Centre d'Ecologie Fonctionnelle et Evolutive (CEFE), CNRS 1919 Route de Mende, 34293 Montpellier Cedex 5, France.
Tree Physiol. 2010 Feb;30(2):214-24. doi: 10.1093/treephys/tpp104. Epub 2009 Dec 9.
Little is known about how environmental factors shape the short- and long-term responses of leaf respiration to temperature under field conditions despite the importance of respiration for plant and stand carbon balances. Impacts of water availability and canopy cover on leaf dark respiration (R) and temperature sensitivity were assessed in beech (Fagus sylvatica L.) seedlings in a sub-Mediterranean population. We studied seedlings established within canopy gaps (39% global site factor; GSF) that were subject to either no watering (unwatered plants; UW) or regular watering (2-10% higher volumetric topsoil water content as summer progressed; W plants) and seedlings established beneath the adjacent understorey (12% GSF). Leaf R rose exponentially with diurnal increases in temperature; the same temperature sensitivity (Q(10): 2.2) was found for understorey and gap plants, irrespective of watering treatment. Respiration estimated at 25 degrees C (R(25)) was lower in the understorey than the gaps and was significantly lower in the unwatered than in the watered gap plants by the end of summer (0.65 versus 0.80 micromol m(-2) s(-1)). R(25) declined with increasing summer temperature in all plants; however, respiration estimated at the prevailing ambient temperature did not change through the summer. There were parallel declines in R(25) and concentrations of starch and soluble sugars with increasing summer temperature for gap plants. We conclude that seasonal shifts in temperature-response curves of beech leaf R occur in both low- and high-light environments; since leaf R decreased with increasing plant water deficit, such shifts are likely to be greater whenever plants experience summer drought compared to scenarios where plants experience high rainfall in summer.
尽管呼吸作用对植物和林分碳平衡很重要，但对于环境因素如何塑造叶片呼吸作用对温度的短期和长期响应，在田间条件下人们知之甚少。本研究在一个亚地中海种群中，评估了水分可用性和冠层覆盖对山毛榉（Fagus sylvatica L.）幼苗叶片暗呼吸（R）和温度敏感性的影响。我们研究了建立在树冠空隙（全球站点因子 39%；GSF）中的幼苗，这些幼苗要么不浇水（未浇水植物；UW），要么随着夏季的进展定期浇水（土壤上层体积含水量增加 2-10%；W 植物），以及建立在相邻林下的幼苗（GSF 为 12%）。叶片 R 随白天温度的升高呈指数增长；无论浇水处理如何，林下和空隙植物的温度敏感性（Q(10)：2.2）相同。与空隙植物相比，林下植物的 25°C 呼吸速率（R(25)）较低，夏季结束时，未浇水的空隙植物的 R(25)显著低于浇水的空隙植物（0.65 比 0.80 微摩尔 m(-2) s(-1)）。所有植物的 R(25)均随夏季温度的升高而降低；然而，在整个夏季，在流行的环境温度下估计的呼吸作用并没有变化。在所有植物中，随着夏季温度的升高，R(25)和淀粉及可溶性糖的浓度呈平行下降趋势。我们的结论是，山毛榉叶片 R 的温度响应曲线在低光和高光环境中都发生季节性变化；由于叶片 R 随植物水分亏缺的增加而降低，因此与植物在夏季经历高降雨的情况相比，植物在夏季经历干旱时，这种变化可能更大。
