Herritt Matthew T, Fritschi Felix B
US Arid Land Agricultural Research Center, United States Department of Agriculture, Agricultural Research Service, Maricopa, AZ, United States.
Division of Plant Science, University of Missouri, Columbia, MO, United States.
Front Plant Sci. 2020 Mar 6;11:153. doi: 10.3389/fpls.2020.00153. eCollection 2020.
Heat stress negatively affects photosynthesis in crop plants. Chlorophyll fluorescence provides information about the efficiency of the light-dependent reactions of photosynthesis and can be measured non-destructively and rapidly. Four soybean () genotypes were grown in controlled environments at 28/20°C (control), followed by imposition of control, 38/28°C, and 45/28°C day/night temperature regimes for 7 days. Coordinated chlorophyll fluorescence, gas exchange, and chloroplast ultrastructure measurements were conducted over the course of the 7-day temperature treatments and revealed contrasting responses among the different genotypes. Although generally similar, the extent of the impact of elevated temperatures on net photosynthesis differed among genotypes. Despite dramatic effects on photosynthetic light reactions, net photosynthetic rates were not reduced by exposure to 45°C on the 1 day of treatment imposition. Temporal dynamics of light reaction characteristics over the course of the 7-day heat-wave simulation revealed distinct responses among the genotypes. Similarly, chloroplast ultrastructure examination identified contrasting responses of DT97-4290 and PI603166, particularly with respect to starch characteristics. These changes were positively associated with differences in the percent area of chloroplasts that were occupied by starch grains. Elevated temperature increased number and size of starch grains on the 1 day of DT97-4290 which was coordinated with increased minimum chlorophyll fluorescence (F) and reduced leaf net CO assimilation (A). Whereas on the 7 day the elevated temperature treatment showed reduced numbers and sizes of starch grains in chloroplasts and was coordinated with similar levels of F and A to the control treatment. Unlike starch dynamics of PI603166 which elevated temperature had little effect on. The genotypic differences in photosynthetic and chloroplast ultrastructure responses to elevated temperatures identified here are of interest for the development of more tolerant soybean cultivars and to facilitate the dissection of molecular mechanisms underpinning heat stress tolerance of soybean photosynthesis.
热胁迫对作物的光合作用产生负面影响。叶绿素荧光提供了有关光合作用光反应效率的信息，并且可以进行无损快速测量。四种大豆基因型在28/20°C（对照）的可控环境中生长，随后分别施加对照、38/28°C和45/28°C的昼夜温度处理7天。在为期7天的温度处理过程中，对叶绿素荧光、气体交换和叶绿体超微结构进行了协同测量，结果显示不同基因型之间存在不同的反应。尽管总体上相似，但高温对净光合作用的影响程度在不同基因型之间存在差异。尽管对光合光反应有显著影响，但在处理开始的第1天暴露于45°C时，净光合速率并未降低。在为期7天的热浪模拟过程中，光反应特征的时间动态揭示了不同基因型之间的明显差异。同样，叶绿体超微结构检查确定了DT97 - 4290和PI603166的不同反应，特别是在淀粉特征方面。这些变化与淀粉粒所占叶绿体面积百分比的差异呈正相关。高温使DT97 - 4290在第1天淀粉粒的数量和大小增加，这与最小叶绿素荧光（F）增加和叶片净CO2同化（A）降低相协调。而在第7天，高温处理使叶绿体中淀粉粒的数量和大小减少，并且与对照处理的F和A水平相似。与PI603166的淀粉动态不同，高温对其影响很小。本文确定的大豆对高温的光合和叶绿体超微结构反应的基因型差异，对于培育更耐热的大豆品种以及促进对大豆光合作用热胁迫耐受性分子机制剖析具有重要意义。
