不同品系高羊茅应答高温胁迫的初级代谢产物分析

为探讨高温对高羊茅初级代谢的影响，对耐热性不同的两个高羊茅基因型PI 578718(耐热)和PI 234881(热敏感)，进行40℃/35℃(昼/夜各12 h)模拟高温胁迫21 d，分别于不同时间段取样测定生理以及代谢产物的变化。结果表明，在高温胁迫下，草坪质量、叶绿素含量、叶片相对含水量、根系活力持续下降，电解质渗漏加剧，与耐热型基因型相比，热敏感基因型各生理指标变化更明显。通过GC-MS分析，检测并鉴定了25种初级代谢产物，主要包括有机酸和脂肪酸(9种)、氨基酸(9种)、糖类和糖醇(7种)，其中氨基酸(如脯氨酸、缬氨酸、谷氨酸)、糖类(如蔗糖)和糖醇(如肌醇)在叶片中大量积累，而有机酸和脂肪酸类(如柠檬酸、棕榈酸)在根系中大量积累。高温胁迫下叶片和根系中代谢产物如缬氨酸、谷氨酸、脯氨酸、蔗糖、肌醇、柠檬酸、棕榈酸含量的升高或维持，可能是耐热基因型PI 578718与热敏感基因型PI 234881之间耐热性差异的主要原因，而且柠檬酸作为抗氧化剂并参与呼吸作用的三羧酸循环途径，它的高积累，可能更有助于提高高羊茅对高温胁迫的耐性和适应性。

Differential metabolic responses of two tall fescue genotypes to heat stress

A study has been undertaken to investigate the effects of heat stress on the primary metabolites of tall fescue. The heat-tolerant genotype PI 578718 and the heat-sensitive genotype PI 234881 were treated with heat stress (40℃/35℃ for 12 h/12 h) for 21 days in order to determine changes in physiological parameters and metabolites. The results showed that grass quality, chlorophyll content, leaf relative water content, and root activity were all higher in the heat-tolerant PI 578718 than in the heat-sensitive PI 234881, while the value of leaf electrolyte leakage was lower in PI 578718. These results indicate that PI 578718 exhibited significantly more heat tolerance than PI 234881. Polar metabolite analysis of leaf and root using gas chromatography-mass spectrometry identified 25 heat-responsive metabolites in the two tall fescue genotypes, mainly consisting of organic acids, amino acids, sugars and sugar alcohols. Most of these metabolites showed higher accumulations in PI 578718 compared with PI 234881, especially following long-term (21 days) heat stress. The differentially accumulated metabolites, including a sugar alcohol (inositol), two organic acids (citric acid and hexadecanoic acid), one sugar (sucrose) and three amino acids (Val, Glu and Pro), may be positively associated with the differential heat tolerance of the two genotypes. Moreover, citric acid mainly served as an antioxidant and intermediate in respiration metabolisms. Its involvement in other defense pathways may play a vital role in tall fescue adaptation to heat stress.