Photosynthesis in variable environments.
Photosynthesis in variable environments.
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DOI：
10.1093/jxb/erv175
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发表时间：
2015-05
影响因子：
6.9
通讯作者：
Lawson T
中科院分区：
文献类型：
--
作者：
Johnson GN;Lawson T
光合作用是最重要的生化过程之一，几乎是所有生命的基础。它也是最容易受到环境压力的动物之一。辐照度在日周期中的变化大体上是可预测的，但是，在该周期的叠加上，云量的变化会导致辐照度在每一秒之间发生数量级的变化。云层覆盖的范围会随着季节的变化而变化，根据短期的天气模式，辐照度会在几天到几周的时间内升高或降低。例如，2012年英国农作物产量低是由于当年夏季日照不足。由于树叶的移动和太阳相对于树冠缝隙的位置造成的太阳斑，也会引起辐照度的快速变化。遮阳的变化也会影响吸收光的光谱质量。光吸收的变化将直接影响植物产生ATP和NADPH的能力。同时，温度的变化会影响植物利用这些电子传递产物的能力。温度的降低将导致酶催化反应速率的降低。在较高的温度下，CO2和O2的溶解度以及Rubisco特异性的变化将改变光呼吸的程度。气温每天都在波动，但也取决于几天到几个月的天气模式。供水的波动，即使是在短时间内，也会导致气孔导度的变化，从而引起二氧化碳供应的波动。上述所有因素都可能导致光合装置在光捕获和光利用之间的不平衡。当光吸收超过能量固定的能力时，就可能发生损伤，要么直接对光合机构（特别是光系统II）造成损伤，要么由活性氧的产生引起更广泛的损伤，如单线态氧、超氧化物和过氧化氢。鉴于此，人们可能会认为植物一直处于白化致死的危险之中。事实上，这种情况并没有发生，大多数植物能够忍受甚至在各种持续波动的环境中茁壮成长，这可以用一系列调节机制来解释，这些机制优化了光合作用装置，使其适应所经历的条件。这些机制在几分钟到几周的时间尺度上运作，通过改变基因表达和蛋白质浓度，对代谢过程的调节进行快速反应，然后对代谢进行重组。植物生物学的大部分工作都集中在稳定状态的植物上。在实验生物学学会2014年年会上，有一场会议专门讨论了植物如何应对环境波动，特别是动态条件对光合作用的影响。这一重点部分包含的论文对这一新兴领域的研究现状进行了极好的概述，涵盖了一系列不同的方法。Schöttler等人关注不同环境如何改变类囊体膜的组成，特别描述了使用光谱方法来理解不同反应重要性的工作。Dietz的这篇综述着眼于使用系统生物学方法来了解植物对光变化的反应的早期事件，检查传感和信号通路。Kaiser等人研究了对波动的功能反应，而Allahverdiyeva等人研究了在压力下防止光合机构受损的过程。此外，……
Photosynthesis is one of the most important biochemical processes, underlying almost all life. It is also one of the most vulnerable to environmental stress. Irradiance changes over the diurnal cycle is broadly predictable but, superimposed on that cycle, changes in cloud cover can cause order-of-magnitude variations in irradiance from second to second. The extent of cloud cover will change with the season and, depending on the shorter term weather patterns, giving periods of days to weeks of higher or lower irradiance. For example, the low crop yields in the UK in 2012 have been attributed to low levels of sunshine during the summer of that year. Rapid changes in irradiance can also arise due to sunflecks caused by the movement of leaves and the position of the sun relative to gaps in the canopy. Variation in shading will also affect the spectral quality of absorbed light. Changes in light absorption will have direct effects on the ability of plants to generate ATP and NADPH. At the same time, changes in temperature will affect the ability of plants to use those products of electron transport. The lowering of temperatures will result in a lowering of the rate of enzyme-catalysed reactions. At higher temperatures, changes in the solubility of CO2 and O2 and in the specificity of Rubisco will alter the extent of photorespiration. Temperatures fluctuate diurnally, but also depend on weather patterns over days to months. Fluctuations in water supply, even over short time periods, can lead to variation in stomatal conductance causing the CO2 supply to fluctuate. All of the above factors can lead to imbalances between light capture and light use by the photosynthetic apparatus. When light absorption exceeds the capacity for the energy to be fixed, damage is likely to occur, either directly to the photosynthetic apparatus (especially Photosystem II) or more widespread damage caused by the generation of reactive oxygen species, such as singlet oxygen, superoxide, and hydrogen peroxide. In view of this, it might be thought that plants are in constant danger of bleaching themselves to death. The fact that this does not occur, that most plants are able to tolerate and even thrive in a wide range of continually fluctuating environments, is explained by an array of regulatory mechanisms that optimize the photosynthetic apparatus to the conditions experienced. These mechanisms operate on time-scales ranging from minutes to weeks, with rapid responses involving the regulation of metabolic processes being followed by reengineering of metabolism through changing gene expression and protein concentrations. Most work in plant biology focuses on plants at a steady state. At the 2014 Annual Meeting of the Society of Experimental Biology, there was a session specifically focusing on how plants respond to fluctuations in the environment, in particular, in relation to the effects of dynamic conditions on photosynthesis. Papers included in this focus section present an excellent overview of the state of research in this emerging field, with a range of different approaches being covered. Schöttler et al. focus on how different environments alter the composition of the thylakoid membrane, describing work in particular that uses spectroscopic approaches to understand the importance of different responses. The review by Dietz looks at work using a systems biology approach in order to understand the early events in the response of plants to changes in light, examining sensing and signalling pathways. Kaiser et al. examine functional responses to fluctuations while Allahverdiyeva et al. look at processes involved in preventing damage to the photosynthetic apparatus during stress. In addition, the …