干旱胁迫对4种决明属植物光合作用和叶绿素荧光特性的影响

以4种决明属植物草决明(Cassia obtusifolia)、望江南(C.occidentalis)、伞房决明(C.corymbosa)、双荚决明(C.bicapsularis)为材料,采用盆栽控水试验,设置轻度干旱、重度干旱和正常灌水处理,研究了干旱胁迫对4种决明属植物的叶绿素含量、光合作用参数和叶绿素荧光特性的影响。结果显示,1)干旱胁迫导致4种决明属植物的叶绿素含量下降,望江南的下降幅度最小,说明望江南在水分减少的情况下仍具有较高的光合作用能力,伞房决明的叶绿素含量在3种处理下都趋于最高水平,表明伞房决明光能吸收、转换和传递能力较强;2)干旱胁迫导致4种决明属植物气孔导度(Gs)降低,气孔限制值(Ls)升高,伴随着胞间CO2浓度(Ci)降低,净光合速率(Pn)下降,表明是气孔因素造成的,此后,除草决明外其它3种植物的Ci均升高,Ls均下降,这是非气孔因素造成的;在干旱胁迫下望江南具有较高的光合速率,伞房决明具有相对较高的气孔开放度;3)干旱胁迫导致4种决明属植物的最大荧光(Fm)和光化学效率(Fv/Fm)下降,初始荧光(Fo)上升,表明PSⅡ结构受到破坏或者植物进行了热耗散。光化学淬灭系数(qP)和电子传递速率(ETR)下降,而非光化学淬灭系数(NPQ)上升,说明干旱胁迫对PSⅡ造成伤害,但其能够有效地避免或减轻因PSⅡ吸收过多光能而引起的光抑制和光氧化。望江南表现的最稳定,说明望江南具有较强的抗旱性。

Effect of drought stress on characteristics of photosynthesis and chlorophyll fluorescence of four species of Cassia

The effects of drought stress on the characteristics of photosynthesis and chlorophyll fluorescence of four species of Cassia were studied by conducting a water control experiment (mild drought,severe drought,and normal irrigation) using four Cassia species (C.obtusi folia,C.occidentalis,C.corymbosa,C.bicapsularis).The results showed that 1) drought stress resulted in a decline in the chlorophyll content in all four species of Cassia,and the stress degree of C.occidentalis was the lowest,meaning that C.occidentalis maintains the highest photosynthetic capacity under low moisture conditions.The chlorophyll content of C.corymbosa was the highest in all three treatments,indicating that the light energy absorption and transformation capacity of C.corymbosa are stronger than those of the other three species.2) Drought stress resulted in all four species of Cassia displaying reduced stomatal conductance (Gs),while the stomatal limitation (Ls) value increased,which was accompanied by a decrease in intercellular CO2 concentration (Ci) and a decline in the rate of photosynthesis (Pn),indicating that drought stress affects stomatal factors.The exception to this was C.obtusifolia,which showed an increase in Ci and decrease in Ls,indicating that the results are because of non-stomatal factors.Under drought stress,C.occidentalis showed a higher photosynthetic rate,and C.corymbosa showed a relatively high degree of stomatal opening.3) Drought stress led to a decrease in Fm and Fv/Fm,and an increase in Fo among the four species of Cassia,indicating that damage to photosystem Ⅱ (PSⅡ) or heat dissipation.The qP and ETR values decreased,while the NPQ value increased,indicating damage to PS Ⅱ by drought stress,but effectively avoiding or reducing photoinhibition and light oxidation,which is caused by PS Ⅱ absorbing excess light energy.C.occidentalis showed the most stable performance,which means that C.occidentalis has a higher drought resistance