三峡库区消落带水淹结束后狗牙根的光合生理生态特性

Photosynthetic characteristics of Cynodon dactylon in hydro-fluctuation belt of Three Gorges Reservoir at the end of flooding

淹水后植物在陆生环境合成和储存碳水化合物的能力及对水淹的耐受机理,是消落带植被恢复和重建中植物材料选择的重要理论依据。狗牙根为三峡库区消落带适生植物之一。本文按照海拔,将消落带分为深水淹没、浅水淹没和未淹3个区段,并分期测定各区段狗牙根的光合特性,研究三峡库区消落带水淹结束后狗牙根的光合生理生态特性。结果表明：（1）生长在深水（22~27 m）和浅水（2~7 m）淹没区段狗牙根的净光合速率显著高于未淹区段,且浅水淹没区段〉深水淹没区段〉未淹对照区段。（2）随着狗牙根在陆生环境中生活时间的延长,净光合速率、表观光能利用效率、表观CO2利用效率等增加,表明狗牙根在淹水后碳水化合物的合成能力增强。（3）深水淹没区段和浅水淹没区段狗牙根的最大光合速率、表观量子利用效率均高于未淹区段,而光补偿点显著降低,反映出在淹水后狗牙根对弱光的利用能力得以提高。（4）狗牙根的净光合速率受气孔因素和非气孔因素共同影响,淹水对狗牙根光合潜力的发挥具有一定的激发作用。淹水和干旱胁迫后积极的自我调节能力和光合补偿机制,可能是狗牙根适生于三峡库区消落带水陆变化生境的重要原因。

Plant’s ability to synthesize and store carbohydrate in terrestrial environment and the tolerance mechanism to flooding are important theoretical basis for vegetation restoration and reconstruction of hydro-fluctuation belt. Cynodon dactylon is one of the adaptive plants of hydrofluctuation belt of Three Gorges Reservoir. In order to understand the photosynthetic physiology of C. dactylon after flooding,the photosynthetic physiology of C. dactylon was measured under deep water（ 22-27 m）,shallow water（ 2-7 m） and non-flooded conditions along an elevation gradient in Three Gorges Reservoir region. The results showed that（ 1） the net photosynthetic rates（ Pn） of C. dactylon growing in deep water and shallow water were higher than that in non-flooded area,and Pnof C. dactylon growing in shallow water was the highest.（ 2） The Pn,apparent light use efficiency and apparent CO2 use efficiency increased with the time extension of C. dactylon in terrestrial environment,indicating that the ability to synthesize and store carbohydrate of C. dactylon was enhanced after flooding.（ 3） The maximum photosynthetic rate and apparent quantum yield of C. dactylon growing in deep water and shallow water were higher than that growing in non-flooded area,while light compensation point significantly decreased,which suggested that the ability of C. dactylon to use low light improved.（ 4） Pnof C. dactylon was affected by the combination of both stomatal and non-stomatal factors and the flooding had a stimulating effect on C. dactylon photosynthetic potential. The positive self-adjustment ability and the photosynthetic compensation mechanism of C. dactylon after flooding and drought stress may be important reasons for its adaptation to flooding-drying habitat changes in hydro-fluctuation belt of Three Gorges Reservoir.