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Light stress-induced chloroplast movement and midday depression of photosynthesis in sorghum leaves
Plant Production Science ( IF 2.5 ) Pub Date : 2019-10-08 , DOI: 10.1080/1343943x.2019.1673666
Eri Maai 1 , Kazusa Nishimura 1 , Rihito Takisawa 1 , Tetsuya Nakazaki 1
Affiliation  

ABSTRACT Plants are exposed to high light intensity, high leaf temperatures and high air-to-leaf water vapor pressure deficit (ALVPD) during the day. These environmental stresses cause stomatal closure and photoinhibitory damage, leading to midday depression of photosynthesis. Chloroplast positioning is essential for the efficient operation of photosynthesis. However, chloroplast behavior before, during, and even after the midday depression of photosynthesis remains unknown. We investigated changes in the intracellular positioning of chloroplasts and photosynthetic traits under a diurnal pattern of light. Sorghum leaves were exposed to a 12-h regime of light mimicking the natural light environment, with constant leaf temperature and ALVPD. Net photosynthetic rate (Pn) showed a diurnal pattern, and midday depression in Pn was observed at 3.8 h of irradiation. Depression in Pn was attributed to stomatal limitation because the decrease in Pn was in accordance with the decrease in stomatal conductance. The maximum efficiency of photosystem II decreased with the increase in light intensity and remained low after 12 h of irradiation. Bundle sheath chloroplasts swelled after 8 h of irradiation, representing the accumulation of starch. Conversely, mesophyll chloroplasts exhibited avoidance response after 4 h of irradiation, and the avoidance position was maintained during the remainder of the daytime. These data suggest that chloroplasts are subject to light stress during and after the midday depression of photosynthesis. The intensity of natural light is excessive for most of the day and this light stress induces chloroplast avoidance response and depression of photosynthesis. Graphical Abstract

中文翻译:

光胁迫诱导的高粱叶片叶绿体运动和光合作用正午抑制

摘要 植物在白天暴露在高光强度、高叶温和高空气对叶水蒸气压差 (ALVPD) 下。这些环境压力会导致气孔关闭和光抑制损伤,从而导致光合作用的中午抑制。叶绿体定位对于光合作用的有效运行至关重要。然而,在光合作用减弱之前、期间甚至之后的叶绿体行为仍然未知。我们研究了昼夜模式下叶绿体和光合特性的细胞内定位的变化。高粱叶子暴露在模拟自然光环境的 12 小时光照条件下,叶片温度和 ALVPD 恒定。净光合速率 (Pn) 显示出昼夜模式,在 3 点观察到 Pn 的正午下降。8 小时的照射。Pn 的降低归因于气孔限制,因为 Pn 的降低与气孔导度的降低一致。光系统 II 的最大效率随着光强度的增加而降低,并在照射 12 小时后保持较低。束鞘叶绿体在照射 8 小时后膨胀,代表淀粉的积累。相反,叶肉叶绿体在照射 4 小时后表现出回避反应,并且在白天剩余时间内保持回避位置。这些数据表明,叶绿体在中午光合作用减弱期间和之后都会受到光胁迫。一天中的大部分时间,自然光的强度都过大,这种光应激会引起叶绿体回避反应和光合作用的抑制。
更新日期:2019-10-08
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