Anion Form Of Zinc Compounds Stress Under Physiological And Ecological Characteristics Of Corn

With the development of economy, soil pollution has been increasingly serious as a result of sewage irrigation, agricultural fertilizers and so on. Soil quality is getting worse. Soil quality and food safety are closely related, so the study of soil pollution and disposal become the focus of widespread attention.Because the heavy metal contamination and the accumulation of salt are more and more serious, the eco-physiological study of crop has important theoretical and practical meaning, which is helpful to know about the relationship between the heavy metal and anions and that between them and plants, is theoretical basis to understand the interaction of heavy metal and anions better and provides reference for the food security strategy.We used 0.1 g kg^-1,0.3 g kg^-1 and 0.5 g kg^-1 of zinc concentration with three zinc compounds which are ZnSO₄,Zn(NO₃)₂ and ZnCl₂, marked as low concentration, middle concentration and high concentration respectively, and the control, chose maize, the important crop in the north, as the object of study to simulate the heavy metal stress artificially. Morphological features, photosynthesis and chlorophyll fluorescence at the jointing , flowering and dough stage, and the zinc content in various organs were measured in order to examine the eco-physiological characteristics of maize under stress of zinc compounds with different anions. The results are as follows:(1) Morphological characteristicsZinc had obvious effects on maize. There was significant difference among different concentration treatments. The growth of maize was promoted under low level and was inhibited under high level. The maize under middle level was in the excessive stage, and grew differently due to the compounds. The organs of maize grew differently under zinc stress. Under the same concentration condition, there are differences among the effect on maize of zinc compounds with different anions. Under the condition of low concentration the maize under ZnSO₄ stress grew best, and under the condition of middle concentration the maize under Zn(NO₃)₂ stress grew best. Under the condition of high concentration ZnCl₂ poisoned the maize strongest, and Zn(NO₃)₂ weakest. The plant height and leaf area of all treatments fluctuated with the growing period.(2) PhotosynthesisThe diurnal change of photosynthetic rate (Pn) and transpiration rate (Tr) presented a single-peak curve. The trends of Pn varied with the growing period. Under the same concentration condition, photosynthetic capacity was different according to the zinc compounds with different anions. The Pn of maize under the S1, N1 and N2 was larger than the control, so S1, N1 and N2 were helpful to the growth of maize. The stomatal limitation might cause the decliner of Pn at jointing stage and the non-stomatal limitation might be the main reason of low Pn at flowering and dough stage. The low Pn might be due to the stomatal limitation also but had nothing to do with the change of chlorophyll content significantly.(3) Chlorophyll fluorescenceThe diurnal change of PSâ…¡quantum efficiency (ΦPSâ…¡) and electron transport rate (ETR) presented a single-peak curve. The maximal quantum yield of PSâ…¡(F_v/F_m) was around 0.8, which meant that the maize of all treatments had high photosynthetic activity. The trends ofΦPSâ…¡and ETR varied with the growing period. Under the same concentration condition, the capacity of using solar energy was difference according to the compounds with different anions. S1, N1, N2 and N3, whoseΦPSâ…¡and ETR were higher than the control, were beneficial to use solar energy efficiently for maize.(4) The absorption of zincZinc content in different position of maize increased with stress level, and was different between organs. Root and stem played an important role in lightening the poison of zinc. Zinc transfer capacity of maize varied with stress level, and different compounds were in different trends. Under the low and middle concentration condition, SO₄^2- was more helpful to the absorption of zinc than others, but under the high concentration condition Cl^- was the best one to simulate zinc absorption. The order of anions in promoting zinc transferring was SO₄^2-, NO₃^- and Cl^-.