Mechanisms of nitrate accumulation under resource-independent plant competition.

非资源依赖型杂草竞争是一个重要的胁迫因子，不仅影响作物幼苗的早期发育，而且在除草后仍会产生长期影响，导致产量潜力显著降低。这些效应是由邻近杂草反射的远红光的重要性引起的，这些远红光使光敏色素光受体受损。最近，我们发现了杂草存在的持续时间增加和光合效率，CO2同化和产量潜力，这不能恢复，如果杂草的存在延长到生殖阶段的减少之间的直接联系。然而，光合作用和呼吸作用比任何其他生理过程都更与氮同化相结合。因此，相邻杂草对主要作物硝酸盐同化的影响的知识是关键的杂草管理策略和杂草胁迫下的氮肥施用的发展取得进展。我们的实验室已经表明，模式植物拟南芥和玉米中的硝酸盐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主要酶的活性降低。尽管建立了这种联系，但我们不能排除硝酸盐转运蛋白参与的可能性，在本提案中，将通过进行高通量测序来研究这种可能性。此外，在拟南芥中的硝酸盐积累在响应邻近杂草似乎是独立的光敏色素B感光体失活。我们假设，在资源独立竞争下，玉米中的硝酸盐积累可能会导致硝酸盐限制或硝酸盐利用不足，如果在除草后维持一段时间，会影响玉米的早期发育和随后的表现。因此，我们的建议的两个主要目标是（1）阐明硝酸盐积累的分子机制，在受控环境下，利用玉米光敏色素B感光体缺陷突变体的资源无关的竞争和（2）扩展我们的研究，田间条件下，并确定杂草存在的持续时间增加和硝酸盐积累和随后的玉米杂草清除后的性能之间的关系。作为本研究的结果产生的新信息是适当的高素质的人员在光生物学和杂草研究的培训，并开辟了新的远红光行动的研究途径，是独立的光敏色素灭活。此外，新的信息可以传递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，不仅减轻了与资源无关的杂草竞争对主要作物的影响，而且减轻了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.