Cotton (Gossypium hirsutum L.) cultivars exhibit varying responses to heat stress. To investigate the heat resistance of various cotton and establish an index system for evaluating their heat resistance, 21 cotton cultivars were selected and subjected to two temperature regimes (CK, average temperature 28°C, 32/24°C; HT, average temperature 38°C, 42/34°C). The results showed that under high temperatures, different changes occurred in individual indexes of cotton, reflecting the differences in heat resistance in cotton cultivars. A total of 21 cotton cultivars could be classified into four types: heat‐tolerant, moderate heat‐tolerant, moderate heat‐sensitive and heat‐sensitive cultivars by multivariate statistical analysis. Moreover, the indexes of net photosynthetic rate (Pn), leaf superoxide dismutase activity (LSOD), the maximum photochemical quantum yield (Fv/Fm), the actual photochemical quantum yield (ΦPSII), leaf malondialdehyde content (LMDA), leaf catalase activity (LCAT), dry matter weight of shoot (SDW) and root malondialdehyde content (RMDA) were determined to be useful for evaluating the cotton heat tolerance by stepwise regression analysis. The pot experiment showed that the reduction of boll number, boll weight and seed cotton yield was more remarkable under HT in the heat‐sensitive cultivar CCRI‐92 than in the heat‐resistant cultivar CCRI‐69, which further verified the screening results. In conclusion, the heat‐sensitive cultivars CCRI‐92 and heat‐resistant cultivar CCRI‐69 which are identified by seedling experiment could serve as ideal experimental materials for studying heat resistance in cotton. The physiological indices such as Pn, LSOD, Fv/Fm, ΦPSII, LMDA, LCAT, SDW and RMDA be employed for assessing the heat tolerance in cotton.

中文翻译：

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棉花耐热性指标综合评价及筛选鉴定指标

棉布 （陆地棉L.) 品种对热应激表现出不同的反应。为考察不同棉花的耐热性，建立评价其耐热性的指标体系，选取21个棉花品种，进行2种温度试验（CK，平均温度28℃、32/24℃；HT，平均温度38℃）。 °C，42/34°C）。结果表明，高温下，棉花个体指标发生不同变化，反映了棉花品种耐热性的差异。通过多元统计分析，将21个棉花品种分为耐热、中度耐热、中度热敏和热敏感品种4个类型。此外，净光合速率指标（磷n）、叶片超氧化物歧化酶活性（LSOD）、最大光化学量子产率（Fv/F米），实际光化学量子产率（ΦPSII）、叶片丙二醛含量（LMDA）、叶片过氧化氢酶活性（LCAT）、地上部干物质重量（SDW）和根丙二醛含量（RMDA）通过逐步回归分析确定可用于评估棉花耐热性。盆栽试验表明，高温处理下热敏品种CCRI-92比耐热品种CCRI-69的铃数、铃重和籽棉产量降低更为显着，进一步验证了筛选结果。综上所述，通过育苗试验鉴定出的热敏品种CCRI-92和耐热品种CCRI-69可以作为研究棉花耐热性的理想实验材料。生理指标如磷n, LSOD,Fv/F米,ΦPSII、LMDA、LCAT、SDW 和 RMDA 用于评估棉花的耐热性。