Inhibition of Carbon Assimilation by excess Radiation: Understanding maize weak Spot (ICARUS)

光对植物来说既是一种资源，也是一种强有力的胁迫因子。光合作用利用来自太阳的能量将二氧化碳固定为糖和生命的蛋白质组成部分，然而，树叶通常接收到的光比光合作用所能处理的光多5倍。为了避免过多的光线伤害，植物进化出了一系列保护自己的方法。然而，由于其他树叶的遮蔽，云层的经过和阳光方向的改变，光线水平是高度动态的。因此，植物需要能够非常迅速地进行调整。过度保护会导致光合作用和生长的丧失，而保护不足则会使叶子容易受到损害。理论预测表明，保护水平的更快变化可能有利于增长和生产率。事实上，我最近证明，当保护水平的变化加快时，这极大地提高了模式作物在田间条件下的光合效率和生产力。理论分析表明，提高对强光的保护和加快恢复速度可能会使玉米受益更多，但我们缺乏对需要改进的具体目标的了解。玉米是全球最主要的作物，全球产量为10.9亿吨。在温带地区，玉米越来越多地被种植，在英国，玉米是动物饲料和厌氧消化器中提供生物能源的热门作物，2017年的总产量为19.5万公顷。有趣的是，玉米似乎很难抵御过多的光线。光害严重限制了玉米的产量，特别是在季初明亮凉爽的日子里，此时植物通常会看起来发黄和发育不良，但在非常炎热或干燥的条件下也会如此。提高玉米的保护水平和调整率预计可使生产率提高30%，并具有巨大的经济价值，特别是对英国等温带气候地区的农业。玉米对光害敏感和适应缓慢的原因尚不清楚。玉米光合作用利用生化泵将二氧化碳（光合作用的基质）浓缩在专门的束鞘细胞中。这种所谓的C4途径提高了光合作用的效率，但也使光合作用的局限性比传统光合作用的植物更难研究。在光系统层面，我们不知道哪一种光合复合体最脆弱，在细胞层面，我们不知道两种光合细胞中哪一种最容易被抑制。因此，该项目的目的是利用一种新的非侵入性测量技术组合来确定玉米光合作用中导致其易受光抑制的弱点。拟议的研究方案将集中于：1)特定的光合电子传递蛋白是主要的潜在瓶颈玉米光抑制2)光合细胞类型是最受光抑制2)光照条件最有可能产生光抑制3)玉米防止太多的能力是否光insufficientThe结果将提供详细了解玉米光合作用中的薄弱环节应对过多的光线和将被合成到一个玉米光合作用和作物改良的优先顺序。

Light is both a resource and a potent stress factor for plants. Photosynthesis harnesses energy from the sun to fix carbon dioxide into sugars and the protein building blocks of life, However, leaves routinely receive up to 5 times more light than can be processed via photosynthesis. To avoid damage by too much light, plants have evolved a range of ways to protect themselves. However, light levels are highly dynamic due to shading by other leaves, clouds passing over and changing direction of sunlight. As a result, plants need to be able to adjust very rapidly. Over-protection leads to a loss of photosynthesis and growth, whereas under-protection renders the leaves susceptible to getting damaged. Theoretical predictions indicated that more rapid changes in protection levels might benefit growth and productivity. Indeed, I recently demonstrated that when changes in protection levels are accelerated, this dramatically improves photosynthetic efficiency and productivity under field conditions in a model crop. Theoretical analysis suggests that maize could benefit even more from improving protection against high light and accelerate recovery rates, but we lack understanding to pin-point the specific targets that need improving. Maize is the most dominant crop globally, with a world-wide production volume of 1.09 billion metric tons. Maize is increasingly being grown in temperate regions and in the UK is a popular crop for animal fodder and for use in anaerobic digesters to provide bioenergy, with a total production area of 195.000 ha in 2017. Intriguingly, maize seems to have a difficult time protecting itself against too much light. Light-inflicted damage strongly limits productivity of maize, especially during bright cool days in early season, when plants can often look yellow and stunted, but also under very hot or dry conditions. Improving the protection level and adjustment rate in maize is predicted to improve productivity by up to 30%, and would hold great economic value, especially for agriculture in temperate climates such as the UK. The reasons for the sensitivity to damage by light and slow adjustment in maize are unclear. Maize photosynthesis utilizes a biochemical pump to concentrate carbon dioxide, the substrate for photosynthesis, in specialized bundle sheath cells. This so-called C4 pathway increases the efficiency of photosynthesis, but also makes photosynthetic limitations more difficult to study than in plants with conventional photosynthesis. At the photosystem level, we don't know which photosynthetic complex is most vulnerable, and at the cellular level, we don't know which of the two photosynthetic cell types is most easily inhibited. The aim of this project is therefore to identify the weaknesses in maize photosynthesis leading to its vulnerability to photoinhibition, using a novel combination of non-invasive measurement techniques. The proposed research programme will focus on: 1) which specific photosynthetic electron transport proteins are the main bottlenecks underlying maize photoinhibition 2) which photosynthetic cell type is most impacted by photoinhibition 2) which light conditions are most likely to give rise to photoinhibition 3) whether the capacity of maize to protect against too much light is insufficientThe results will provide detailed understanding of the weak links in maize photosynthesis in response to too much light and will be synthesized into a priority list of improvements in maize photosynthesis and crop improvement.