NaCl胁迫对西瓜幼苗生长和光合气体交换参数的影响

Effect of NaCl Stress on Growth and Photosynthetic Gas Exchange of Watermelon Seedlings

以早春红玉品种为材料,采用营养液水培法,研究了不同浓度NaCl胁迫对西瓜幼苗生长、叶片光合气体交换参数、质膜透性和脯氨酸含量的影响.结果表明:25 mmol·L-1NaCl处理9 d后对西瓜幼苗生长有促进作用,>75 mmol·L-1NaCl处理则显著抑制幼苗生长;NaCl处理显著提高了叶片光合色素含量,并在100 mmol·L-1NaCl处理下达到最大;叶片净光合速率、气孔导度和蒸腾速率均随NaCl浓度提高而显著降低;胞间CO2浓度随NaCl浓度提高呈先降低后升高的趋势,在75 mmol·L-1NaCl处理下降到最小;气孔限制值随NaCl浓度提高而增加,在75 mmol·L-1NaCl处理下达到最大值后趋于稳定;水分利用率随NaCl浓度提高呈先增加后降低的趋势,在75 mmol·L-1NaCl处理下达到最大;叶片质膜透性和脯氨酸含量均随NaCl浓度提高而显著增加.结果说明:NaCl胁迫显著抑制了西瓜叶片光合作用,且低浓度处理下光合速率降低的主要原因是气孔因素限制,高浓度胁迫下则转变为非气孔因素限制.

The experiment was carried out with watermelon [Citrullus lanatus （Thunb.） Matsum. et Na- kai] cv. ‘Zaochun-hongyu’ to study the effect of different concentration NaCl stress on plant growth,pho- tosynthetic gas exchange parameters,membrane permeability and proline content of seedlings grown hydroponically. The results showed that 9 d after treatment,25 mmol · L^-1 NaCl improved watermelon seedlings growth,and NaCl stress beyond 75 mmol·L^-1 significantly inhibited its growth. The photosynthetic pigments content in leaves were obviously increased and reached highest value at 100 mmol· L^-1 NaCl. With increasing NaCl concentration,the net photosynthetic rate,stomatal conductance,transpiration rate significantly declined, and intercellular CO2 concentration apparently decreased under lower concentration of NaCl,increased beyond 75 mmol· L^-1. The stomatal limitation value and water use efficiency increased under lower concentration of NaCl,tended to stabilization for stomatal limitation value and declined quickly for water use efficiency beyond 75 mmol· L^-1. With increasing NaCl concentration,membrane permeability and proline content in leaves significantly increased. The research revealed that NaCl stress significantly inhibited the photosynthesis of watermelon leaves,and the reduction of net photosynthetic rate under lower concentration NaCl was the result of stomatal limitation, and non-stomatal limitation was the main reason for the decrease of photosynthetic rate under higher salinity.