Effect Of Low Light Stress On Nutrient Absorptionand Quality Of Cassita Rotunaifolia

In Production, it is a serious problem that plants growth and development will be affected under low light stress, eventually leading to yield and quality decline. The Effect of low light stress on nutrient absorption mechanisms and quality of plant is not fully understood. This article is to study the effect of low light stress on nutrient absorption of Cassita rotunaifolia from the aspect of root activity , reactive oxygen metabolism of root, nitrogen metabolism of root, the content of photosynthate in root, nutrient absorption, quality parameters and so on, providing a theoretical basis to explore the integrate between the growth of plants and the changes of physiological and biochemical characteristics, and to explore ways to improve plant adaptation to low light conditions.The main conclusions are as follows:1 As for the characterization of plant growth from the characters of plant height, stem diameter, leaf number, branch number, root volume, root-shoot ratio, biomass, CK(natural light) treatment grew the best, and the differences between 50%LI(light intensity),30%LI,10%LI and CK were significant. Low light could inhibit the growth of Cassita rotunaifolia, and this inhibition will improve with the degree of shading.2 the root activity and Na+-K+-ATPase of Cassita rotunaifolia root decreased under low light stress, and the remaining differences between each treatment with CK were very significant,in addition to the 50%LI treatment Na+-K+-ATPase and CK were no significant differences.3 SOD and CAT activities of Cassita rotunaifolia root decreased while POD activity increased significantly under low light stress which resulted in the increase of O2.- producing rate,H2O2 and MDA content. Low light stress eventually caused the increase of membrane permeability.4 Low light stress reduced the activity of nitrate reductase and enhanced the activity of protease and ribonuclease in Cassita rotunaifolia root,which lead to the reduce of protein nitrogen and nucleic acid contents. 5 Net photosynthetic rate(Pn) of Cassita rotunaifolia leaves under low light stress was reduced significantly.The contents of soluble sugar and starch in root,stem and leaves were reduced very significantly under low light stress, while the distribution ratio of soluble sugar and starch in root was decreased.6 The Cassita rotunaifolia root absorbing rates of NO3—N,H2PO4- and K+ were decreased under low light stress. The low light also decreased the contents of N,P,K,Mg,Fe,Mn,Zn in root,stem and leaves. Because the decrease amplitude of dry matter quantity under low light was biger than the decrease of nutrient uptake, the contents of N,P,K,Mg,Fe,Mn,Zn in root,stem and leaves were decreased.7 The low light stress increased the contents of fat,crude ash while decreased the contents of tannin, NDF and lignin in chamecrista rotundifolia,these changes are beneficial to the enhance of quality of Cassita rotunaifolia. So it can be considered that the moderate low light stress can enhance the quality of Cassita rotunaifolia.