棉纤维发育对温度反应极为敏感，棉纤维发育不同时期对高温胁迫的响应不同。随着全球温室化效应加剧及花铃期短期极端高温气象条件爆发日趋频繁，短期高温胁迫势将成为影响我国棉花高产、稳产、优质的重要自然灾害之一。因此，进行棉纤维发育响应短期高温胁迫的关键时间窗口及其生理变化研究可对棉花生产中适时、适度评估棉株胁变程度以及相应高温抗逆栽培技术的制定提供理论依据，为提高我国原棉供给保障能力做出重要贡献。本研究以温度敏感性不同的两个棉花品种为材料(温度弱敏感性品种：2013年为科棉1号，2014年为美国品种PHY370WR；温度敏感性品种：两年均为苏棉15。下同)，于2013年和2014年在南京农业大学进行盆栽试验，试验通过人工气候室模拟自然温周期设置高温(34℃[38/30℃]，HT下同)和对照(26℃[30/22℃]，CK下同)两个温度处理，通过研究不同起始时间高温处理5天条件下，棉花主要品质指标变化以及棉纤维发育相关生理指标的变化，以明确棉纤维发育响应短期高温胁迫的关键时间窗口及其生理变化。主要研究结果如下： 1.不同起始时间短期高温胁迫下棉纤维品质的变化以及棉纤维发育响应高温胁迫的关键时间窗口的确定 在不同起始时间日均温34.0℃持续处理5天条件下，温度敏感性品种纤维长度变短，纤维比强度上升马克隆值下降并偏离最适范围，纤维品质变差，两年结果一致。2013年温度敏感性品种苏棉15的纤维长度，纤维比强度，马克隆值响应高温胁迫的关键时间窗口分别为花后0—18.3天，花后10.9—26.1天和花后10.5—34.0天。2014年分别为花后0—20.6天，花后13.5—27.1天和花后11.2—33.2天。温度弱敏感型品种科棉1号及PHY370WR的上述纤维品质指标与敏感性品种苏棉15变化趋势一致、敏感时间窗口相近，仅品质指标变化幅度相对较小。上述结果表明：短期高温胁迫会导致棉纤维的最终纤维品质的变劣，花后10天到20天左右是棉花综合纤维品质形成响应高温胁迫的关键时间窗口。 2.不同起始时间高温处理对棉铃对位叶“源能力”的影响 2013年和2014年，在不同起始时间日均温34.0℃持续处理5天条件下，两棉花品种净光合速率下降，叶绿素a和叶绿素b总量下降，叶绿素a与叶绿素b的比值上升。在花后10天，15天，20天三个不同起始时间点进行高温处理，温度敏感性品种棉铃对位叶中的蔗糖含量、可溶性糖含量、氨基酸含量均下降，淀粉含量上升。温度弱敏感型品种上述棉铃对位叶源能力指标变化趋势与温度敏感性品种一致，仅变化幅度较小。综上所述：不同起始时间日均温34℃高温处理5天条件下，棉铃对位叶的“源能力”会受到影响。关键时间窗口范围内短期高温处理对棉纤维品质造成的不良影响有可能是部分通过影响棉铃对位叶光合同化物的产生、转运与分配而实现的。 3.不同起始时间高温处理对纤维发育相关物质含量和酶活性的影响 两年试验中，在花后10天，15天，20天三个不同起始时间进行日均温34.0℃高温处理持续5天条件下，温度敏感性品种纤维中的蔗糖含量相对常温条件下呈先降低后增加变化趋势，胼胝质含量上升，纤维素含量下降，蔗糖合成酶(分解方向)活性、磷酸蔗糖合成酶活性、β-1,3-葡聚糖酶活性均呈先升后降趋势，酸性蔗糖酶活性降低。温度弱敏感型品种的上述棉纤维发育相关酶活性与敏感性品种苏棉15变化趋势一致，仅变化幅度相对较小。因此，关键时间窗口下短期高温胁迫对棉纤维发育过程中相关物质含量和酶活性的变化的影响，同样是短期高温处理导致纤维品质变差的内在生理因素。

Fiber development is extremely sensitive to temperature, and at different developmental stage it has different responses to heat (high temperature) stress. With global warming, more and more extreme weather of high temperature happened world widely. Short-term high temperature stress would become one of the most important natural disasters which would impact the production and quality of China Cotton Belt. Therefore, the study of key time region of fiber quality formation and its mechanism in response to short-term higher temperature stress can help us timely and moderately assess the tolerant rang of cotton under this stress, and provide a theoretical basis for the arise of high temperature resilience cultivation techniques. It will also make a good contribution to China''''s ability of cotton supply. By taking two cotton cultivars with different temperature-sensitivity (Sumian 15, temperature-sensitive cultivar and Kemian 1, temperature-insensitive cultivar in 2013, PHY370WR temperature-insensitive cultivar form USA in 2014) as materials, a experiment with two different temperatures regimes (high temperature: 34℃[38/30℃], HT and control: 26℃[30/22℃], CK) were set in climate chamber in Nanjing Agricultural University to study the changes of the key physiological matters and fiber qualities in different genotypes in response to high temperature, In order to study key time region of fiber quality formation and physiological changes in response to short-term high temperature stress. The main findings are as follows: 1. Changes of cotton fiber quality in response to the high temperature stress which stared at different DPAs and the determination of key time region for fiber quality formation. As treated in the 34.0℃ high-temperature regime for 5 days at