金沙江干热河谷坡柳的光合特性

为探明金沙江干热河谷地区主要造林树种抗旱的生理生化特征 ,对干热河谷造林树种的选择提供依据 ,作者在 2 0 0 2年 5月初 ,利用LI 6 40 0便携式光合仪和植物效能仪等测定系统 ,研究了云南省元谋盆地干旱季节在不同水分和光强处理下坡柳 (Dodonaeaviscosa)的光合及水分等生理参数的日变化情况 .结果表明 :浇水、遮荫处理的净光合速率日变化平稳 ;不浇水处理、浇水处理日变化曲线为双峰型 ,13:0 0时净光合速率出现最低值 .光抑制是造成净光合速率下降的主要原因 .遮荫处理的日变化曲线为单峰型 ,在 11:0 0净光合速率出现最高值 .造成净光合速率下降的原因既有气孔限制又有非气孔限制因素 .在干旱季节坡柳仍维持着气孔开放 ,进行光合作用 ,表现出很强的忍耐干旱能力 ,干旱季节坡柳具有较高的水分利用效率和较低的光合速率和净光合速率来适应水分胁迫 .

Characteristics of photosynthesis of Dodonaea viscosa in the dry-hot valley of Jinsha River

The intense soil and water loss has become mainly sediment sources of the upper reaches of the Yangtze River. So it is important to investigate some important silvicultural species with physiological and biochemical characteristics and the influential factors on drought-risistance. Using Li--6400 photosynthetic instruments and PEA measure systems, the authors study the diurnal changes of photosynthesis and water parameters of Dodonaea viscosa.The study was conducted in dry-hot valley of Yuanmou County (25°40′N,101°55′E) in Yunnan Province in May 2002.Diurnal changes in gas exchange and chlorophyll fluorescene were measured in an artificial 3 years old D.viscosa stand. The results showed that the watered plants had higher photosynthetic rates,stomatal conductances and F V/F m than non-watered plants. Diurnal change of photosynthetic rates assumed bimodal pattern under the non-shading treatment, and showed a pronounced midday depression at 13:00 , high irradiance resulted in the marked midday reduction in P n. F V/F m,F′ V/F′decreased following the increasing of photosynthetically active radiation. And P n reached the lowest values at 13:00.It indicated down-regulation of photochemical processes and an effective thermal dissipation of excess light energy. Stomata of D. viscosa remained partially open during the water stress and supported a positive net photosynthetic rate,suggesting that D. viscosa can be considered as mechanisms of drought tolerance. D.viscosa adapt to dry-hot season with higher WUE and lower rates of photosynthesis.