盐胁迫对国槐和核桃幼苗光合作用的影响

Comparison Study on Photosynthesis of Pagoda Tree and Walnut Seedlings under Salinity

研究了国槐与核桃半年生蛭石盆栽苗在盐 (NaCl溶液处理浓度为 5 0 ,10 0 ,2 0 0mmol·L- 1)胁迫条件下光合作用的变化。结果表明 ,核桃受盐胁迫后净光合速率明显下降 ,并且随盐浓度增大、胁迫时间延长而下降更多。国槐受盐胁迫后净光合速率增加 ,在短时间胁迫下增加多 ,随胁迫时间延长增加幅度变小。国槐与核桃在 2 0 0mmol·L- 1NaCl胁迫 2 4d内叶绿素a和b的含量变化不大 ,但核桃的叶绿素a/b之值下降。并且国槐的类胡萝卜素含量在盐胁迫后先增加后与对照相平 ,而核桃则明显下降。两个树种CO2 响应曲线的主要差别为国槐光呼吸速率下降为对照的4 3 7% ,核桃则比对照增加了 71.6 0 % ;国槐的CO2 补偿点比对照下降了 13.5 8% ,而核桃则比对照上升了 194 .15 %。两个树种在光响应曲线上的差别为国槐的暗呼吸速率比对照增加了 3倍多 ,而核桃则下降为对照的 6 5 .2 8%。

Photosynthesis of half year seedlings of pagoda tree and walnut were determined after different time treatment of 50,100 and 200 mmol·L -1 NaCl. Results showed that photosynthetic rate of walnut decreased distinctly and decreased more when the salinity increased and treatment time lengthened. Photosynthetic rate of pagoda tree increased after salt treatment and increment was less when treatment time lengthened. The content of chlorophyll a and b of both tree species changed little during 24 stressed days of 200 mmol·L -1 NaCl with the exception of ratio of chlorophyll a to b reduction in walnut. The content of xanthophyll in pagoda tree increased firstly and then kept the level as that of the control. In contrast to pagoda tree, the content of xanthophyll in walnut decreased obviously. Main difference between pagoda tree and walnut in CO 2 response curves was that photorespiratory rate in pagoda tree decreased to 43.7% of the control with 71.6% of the control increase in walnut and that CO 2 compensation point decreased 13.58% in pagoda tree with 194.15% increase in walnut both compared to the control. Light response curves revealed that dark respiratory rate of pagoda tree was 3 folds more than that of the control while that of walnut decreased to 65.28% of the control. And photo inhibition occurred in salt stressed walnut.