Abstract Complex phytohormonal analyses revealed hormone changes underlying the freezing response of perennial ryegrass (Lolium perenne L.). Comparisons among sensitive (code of accession 1/61), highly tolerant (5/101) and semi-tolerant (6/104; sensitive without acclimation, but tolerant after acclimation) genotypes allowed identification of changes associated with freezing tolerance. The main response to freezing stress (−7 °C for four days) was a significant elevation of abscisic acid (ABA) in all tissues of all genotypes, supported by elevation of jasmonic acid (JA) in leaves, and of salicylic acid (SA) in crowns and roots. Jasmonate-isoleucine increase was observed in roots of the tolerant genotype. The auxin (indole-3-acetic acid) levels showed relatively minor changes, while cytokinins exhibited up-regulation in crowns of sensitive genotypes. Tolerant genotypes exhibited decreased levels of highly active cytokinin trans-zeatin compensated by elevated low-active cis-zeatin, involved in stress responses. Cold acclimation (3 °C for seven days) applied prior frost treatment was associated with stimulation of plant defences, especially expression of ice recrystallisation inhibition protein LpIRI3. Acclimation diminished the impact of subsequent freezing treatment as indicated by lower up-regulation of stress hormones ABA, JA and SA in all tested tissues (with the exception of SA in crowns and roots of sensitive genotype) and up-regulation of active cytokinins in tolerant and semi-tolerant genotypes, especially in crowns and roots.

中文翻译：

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多年生黑麦草适应冰冻胁迫的激素反应

摘要 复杂的植物激素分析揭示了多年生黑麦草 (Lolium perenne L.) 冷冻反应背后的激素变化。敏感（加入代码 1/61）、高度耐受（5/101）和半耐受（6/104；未经驯化敏感，但驯化后耐受）基因型之间的比较允许鉴定与冷冻耐受性相关的变化。对冷冻胁迫（-7 °C 持续四天）的主要反应是所有基因型的所有组织中脱落酸 (ABA) 的显着升高，这得到叶子中茉莉酸 (JA) 和水杨酸 (SA) 的升高的支持) 在冠和根。在耐受基因型的根中观察到茉莉酸-异亮氨酸增加。生长素（吲哚-3-乙酸）水平显示出相对较小的变化，而细胞分裂素在敏感基因型的冠中表现出上调。耐受基因型表现出高活性细胞分裂素反式玉米素水平降低，由升高的低活性顺式玉米素补偿，参与应激反应。在霜冻处理之前应用冷驯化（3°C 7 天）与植物防御的刺激有关，尤其是冰重结晶抑制蛋白 LpIRI3 的表达。驯化降低了随后冷冻处理的影响，这表现为所有测试组织中应激激素 ABA、JA 和 SA 的上调降低（敏感基因型的冠和根中的 SA 除外）和耐受中活性细胞分裂素的上调和半耐受基因型，尤其是在冠和根中。在霜冻处理之前应用冷驯化（3°C 7 天）与植物防御的刺激有关，尤其是冰重结晶抑制蛋白 LpIRI3 的表达。驯化降低了随后冷冻处理的影响，这表现为所有测试组织中应激激素 ABA、JA 和 SA 的上调降低（敏感基因型的冠和根中的 SA 除外）和耐受中活性细胞分裂素的上调和半耐受基因型，尤其是在冠和根中。在霜冻处理之前应用冷驯化（3°C 7 天）与植物防御的刺激有关，尤其是冰重结晶抑制蛋白 LpIRI3 的表达。驯化降低了随后冷冻处理的影响，这表现为所有测试组织中应激激素 ABA、JA 和 SA 的上调降低（敏感基因型的冠和根中的 SA 除外）和耐受中活性细胞分裂素的上调和半耐受基因型，尤其是在冠和根中。