Mechanisms of nitrate accumulation under resource-independent plant competition.

与资源无关的杂草竞争是一个重要的胁迫因素，它不仅影响作物幼苗的早期发育，而且即使在除草后也会产生长期影响，导致产量潜力显着下降。这些效应是由于从邻近杂草反射的远红光的核心重要性，它使光敏素光感受器失活。最近，我们发现杂草存在时间的延长与光合作用效率、二氧化碳同化和产量潜力的下降之间存在直接的联系，如果杂草存在到繁殖阶段，这种联系就无法恢复。然而，与其他任何生理过程相比，光合作用和呼吸作用更多地与氮同化结合在一起。因此，了解相邻杂草对主要作物硝酸盐同化的影响，对于杂草管理策略的制定和杂草胁迫下氮肥的应用具有重要意义。我们的实验室已经证明，模式植物拟南芥和玉米中硝酸盐的积累是对邻近杂草和模拟远红光的早期反应。这种反应似乎是由于硝酸盐同化途径中的一种主要酶的活性降低所致。尽管建立了这种联系，但我们不能排除硝酸盐转运体参与的可能性，在这项提案中，将通过进行高通量测序来研究这种可能性。此外，拟南芥对邻近杂草的硝酸盐积累似乎不依赖于光敏色素B光感受器的失活。我们推测，在资源独立竞争下，玉米体内硝酸盐的积累可能会导致硝酸盐限制或硝酸盐利用不足，如果在除草后保持一段时间，会影响玉米的早期发育和随后的表现。因此，我们建议的两个主要目标是(1)利用光敏色素B感光受体缺失的玉米突变体，阐明在受控环境下硝酸盐积累响应于资源无关竞争的分子机制；(2)将我们的研究扩展到田间条件，并确定杂草存在时间的增加和硝酸盐积累与玉米除草后表现的关系。作为这项研究的结果产生的新信息适合于培训高素质的光生物学和杂草研究人员，并为研究独立于光敏色素失活的新的远红光作用开辟了途径。此外，新的信息可以被转移给田间生物学家和农民，以便在杂草控制的关键时期之前制定杂草控制计划，并不仅减轻与资源无关的杂草竞争对主要农作物的影响，而且还减轻过量硝酸盐对环境的影响。

Resource-independent weed competition is an important stress factor that not only affects early development of crop seedlings but also exerts long-lasting effects even after weed removal resulting in significant reductions in yield potential. These effects result from the central importance of far-red light reflected from neighbouring weeds that inactivate phytochrome photoreceptors. Recently, we found a direct link between increasing duration of weed presence and decreases in photosynthetic efficiency, CO2 assimilation, and yield potential, which could not be recovered if weed presence extended to reproductive stages. Photosynthesis and respiration, however, more than any other physiological processes are integrated with nitrogen assimilation. Therefore, the knowledge of the effects of neighbouring weeds on nitrate assimilation in major crop plants is pivotal to making progress in the development of weed management strategies and nitrogen fertilizer application under weed stress. Our laboratory has shown that nitrate accumulation in the model plant Arabidopsis and maize is an early response to neighbouring weeds and simulated far-red light. This response appears to be due to reduced activity of a major enzyme in the nitrate assimilation pathway. Despite establishing this link, we cannot exclude the possibility of the involvement of nitrate transporters and in this proposal this possibility will be investigated by conducting high throughput sequencing. Further, nitrate accumulation in Arabidopsis in response to neighbouring weeds appears to be independent of phytochrome B photoreceptor inactivation. We hypothesize that nitrate accumulation in maize under resource-independent competition may cause nitrate limitation or inadequate nitrate utilization, which if maintained for some time after weed removal, affects early development and subsequent performance of maize. Therefore, two major objectives of our proposal are (1) to elucidate the molecular mechanisms of nitrate accumulation in response to resource-independent competition under controlled environment using maize mutants deficient in phytochrome B photoreceptor and (2) extend our research to field conditions and determine the relationship between the increasing duration of weed presence and nitrate accumulation and subsequent performance of maize following weed removal. The new information generated as the outcome of this research are appropriate for training of highly qualified personnel in photobiology and weed research and open up avenues for research on new far-red light actions that are independent of phytochrome inactivation. In addition, the new information can be transferred to field biologist and farmers to devise weed control plans prior to critical periods for weed control and mitigate not only the impact of resource-independent weed competition on major crop plants but also the impact of excess nitrate on the environment.