The physiology of shade avoidance

传统上，作物和杂草之间的竞争被认为是对光、水和养分等资源的争夺。 人们对杂草造成作物产量损失的生理机制知之甚少。 通过红远红（R：FR）比早期检测相邻植物可能是影响植物竞争的一个重要机制。 作物可以检测到由相邻杂草的存在引起的R：FR比率的变化，因此最初会长得更高，分枝较少，根发育较少。 这种避荫反应可能会延迟物候发育，并以生殖健康为代价。 以前没有进行过研究，将R：FR比率的早期检测作为解释作物和杂草竞争结果的机制。 在本研究中，我打算探讨玉米和大豆的避荫反应所涉及的生理和分子机制的杂草的存在引起的。初步研究已经确定了广泛的玉米和大豆种质表型反应的R：FR比率反映从叶表面的杂草。 我计划在作物变异中使用这一点来探索以下假设：目标1：确定玉米杂交种和大豆品种对R：FR的反应是否不同，在其发育过程中是否受到表型限制，并在生物量积累方面表现不佳。 目标二：以确定玉米杂交种和大豆品种是否对R：FR反应不同，经历相似的避荫成本，如通过对随后的非生物胁迫的表型可塑性损失或表示为产量损失来测量的。 目标三：发现在对R：FR比率反应不同的玉米杂交种和大豆品种中，与杂草诱导的避荫相关的关键代谢和信号通路是否存在改变。 这项研究产生的新知识将被植物育种家用来开发更耐胁迫的玉米杂交种和大豆品种。

Competition between crop and weed has been regarded traditionally as a struggle for resources such as light, water and nutrients. The physiological mechanism by which weeds cause yield losses in crops is understood poorly. Early detection of neighbouring plants through the red-to-far red (R:FR ) ratio may be an important mechanism affecting plant to plant competition. Crop plants can detect changes in the R:FR ratio caused by the presence of neighbouring weeds and as a result will grow initially taller, with less branching and less root development. This shade avoidance response may delay phenological development and come at a cost to reproductive fitness. No study has been conducted previously to associate the early detection of the R:FR ratio as a mechanism to explain the outcome of crop and weed competition. In this study, I propose to explore the physiological and molecular mechanisms involved in the shade avoidance response of corn and soybean caused by the presence of weeds. Preliminary research has identified a wide range in corn and soybean germplasm phenotypic response to R:FR ratio reflected from the leaf surface of weeds. I plan to use this within crop variation to explore the following hypotheses: Objective 1: to determine if corn hybrids and soybean cultivars differing in response to R:FR are constrained phenotypically during their development and perform suboptimally in terms of biomass accumulation. Objective 2: to determine if corn hybrids and soybean cultivars differing in response to R:FR experience a similar cost of shade avoidance, as measured by a loss of phenotypic plasticity to subsequent abiotic stresses or expressed as yield loss. Objective 3: to discover if alterations exist in key metabolic and signalling pathways associated with weed-induced shade avoidance in corn hybrids and soybean cultivars that differ in their response to R:FR ratio. New knowledge generated from this study will be used by plant breeders to develop more stress tolerant corn hybrids and soybean cultivars.