Midday depression of tree root respiration in relation to leaf transpiration
Midday depression of tree root respiration in relation to leaf transpiration
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DOI：
10.1007/s11284-011-0838-z
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发表时间：
2011-07-01
影响因子：
2
通讯作者：
Nakano, Takashi
中科院分区：
文献类型：
--
作者：
Bekku, Yukiko Sakata;Sakata, Tsuyoshi;Nakano, Takashi
在实验室条件下，根呼吸速率常与温度呈指数或线性关系。然而，在野外完整条件下，一些树种的根呼吸速率在中午前后下降，尽管根温度有所升高（Bekku et al. 2009）。为了弄清午间郁灭的原因，我们通过对冠层乔木栎（Quercus crispula）和柞树（Chamaecyparis obtusa）叶片和根系的气体交换同时进行野外测量，研究了完整根系呼吸与叶片气体交换参数之间的关系。根呼吸速率（R-r）与田间叶片气体交换参数之间无显著关系。然而，在测量R-r前1 h，黑草R-r与蒸腾速率(E)之间的关系采用对数函数拟合，决定系数为0.60 ~ 0.89。在光处理实验中，幼树R-r与测量前20 min的E、根温（T-r）和测量前20 min的光合作用（P-n）呈显著正相关。在恒定的空气温度和光合光子通量密度下，利用独立调节环境CO2浓度和相对湿度的生长室，研究了P-n或E对根呼吸速率的影响。结果表明，根呼吸速率随E而非P-n的变化而变化。这些结果表明，树木的根呼吸速率在白天变化显著，受叶片蒸腾速率和温度的影响。
The root respiration rate often shows an exponential or a linear relationship with temperature under laboratory conditions. However, under intact conditions in the field, the root respiration rates of some tree species decreased around midday despite an increment of the root temperature (Bekku et al. 2009). To clarify the cause of midday depression, we examined the relationships between the intact root respiration and parameters of leaf gas exchange through the simultaneous field measurement of the gas exchange in the leaf and root of Quercus crispula and Chamaecyparis obtusa, which are canopy trees. There were no significant relationships between the root respiration rates (R-r) and the parameters of leaf gas exchange in the field. However, in C. obtusa, the relationships between R-r and the transpiration rates (E) at 1 h before the measurement of R-r were fitted by logarithmic function with a determination coefficient of 0.60-0.89. In the light-manipulation experiments using saplings, R-r had significant positive correlations with E at 20 min before the measurement of R-r, root temperature (T-r), and the photosynthesis (P-n) at 20 min before the measurement of R-r. We examined which factor, P-n or E, affects the root respiration rate through a manipulation experiment using a growth chamber regulating the ambient CO2 concentration and relative humidity independently under constant air temperature and photosynthetic photon flux density. As a result, the root respiration rates changed corresponding to E and not P-n. These results suggest that the root respiration rate of trees changes significantly in the daytime and is affected by the leaf transpiration rate as well as the temperature.