Effects Of Precipitation And Nitrogen Addition On Morphological Characteristics Of Root System And Physiological Indexes Of Reaumuria Soongorica

Water and nitrogen is the main limiting factors for plant growth desert ecosystem,understand how precipitation change and the nitrogen deposition affect the typical desert plant root morphological characteristics and physiological indexes,help reveal desert plants under the background of global climate change,the typical response and adaptation mechanism,to effectively provide theoretical basis for construction and administration of desert vegetation restoration.In this study,Reaumuria soongorica was taken as the research object,and different precipitation gradients?precipitation decreased by 30%?W_-?,natural precipitation?W?,precipitation increased by 30%?W₊??and nitrogen addition levels(N₀(0g?m^-2?a^-1),N₁(4.6g?m^-2?a^-1),N₂(9.2g?m^-2?a^-1)and N₃(13.8g?m^-2?a^-1)were set.The biomass,physiological indexes and root morphological characteristics of red sand under different precipitation and nitrogen addition were measured,and the differences were compared to reveal the response mechanism of Reaumuria soongorica to precipitation change and nitrogen addition,which is of great significance for understanding the morphological and physiological adaptation mechanism of desert plants under the background of global climate change.The main research results are as follows:?1?The influence of precipitation,nitrogen addition and their interaction on the seedling height of Reaumuria soongorica was extremely significant?P<0.01?.However,precipitation,nitrogen addition and their interaction had no significant effect on the base diameter of Reaumuria soongorica?P>0.05?.Under the condition of natural precipitation?W?,the relative increase of plant height of Reaumuria soongorica seedlings showed a trend of increasing first and then decreasing with the increase of nitrogen addition,and reached the maximum value under the treatment of low nitrogen?N₁?,indicating that the increase of appropriate amount of nitrogen fertilizer under good water conditions can promote the growth of Reaumuria soongorica plant height.Under the conditions of natural precipitation and precipitation reduction of 30%?W,W_-?,the biomass and its proportion of Reaumuria soongorica leaves showed a trend of increasing first and then decreasing with the increase of nitrogen addition,and reached the maximum level of medium nitrogen?N₂?.This indicates that under the condition of poor soil moisture,the Reaumuria soongorica of desert plants promotes leaf accumulation by absorbing nutrients.The maximum value of the above-ground biomass appeared under the treatment of high water nitrogen?W₊N₂?,indicating that under good water conditions,the accumulation of above-ground biomass could be promoted by the appropriate amount of nitrogen addition.The root biomass proportion was significantly affected by precipitation and nitrogen addition?P<0.01?.Under the treatment of precipitation reduction of 30%?W_-?,the root biomass first increased and then decreased with the increase of nitrogen addition,and reached the maximum level of medium nitrogen?N₂?.It can be seen that in the environment of less precipitation,the Reaumuria soongorica seedlings can promote the accumulation of biomass by the growth of nutrient absorption by the root system.?2?Leaf root weight ratio was significantly affected by precipitation change?P<0.05?,and root shoot ratio was significantly affected by precipitation change and nitrogen addition?P<0.01?.Under the same precipitation condition,the leaf root weight ratio,leaf weight ratio and sink weight ratio of Reaumuria soongorica tended to increase first and then decrease with the increase of nitrogen addition,while the root shoot ratio showed the opposite trend.Among them,the leaf root weight ratio reached the maximum at the level of high water and low nitrogen?W₊N₁?,and the leaf weight ratio and source sink weight ratio reached the maximum under the treatment of high water nitrogen?W₊N₂?,indicating that when the water condition was good,the appropriate addition of nitrogen fertilizer could promote the growth of Reaumuria soongorica leaves.Under the same nitrogen treatment,with the gradual increase of precipitation,the leaf root weight ratio,leaf weight ratio and source sink weight ratio of Reaumuria soongorica all showed an increasing trend,and the values under the treatment of precipitation increase by 30%?W₊?all reached the maximum,while the root shoot ratio presented an opposite rule.?3?Precipitation had a significant effect on total root length,total surface area,specific root length and specific surface area of red sand seedlings?P<0.01?.The interaction between precipitation change and nitrogen addition had no significant effect on the morphological index of red sand root?P>0.05?.At the same nitrogen level,the total root length,total surface area,specific root length and specific surface area of Reaumuria soongorica all showed an increasing trend with the increase of precipitation,and all the relevant indexes reached the maximum under the treatment of 30%increase of precipitation?W₊?.In precipitation decreased by 30%?W_-?and precipitation?W?under the condition of constant Reaumuria soongorica with the increase of nitrogen content of root the morphological index showed a trend of decrease the increase,then the precipitation increased by 30%?W₊?under the condition of each index increased with the increase of nitrogen content in a trend of increase with the decrease of the first,and various indexes in high water high nitrogen?W₊N₃?level is the largest.It can be seen that the root growth of Reaumuria soongorica mainly depends on precipitation,and the root growth of Reaumuria soongorica has obvious coupling effect of water and nitrogen.Under the condition of high water and nitrogen,the growth promotion effect of Reaumuria soongorica root is the most obvious.?4?Precipitation change and nitrogen addition have different effects on each physiological index of Reaumuria soongorica.Proline content and soluble protein were significantly affected by nitrogen addition?P<0.01?.Chlorophyll and superoxide dismutase were significantly affected by nitrogen addition?P<0.001?.Soluble sugar was significantly affected by nitrogen addition?P<0.05?.Under the condition of natural precipitation?W?,the contents of proline and chlorophyll in Reaumuria soongorica seedlings increased with the increase of nitrogen application.Under the condition of natural precipitation?W?,SOD activity in Reaumuria soongorica increased with the increase of nitrogen content,indicating that nitrogen could effectively improve SOD activity in Reaumuria soongorica.POD activity reached its maximum under low water nitrogen-free?W_-N₀?condition.Under the conditions of natural precipitation?W?and precipitation increase by 30%?W₊?,the soluble sugar content of Reaumuria soongorica shows an increasing trend with the increase of nitrogen addition,and its value reaches the maximum at the high nitrogen?N₃?treatment,indicating that the increased nitrogen application can promote the synthesis of soluble sugar in Reaumuria soongorica.Under the condition of natural precipitation?W?,the soluble protein content of Reaumuria soongorica firstly increases and then decreases with the increase of nitrogen addition,and the level of medium nitrogen?N₂?reaches the maximum value,indicating that an appropriate amount of increased fertilizer application can promote the synthesis of soluble protein in Reaumuria soongorica.