Effects Of Nitrogen On Drought Signal Induction And Drought Tolerance In 84K Poplar Roots Under Local Drought

Poplar(Populus species)is a fast-growing tree with characteristics of easy survival,fast growth,tall tree shape,large biomass,and strong resistance.It is the main afforestation tree species in the "three north" areas of my country.The double shortage of water and nitrogen is currently the main factor restricting the productivity of poplar plantations in my country.In view of the severe limitation of productivity of poplar plantations in my country due to the double shortage of water and nitrogen,a large number of studies have been carried out on the resistance of poplar to drought stress and water use efficiency,low nitrogen stress tolerance and nitrogen nutrition efficiency.However,there are few reports on nitrogen tolerance of poplar roots to drought stress.Compared with cultivated soil,forest soil has a higher degree of water heterogeneity in both horizontal and vertical directions,resulting in local drought in horizontal and vertical directions.However,there is no research on how nitrogen affects and regulates the signal response and drought tolerance of poplar trees to local soil drought.This paper will study the effect of nitrogen on drought signal induction and drought tolerance of poplar roots under local drought,and clarify the regulation mode of soil local drought and nitrogen nutrition coupling on poplar root plasticity and drought stress tolerance.It is of great theoretical guiding significance to realize scientific management and efficient cultivation of poplar plantation forests on sites with drought,water shortage and low nitrogen difficulties,increase the yield and quality of poplar wood,and improve the productivity of poplar plantation forests.The main conclusions of the study are as follows:(1)Under the unilateral irrigation mode,low nitrogen stress can promote the increase of the root coefficient of the root zone of the arid side and the growth of the root system to obtain the water required for growth,and alleviate the damage caused by drought stress.Nitrate nitrogen can increase the root length,root surface area,number of root tips and fine root length of the deep root zone under the overall arid soil.Through the growth of the root system and the expansion of the contact area with the soil,the water absorption area of the root system is increased to alleviate the overall drought.Poplar's damage to a certain extent.(2)Nitrogen can reduce the content of malondialdehyde in the root system treated by unilateral drought(unilateral irrigation)under the overall arid water environment,and also reduce the content of the moist side root area under the unilateral drought water environment,alleviating the drought stress.Membrane lipid peroxidation.The overall arid water environment can aggravate the free proline content in the surface root zone and deep root zone treated by surface drought(deep irrigation),and accelerate membrane lipid peroxidation.After applying nitrogen,the unilateral arid environment promoted the accumulation of NO in the root system of the arid side,reducing cell damage,while the overall arid water environment reduced the accumulation of NO in the root system of the arid side,and the reason for the NO in the moist side root area was the opposite.(3)Nitrogen supply under the surface drought and the overall arid water environment reduces the GR activity of the surface root system and weakens the ability to remove active oxygen and free radicals.Nitrogen increased the antioxidant capacity of the surface root zone under a humid control water environment.Under low nitrogen stress,local drought and overall drought can aggravate the peroxidation of root cell membranes on the R and L sides by reducing the production of catalase and reduce the antioxidant capacity of the root system.The surface drought(deep irrigation)mode reduces APX activity of the root system and may produce other substances to resist adversity stress;nitrogen promotes accumulation of APX in the deep root zone under humid conditions,which is beneficial to resist drought stress.(4)Nitrate nitrogen improves the ability of surface roots to resist drought stress in the surface arid water environment;ammonium nitrogen promotes the ability of deep roots to resist drought stress in the overall arid water environment.Under nitrate nitrogen conditions,the unilateral drought water and the overall drought water increased the NO content in the L-side(wet side)root zone,reducing the impact of abiotic stress,and the unilateral drought water under the ammonium nitrogen condition increased the L-side(wet side)root zone NO content;increase the GR activity in the deep root zone under the moist control moisture environment,improve the antioxidant capacity.