干旱胁迫下三江平原湿地毛苔草光合作用日变化特性研究

The Diurnal Variation of Photosynthesis of Carex lasiocarpa under Drought Stress in the Sanjiang Plain

为了探讨干旱胁迫下毛苔草的光合特性，选三江平原湿地毛苔草（Carex lasiocarpa）无性系种群进行桶栽模拟实验，采用Li6400型便携式光合仪测定毛苔草光合作用日变化特性。结果表明：毛苔草对干旱的适应能力较强，在土壤含相对水量保持在300g／kg的干旱处理（S1）下，仍能进行光合生产，但其光合参数除气孔限制值（Ls）外，均较对照（CK，水位在0—10cm波动的自然降水）有所降低。2种水分处理下毛苔草的光合速率（Pn）、气孔导度（Gs）和蒸腾速率（Tr）的日变化趋势均呈单峰曲线变化，干旱处理的峰值均出现在8：30，而对照处理的峰值出现在10：30；胞间CO2浓度（Ci）的日变化均呈“V”字型，干旱和对照处理的最低值分别出现在10：30和12：30。毛苔草Pn日变化过程即有气孔限制的贡献也有非气孔限制的作用。毛苔草在干旱处理下Pn与Gs和Tr均呈极显著正相关，与Ci和Ls的日变化呈不显著的负相关关系；而在对照处理下Pn与Ci极显著负相关，与Tr呈极显著正相关，而与Gs呈显著正相关关系，与Ls呈不显著的相关关系。干旱胁迫使光合速率与其它光合参数之间的相关性发生较大变化。

The diurnal variation of photosynthesis and the relations between the photosynthetic parameters of Carex lasiocarpa clonal population in the Sanjiang Plain wetland were studied by barrel seedling simulation experiment. The results showed that C. lasiocarpa has high adaptability to drought. When the soil moisture content was 300 g/kg during the growing season, C. lasiocarpa can photosynthesize normally but the values of the photosynthesis parameters were lower than the control （natural rainfall）. The diurnal changes of net photosynthetic rate （Pn）, transpiration rate （Tr） and stomatal conductance （Gs） of the drought treatment and the control were both present as single- apex curves, while the maximums were present at 8：30 AM and 10：30 AM, respectively. The diurnal change of intercellular CO2 concentration （Ci） was a ＂V＂ style, and the minimums were present at 10：30 AM and 12：30 AM, respectively. The reasons of diurnal variation of Pn of C. lasiocarpa can be attributed to the effects of the stomatal limitation as well as the nonstomatal limitation. Pn had extremely significantly positive correlations with Gs and Tr, while had extremely significantly positive correlations with insignificantly negative correlations with Ci and Ls for the drought treatment. However, Pn had extremely significantly negative correlation with Ci, had extremely significantly positive correlation with Tr, had significantly positive correlation with Gs, and had insignificant correlation with Ls. It can be concluded that drought stress resulted in the change of the relation between Pn and the other photosynthetic parameters of C. lasiocarpa.