梭鱼草对铜胁迫的光合适应性

Photosynthetic Adaptability of Pontederia cordata to Copper Stress

以液培方法研究了不同质量浓度(0、5、10、20 mg·L-1)铜离子(Cu 2+)对梭鱼草叶片光合色素、气体交换参数和叶绿素荧光参数的影响,以探究梭鱼草对Cu 2+的光合适应能力。结果显示:低质量浓度Cu 2+对梭鱼草叶片光合色素质量分数没有显著影响,而较高质量浓度Cu 2+(≥10 mg·L-1)导致光合色素质量分数显著下降;随着溶液中Cu 2+质量浓度的升高,梭鱼草叶片净光合速率(P n)、蒸腾速率(E)、气孔导度(G s)和水分利用率(W U,E)显著下降,叶片饱和蒸气压亏缺(V P,D)增加,而饱间CO 2摩尔分数(C i)和气孔限制值(L s)无明显变化;在最高质量浓度Cu 2+处理条件下,梭鱼草叶片叶绿素最大荧光(F m)、可变荧光产量(F v)、PSⅡ潜在光合活性(F v/F o)、PSⅡ最大光化学效率(F v/F m)、单位面积电子传递的量子产额(E T,o/C S,o)及光合性能指数(P I,a,b,s)显著下降,反应中心净关闭速率(d V,G/d t,o和d V/d t,o)、比活性参数A B,S/R C、T R,o/R C、D I,o/R C及单位面积耗散掉的能量(D I,o/C S,o)则呈相反的变化趋势。梭鱼草叶片对5 mg·L-1 Cu 2+表现出较好的光合适应能力。随Cu 2+质量浓度升高,非气孔因素是梭鱼草叶片P n下降的主要原因。较高质量浓度Cu 2+处理下,梭鱼草叶片光合机构可以通过关闭部分反应中心、增加热耗散等途径缓解过量Cu 2+对光合机构的破坏。

The effects of different concentrations(0,5,10 and 20 mg·L-1)of copper ions(Cu 2+)on photosynthetic pigment,gas exchange parameters and chlorophyll fluorescence parameters in the leaves of Pontederia cordata were studied by solution cultivation,so as to explore the photosynthetic response of P.cordata to Cu 2+.Low concentration of Cu 2+had no significant effect on the photosynthetic pigment content in the leaves of Pontederia cordata,while high concentration of Cu 2+(≥10 mg·L-1)led to a significant decrease in the photosynthetic pigment content.with increased concentration of Cu 2+,the net photosynthetic rate(P n),transpiration rate(E),stomatal conductance(G s)and water use efficiency(W U,E)of P.cordata’s leaves decreased significantly.The vapor pressure deficit(V P,D)increased,while the intercellular CO 2 concentration(C i)and stomatal limit(L s)had no significant change.At the highest concentration of Cu 2+processing conditions,the maximum fluorescence(F m),maximum variable fluorescence(F v),PSII potential photosynthetic activity(F v/F o),maximum photochemical efficiency(F v/F m),the electron transport flux per center section(E T,o/C S,o)and performance index(P I,a,b,s)of P.cordata’s leaves were significantly reduced,and net closing rate of reaction center(d V,G/d t,o and d V/d t,o),the specific activity parameter(A B,S/R C,T R,o/R C and D I,o/R C)and dissipate flux per center section(D I,o/C S,o)increased,respectively.The leaves of P.cordata showed good photosynthetic adaptability to 5 mg/L Cu 2+.With the increase of Cu 2+concentration,non-stomatal factors were the main reason for P n decline in the leaves of P.cordata.With higher concentration of Cu 2+,the photosynthetic mechanism of P.cordata’s leaves could alleviate the damage of excessive Cu 2+to photosynthetic mechanism by closing some reaction centers and increasing heat dissipation.