敏色素介导的植物避荫反应。 它将提供重要的见解，这些反应在自然种群中的作用。 这些结果也将为植物分子生物学家和发育生物学家目前关于植物对光反应的潜在遗传基础的研究提供生态和进化背景。 由于大多数作物生长在密集的立场，这项研究也将提供深入了解可能的选择策略，以提高农业产量。

9708114 Schmitt Many plant species exhibit characteristic morphological responses to crowding and vegetation shade, such as stem elongation and reduced branching. This "shade avoidance response" is cued by a reduction in the ratio of red to far-red wavelengths (R:FR) in light transmitted or reflected from green vegetation; this R:FR signal is perceived by light-sensing molecules called phytochromes. It has been hypothesized that phytochrome-mediated shade avoidance responses are beneficial to plants by enabling them to anticipate and avoid competition for light in dense stands. Recent results from this project strongly support this hypothesis. In a field experiment, stem elongation increased the reproduction of the common annual Impatiens capensis in dense stands, but plants induced to display the shade avoidance response at low density suffered reduced fitness relative to nonelongated plants, apparently due to an unmeasured physiological cost. The goals of the proposed research are to examine the genetic basis of the shade avoidance response and potential mechanisms for selection on the response in the field, and to test for physiological, ecological, and genetic costs of the response. Replicated inbred lines differing in the magnitude of morphological response to R:FR will be planted into a natural population at manipulated densities and group compositions to study the level at which selection acts on shade avoidance traits. Elongated and nonelongated seedlings will be grown under different levels of water and nutrients, to determine the conditions under which shade avoidance traits may be costly. This research will integrate genetic, physiological, and population biology approaches to the study of phytochrome-mediated shade avoidance responses in plants. It will provide important insights into the role of these responses in natural populations. The results will also provide an ecological and evolutionary context for current research by plant molecular biolog ists and developmental biologists on the underlying genetic basis for plant responses to light. Since most crops are grown in dense stands, this study will also provide insight into possible selection strategies for improvement of agricultural yields.