棉花叶片响应高温的差异与夜间淀粉降解密切相关

Different response of cotton leaves to heat stress is closely related to the night starch degradation

叶片对光合产物的转运输出是其源能力的重要体现,高温胁迫导致的源能力不足是棉花减产降质的重要原因之一。为探究棉花对位叶光合产物输出能力对短期高温胁迫的响应及其在不同热敏感性品种间的差异,本研究以耐热型棉花品种PHY370WR和热敏感型棉花品种苏棉15为材料,于2015—2016年在南京农业大学牌楼试验站进行盆栽试验,在棉花花铃期设置持续5 d的温度处理[对照日均温为26℃(CK,昼夜温度循环为30/22℃),高温处理日均温为34℃(HT,昼夜温度循环为38/30℃)],在高温胁迫5 d和胁迫解除后5 d对叶片光合产物输出能力和光合产物含量进行研究。结果表明,高温胁迫5 d显著降低棉花铃重,提高对位叶比叶重,耐热型棉花品种PHY370WR铃重降低幅度及比叶重升高幅度均较热敏感型棉花品种苏棉15低。^(13)C标记光合产物的结果表明,高温5 d显著降低棉花叶片光合产物的输出效率,与CK相比,苏棉15的降幅为22.1%,下降斜率为-2.48,显著高于PHY370WR的降幅15.7%和下降斜率-1.82;恢复5 d后棉花叶片光合产物输出效率降低幅度变小,但品种间差异由高温5 d时的6.4%增加为胁迫解除后5 d的10.2%,且苏棉15的恢复斜率仅为0.44,远小于PHY370WR的0.89。此外,与高温5 d时相比,恢复5 d后蔗糖含量日变化幅度的品种间差异减小,而淀粉含量日变化幅度品种间差异表现为增大,与碳水化合物输出效率的趋势一致,相关性分析亦表明,高温胁迫5 d及恢复5 d时淀粉含量日变化幅度与碳水化合物输出效率相关性更显著。通过大田试验和盆栽试验确定淀粉最大、最小含量出现时间,在此基础上进一步分析发现,在高温胁迫5 d及胁迫恢复后5 d,淀粉日最小(夜间)含量升高幅度品种间差异较日最大(白天)含量降低幅度更为显著,且恢复后5 d时品种间差异较高温5 d时显著增大。综上,热敏感性差异的棉花叶片碳水化合物输出效率对高温胁迫响应的差异不仅表现在胁迫发生时,更表现在胁迫解除后;耐热型棉花品种PHY370WR的叶片在高温胁迫发生时及胁迫恢复后表现出更强的抵御高温逆境能力及更好的恢复能力,与其夜间淀粉降解能力即叶片最小(夜间)淀粉含量增加幅度较小密切相关。

The export rate of photosynthetic products from leaves is an important manifestation of their source capacity.Heat induced source capacity shortage is one of the major reasons for cotton yield reduction and quality deterioration.To explore the difference and mechanism of leaf carbohydrate export in response to short-term heat stress between cotton cultivars with different heat sensitivity,pot experiments were carried out using two cotton cultivars PHY370WR(heat tolerance)and Sumian 15(heat sensitivity)as experimental materials in 2015 and 2016.Two temperature treatment(CK,average temperature 26℃;HT,average temperature 34℃)was conducted at flowering and boll forming stages lasting for five days.Results showed that cotton boll weight was significantly decreased and specific leaf weight was increased by HT.The reduction of boll weight and increase of specific leaf weight of PHY370WR were lower than that of Sumian 15.The results of ^(13)C labeled photosynthetic products showed that the carbohydrate export efficiency(CEE)of cotton leaves was significantly reduced by HT.Compared with CK,the decrease rate of CEE in Sumian 15 was 22.1%and the decline slope was-2.48,significantly higher than that of PHY370WR by 15.7%and-1.82,respectively.The decrease after five days of recovery in CEE diminished,but the differences at five days of HT between varieties were increased from 6.4%to 10.2%compared with at five days after HT released.The recovery slope of CEE in Sumian 15 was only 0.44,far less than 0.89 of PHY370WR.In addition,compared with HT,the difference of daily variation amplitude of sucrose content was decreased and the difference of daily variation amplitude of starch content was increased between cultivars after five days recovery.The latter was consistent with the trend of CEE in response to HT.Correlation analysis revealed that starch content of daily variation amplitude was more significantly correlated with CEE than sucrose.Further analysis showed that at both five days of HT and five days after HT released,the difference of increase in the minimum(night)starch content between cultivars was more significant than that of decrease in the maximum(day)starch content.The differences between cultivars at five days after HT released were significantly larger than that at five days of HT.In conclusion,there were the differences of cotton leaf CEE with different heat sensitivities not only during high temperature stress but also after the relief of stress.The heat tolerant cultivar PHY370WR indicated stronger resistance to HT and better recovery ability after HT released,which was closely related to a better starch degradation ability with a less increase in the minimum starch content in leaves at night.