Studies On Mechanisms Of Zinc Uptake And Accumulation In Different Wheat Cultivars

Zinc deficiency in humans has been received global attention in recent years,especially the problem of low Zn content in cereal grains.Zn is important for the growth of plant and animals,as well as humans.It participates in a series of metabolic activities in the humans.Wheat is the important staple foods for humans.The content and distribution of Zn are very important for the Zn nutrition of groups mainly composed of wheat and its products.However,the physiological and molecular mechanisms of Zn nutrition efficiency in wheat are still not very clear.In this experiment,first of all,through the research and analysis of Zn nutritional characteristics of different wheat genotypes commonly grown in Henan Province,two different wheat cultivars with large differences in Zn sensitivity,Zn content,Zn accumulation and Zn efficiency were selected.Subsequently,the nutrient solution culture method was used to investigate the response of the two wheat cultivars to Zn addition.The growth and development of wheat seedlings,root morphology,photosynthetic capacity,antioxidant capacity,subcellular distribution,and Zn transporter changes under different Zn supply levels were studied.Through the absorption and transport laws of Zn content in wheat,the difference in response to Zn about different wheat cultivars is obtained,and the physiological and molecular mechanisms of different wheat cultivars in Zn nutrition efficiency are revealed.It provides a certain theoretical reference for the scientific selection of wheat cultivars,scientific fertilization and management.The results of this experiment are listed as follows:1.Appropriate Zn concentration can increase the biomass of wheat,with an increase of 17.0%-79.1%.Among them,the maximum increase in biomass of wheat was obtained under Zn0.25 treatment.When Zn supply is higher than Zn0.25 or higher,the growth and development of wheat will be inhibited,causing toxic effects.In addition,the two wheat cultivars showed different responses to Zn treatments.When treated with low Zn,AiKang58 has obvious growth advantages,with the largest increase,and is more sensitive to Zn;When treated with high Zn,AiKang58 was significantly inhibited and the decrease was greater,while ZhengMai0856 showed a smaller decrease and a stronger tolerance to Zn.2.Treatment with low Zn(0.05～0.25 mg·L-1)significantly promoted the elongation of wheat root system(root length,surface area,root volume,root diameter,number of fractions).Among them,AiKang58 had the most significant effect under Zn0.05 treatment,with an increase of 5.4%to 146.5%,and Zhengmai0856 had the most significant effect(except for root diameter)under Zn0.25 treatment,with an increase of 33.7%to 47.9%.High Zn(2.5 mg·L-1)treatment significantly reduced the root length,root surface area,root volume,and average root diameter of the two wheats,with a decrease of 3.4%to 30.3%.3.Zn application significantly increased the chlorophyll content and photosynthetic parameters of wheat,and enhanced the photosynthetic capacity of wheat.However,with the amount of Zn application increased,photosynthesis decreased and its growth was inhibited.Meanwhile,the excessive supply of Zn increased the content of malondialdehyde(MDA),enhanced the activity of SOD and POD,and activated the protection system of oxidative stress in plants.The tolerance of Zn to the two wheat cultivars may not be directly related to the antioxidant defense system,but there is a close relationship between Zn and antioxidant enzyme activity.4.Zn supply significantly increased the Zn content in wheat plants and reduced the Cu,Fe,and Mn contents in the roots of wheat,but the Cu,Fe,and Mn contents in the shoots were different in two wheat cultivars.Among them,the content of Zn in AiKang58 was significantly lower than that of ZhengMai0856,and the translocation factor from root to shoot gradually decreased,but ZhengMai0856 could transfer more Zn from roots to shoots or from cytoplasm to in the vacuole,its transport capacity was significantly higher than that of AiKang58.The results show that there is competition between Zn and other heavy metal elements(Cu,Fe,Mn,etc.)in the root system of wheat,and wheat’s transport ability may be related to its sensitivity to Zn.5.Zn supply significantly changed the distribution of Zn in the subcellular components of wheat.The application of Zn significantly increased the proportion of organelle components,reduced the proportion of cellular fluid components,increased the proportion of cellular fluid components at the root,and reduced the proportion of cell wall components.In the shoots of ZhengMai0856,the proportion of cell wall components was increased and the proportion of organelles was decreased.In the roots,the proportion of cell wall components was increased and the proportion of organelles was decreased.6.Under different Zn supply levels,the transcription levels of TaZIPs genes showed different differences on wheat.Zn application significantly altered the regulation of Zn-related homeostasis genes(TaZIPs)in roots and shoots of wheat.Under low and high Zn treatments,TaZIP3 and TaZIP7 gene expression in roots of two wheats were significantly down-regulated,TaZIP13 expression was slightly up-regulated,while and-5 were oppositely expressed under low and high Zn treatments;TaZIP6 in two wheat shoots Transcriptional expression of and-13 was up-regulated,TaZIP7 expression was down-regulated,while TaZIP3 was expressed differently in the two wheats but ZhengMai0856 had a higher expression level.7.The TaZIPs gene has a high transcription level in the internode,spike stem,cob,and stem node tissues;under the stress of other metal elements and the external environment,the TaZIPs gene is easily regulated by the external environment and the concentration of metal elements,and there are different differences in transcription levels.