高温干旱复合胁迫及复水对构树(Broussonetia papyrifera)幼苗光合特性和叶绿素荧光参数的影响

Effects of combined stress of elevated temperature and drought and of re-watering on the photosynthetic characteristics and chlorophyll fluorescence parameters of Broussonetia papyrifera seedlings

近年来,全球气温不断升高,亚热带部分地区夏季高温和临时性干旱现象日益显著,高温与干旱严重威胁着植物的生存与生长。本文通过设置不同的温度和土壤水分梯度,研究了高温与干旱复合胁迫及复水对构树幼苗光合特性和叶绿素荧光参数的影响。结果表明:高温干旱复合胁迫下,构树幼苗净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)、最大荧光(Fm)、PSII最大原初光化学量子效率(Fv/Fm)呈现下降趋势,初始荧光(F0)呈上升趋势;复合胁迫对Pn、Gs、Tr的影响具有叠加效应;胞间CO2浓度(Ci)、Gs、Fm和Fv/Fm受温度影响显著(P<0.05),Gs、Tr、F0受土壤水分影响显著(P<0.05),而Pn和F0受温度和土壤水分双因素影响显著(P<0.05);在25和33℃下,复水对胁迫具有一定的缓解作用,复水后光合特性和Fv/Fm有一定程度提升,对F0和Fm效果不明显。试验表明,复合胁迫对植物光合特性和叶绿素荧光参数的影响程度比单一胁迫大,且在一定温度范围内,复水对干旱胁迫具有缓解作用。

In recent years, with the global climate change, high temperature and temporal drought during summer seasons have increasingly taken place in some subtropical regions. Consequently, the survival and growth of plants are restrained under the combined stress of high temperature and drought. In the present study, at different controlled temperature and soil moisture levels, the combined stress of high temperature and drought on the photosynthetic characteristics and chlorophyll fluorescence parameters of Broussonetia papyrifera seedlings, as well as the alleviation role of re-watering, were measured. The results showed that, under the combined stresses, the net photosynthetic rate （Pn）, stomatal conductance （Gs）, transpiration rate （Tr）, maximal fluorescence （ Fm ）, optimal/maximal photochemical efficiency of PS 1I （ F/Fm ） of B. papyriferas seedlings presented a decreasing tendency, while minimal fluorescence （ F0） presented an increasing tendency. Combined stress showed synergistic effects on Pn, Gs, and T. The parameters such as intercellular CO2 concentration （ Ci ）, Gs, Fm and Fv/Fm showed significant differences among various temperature levels, and the parameters such as Gs, Tf, F0 showed significant variations among different soil moisture levels, while Pn and F0 were influenced by both temperature and soil moistures levels. Re-watering alleviated the stress at 25 and 33 ℃ through improving the photosynthesis performance and Fv/Fm to some degree, but no obvious variation in terms of F0 and Fm after re-watering. Our results suggest that the combined stress has stronger effects on the photosynthetic characteristics of plants than the single stress, and re-watering can release the stress in a certain temperature range.