不同淹水条件下河竹叶片光合生理特性的变化

摘要

为阐明淹水条件下河竹( Phyllostachys rivalis H. R. Zhao)叶片的光合生理特性,设置对照组( CK,正常供水)及中度淹水(T1,水面高出基质表面5 cm)和重度淹水(T2,水面高出基质表面10 cm)处理组,对持续淹水360 d内2年生河竹幼苗叶片的光合气体交换参数、光响应曲线、光合特征参数、资源利用效率参数、光合色素含量及比值的变化进行了分析；在此基础上,探讨了河竹对淹水环境的适应性。结果表明：随淹水时间延长,2个处理组的多数光合生理参数呈“升高—降低—升高”的变化趋势,且多数参数在淹水90 d时达到峰值、在淹水270 d时达到谷值；T1组的各项光合生理参数总体上高于T2组。淹水30~180 d,与CK组相比,2个处理组的净光合速率( Pn)、蒸腾速率( Tr)、气孔导度( Gs)、胞间CO2浓度( Ci)和叶面饱和水汽压亏缺( Vpdl)总体上降低,表观量子效率( AQY)显著降低；气孔限制值(Ls)升高,而光饱和点(LSP)和光补偿点(LCP)显著升高；T1组的最大净光合速率(Pmax)略降低,而T2组的Pmax值则显著降低；但2个处理组的水分利用效率( WUE)、表观CO2利用效率( CUE)和表观光能利用效率(LUE)却无明显变化。淹水270和360 d,与CK组相比,2个处理组的Pn、Tr、Gs、Ls和Vpdl值降低,Pmax、LSP、LCP、WUE、CUE和LUE值显著降低,仅Ci值升高；T1组的AQY值略降低,而T2组的AQY值则显著降低。2个处理组的光响应曲线变化趋势与CK组相似,但随淹水时间延长,2个处理组的Pn值变幅不同,其中T1组的Pn值总体上高于T2组。淹水30和90 d,与CK组相比,T1组的叶绿素b( Chlb)和总叶绿素( Chl)含量总体上显著升高,而T2组的Chlb和Chl含量总体上显著降低；2个处理组的叶绿素a(Chla)和类胡萝卜素(Car)含量以及Chla/Chlb和Chl/Car值也显著降低。淹水180~360 d,仅2个处理组的Chla/Chlb值显著升高,而其他光合色素含量及比值总体上显著降低。综合分析结果显示：河竹叶片Pn值在淹水前期和中期下降的主要原因为气孔限制,而在淹水后期下降的主要原因为非气孔限制。河竹对淹水环境有较强耐受性,并对长期淹水有一定的适应性；此外,中度淹水条件下河竹叶片的光能转化效率、对光辐射的利用范围和对光变化的适应能力均高于重度淹水条件。%In order to clarify photosynthetic and physiological characteristics of leaf of Phyllostachys rivalis H. R. Zhao under flooding condition, the control group ( CK, normal water supplying) , moderate flooding (T1, water surface higher than substrate surface 5 cm) and severe flooding (T2, water surface higher than substrate surface 10 cm ) treatment groups were set up, changes in photosynthetic gas exchange parameters, light response curve, photosynthetic characteristic parameters, resource use efficiency parameters, contents and ratios of photosynthetic pigments in leaf of two-year-old seedling ofP. rivalis during continuously flooding for 360 d were analyzed. On this basis, adaptability of P. rivalis to flooding environment was discussed. The results show that with prolonging of flooding time, most photosynthetic and physiological parameters of two treatment groups appear the changing trend of“increasing-decreasing-increasing”, and most parameters reach the peak value when flooding for 90 d and reach the valley value when flooding for 270 d. Various photosynthetic and physiological parameters of T1 group are generally higher than those of T2 group. When flooding for 30-180 d, compared with CK group, net photosynthetic rate ( Pn) , transpiration rate ( Tr) , stomatal conductance ( Gs) , intercellular CO2 concentration ( Ci ) and vapor pressure deficit of leaf surface ( Vpdl ) of two treatment groups decrease generally, apparent quantum yield ( AQY) decreases significantly;limited stomatal value ( Ls) increases, while light saturation point ( LSP) and light compensation point ( LCP) increase significantly;the maximum net photosynthetic rate ( Pmax ) of T1 group decreases slightly, while that of T2 group decreases significantly;but there are not obvious changes in water use efficiency ( WUE) , apparent CO2 use efficiency ( CUE) and apparent light use efficiency ( LUE) of two treatment groups. When flooding for 270 and 360 d, compared with CK group, Pn, Tr, Gs, Ls and Vpdl values of two treatment groups decrease, while their Pmax , LSP, LCP, WUE, CUE and LUE values decrease significantly, only Ci value increases;AQY value of T1 group decreases slightly, while that of T2 group decreases significantly. Changing trend of light response curve of two treatment groups is similar to that of CK group, but changing range of Pn value of two treatment groups is different with prolonging of flooding time, in which, Pn value of T1 group is generally higher than that of T2 group. When flooding for 30 and 90 d, compared with CK group, contents of chlorophyll b ( Chlb ) and total chlorophyll ( Chl ) of T1 group increase significantly in general, while those of T2 group decrease significantly in general;contents of chlorophyll a ( Chla) and carotenoid ( Car) and Chla/Chlb and Chl/Car values of two treatment groups also decrease significantly. When flooding for 180-360 d, only Chla/Chlb value of two treatment groups increases significantly, while other photosynthetic pigment contents and ratios decrease significantly in general. The comprehensive analysis result shows that the main reason for decreasing of Pn value of leaf of P. rivalis at early and middle flooding stages is stomatal limitation, while that at later stage is mainly non-stomatal limitation. P. rivalis has stronger tolerance to flooding environment, and has a certain adaptability to long-term flooding. In addition, efficiency of light energy conversion, utilization range to light radiation and adaptability to light change of leaf of P. rivalis under moderate flooding condition all are higher than those under severe flooding condition.