different DPA, significant changes in fiber quality would be observed in the temperature-sensitive cultivar Sumian 15. Fiber length decreased, while fiber strength increased and Micronaire decreased, and the general fiber quality deteriorated. The “key time region” of 2013 for fiber length, fiber strength and Micronaire in response to the high temperature stress were 0 to 18.3 DPA, 10.9 to 26.1 DPA and 10.5 to 34.0 DPA, respectively. The “key time region” of 2014 for fiber length, fiber strength and Micronaire in response to the high temperature stress were 0 to 20.6 DPA, 13.5 to 27.1 DPA and 11.2 to 33.2 DPA, respectively. Similar changes and trends could also be observed in the temperature-insensitive cultivar except that the variation degree was comparatively lower. So it could be concluded that the general fiber quality deteriorated by high temperature stress and the “key time region” of cotton fiber development in response to high temperature stress was around 10 to 20 DPA. 2. Effect of high temperature stress which stared at different DPAs on the photosynthesis ability of subtending leaves As treated in the 34.0℃ high-temperature regime for 5 days at different DPA in 2013 and 2014, the net photosynthetic rate and the total chlorophyll a content and chlorophyll b content of leaves subtending to boll in two cotton cultivar decreased, while the ratio of chlorophyll a and chlorophyll b increased. When subjected the two different temperature-sensitivity cotton cultivar to the high temperature stress at the “key time region”, the content of sucrose, soluble sugar, amino acid in subtending leaves of the temperature-sensitive cultivar all decreased, while the content of starch increased. Similar changes and trends could also be observed in the temperature-insensitive cultivar except that the variation degree was comparatively lower. So it could be concluded that the “source capacity” of leaves subtending to boll affected by the high temperature stress which stared at different DPAs, and the production, transport and distribution of photoassimilate in leaves subtending to boll affected by the high temperature stress at the “key time region”. 3. Effect of high temperature stress which stared at different DPAs on the substance content and enzyme activity related to fiber development When force two temperature-sensitive type cotton cultivar to the high temperature stress at the “key time region” in 2013 and 2014, the content of sucrose in fiber decreased firstly then increased as compared with those in control, the content of callose increased and cellulose decreased. While the activity of sucrose synthase, sucrose phosphate synthase andβ-1,3-gulcanase all decreased firstly then increased, and the activity of acidic invertase decreased as compared with those in control. Similar changes and trends could also be observed in the temperature-insensitive cultivar except that the variation degree was comparatively lower. So we speculate that the changes of substance content and enzyme activity related to fiber development would be effected by the high temperature stress at the “key time region”, and then affect fibroblasts cellulose synthesis and accumulation, and ultimately affect the quality of fiber formation.