干旱复水对棉花苗期抗氧化系统及光合荧光参数的影响

为研究水分胁迫对棉花光合作用及相关生理指标的影响,揭示水分胁迫与棉花生理指标及光合作用之间的关系,采用盆栽称重控水法对新陆早19号进行干旱胁迫0、2、4、6、8 d及复水2 d处理,测定棉花叶片MDA、H_2O_2含量,SOD、POD、CAT等指标以及光合参数和叶绿素荧光参数的变化。结果显示:随着干旱胁迫的加强,棉花叶片活性氧含量、电导率和MDA含量增加,复水后除H_2O_2含量外,其它均降到对照值;在活性氧含量最高时,抗氧化酶CAT和SOD的活性最高,以清除棉花叶片内过量的活性氧;棉花功能叶片的光合作用、气孔导度、蒸腾速率随着干旱胁迫强度的增加逐渐下降,在干旱第8天达到最低,复水后恢复;光化学猝灭系数(qP)和光量子产量(Yield)随着干旱胁迫的加强而降低,复水后不能恢复。说明水分胁迫下棉花可通过提高抗氧化酶活性清除过量活性氧,通过调节气孔导度抑制棉花的光合作用,降低蒸腾速率。

Effects of drought and rewatering on antioxidant system and photosynthetic fluorescence parameters of cotton seedling

In order to study the effects of water stress on photosynthesis and associated physiological characteristics of cotton,and to reveal the relationships between photosynthetic traits,physiological indexes and drought tolerance,drought and rewatering treatments were employed on Xinluzao 19 by weighting the pot to control water amount.The treatmeres included drought for 0,2,4,6,8 d and rewatering for 2 d,then the changes in MDA content,H2O2 content,SOD,POD,and CAT indexes and photosynthetic fluorescence parameters of cotton were measured.Reactive oxygen,conductivity and MDA content of cotton leaf were increased with the enhancement of drought stress.Except for H2O2 content,the others were reduced to the control values after rewatering.SOD and CAT of antioxidant enzymes reached the highest activities to clear the excessive reactive oxygen species when the active oxygen content was the highest in cotton leaf.The photosynthesis,stomatal conductance and transpiration rate of cotton function leaf became decreased with the increase of drought stress,and reached the lowest at the 8 th day after drought,then rebounded after rewatering.Photochemical quenching (qP) and yield were reduced with the severity of drought stress,and could not become rebounded after rehydration.Obviously,excessive reactive oxygen species were cleared by increasing the antioxidant activity of cotton under water stress through controlling the stomatal conductance to inhibit photosynthesis and transpiration rate of cotton under water stress.