Effects of different nitrogen levels on seedling growth,nitrate and its secondary metabolites content in Aloe vera seeding

A pot experiment was carried out to investigate the effects of different N levels(5.0,7.5,10.0,15.0,17.5 mmol/L) on plant growth,nitrate accumulation and its secondary metabolites content in two-year old Aloe vera seedlings. The results indicated that shoot fresh weight and total biomass increased drastically with N supply level increasing from N 5.0 to 10.0 mmol/L,while above 10.0 mmol/L,no significant difference in plant growth was observed.Root biomass and root/shoot ratio decreased with the increasing of N supply rate.Nitrate concentration in leaf and root showed an upward tendency with increasing N supply rate.The highest content of leaf Vitamin C was obtained at N 10.0 mmol/L supply level,while a strong decrease in the content of leaf Vitamin C occurred when N supply level was higher than 10.0 mmol/L.Within the range of N 5.0 to 10.0 mmol/L,anthraquinon content increased with the increasing of N supply level.However,anthraquinon content was rather identical at higher N supply levels.Aloin content show the same trend as Vitamin C,with the highest aloin content found at N 10.0 mmol/L.Taken together,we recommended N level 10.0 mmol/L for Aloe vera under sandy culture.