Effects Of Waterlogging And Salinity On Seedling Growth Of Cotton (Gossypium Hirsutum L.)

Salinity is recognized as one of the major limiting factors for plant growth and agricultural productivity,thus restricting food production and sustainable development.Cotton is one of the most important commercial crops in salt-alkali land of the middle and lower reaches of Yangtze River.However,there would be an increase in heavy rainfall events during cotton growth in this area.Plant growth can be hit by salinity and waterlogging stress at the same time.Therefore,it is necessary to investigate the effect of waterlogging on cotton growth in saline-alkali soil.Meanwhile,the results from the current work would provide a theoretical basis for cotton resistance cultivation in salt-alkali land.To address the problem mentioned above,salinity-tolerant variety ’CCRI-79’ and salinity-sensitive variety ’Siza 3’ were used in this study.Plant height,chlorophyll content,ion distribution,and biomass accumulation will be closely determined over this process.Moreover,antioxidant enzyme activities and membrane permeability in the root will be also discussed.The main results were as follows:1.Effect of combined salinity and waterlogging stress on seedling growth at germinating and seedling stage in cotton(Gossypium hirsutum L.)To investigate the effect of salinity and waterlogging on cotton growth at germinating and seedling stage,salinity-tolerant variety ’CCRI-79’ and salinity-sensitive variety ’Siza 3’were used in this study.The work was performed at Pailou Demonstration Base of Nanjing Agricultural University in 2014.The soil was set at 0 and 0.35%salinity levels,followed by waterlogging for 0,3,6,9,and 12 days,respectively.The results indicated that germination energy and germination rate of cotton seeds were all dramatically decreased under salinity condition.When subjected to a stress combination of salinity and waterlogging,plant height,SPAD,photosynthesis,and ion homeostasis of cotton were all disturbed,thereby making a difference in plant growth as well as biomass accumulation.The stress caused by salinity together with waterlogging was more serious than that caused by single stress,which showed a cumulative effect.Plant growth got a recovery but still fell behind after terminating waterlogging.As a result,cotton cultivation in saline-alkali land should pay more attention to preventing and controlling the double effect caused by salinity and waterlogging.2.Effect of combined salinity and waterlogging stress on cotton(Gossypium hirsutum L.)plant growth at trefoil stageTo investigate cotton growth at trefoil stage under climate environment and salt-alkali land of the middle and lower reaches of Yangtze River,cotton seedlings were subjected to salinity and waterlogging.Cotton growth after terminating waterlogging was also analyzed.The results suggested that carrot growth was weaker under a combination stress of salinity and waterlogging than that under single stress.The effect was not so obvious when a slight stress happened because of antioxidant enzymes in cotton roots.However,when the condition became serious,reactive oxygen species started to accumulate in great amount and root membrane esterification got aggravated,which hinders normal plant growth.After terminating waterlogging,the trend was still continuing,and the plant growth did not get a recovery.Therefore,cotton cultivation in coastal saline soil should take care and prevent the harm caused by salinity and waterlogging.3.Effect of combined salinity and waterlogging stress on cotton(Gossypium hirsutum L.)plant growth at bud stageTo investigate the effect of waterlogging on cotton growth during bud stage in salt-alkali land,cotton growth and root physiological characteristics in saline or saline-waterlogged soil were analyzed.When subjected to salinity,the potential ability of antioxidant enzymes in cotton roots was decreased,while root membrane permeability was increased.Meanwhile,leaf photosynthesis and plant growth were also strongly affected,which hampered the accumulation of cotton dry matter.All the characteristics mentioned above got worse when the saline soil was treated with waterlogging.After terminating waterlogging,cotton recovery capability was decreasing as saline content and waterlogging time got heavier.As a result,cotton farmers should take care of torrential rains in coastal saline soil.Besides,puddles should be drained in cotton field to prevent the harm caused by salinity and waterlogging.