低温胁迫对水稻胚芽中葡萄糖和水分状态的影响及其与种子出苗成活间的关系

Effect of low-temperature stress on glucose and water status in rice germ and its relationship with seedling emergence

为了探明低温逆境下水稻种子出苗成活的品种间差异,解析水稻芽苗期耐低温机理,本研究以4个低温耐性不同的品种为试验材料,设置低温和常温2个处理,分析了水稻出苗过程中种子和胚芽组织的碳水化合物含量、含水量,种子的α-淀粉酶、胚芽蔗糖合酶和抗氧化酶活性,胚芽的过氧化氢与丙二醛含量随时间的变化,及其与胚芽存活率的相关性。研究发现,低温下冷敏感品种中嘉8号(S1)、中嘉早17(S2)胚芽的葡萄糖含量、抗氧化酶(SOD、POD、CAT)比蛋白活性在低温4 d后显著下降,而H2O2、MDA含量逐渐增加,其胚芽尖端逐渐枯死卷曲;而耐冷品种日本晴(T1)、耘两优玖48(T2)的胚芽葡萄糖含量维持在一个较高水平,抗氧化酶(SOD、POD、CAT)比蛋白活性、H2O2、MDA含量也都保持不变,其胚芽保持挺立生长状态。分析发现低温抑制了种子的α-淀粉酶活性,但增加了胚芽的蔗糖合酶活性;低温延缓了耐冷品种T1和T2的胚根向种子根发育的进程,却抑制了冷敏感品种S1和S2胚根的发育,低温下冷敏感品种S1、S2的根系活力显著低于耐冷品种T1、T2,冷敏感品种S1、S2种子和胚芽的含水量随低温时间的延长不断降低,而耐冷品种T1、T2相对稳定。相关分析发现,胚芽的存活率与胚芽和种子的葡萄糖含量、含水量和胚根的长度、体积、活力呈极显著正相关,但与种子中淀粉和胚芽中蔗糖的含量呈极显著负相关。外源增加S1、S2的水分供应能够显著地提高种子和胚芽在低温下的存活率。上述结果表明,在种子出苗过程中,低温胁迫在抑制种子α-淀粉酶活性的同时,也抑制了胚根的生长发育,降低了根系向种子和胚芽运输水分的能力,导致种子中淀粉和胚芽中蔗糖的分解能力下降,胚芽葡萄糖供应不足,使得胚芽抗氧化代谢失衡、存活率降低,而外源增加水分供应可在一定程度上提高低温下胚芽的存活率。

To investigate varietal differences in rice germ survival and seedling emergence under low-temperature stress and to analyze the mechanisms of low-temperature tolerance during seedling emergence,germinated seeds of four rice varieties with different cold tolerance were used as experimental material and exposed to low temperature and ambient temperature(control)conditions.Carbohydrate and moisture content of seed and germ,seedα-amylase activity,sucrose synthase,antioxidant enzyme activity,hydrogen peroxide(H2O2)and malondialdehyde(MDA)content of germ during seedling emergence were analyzed over time,along with their correlation with germ survival.The study found that the glucose content and antioxidant enzyme activity(SOD,POD,and CAT)in the germ of the cold-sensitive varieties Zhongjia 8(S1)and Zhongjiazao 17(S2)decreased significantly after 4 days of cold treatment,while H2O2 and MDA contents increased gradually,leading to phenotypical stagnation of germ growth and symptoms of death under low-temperature stress.In contrast,the glucose content in the germ of cold-tolerant varieties Nipponbare(T1)and Yunliangyoujiu 48(T2)remained relatively high,and the enzyme activity of SOD,POD,and CAT,as well as H2O2 and MDA contents,remained stable after 8 days of cold treatment,allowing the germ to maintain upright growth.Analysis revealed that cold inhibited seedα-amylase activity but promoted germ sucrose synthase activity.Cold also delayed root development in cold-tolerant varieties T1 and T2 but inhibited root development in cold-sensitive varieties S1 and S2.Additionally,the root vigor of cold-sensitive varieties was significantly lower than that of cold-tolerant varieties,and the water content of seeds and germs in cold-sensitive varieties S1 and S2 decreased continuously,while that of cold-tolerant varieties T1 and T2 remained stable.Correlation analysis demonstrated that germ survival rate was significantly positively correlated with germ and seed glucose content,germ water content,CAT activity,root length,volume,and root vigor,but significantly negatively correlated with seed starch and germ sucrose content.Moreover,increasing water supply to S1 and S2 exogenously significantly improved their survival rate under low temperature.In conclusion,low-temperature stress not only inhibited seedα-amylase activity but also suppressed root growth and development,reducing the ability to transport water to seeds and germs.This,led to a decrease in the ability to degrade seed starch and germ sucrose during the seedling emergence process,resulting in inadequate glucose supply to germs,an imbalance in germ antioxidant metabolism,and reduced survival rate.However,exogenous increase in water supply could improve germ survival rate to some extent under low temperature.