蕾期土壤盐度降低后棉花叶片的生理功能恢复

摘要

试验于2011—2012年在江苏南京江苏省农业科学院经济作物研究所试验田进行,采用盆栽方法,以鲁棉研37号和苏棉22号为供试材料,设置土壤盐度降低试验(初始土壤含盐量为0.2%,棉花进入二叶期后每7d加入混合盐1次,每次增加0.1%,使土壤含盐量逐渐达到0.5%,蕾期进行盐度降低处理,使土壤含盐量降低到0.2%左右),研究蕾期土壤盐度降低后棉花叶片的生理代谢动态特征。结果表明：土壤盐度降低后,棉花叶片叶绿素( Chl)、类胡萝卜素( Car)含量和Chl/ Car升高；净光合速率和气孔导度升高,且分别在土壤盐度降低后第14天和7天接近于低盐对照；土壤盐度降低后棉花叶片超氧化物歧化酶( SOD)和过氧化物酶(POD)活性升高,过氧化氢酶(CAT)活性和丙二醛(MDA)含量降低,MDA含量在土壤盐度降低后第14天接近于低盐对照；土壤盐度降低后棉花叶片中可溶性糖、游离氨基酸和脯氨酸含量降低,且接近于低盐对照。上述结果表明土壤盐度降低后,棉花叶片生理功能逐渐恢复,进而实现棉花生长发育的恢复补偿。棉花叶片生理功能在土壤盐度降低后的恢复能力存在品种间差异,鲁棉研37号较苏棉22号叶片生理功能表现出更强的恢复能力。%Soil salinity is considered a major limiting factor on crop productivity worldwide. Soil salt accumulation is affected throughout the year by weather conditions, which can enhance or reduce the effects of on the physiological functions of plants, in turn affecting plant growth and development. Thus, crop productivity in saline environments depends on not only on tolerance to salt stress but also on capacity to recover from salt stress. The objective of this study was to elucidate the physiological mechanisms of recovery in cotton leaves after salt stress. Changes in photosynthetic pigments, photosynthesis, lipid peroxidation, antioxidant enzyme activity, and soluble sugar, free amino acid and proline content in leaves after relief from salt stress were studied in two cotton cultivars ( Lumianyan 37 and Sumian 22 ) grown under control ( soil salt concentration 0.2%) , salt-stressed ( soil salt concentration 0. 5%) and salt-recovered ( soil salt content decreased from 0.5% to 0. 2%) conditions. After soil salt content was reduced, chlorophyll and carotenoid content, and chlorophyll/carotenoid ratio, increased compared to those in salt-stressed cotton plants, and the increases were more pronounced in Lumianyan 37 than Sumian 22. Net photosynthetic rate ( Pn ) and stomatal conductance ( Gs ) values increased in salt-relieved plants compared with those in the salt-stressed cotton plants and exceeded those in control ( CK) cotton plants at 7 d and 14 d after reducing soil salt concentration. The increase in Pn for Lumianyan 37 was higher than that of Sumian 22. The malondialdehyde ( MDA) content of salt-relieved cotton leaves decreased compared with those of salt-stressed cotton plants and approximated that of the CKs at 14 d after reducing soil salt concentration. Additionally, superoxide dismutase ( SOD) and peroxidase ( POD) activity in salt-relieved cotton leaves increased, but catalase ( CAT) activity decreased after reducing soil salt concentration. The reduction of MDA content in leaves of Lumianyan 37 was greater than that in Sumian 22, as were SOD, CAT, and POD activity. After reducing soil salt concentration, cotton leaves showed decreases in soluble sugar, free amino acid, and proline content, especially Lumianyan 37. In summation, the metabolic activity of cotton leaves gradually recovered after reducing soil salt concentration, resulting in gradual compensation in growth. The two cotton cultivars differed in the ability of their leaves to recover from salt stress. Lumianyan 37 was better able to recover than Sumian 22. Cotton has indeterminate growth characteristics. Although salt stress restricts the growth of cotton plants, after relief from salt stress fruit branches and fruit nodes, as well as buds and bolls, can grow and develop again, partly compensating for the potential yield losses caused by the salt stress. Understanding the physiological mechanisms of cotton recovery from salt stress will aid in breeding new cotton cultivars and in developing new agronomic solutions to enhance recovery after relief from salt stress.