Responses Of Growth And Nutrition Uptake In Wheat Seedlings To Partial Root-zone Water Stress And Its Mechanisms

In this paper, the effects of partial root-zone water stress on growth and nutrientabsorption of wheat seedlings, and the regulatory effects of nitrogen form, calcium andexogenous nitric oxide in wheat seedlings were investigated by using hydroponics method.The interaction effects of calcium and nitric oxide on improving drought resistance of wheatwere studied. The results showed that:i) Biological traits of wheat changed under water stress, i.e., plant height, root length, drymatter accumulation, relative water content, as well as the concentration and accumulation ofmajor mineral nutrients declined. Moderate water stress(with water potential at about-0.56MPa) in partial root-zone significantly promoted wheat growth, dry matter accumulation,relative water content and the concentration, accumulation and specific absorption rate ofmain mineral nutrients increased. Partial root-zone supplied with water under severestress(with water potential at about-0.93MPa) could significantly mitigate the inhibitoryeffects of water stress on growth and mineral nutrients uptake and accumulation in wheatseedlings. Therefore, partial root-zone water stress could improve drought resistance of wheatseedlings by improving water status, growth and absorption of mineral nutrients underdrought conditions.ii) Under partial root-zone water stress, nitrogen supplied two compartments andnon-water stress compartment were beneficial for growth and mineral nutrients absorption ofwheat seedlings, nitrogen supplied to water stress compartment was unfavourable. Whensupplied with urea or nitrate rather than ammonium, wheat seedlings grew better, withenhanced root absorption capacity, higher mineral nutrient concentration, and greateraccumulation. On the contrary, ammonium significantly inhibited the growth and nutrientuptake of wheat seedlings. Under partial root-zone supplied with water, wheat adaptability towater stress of nitrogen supplied to water stress compartment was weakest. Nitrogen formswere closely associated with drought resistance of wheat and ammonium reduced it. iii) Calcium played an important regulatory role in the growth and nutrient absorptionprocess of wheat seedlings under water stress. Calcium and exogenous NO promoted growthand nutrient uptake of wheat seedling, relieved the inhibitory effects of water stress, andthereby enhanced the drought resistance of wheat. Calcium and exogenous NO had asignificant interaction effect on improving drought resistance of wheat, and this interactionwas more significant under partial root-zone water stress. Therefore calcium and exogenousNO played an important role in regulating the growth and mineral nutrition absorption ofwheat under partial root-zone water stress.Main conclusions: partial root-zone supplied with water improved drought resistance ofwheat by improving growth status and promoting nutrient absorption. Under partial root-zonewater stress, nitrogen supplied to two compartments or non-water stress, urea, and nitratewere conducive to improve drought resistance of wheat. Calcium and exogenous NO had asignificant interaction effect on improving drought resistance of wheat, and this interactionwas most significant under partial root-zone supplied with water.