茶树叶片蒸腾速率、气孔导度和水分利用率的研究

夏、秋季节,在田间自然条件下,茶树叶片蒸腾速率、气孔导度以中午前后最大,蒸腾速率与气孔导度呈显著正相关。净光合率以上午10时前最高,以后明显降低,晴天强光的光抑制是引起茶树光合作用降低的主要原因。茶树叶片净光合率与气孔导度之间不呈平行变化关系,净光合率与VPD之间也不呈显著负相关。气孔导度与叶片水分利用率(净光合率与蒸腾速率的比值表示)呈显著负相关。在一日中,以上午10时前和下午3时后水分利用率最高、中午前后最低。秋季茶树叶片水分利用率高于夏季。

STUDIES ON TRANSPIRATION RATE, STOMATAL CONDUCTANCE AND WATER USE EFFICIENCY OF TEA PLANT (Camellia Sinensis)

Transpiration rate (Tr), stomatal conductance (Gs) of tea leaves, leaf temperature (TL), Photon flux density (PFD) and relative humidity (RH) were measured by LI-1600 porometer under field conditions. Net photosynthetic rate (Pn) of tea leaves was simultaneously measured with an infrared gas anlyser. It was shown that transpiration rate and stomatal conductance of tea leaves were highest at noon in summer and autumn. Pn increased rapidly with increase in PFD and temperature during the morning, a maximam Pn occurred at around 9: 30 a.m., but declined greatly after reaching the morning maximum, and got to its minimum at midday. Pn recovered not strongly with the depression of PFD, temperature and VPD at around 3: 00-4: 00 a.m., the photosynthesis of tea leaves was insignificantly strong, Pn was at low levels in the whole afternoon. It concluded that on a clear day of either summer or autumn, the photosynthesis depression of tea leaves was mainly caused by an inhibition of photosynthetic apparatus itself, i. e., photoinhibition by high PFD was the main reason of photosynthetic depression. Thus, declines and recoveries in photosynthesis and in stomatal conductance were not simultancous, namely no significant correlation between Pn and stomatal conductance was found in tea leaves, and depression of Pn was not significantly correlated with the increase of leafto-air water vapor mole fraction difference (VPD). The lineal relationship between transpiration rate and stomatal conductance of tea leaves in the summer and autumn under the field conditions was observed. Increase of stomatal conductance was significantly correlated with the depression of water use efficiency (Pn/Tr). In daily time coureses, water use efficiency reached its highest before 10: 00 in the morning and after 3: 00 in the afternoon, during midday reached its lowest. Water use efficiency of tea leaves was higher in autumn than in summer under the field conditions.