夏玉米光合特性及产量对花期高温胁迫的响应

Responses of photosynthetic characteristics and yield of summer maize to high temperature stress during flowering

  • 摘要: 【目的】探讨花期高温胁迫对夏玉米田间温湿状况、叶片光合特性、水分利用效率及产量构成的影响,为夏玉米抗高温栽培提供理论依据。【方法】以玉米耐热型品种浚单20(XD20)和热敏感型品种农华101(NH101)为试验材料,利用聚烯烃(PO)薄膜温室模拟花期高温,以大田常温处理为对照(CK),于抽雄期设置连续10 d的模拟高温胁迫处理(HT),测定不同处理的田间空气温湿状况及夏玉米叶片光合特性、水分利用效率和产量。【结果】玉米田间空气温度和饱和水汽压差日变化均呈早晚低而平稳、日间高而波动的单峰曲线,且日间时段冠层高于穗层;相对湿度日变化呈早晚高而平稳、日间低而波动的单谷曲线,且日间时段冠层低于穗层。2个处理的田间实际水汽压和空气焓值日变化趋势不一致,CK处理下日变化趋势不明显,早中晚差异较小,而HT处理下日变化呈早晚低而平稳、日间高而波动的单峰曲线,日间显著高于夜间;HT处理增强了田间实际水汽压和空气焓值与空气温度和相对湿度的关联性。高温处理期间,与CK相比,HT处理提高了日间空气温度、增大了上午时段的饱和水汽压差,引起蒸散增强,进而使得田间相对湿度、实际水汽压和空气焓值增加,且冠层的增幅大于穗层,进而影响2个品种叶片的光合性能。高温处理期间,HT处理导致XD20和NH101穗位叶气孔导度、胞间CO2浓度和蒸腾速率分别平均增加36.60%、157.20%、19.72%和41.67%、143.90%、27.08%,叶片羧化效率、气孔限制值、瞬时水分利用效率和内在水分利用效率平均降低59.61%、29.94%、25.08%、31.65%和63.09%、31.00%、33.54%、33.45%,而净光合速率随空气温度变化而波动,造成植株整体光合性能下降。高温胁迫结束后,随玉米生育进程推进,HT处理的穗位叶各光合参数均能逐渐恢复至CK水平。HT处理导致玉米植株生育后期的干物质积累量显著降低(P<0.05,下同),穗粒数显著减少,百粒重略有增加,但籽粒产量显著下降。与CK相比,HT处理下XD20穗粒数和产量分别降低33.55%和35.49%,NH101则分别降低36.89%和37.63%,NH101的降幅大于XD20。【结论】高温胁迫下空气升温快、温度高且水汽压差大,增强了农田蒸散,使得田间相对湿度、实际水汽压和空气焓值增加,导致玉米叶片气孔导度增大、蒸腾散热增强,水分利用效率降低,气孔限制值降低而胞间CO2浓度增加,叶片羧化效率降低且净光合速率随空气温度波动,造成植株整体光合性能下降,干物质积累量显著降低,进而导致穗粒数减少、籽粒产量显著降低。热敏感型品种农华101减产幅度大于耐热型品种浚单20。

     

    Abstract: 【Objective】To explore the effects of high temperature stress during flowering on the temperature and humidity conditions in summer maize fields, photosynthetic characteristics of leaves, water use efficiency and yield composition,which could provide theoretical basis for high-temperature resistant cultivation of summer maize. 【Method】This study used heat resistant variety Xundan 20(XD20)and heat sensitive variety Nonghua 101(NH101)as materials,and a polyolefin(PO) film greenhouse was used to simulate high temperature during flowering, with field normal temperature treatment as the control(CK). A continuous 10 d simulated high temperature stress treatment(HT) was set at the tasseling stage to determine the field air temperature and humidity conditions, leaf photosynthetic characteristics, water use efficiency, and yield of summer maize under different treatments. 【Result】The daily changes of air temperature and water vapor pressure difference in the maize field showed a single peak curve of low and stable in the morning and evening,and high and fluctuating during the day,and the canopy was higher than the ear layer during the day. The daily variation of relative humidity showed a single valley curve with high and stable morning and evening,and low and fluctuating daytime,and the canopy was lower than the panicle during the daytime period. The daily variation trends of actual water vapor pressure and enthalpy values in the fields of the 2 treatments were inconsistent. Under CK treatment,the daily variation trend was not obvious,and the difference in morning,noon and evening was small. However,under HT treatment,the daily variation showed a single peak curve with low and stable morning and evening,and high and fluctuating day,which was significantly higher during the day than at night;HT treatment enhanced the correlation between actual field water vapor pressure and enthalpy values with temperature and relative humidity. During the high-temperature treatment period,compared with CK,HT treatment increased daytime air temperature and increased the water vapor pressure difference in the morning,leading to increased evapotranspiration. This in turn led to an increase in field relative humidity,actual water vapor pressure and enthalpy values,and the increase in canopy was greater than that in spike layer,affecting the photosynthetic performance of the leaves of the 2 varieties. During high-temperature treatment,HT treatment increased the stomatal conductance,intercellular CO2 concentration and transpiration rate of XD20 and NH101 ear leaves by 36.60%,157.20%,19.72%,and 41.67%,143.90%, 27.08% respectively. The leaf carboxylation efficiency,stomatal limit value,instantaneous water use efficiency and intrinsic water use efficiency decreased by 59.61%,29.94%,25.08%,31.65%,and 63.09%,31.00%,33.54%,33.45% on average,while the net photosynthetic rate fluctuated with air temperature,causing a decrease in the overall photosynthetic performance of the plant. After the end of high temperature stress,as the growth process of maize progresses,the photosynthetic parameters of the ear leaves treated with HT could gradually recover to the CK level. HT treatment resulted in a significant decrease in the dry matter accumulation in the late growth stage of maize plants(P<0.05, the same below) and the number of grains per spike, a slight increase in 100-grain weight,but a significant decrease in grain yield. Compared with CK,under HT treatment,the number of grains per ear and yield of XD20 decreased by 33.55% and 35.49% respectively,while NH101 decreased by 36.89% and 37.63% respectively. The decrease in NH101 was greater than that of XD20. 【Conclusion】High temperature stress leads to faster air heating,higher temperature and larger vapor pressure deficit. This enhances farmland evapotranspiration,leading to an increase in relative humidity,actual water vapor pressure and enthalpy in the field. These conditions increase stomatal conductance,enhance transpiration heat dissipation,decrease water use efficiency,lower stomatal limit values,and raise intercellular CO2 concentration. Additionally,leaf carboxylation efficiency declines,and net photosynthetic rate fluctuates with air temperature. Collectively,these changes reduce the overall photosynthetic performance of the plants,significantly decrease dry matter accumulation,and consequently reduce the number of grains per ear and cause a significant reduction in grain yield. The yield reduction of the heat sensitive variety NH101 is greater than that of the heat tolerant variety XD20.

     

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