CIRAD, UMR AGAP, F-34398 Montpellier, France.
International Rice Research Institute (IRRI), Crop and Environment Science Division (CESD), DAPO Box 7777 Metro Manila, Philippines.
J Exp Bot. 2015 Jul;66(13):3931-44. doi: 10.1093/jxb/erv193. Epub 2015 May 7.
Global warming causes night temperature (NT) to increase faster than day temperature in the tropics. According to crop growth models, respiration incurs a loss of 40-60% of photosynthate. The thermal sensitivity of night respiration (R(n)) will thus reduce biomass. Instantaneous and acclimated effects of NT on R(n) of leaves and seedlings of two rice cultivars having a variable level of carbohydrates, induced by exposure to different light intensity on the previous day, were investigated. Experiments were conducted in a greenhouse and growth chambers, with R(n) measured on the youngest fully expanded leaves or whole seedlings. Dry weight-based R(n) was 2.6-fold greater for seedlings than for leaves. Leaf R(n) was linearly related to starch (positive intercept) and soluble sugar concentration (zero intercept). Increased NT caused higher R(n) at a given carbohydrate concentration. The change of R(n) at NT increasing from 21 °C to 31 °C was 2.4-fold for the instantaneous response but 1.2- to 1.7-fold after acclimation. The maintenance component of R(n) (R(m)'), estimated by assimilate starvation, averaged 28% in seedlings and 34% in leaves, with no significant thermal effect on this ratio. The acclimated effect of increased NT on R(m)' across experiments was 1.5-fold for a 10 °C increase in NT. No cultivar differences were observed in R(n) or R(m)' responses. The results suggest that the commonly used Q10=2 rule overestimates thermal response of respiration, and R(n) largely depends on assimilate resources.
全球变暖导致热带地区夜间温度（NT）的上升速度快于白天温度。根据作物生长模型，呼吸会导致 40-60%的光合作用产物损失。因此，夜间呼吸（R(n)）的热敏感性会降低生物量。本研究通过前一天不同光照强度的暴露，调查了两个具有不同碳水化合物水平的水稻品种叶片和幼苗的 NT 对 R(n)的即时和驯化效应。实验在温室和生长室中进行，使用 youngest fully expanded leaves 或 whole seedlings 测量 R(n)。基于干重的 R(n)，幼苗是叶片的 2.6 倍。叶片 R(n)与淀粉（正截距）和可溶性糖浓度（零截距）呈线性关系。在给定的碳水化合物浓度下，升高的 NT 会导致更高的 R(n)。在即时响应中，NT 从 21°C 增加到 31°C 时，R(n)的变化是 2.4 倍，但驯化后，R(n)的变化是 1.2-1.7 倍。通过同化饥饿估计的 R(n)维持成分（R(m)’），在幼苗中平均为 28%，在叶片中平均为 34%，该比例对热没有显著影响。跨实验中，升高的 NT 对 R(m)’的驯化效应是 NT 升高 10°C 的 1.5 倍。在 R(n)或 R(m)’响应方面，没有观察到品种差异。结果表明，常用的 Q10=2 规则高估了呼吸的热响应，并且 R(n)在很大程度上取决于同化资源。
