干旱对不同授粉方式玉米籽粒生长和光合特性的影响

玉米早期籽粒建成过程中干旱胁迫会导致果穗顶部籽粒的败育,使穗粒数降低,进而减少玉米产量.为探明干旱胁迫对玉米籽粒生长发育影响的生理机制,利用旱池控水和控制授粉技术,在授粉后前10 d设置轻度干旱、中度干旱和正常供水3个处理,研究了2个玉米品种统一完全授粉和底部不授粉植株籽粒生长和光合特性等.结果表明,干旱胁迫使玉米的光合速率(Pn)和叶绿素相对含量(SPAD值)显著降低,复水后二者均恢复到正常.干旱胁迫降低了植株干重、穗重和穗粒重,水分胁迫期间植株干重的降低幅度相对明显.干旱胁迫使统一完全授粉处理玉米顶部籽粒干重和体积分别在授粉后12～16或16d显著或极显著下降,最终表现为败育或灌浆不充实,导致籽粒干重和体积的显著降低.而底部不授粉玉米由于从根本上阻止了底部籽粒的生长,确保了中上部籽粒有相对充足的同化物供应,干旱胁迫处理顶部籽粒生长发育正常.说明籽粒建成初期需要光合产物的持续供应,干旱胁迫通过降低同化物生产而增大了籽粒败育与生长不良的可能性,同化物供应不足是干旱胁迫诱导玉米籽粒败育和生长不良的根本原因.

Effects of drought stress on maize kernel growth and photosynthetic characteristics under different pollination types

Drought stress during early kernel growth and development can induce the kernel abortion and decrease kernel number per ear and then reduce the yield in maize (Zea may L.).In order to clarify the physiological mechanism of drought stress on maize kernel abortion,we conduct this experiment with three water treatments including normal water supply,mild stress and moderate stress using the control pollination technique under precipitation control condition.The results showed that drought stress decreased photosynthetic rate (P_n) and relative chlorophyll content (SPAD),and they returned to normal after water supply.Drought stress reduced plant dry weight,ear dry weight and ear kernel dry weight,and the range of decrease in plant dry weight was obvious compared to ear dry weight and ear kernel dry weight.Drought stress significantly decreased the apical kernel dry weight and volume of complete pollination maize at 12-16 d after pollination (DAP) or 16 DAP,respectively,and finally aborted or grew abnormally,as a result,the dry weight and volume of apical kernel at maturity stage decreased significantly.However,the apical kernel of no-pollination in ear basal position grew normally under drought stress condition,because it prevented the ovary development in ear basal position and ensured the relatively plentiful supply of assimilates for apical kernels.These data indicate that maize kernel growth and development need continuous supply of assimilates at early stage,drought stress increase the probability of developmental failure and abnormal growth of the apical kernels by reducing assimilates generation,the shortage of assimilates supply may be the fundamental reason of kernel abortion and kernel abnormal growth.