干旱对夏玉米籽粒充实和生理特性的影响及其外源亚精胺调控

为明确干旱胁迫影响灌浆期籽粒充实的生理机制,以及喷施外源亚精胺(Spd)缓解干旱胁迫的作用效果,本研究以强抗旱性玉米品种郑单958和弱抗旱性玉米品种蠡玉16为材料,利用具有遮雨棚的隔离池严格控制土壤水分条件,设置吐丝期土壤干旱胁迫和外源Spd喷施组合试验,分析外源Spd对干旱胁迫下玉米叶片抗氧化物酶活性、叶绿素荧光参数、灌浆期籽粒内源激素含量和籽粒充实的影响。结果表明,干旱胁迫显著降低了两品种穗位叶PSⅡ最大光化学效率(F_v/F_m)和PSⅡ潜在活性(F_v/F_o),使丙二醛(MDA)积累量增加了16.95%~23.16%,超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性降低了11.93%~26.69%。同时,干旱胁迫下籽粒中Spd和脱落酸(ABA)含量显著提高15.79%~22.28%,玉米素和玉米素核苷(Z+ZR)和吲哚乙酸(IAA)含量降低10.39%~13.30%,最终影响灌浆期籽粒充实,造成蠡玉16和郑单958的粒重分别降低36.33和24.03 mg。喷施外源Spd可缓解干旱对穗位叶F_v/F_m和F_v/F_o的影响,有助于弱化干旱对细胞膜的氧化损伤,提高灌浆期粒重5.60~11.74,蠡玉16和郑单958的最终粒重分别提高了11.74和9.11 mg,但外源Spd对籽粒中内源激素含量的影响不显著。此外,干旱胁迫下强抗旱性品种郑单958具有较高的F_v/F_m、F_v/F_o和抗氧化物酶活性,以及较低的MDA积累,而喷施外源Spd对弱抗旱性品种蠡玉16具有更强的调控效应,建议在生产中应用外源Spd时,应结合品种的抗旱特性选择合适的喷施时间以利于籽粒灌浆和产量形成。本研究为玉米抗旱栽培提供了理论依据和技术支持。

Effect of Drought Stress on Grain-Filling and Physiological Properties of Summer Maize and the Exogenous Spermidine Regulation

To clarify the physiological mechanism of drought stress on grain filling and the effect of spraying exogenous spermidine (Spd) on alleviating drought stress, maize varieties with strong drought-resistance, Zhengdan958 and weak drought-resistance, Liyu16 were used as research materials and cultivated in the isolated pool with rain shelter in order to control soil-water conditions. And the combined experimental treatments of soil drought stress and spraying exogenous Spd at silking stage were conducted to analyze the influences of exogenous Spd on antioxidant enzyme activities and chlorophyll fluorescence parameters of leaves, endogenous hormone content and grain plumpness during grain filling. The results indicated that drought stress significantly reduced F_v/F_m and F_v/F_o, increased malondialdehyde (MDA) accumulation by 16.95%~23.16%, but decreased superoxide dismutase (SOD), peroxidase (POD) and hydrogen peroxidase (CAT) activities by 11.93%~26.69% of ear leaves for two maize varieties. Simultaneously, drought stress significantly increased the Spd and abscisic acid (ABA) contents by 15.79% ~ 22.28%, and decreased zeatin and zeatin riboside (Z+ZR) and indole-3-acetic acid (IAA) contents by 10.39% ~ 13.30%, then finally affected the grain plumpness at grain filling stage, resulting in a decrease of 36.33 and 24.03 mg in grain weight for Liyu16 and Zhengdan958, respectively. Spraying exogenous Spd alleviated the effects of drought stress on F_v/F_m and F_v/F_o of ear leaves, contributed to weakening the oxidative damage for cell membrane, and increased the grain weight of 5.60~11.74 mg during grain filling stage. The final grain weight of Liyu16 and Zhengdan958 increased by 11.74 and 9.11 mg, respectively. However, exogenous Spd had no significant effect on endogenous hormone contents in grains. In addition, Zhengdan958 with strong drought-resistance had higher F_v/F_m, F_v/F_o and antioxidant enzyme activities, lower MDA accumulation under drought stress, whereas spraying exogenous Spd had a stronger regulatory effect on Liyu16 with weak drought-resistance. It is suggested that when applying exogenous Spd in maize production, the suitable spraying time should be selected according to the drought-resistance characteristics of varieties to facilitate grain filling and yield formation. This study provides theoretical basis and technical support for drought-resistant cultivation of maize.