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Analysis of the Relative Increase in Photosynthetic O2 Uptake When Photosynthesis in Grapevine Leaves Is Inhibited following Low Night Temperatures and/or Water Stress1

机译:夜间低温和/或水分胁迫后抑制葡萄叶片光合作用时光合作用O2吸收的相对增加1

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摘要

We found similarities between the effects of low night temperatures (5°C–10°C) and slowly imposed water stress on photosynthesis in grapevine (Vitis vinifera L.) leaves. Exposure of plants growing outdoors to successive chilling nights caused light- and CO2-saturated photosynthetic O2 evolution to decline to zero within 5 d. Plants recovered after four warm nights. These photosynthetic responses were confirmed in potted plants, even when roots were heated. The inhibitory effects of chilling were greater after a period of illumination, probably because transpiration induced higher water deficit. Stomatal closure only accounted for part of the inhibition of photosynthesis. Fluorescence measurements showed no evidence of photoinhibition, but nonphotochemical quenching increased in stressed plants. The most characteristic response to both stresses was an increase in the ratio of electron transport to net O2 evolution, even at high external CO2 concentrations. Oxygen isotope exchange revealed that this imbalance was due to increased O2 uptake, which probably has two components: photorespiration and the Mehler reaction. Chilling- and drought-induced water stress enhanced both O2 uptake processes, and both processes maintained relatively high rates of electron flow as CO2 exchange approached zero in stressed leaves. Presumably, high electron transport associated with O2 uptake processes also maintained a high ΔpH, thus affording photoprotection.
机译:我们发现低温(5°C–10°C)和缓慢施加水分胁迫对葡萄(Vitis vinifera L.)叶片的光合作用具有相似性。户外生长的植物暴露于连续的寒冷夜晚,导致光和CO2饱和的光合作用O2的释放在5天内下降至零。经过四个温暖的夜晚,植物恢复了活力。这些光合作用的反应在盆栽植物中得到了证实,即使根系被加热。光照一段时间后,冷气的抑制作用更大,可能是因为蒸腾作用导致了更高的水分亏缺。气孔关闭仅占光合作用抑制的一部分。荧光测量显示没有光抑制的迹象,但是胁迫植物中非光化学猝灭增加。即使在高外部CO2浓度下,对两种应力的最典型响应是电子传输与净O2释放的比率增加。氧同位素交换表明,这种不平衡是由于O2摄取增加所致,它可能具有两个组成部分:光呼吸作用和Mehler反应。寒冷和干旱引起的水分胁迫都增强了O2的吸收过程,并且当胁迫叶片中的CO2交换接近于零时,这两个过程都保持了较高的电子流量。据推测,与O 2吸收过程相关的高电子传递也保持了高ΔpH,从而提供了光保护。

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