水分胁迫下柱花草叶水势、光合及叶绿素荧光特性的变化特征

以热研2号柱花草为供试材料,采用盆栽控制实验研究了不同土壤水分条件下柱花草叶水势、光合特性和叶绿素荧光参数的变化特征。结果表明：（1）柱花草叶水势随着水分胁迫程度的增加而降低,其日变化呈双峰曲线特征,日平均值表现为充分供水〉轻度胁迫〉中度胁迫〉重度胁迫。（2）充分供水条件下柱花草净光合速率最大,而在重度胁迫下最小,水分胁迫下柱花草光合速率的降低主要为非气孔限制因素所致;柱花草气孔导度在充分供水和轻度胁迫下随光合有效辐射的增强而增大,但在中度和重度水分胁迫下变化不明显;充分供水和轻度水分胁迫下,气孔导度均随蒸腾速率的增加而增加,中度、重度水分胁迫下蒸腾速率分别达到0.46、0.31mmol·m-2·s-1时气孔开始关闭;中度胁迫下水分利用效率高于轻度胁迫,可能是植物对胁迫环境的生理适应所致。（3）初始荧光F0随着干旱胁迫程度的增加而增加,而光系统Ⅱ的最大光化学效率Fv/Fm和潜在活性Fv/F0均降低,表明随着胁迫程度的加深,PSⅡ光抑制的程度也加深,水分胁迫抑制了PSⅡ的光化学活性,使其反应中心受到一定程度的破坏或可逆失活。

Variation Characteristics of Leaf Water Potential,Photosynthesis and Chlorophyll Fluorescence in Stylosanthes Guianensis Leaves Under Soil Water Stress

The leaf water potentia（lLWP）,photosynthesis and chlorophyll fluorescence parameters of Stylosanthes guianensis Reyan No.2 were measured in potted experiment controlled by water stress.The results showed：（1）The LWP decreased with water stress increasing,and its diurnal variation showed a bimodal curve shape.The LWP was maximum under full water supply,and decreased by order of light water stress,moderate water stress and severe water stress（.2）The net photosynthesis rate reached the maximum under the water enough supply,and the least under the severe water stress.The main reason of the reduction of P n was nonstomatal limitation under water stress.The stomatal conductance（G s）increased as a result of the increasing of PAR（Photosynthetically Active Radiation）under the water enough supply and light water stress conditions,and didn＇t apparently vary under the moderate water stress and severe water stress.Under water enough supply and light water stress,G s increased with the increasing of T r,and under moderate and severe water stress with T r of 0.46 mmol·m-2 ·s-1 and 0.31 mmol·m-2 ·s-1,respectively,the stomata began to close.The leaf water use efficiency（WUE）under the moderate water stress was higher than that under light water stress,which should be possibly attributed to the physiological mechanism of plant adaption to the stress settings.（3）The fluorescence parameter of F 0 increased,while the Fv/Fm,Fv/F0 decreased with the increase of water stress.It meant that with the increase of drought extent,the degree of photoinhibition increased,i.e.,water stress restrained the photochemical activity in PS Ⅱ and reduced the light part used in photochemical reactions and actual photochemical efficiency,resulting in response center in PSⅡ damaged or reversible inactive.