Effects Of Cadmium On Physiological And Metabolic Characteristics Of Fuyou 9 And Shenyu 33 Maize During Germination

Maize?Zea mays L.?is an important cereal crop widely planted in China,Cadmium?Cd?pollution exists in many planting areas,which affects the yield and nutritional value of grains.The germination stage represents the period when the plant is most sensitive to the environmental impact,and is a critical stage for seedling establishment,and directly affects the emergence,nutritional growth and reproductive growth of plants.In agricultural production,the germination period of corn continued to the end of the three leaf and one core period,when the nutrition stored in corn seeds was exhausted,the germination ended.Under hydroponic condition,two maize varieties with different Cd sensitivity were used as materials,and by measuring the changes of dry matter accumulation,antioxidant properties,carbohydrate metabolism and endogenous hormone content of these two aboveground and belowground maize varieties.under Cd stress in germination period,the differences in response to physiological and metabolic characteristics of different sensitive maize varieties under Cd stress were compared in germination period and the mechanism of physiological differences was analyzed with the aim to provide a theoretical basis for the selection and cultivation of Cd tolerant varieties.The findings are as follows:?1?A comprehensive evaluation of different maize varieties was made based on germination rate,germination index,vitality index and other indicators.What's more,combined with the germination rate,Cd-tolerant maize variety Fuyou 9?Fy9?and Cd-sensitive maize variety Shenyu33?Sy33?were screened out for follow-up research.?2?Under Cd treatment,aboveground and belowground biomass,plant height,root length,root characteristic parameters were inhibited in varying degrees.The inhibition degree of Sy33 was higher than that of Fy9,and the Cd content of above-ground in Sy33 was greater than Fy9,while the Cd content of below-ground was less than Fy9.It indicated that Sy33 transfers most of the Cd to the above-ground,which severely inhibited growth,while Fy9 stores Cd mainly in the below-ground with less inhabitation on growth.?3?Under Cd treatment,the conductivity of the above ground and underground parts of the two varieties increased,the activity of Lipoxygenase?LOX?increased,more superoxide anion(O₂^-·)and malondialdehyde?MDA?accumulated,and the peroxidation reaction was induced.At the same time,the content of proline and anthocyanin increased,the activity of protective enzyme increased,and the antioxidant capacity of the plants increased,but the change range of the two varieties was significantly different.The antioxidant capacity of Fy9 was significantly improved to reduce the damage of Cd induced peroxidation to plants;compared with Fy9,the antioxidant capacity of Sy33 increased slightly,which was not enough to resist Cd induced peroxidation.?4?Under Cd treatment,the sucrose synthesis ability of the above ground and underground parts of the two varieties decreased,the decomposition ability increased,and the content of soluble sugar increased.In Sy33,the decrease of direction enzyme activity of SPS and SS synthesis was greater than that of Fy9,while the increase of direction enzyme activity of SS decomposition,acid invertase and neutral invertase activity was greater than that of Fy9,which increased the content of fructose and glucose in all parts of Sy33.Compared with Fy9,Sy33 produced more small molecules to improve its osmotic regulation ability.In conclusion,the physiological and metabolic responses of different sensitive maize varieties to Cd stress were different during the germination period.With the increase of stress time,Fy9 mainly resisted the damage caused by Cd stress by improving its antioxidant capacity to reduce its impact on the growth and development of maize at germination stage,and the storage materials in seeds were more used to maintain normal growth.However,the peroxidation reaction was intense in Sy33.Athough the antioxidant capacity was slightly increased,it was not enough to resist the stress of Cd,so the carbohydrate stored in the seed was more decomposed into soluble sugar and was used as the osmotic regulator to improve the osmotic regulation capacity and resist the damage caused by Cd stress on plants,which causes the insufficient supply of growth materials and poor conditions of growth and development.