Attenuation of low-temperature stress in rice seedlings

ABSTRACT Rice is a cold-sensitive crop, and its exposure to low-temperature stress, during germination and early seedling growth, can negatively affect the initial stand establishment. Substances that act as growth regulators can be used to mitigate this initial stress. Thus, the influence of gibberellic acid, thiamethoxam and a phytohormone was investigated at the growth variables and antioxidant enzyme activity of the 'Irga 424' and 'Puita Inta CL' rice cultivars, at low-temperature (17 ºC). The products act on the germination percentage of 'Puita Inta CL', but vigor is only influenced by giberellic acid. Giberellic acid influences shoot length, irrespective of cultivar, while thiamethoxam and the phytohormone only affect length in 'Puita Inta CL'. The antioxidant activity depends on the cultivar and organ tested (shoot or root). These products mitigate the effects of cold, thereby preventing the formation of reactive-oxygen species and lipid peroxidation, and positively influence the superoxide dismutase enzyme activity.

摘要 水稻是冷敏感作物，在发芽及幼苗早期生长阶段遭遇低温胁迫时，会对其初始建苗产生负面影响。可通过施用生长调节物质缓解此类初始胁迫。为此，本研究探究了赤霉素（gibberellic acid）、噻虫嗪（thiamethoxam）及一种植物激素（phytohormone）对‘Irga 424’与‘Puita Inta CL’两个水稻品种在低温（17℃）条件下的生长性状及抗氧化酶活性的影响。结果表明，上述药剂对‘Puita Inta CL’的发芽率具有调控作用，但仅赤霉素会影响其种子活力。赤霉素可不受品种限制地影响幼苗地上部长度，而噻虫嗪与该植物激素仅对‘Puita Inta CL’的地上部长度产生影响。抗氧化活性因品种及检测器官（地上部或根部）的不同而存在差异。这些药剂能够缓解低温胁迫带来的损伤，具体表现为抑制活性氧（reactive-oxygen species）的生成与脂质过氧化反应，并可正向提升超氧化物歧化酶的酶活性。