不同时期NaCl胁迫对甜菜生长及光合作用的影响

为了解NaCl胁迫对甜菜幼苗不同阶段的危害差异,对甜菜生长至子叶期、一对真叶期和三对真叶期均进行3（CK）、140（LS）和280mmol/L Na⁺（HS）处理,处理后分别测定甜菜幼苗不同生长时期的生长和光合生理指标。结果表明,NaCl胁迫后甜菜幼苗植株干重与CK相比显著下降,且子叶期变化幅度较真叶期明显;随NaCl浓度增加,甜菜幼苗叶片的气孔导度（G_s）、蒸腾速率（T_r）、胞间CO₂浓度（C_i）和净光合速率（P_n）显著降低,同时也发现子叶期下降幅度明显高于真叶期;随着NaCl浓度增加,叶绿素含量也显著降低,子叶期比真叶期下降幅度大。此外,NaCl胁迫导致甜菜幼苗的Hill反应和RuBPCase活力下降。同时发现在LS处理后PEPC活性显著升高,在三对真叶期增幅最大,但在HS处理后PEPC活性有一定程度下降。因此随着NaCl浓度的提高,甜菜幼苗生长及光合作用都会受到不同程度的抑制;随着甜菜苗龄的增加,幼苗对NaCl胁迫的耐受性也在不断增强。

The Effects of NaCl Stress on Growth and Photosynthesis of Sugarbeet at Different Growth Stages

In this study, sugarbeet seedlings were treated with 3 (CK), 140 (LS), and 280mmol/L Na⁺ (HS) during cotyledon stage, one pair of true leaves stage, and three pairs of true leaves stage to understand the difference of NaCl stress on sugarbeet seedlings at different stages. After NaCl treatment, growth indexes and photosynthetic physiological indexes of sugarbeet seedlings at different growth stages were measured. The results showed that the dry weight of sugarbeet seedlings under NaCl stress was significantly lower than that of CK and the range of change at cotyledon stage was more obvious than at the true leaf stages. The stomatal conductance (G_s), the transpiration rate (T_r), intercellular CO₂ concentration (C_i), and net photosynthetic rate (P_n) of seedling leaves were significantly decreased by NaCl stress and the decrease at the cotyledon stage was significantly higher than that at true leaf stages. With the increase of NaCl concentration, the chlorophyll content also decreased significantly and decreased more at cotyledon stage than at the true leaf stages. In addition, NaCl stress resulted in decreases of Hill response and RuBPCase activity of sugarbeet seedlings. At the same time, it was found that PEPC activity increased significantly after LS stress with the maximum increase after three pairs of true leaves, but decreased to a certain extent after HS treatment. Therefore, with the increase of NaCl concentration, the growth and photosynthesis of sugarbeet seedlings were inhibited. With the growth of sugarbeet seedlings, the tolerance of the seedlings to NaCl stress was also increased.