Study On The Adaptability Of Paspalum Wettsteinii Hackel In Karst Habitat

In order to reveal the adaptive mechanisms of Paspalum wettsteinii Hackel in karst habitat,P.wettsteinii was used as material to study the effect of different nitrogen levels,drought stress,calcium treatments,common action of drought stress and calcium treatments on seed germination,Morphological indicators,physiological indexes.It is expected to provide a theoretical basis for the promotion and planting of P.wettsteinii in Southwest China.The main achievements of our studies are as following:P.wettsteinii treated with 3 mmol·L^-1N,which's growth index,biomass and nitrogen content were higher,soluble protein?SP?content and proline?Pro?content,peroxidase?POD?activity,catalase?CAT?activity and superoxide dismutase?SOD?activity were higher,and chlorophyll contents,net photosynthetic rate?P_n?,transpirationrate?T_r?andstomatalconductance?G_s?werehigher,while malondialdehyde?MDA?content and intercellular CO₂ concentration?C_i?were lower.If nitrogen deficiency(1 mmol·L^-1)and excess(7⁹ mmol·L^-1),SP and Pro content,enzyme activity and chlorophyll content of P.wettsteinii would be reduced,and plant growth is inhibited.The conclusion is drawn from 24 indexes of plant morphological index and physiological index,optimum nitrogen level for the growth of P.wettsteinii is 3 mmo·L^-1N.-0.1MPaPEG drought stress were beneficial to seed germination and radicle growth during P.wettsteinii seed germination period.Light drought stress could obviously promote root development,there are a way for the adaptation of P.wettsteinii to drought in growing stage.The experiment showed that SP content,SS content and Pro content,POD activity,CAT activity and SOD activity increased,they can play a critical role in the maintenance of osmotic pressure.Meanwhile,the Chlorophyll content of the leaf were also increased significantly by the drought stress,fully use and enhance photo-synthetic capability.5 mmol·L^-11 and 25 mmol·L^-1CaCl₂ treatment were beneficial to seed germination during P.wettsteinii seed germination period.Compared with the seed stage,the tolerance of the P.wettsteinii to the seedling stage was relatively strong.The appropriate concentration of calcium stress can increase the signal in the plant,regulate the infiltration of cells inside and outside,and increase the activity of protective enzymes,which is conducive to the growth of P.wettsteinii.From the comprehensive analysis of the morphological and physiological characteristics of the P.wettsteinii.under calcium stress,it was concluded that the treatment of 5¹00mmol·L^-11 CaCl₂ treatment could promote the growth of the P.wettsteinii.For the comprehensive stress of the P.wettsteinii,10 treatments were set up in this experiment.Under drought stress,moderate calcium treatment can significantly increase plant height,root system,fresh weight and dry weight,increase POD activity,CAT activity and SOD activity and reduce the degree of peroxidation of cells.P.wettsteinii could grow well under the combined treatment of-0.1^-0.3 MPaPEG drought stress and 5⁵0 mmol·L^-1CaCl₂ treatment.To sum up,the low nitrogen level is more suitable for the growth of P.wettsteinii.For drought stress,P.wettsteinii has a very strong defensive ability,but increased drought intensity will affect its growth.Calcium can effectively relieve the drought damage to the P.wettsteinii,and improve the resistance of the P.wettsteinii in adversity.