Effects Of Zinc On The Growth Of Female And Male Morus Alba Seedlings Under Lead Stress

As the unreasonable and industrial development in a long period of time, lead to the serious heavy metal pollution increasingly. At present, there are a large number of reports about the effects of heavy metal pollution on plants. In this study, the mulberries of male and female seedlings planted in the pots were used as experiment materials to study the effects of zinc on the growth of female and male Morus alba seedlings under lead stress. In order to explore the sexual differences of mulberries of male and female seedlings in morphological growth, antioxidant enzyme activity, gas exchange, photosynthetic pigment content, cell membrane permeability, chlorophyll fluorescence characteristics, biomass and accumulation of heavy metals. The purpose of the study is aimed at revealing that adding exogenous Zn2+will mitigate lead toxicity in both female and male individuals, and exogenous Zn2+ application reduces lead-induced stresses more in males than in females of Morus alba. The main results were as follows:1. Effects of zinc on the morphology growth and biomass of female and male Morus alba seedlings under lead stressCompared with controls, in the lead treatment, it significantly inhibits the the morphology growth index, total length of root, total surface area of root, average diameter of root, root volume, leaf biomass and total biomass, and there are no significantly influences in males, while significantly inhibits the males of the number of leaf, total length of root, and males have a higher index than females. Meanwhile,in the zinc treatment, females have a higher than males in morphlolgy, root growth and biomass. Moreover, the interaction of lead and zinc made a higher in morphlolgy,root growth and biomass when compare with the lead stress alone, and males have a higer than females. The study indicate that adding exogenous Zn2+will mitigate lead toxicity in both female and male individuals, and exogenous Zn2+ application reduces lead-induced stresses more in males than in females of Morus alba. In control conditions, chloroplasts showed a lenticular shape, and mitochondria showed a typical structure and clear cristae. Under lead stress alone, the number of grana decreased, starch granules exhibited serious distortion of chloroplasts and numbers of plastoglobuli emerged in females. However, there was no significant decrease in the number of grana compared with control males and at the same time, plastoglobuli emerged in males. Zinc treatments did not lead to a significant difference in the number of grana in either sex compared with the controls. When the plants wereexposed to the combined treatment, there were significant decreases in the number of grana in females, whereas no significant decreases in males.2. Effect of zinc on photosynthetic physiology indexes of female and male Morus alba seedlings under lead stressCompared with controls, in the lead treatment, it decreases the males and females of the Morus alba in the chlorophyll content and gas exchange, and males have a higher than females. Meanwhile, in the zinc treatment, females have a higher than males in chlorophyll content and gas exchange. Moreover, in the interaction of lead and zinc, when adding to zinc, it significantly increase the Chl a, Tchl, SPAD, Ci,Gs and Tr, Chl b has increased but has no significantly, and males have a higher than females. Compared with controls, in the lead treatment, it significantly inhibits the Yield, qP, Fv/Fm and qN of the males and females. Meanwhile, in the zinc treatment,it significantly increased the Fv/Fm, and had no significantly influence in Yield, qP and qN. Moreover, in the interaction of lead and zinc, when adding the zinc, then it increase the Fv/Fm and qP but have no significantly, and males have a higher Fv/Fm and qP than females.3. Effects of zinc on physiological and biochemical of female and male Morus alba seedlings under lead stressCompared with controls, with the constantly increasing lead level, the MDA, Pr and REL increased gradually, and SOD, CAT, POD and GR show a first rise after falling trend. In the zinc treatment, MDA and SOD have no significantly influence.While, in the interaction of the lead and zinc, adding to the zinc, the MDA and REL significantly decrease than lead stress alone. When in the interaction of lead and zinc,adding to the zinc, it makes the SOD, CAT and POD increased of males and females,While when lead level is 2 000 mg/kg, adding to the zinc, the SOD of males have increasedand the SOD of females have decreased. Meanwhile, in the interaction of the lead and zinc, the GR of males and female have increased, the Pr have decreased,and males have a higher GR and Pr than females.4. Contents in roots, stems and leaves of female and male Morus alba seedlings exposed to lead, zinc and their interactionThe lead accumulation in every organ of the Morus alba are increased gradually,In the different lead level, the contents in roots, stems and leaves have significantly sexual differences, and the orderliness of lead distributes is: root >leaf> stem, andmales have a higher capacity in accumulating lead pollution than females. The transfer factor and tolerance index of Morus alb are greater than one, and males have a higher index than females. In the interaction of lead and zinc, the transfer factor and tolerance index of Morus alb are higher than lead stress alone, and males are higher than females. In different lead level, the biological concentration factor of males and females are greater than 0.3, and males are greater than females. While adding to zinc,the biological concentration factor exhibits decrease.