氮素对棉花幼苗生长、养分分配及氮素利用效率的影响

Cotton is an important economic crop with high N requirements for its growth, but its nitrogen use efficiency is low. In this study, six N concentrations(0,0.04, 0.4, 1,4, 8 mmol•L-1Ca (NO3)2, named N0, N0.04,N0.4,N1, N4, N8) were set to study their effects on root and shoot morphology, biomass and macronutrients absorption and distribution, photosynthetic capacity, N uptake(NUpE)efficiency and utilization(NUtE) efficiency ofcotton seedlings. The results showed that with the increase ofN concentration, the cotton growth(include root and shoot), biomass, macronutrients accumulation, and photosynthetic capacity all showed a trend of first increasing and then decreasing, and 4 mmol•L-1Ca(NO3)2 is the most appropriate N concentration for cotton seedling growth. The maximum accumulations of N, P, K and Ca in cotton seedlings were 35.1 mg,6.5 mg,40.4 mg, and 16.9 mg per plant, respectively, and the N:P:K:Ca in plants was about 1:0.2:1.2:0.5. There was a significant positive correlation between NUpE, NUtE and the root-shoot ratio. In addition, NUpE and NUtE were also consistent with changes in the root biomass distribution proportion, root average diameter, and the root macronutrients distribution proportion, all of which decreased significantly with the increase of N concentration. The plant N content, plant Ca content, shoot K content, leaf biomass and the shoot macronutrients distribution proportion were all increased significantly with the increase of N concentration. The above results showed that the appropriate N concentration significantly promoted the absorption of macronutrients, increased the Pa and T, and significantly increased the proportion of macronutrients distribution in the shoot, thus making the plant grow vigorously. Moderate N deficiency inhibited shoot growth, increased root macronutrients distribution proportion, promoted root elongation and proliferation, and increased NUpE and NUtE, while extreme N deficiency reduced root number but increased root diameter. High N concentration significantly inhibited overall root growth and decreased NUpE and NUtE.