Physiological And Biochemical Responses Of Different Varieties Of Sugar Beet(Beta Vulgaris L.) Under Saline-alkali Stress

As a peculiar cash crop in northern China, Sugar beet is also the second-largest sugar crop in China and the world. Its cultivation range is so wide that it has been grown in nearly40countries and regions worldwide. Because of its high ability of resistance to salinization, the study of the physiological response mechanism under saline-alkali stress on Sugar beet plays a very important role in the further study of adaptation of Sugar beet to salinization. On the basis of germination test, this research takes KWS0143and ACERO as test material to clarify the influence of saline-alkali stress on key enzymes activity, membrane permeability, yield and sugar content. By conducting pot experiment, we set5samples in which the proportions of sodium carbonate in soil are set to five levels:0、0.5%、1%、1.5%、2%, and the corresponding values of the soil solution pH is7.14、8.9、9.45、10.19、10.56respectively. In this way, we can study the influence of saline-alkali stress on the activities of nitrate reductase(NR)、glutamine synthetase(GS)、glutamate synthase(GOGAT)-superoxide dismutase(SOD) peroxidase(POD)、malondialdehyde(MDA), the content of malondialdehyde(MDA), membrane permeability, and yield and sugar content. This paper aims at clarifying the adaptability of Sugar beet to saline-alkali stress, and the physiological basis of the influence of saline-alkali stress on Sugar beet in order to provide a reference for the exploitation and utilization of saline-alkali land. The main conclusions of the research are as follows:1. Varying degrees of saline-alkali treatment on Sugar beet have different impacts on seed germination potential, germination rate and emergence rate which are in the decline generally as saline-alkali stress increases. Moreover, the time of germination has also been affected to some degree. Through the comparison between different varieties, we can find out that ACERO has higher germination potential and germination rate than KWS0143. Therefore, we can draw the conclusion that saline-alkaline resistance of ACERO is higher than KWS0143in the germination and seedling stage.2. Saline-alkali stress makes the enzymatic activities of nitrate reductase(NR), glutamine synthetase(GS) and glutamate synthase(GOGAT) in Sugar beet leaf decrease. What’s more, the deeper the degree of saline-alkali stress is and the longer the stress time is, the greeter the declining degree is. By comparing the two varieties, enzymatic activity of ACERO is higher than that of KWS0143, which demonstrates that the nitrogen assimilation capacity of ACERO is higher than that of KWS0143under saline-alkali stress.3.With the increase in the degree of saline-alkali stress and stress time, the activity of superoxide dismutase(SOD) and peroxidase(POD) increases at first but later decreases. In the stress process, the activity of SOD, POD reaches a maximum in the sample in which the proportion of sodium carbonate is1%, but it decreases as the degree of saline-alkali stress increases. The enzymatic activities of ACERO is higher than that of KWS0143, which shows that oxidation resistance of ACERO is stronger.4. With the increasing degree of saline-alkali stress and prolonged stress time, malondialdehyde(MDA) content and leaf membrane permeability shows an upward trend. Compared the two varieties, MDA content and leaf membrane permeability of ACERO are all below KWS0143, which indicates that the salinity damage of ACERO is less serious than that of KWS0143.5. Sugar beet nitrogen metabolizing enzymes and yield under Saline-alkali stress in general is in a significantly positive correlation. Before the accumulation of sugar on August23rd, NR and sugary rate is significantly correlated in general, but then NR and sugary rate shows a significantly negative correlation. Sugar content of GS and GOGAT is positively correlated; Suger beet nitrogen metabolizing enzymes under Saline-alkali stress and protective enzymes is,generally through not significantly, negatively correlated; Suger beet nitrogen metabolizing enzymes and MDA is significantly negatively correlated in terms of leaf membrane permeability.