夏玉米苗期对不同时长干旱-复水的生理响应机制

Physiological response mechanism of summer maize seedlings to drought-rewatering of different durations

为探究干旱-复水环境下夏玉米苗期的生理调节机制,采用桶栽的方式,设置3个水分处理:正常处理(CK):75%~85%θf(田间持水量),轻度胁迫(W1):60%~70%θf,中度胁迫(W2):50%~60%θf;设置3个胁迫时长,7 d(T1)、10 d(T2)、13 d(T3);于胁迫与复水期间测定夏玉米苗期叶片的渗透调节物质、抗氧化酶及光合指标。结果表明:在轻度和中度胁迫下,脯氨酸(Pro)含量呈先增大后减小趋势,第3天达到峰值,相较于CK分别提高32.7%、44.1%;复水后,胁迫10 d处理的Pro累积量高于胁迫7 d的处理,而胁迫13 d无明显累积效应。超氧化物歧化酶(SOD)活性在胁迫期间呈先增大后减小趋势,第3天达到峰值,相较于CK分别提高22.0%、12.4%;复水后活性增强,且胁迫13 d处理的SOD活性高于胁迫10 d和胁迫7 d处理。过氧化物酶(POD)活性在轻度胁迫处理下呈先增大后减少趋势,在第3天达到峰值,相较于CK提高28.5%,而在中度胁迫处理下POD活性呈减小趋势,且低于CK;复水后酶活性均恢复至正常处理水平。丙二醛(MDA)含量在胁迫期间呈增高趋势,且胁迫时长越长,增幅越大,在胁迫13 d处理下,中度和轻度胁迫下的MDA含量相较于CK分别提高140%和281%;复水后胁迫缓解,所有处理组的MDA含量均恢复至正常处理水平。在轻度和中度胁迫下,夏玉米的净光合速率、气孔导度以及蒸腾速率分别为CK的92.5%和77.7%、93.9%和74.3%、87.9%和74.5%,光合作用受到限制;复水后,中度胁迫处理表现出光合补偿效应,光合指标值均高于其他处理。研究表明,持续10 d维持土壤50%~60%θf较利于夏玉米生长,其复水后出现显著的光合补偿效应。

To investigate the physiological regulation mechanism of summer maize seedlings under drought-rewatering conditions,this experiment adopted a method of barrel planting by using three water stress treatments:normal treatment 75%~85%ofθf(θf is field moisture capacity)(CK),mild(W1)at 60%~70%ofθf,moderate(W2)at 50%~60%ofθf,and three stress durations:7 days(T1),10 days(T2),and 13 days(T3).Osmotic adjustment substances,antioxidant enzymes and photosynthetic indexes in leaves of summer maize seedlings during stress and rewatering were determined.The results showed that under mild and moderate stresses,the content of proline(Pro)showed a trend of increasing first and then decreasing.It peaked on the third day and increased by 32.7%and 44.1%,respectively,compared with the normal treatment.After rewatering,the cumulative amount of 10 day stress treatment was higher than that on 7 day stress treatment,but no significant cumulative effect on 13 day stress treatment.The activity of superoxide dismutase(SOD)increased first and then decreased during the stress period,and peaked on the third day,which increased by 22.0%and 12.4%,respectively,compared with the normal treatment.The activity was enhanced after rewatering,and the activity of 13 day stress treatment was higher than that of 10 day stress and 7 day stress.The activity of peroxidase(POD)increased first and then decreased under mild stress treatment,and peaked on the third day,which was 28.5%higher than that of normal treatment.But,under moderate stress treatment,POD activity showed a decreasing trend and was lower than normal treatment,and after rewatering,the enzyme activity returned to normal level.The content of malondialdehyde(MDA)increased during the stress period,and the longer the stress duration,the greater the increase was.Under the 13 day stress treatment,the MDA content under moderate and mild stresses increased by 140%and 281%compared with the normal treatment.After rewatering,the stress was relieved and the MDA content of all treatment groups returned to normal level.Under mild and moderate stresses,the net photosynthetic rate,stomatal conductance and transpiration rate of summer maize were 92.5%and 77.7%,93.9%and 74.3%,87.9%and 74.5%of normal treatment,respectively,and photosynthesis was restricted.After rewatering,the photosynthesis compensation effect appeared in the moderate stress treatment,and the photosynthesis indicators were higher than other treatments.This study indicated that maintaining soil water holding capacity of 50%to 60%in the field for 10 days was more suitable for the growth of the summer maize.After rewatering,it had a significant photosynthesis compensation effect.