The Research Of Response Of Seed Germination And Seedling Growth Of Gleditsia Microphylla To Drought Stress And Exogenous Ca²⁺

Most of Gleditsia microphylla grow in north China.This species has strong water retention ability and nitrogen fixation,so it has high economic and ecological utilization value.In this study,the effects of drought,exogenous Ca²⁺and their interactions on seed germination and seedling growth were studied.This experiment adopts the method of simulated drought PEG,by adding different concentrations of exogenous Ca²⁺treatment field of Gleditsia microphylla seeds and seedlings under drought stress,to reveal the limestone mountain wild honeysuckle relations with exogenous Ca²⁺and drought resistance mechanism of drought tolerance for future development and utilization,the ecological environment restoration,soil restoration,etc.To provide theoretical basis and reference value.In this study,different drought levels(5,10,15,20,25%)and different levels of exogenous Ca²⁺(15,20,25,30mmol·L^-1)were combined to detect a series of effects on the morphological and physiological indicators of Gleditsia microphylla seeds and seedlings.The main research results are as follows:(1)Under single drought treatment,with the increase of PEG concentration,the germination rate,germination potential,germination index and vigor index of Gleditsia microphylla seeds showed a gradual decline.However,under the treatment of single exogenous Ca²⁺,the germination potential and germination index of seeds with high concentration of exogenous Ca²⁺had obvious inhibitory effect,while the germination rate and vigor index were not significantly affected,indicating that the inhibitory effect of single exogenous Ca²⁺on seed germination was not so obvious.The interaction between exogenous Ca²⁺and drought had an obvious effect on the germination of Gleditsia microphylla seeds.Under drought conditions,exogenous Ca²⁺of 15,20 and 25mmol·L^-1had an obvious promoting effect on seed germination,of which 20mmol·L^-1had the best effect.(2)Different morphological changes of Gleditsia microphylla seedlings were observed under drought conditions.The results showed that plant height,root length,aboe biomass and root activity all decreased,while the dry weight of underground part increased.Moreover,in the case of drought,the growth and development of plants were restricted,and the accumulation of organic matter in plants decreased.20mmol·L^-1exogenous calcium had the strongest mitigation effect on morphological indexes of wild saponata seedlings under drought conditions.(3)Under drought stress,the soluble protein and chlorophyll contents in the plant body of wild sapontia japonica showed a decreasing trend,the contents of SOD,POD and CAT first increased and then decreased,while the content of free proline gradually increased,indicating that the photosynthesis,respiration and metabolism of plants under drought stress all decreased.However,only malondialdehyde and chlorophyll contents were affected by single exogenous calcium treatment.It indicates that the MDA content in cells will rise due to the action of high concentration of exogenous calcium,and thus cause toxicity to plant cells.The low and medium concentrations of exogenous calcium can increase the content of chlorophyll and speed up the rate of photosynthesis.When different concentrations of exogenous calcium were applied to Gleditsia microphylla seedlings under drought conditions,exogenous Ca²⁺of 15,20 and 25mmol·L^-1could effectively improve the metabolic level of plants,among which,exogenous calcium of 25mmol·L^-1was undoubtedly the best.In this experiment,medium and low concentrations of exogenous calcium significantly stimulated seed germination and seedling growth of Gleditsia microphylla,among which 25mmol·L^-1exogenous Ca²⁺had the best effect on drought relief.