Respiration is an essential link between assimilation of carbon and energy in photosynthesis and subsequent growth and yield of all crops. It provides usable energy and biochemical building blocks (carbon skeletons) required for growth and maintenance, releasing CO2 and heat as byproducts in the process. Field data indicate that from about 30 % to well over 50 % of photosynthetically assimilated carbon (net of photorespiration) is released as respiratory CO2 over a season, varying between crops, developmental stages, and environments. Unstressed crops have a relatively small CO2-based respiration/photosynthesis (R/P) ratio during early vegetative growth, but it can markedly increase with ontogeny, especially during reproductive growth in oilseed crops, and with stress. It is suggested that considerations of energy transformations, in addition to CO2 exchanges, provide meaningful insights into respiration-photosynthesis-yield relationships. Both rate and efficiency of respiration are important, with efficiency of ‘growth respiration’ relatively well understood, and perhaps near potential maximum values in crops. Conversely, a minimum crop ‘maintenance respiration’ requirement remains unclear. The contribution that unwitting selection for favorable respiration made to past yield gains is unknown but may have been significant in maize at least. The quantitative importance of respiration to crop carbon and metabolic energy budgets raises the questions, Is a fraction of present crop respiration inefficient or nonessential, is there genetic variation associated with that fraction that can be used in selection, and can directed enzyme evolution improve efficiency of respiration or curtail any unproductive components? To the extent that maintenance processes such as protein turnover and active transport to counteract leaks across membranes can be reduced without detriment, they are targets for modification to increase yield. Technologies now available to quantify crop respiration, at least of individual organs, can be put into action for high-throughput screening, and advances in bioengineering imply that modifications to respiration need not be limited by existing genetic variation in crops and their wild relatives. In short, yield gains via directed respiratory changes are possible, though prospects for success may require a moderate shift in research priorities from photosynthesis to respiration as an additional path to crop improvement.

中文翻译：

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光合作用后，然后是什么：呼吸作用对作物生长和产量的重要性


呼吸作用是光合作用中碳和能量的同化与所有作物随后的生长和产量之间的重要联系。它提供生长和维持所需的可用能量和生化构件（碳骨架），在此过程中释放二氧化碳和热量作为副产品。现场数据表明，在一个季节中，大约 30% 到超过 50% 的光合作用同化碳（扣除光呼吸作用）以呼吸 CO2 的形式释放，因作物、发育阶段和环境而异。在营养生长早期，未胁迫作物的基于 CO2 的呼吸/光合作用 （R/P） 比率相对较小，但随着个体发育，尤其是在油籽作物的生殖生长期间和胁迫期间，它可以显着增加。建议除了 CO2 交换之外，对能量转换的考虑为呼吸-光合作用-产量关系提供了有意义的见解。呼吸的速度和效率都很重要，“生长呼吸”的效率相对容易理解，并且可能接近作物的潜在最大值。相反，最低作物“维持呼吸”要求仍不清楚。无意中选择有利的呼吸对过去产量增加的贡献尚不清楚，但至少在玉米中可能很重要。呼吸对作物碳和代谢能量收支的定量重要性提出了以下问题：当前作物呼吸的一小部分是无效的还是非必要的，是否存在与该部分相关的遗传变异可用于选择，以及定向酶进化能否提高呼吸效率或减少任何非生产性成分？ 在某种程度上，可以在不损害的情况下减少维持过程，例如蛋白质周转和主动运输以抵消跨膜泄漏，因此它们是修饰以提高产量的目标。现在可用于量化作物呼吸的技术，至少是单个器官的呼吸，可以用于高通量筛选，生物工程的进步意味着对呼吸的改变不需要受到作物及其野生亲缘种现有遗传变异的限制。简而言之，通过定向呼吸变化提高产量是可能的，但成功的前景可能需要将研究重点从光合作用适度转变为呼吸，作为作物改良的额外途径。