Effects Of NH₄⁺-N/NO₃^--N Ratio And N, P, And K Nutrition Ratio On The Growth And Active Components Of Isatis Indigotica Fort

The paper is aimed to the related effects from the view point of plant nutrition and plant physiology. The sand culture experiment was conducted in the greenhouse, Nanjing Agriculture University, P.R.china. Under different NH4+-N/NO3--N ratios treatments the measurements of Isatis indigotica Fort. as follows were included:the biomass, nitrogen metabolis related enzymes activity(NR and GS), nitrate and ammonium nitrogen content, photosynthetic characteristics,4mineral elements(N,P,K,Mg) and main components(indigo, indirubin and polysaccharide) contents. Moreover, another sand culture experiments was conducted to study the effects of N, P, and K levels on the growth, nitrate nitrogen content, NR and GS activity, photosynthetic characteristics, NPK contents and the three active components of Isatis indigotica Fort. Results obtained were as follows.1. The biomass of Isatis indigotica Fort. increased at first when the supplementary N of NH4+-N/NO3--N ratio changed from100:0to50:50and decreased afterwards. The maximum value was at50:50and the minimum at100:0. But the root-shoot ratio was the lowest when the NH4+-N/NO3--N ratio was50:50.2. With the decrease of the NH4+-N/NO3--N ratio, the activity of NR and GS increased and then decreased and the relationship between the activity and the ratio could be described with an approximate parabola curve. The maximum value of NR activity was at25:75(NH4+-N/NO3--N ratio), while the highest GS activity was at50:50and the lowest at100:0. The trends of nitrate and ammonium nitrogen content were similar to that of NR and GS activity and the differences among the treatments were significant. 3. With the NH4+-N/NO3--N ratio decreasing, the chlorophyll content first increased and then decrease and The maximum value was at75:25. The regularity was the same as that of Pn and the lowest Pn at100:0.4. Effeets of the NH4+-N/NO3--N ratios on mineral elements contents were notable. NH4+-N was beneficial to the accumulation of N and P, while NO3--N could promote the accumulating quantity of K and Mg. With the ratio of NH+4-N increasing, the content of indirubin in leaf and polysaccharide in root increased as well and when NH4+-N/NO3--N ratio was0:100, the content of indigo reached maximum at11.40mg·g-1which was3times higher than the lowest content.5. The requirement of Isatis indigotica Fort. for NPK was different in various vegetative growth phase. The interaction of NPK was important to the biomass accumulation in later stage of Isatis indigotica Fort.’s vegetative growth phase and the root-shoot ratio of lower N treatments were higher.6. Improving the K levels under certain N can promote the nitrate nitrogen accumulation in Isatis indigotica Fort. leaf and the NR and GS activities were effected by both N and K. The chlorophyll contents of N2levels were higher than other treatments and lower P decreased the net photosynthetic rate. Proper content of P and K raised the light saturation point(LSP) and lowed the light compensation point(LCP) of Isatis indigotica Fort.7. The NPK contents in leaves were higher than that in roots. The N content of Isatis indigotica Fort. was influenced by the interaction of NPK and in the earlier stage, increasing N and K under low P level could accelerate the absorption of P. High N level improved the K accumulation in shoots, while decreaced the K content in roots. During the vegetative growth phase of Isatis indigotica Fort., the content of indigo, indirubin and polysaccharide decreased as a whole. Low N level was beneficial to the accumulation of indigo and indirubin and in the earlier stage, the polysaccharide content was the lowest at N2P2K1treatment, while later under N0or N1levels treatments had a lower polysaccharide content.