Effects of drought on nitrogen uptake and distribution in Camellia oleifera root under nitrogen addition
[Objective]This study investigates the growth response and nutrient utilization of the Camellia oleifera root system across different root orders under drought and nitrogen application.It aims to analyze how water and nitrogen affect root growth,nitrogen uptake,distribution and utilization,and to provide theoretical support for understanding the relationship between plant root architecture and nutrient strategies under climate warming.[Method]Two-year-old C.oleifera'Changlin 53'trees were used.A pot experiment with 15N isotope tracing technology was conducted,setting two drought levels:normal irrigation(soil moisture content 75％±5％)and drought(soil moisture content 30％±5％).Two nitrogen application levels were used:no nitrogen and 15N-labeled ammonium nitrate(2.88 g/plant).After 75 days of drought treatment,the biomass,total nitrogen content,percentage of nitrogen from fertilizer(Ndff),and nitrogen use efficiency of roots of different diameter classes of C.oleifolia seedlings were measured.[Result]Under drought stress,there was a negative correlation between biomass and nitrogen content in grade 1-3,grade 5,and grade 6 roots,while a positive correlation was observed in grade 4 roots.Drought significantly affected 15N content and Ndff in all root diameter classes(P＜0.05).Drought inhibited 15 N accumulation in all root diameter classes,with Ndff in grades 1-3 being most affected.Drought increased nitrogen distribution in roots,especially in grade 5 roots,which saw a 93.10％increase.However,the nitrogen use efficiency was inhibited to varying degrees across different root diameter classes.[Conclusion]Nitrogen application increased root biomass and nitrogen allocation to coarse roots under drought but reduced fine root biomass and nitrogen accumulation.Drought significantly impacted the absorption,utilization,and distribution of fertilizer nitrogen in roots of all levels,enhancing nitrogen distribution,particularly in roots above grade 5,but inhibiting 15 N absorption and utilization in roots of grades 1-4.
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