Growth And Physiological Biochemical Characteristics Of Seedling In Different Myrica Rubra Species Under Drought Stress

Drought stress, the most severe abiotic stress in damaging plant growth and development, restrictsplant growth. It is of great importance to study and explore the drought resistance mechanism and selectthe most drought resistant and adaptable species to solve problems, such as in non-arid areas withfrequent water shortages and in semi-arid and semi-humid region with vegetation restoration. With theaim of laying a solid foundation for breeding drought resistant Myrica rubra and offering scientificbasis for its promotion and application, one-year-old grafting seedlings of three Myrica rubra forestspecies were studied on the growth characteristics and physiological responses under drought stress,simultaneously through exogenously applied salicylic acid to study their regulated pathway of droughtresistant and reveal the mechanism of drought resistant. the main results are as follows:(1) Drought stress inhibited the individual growth and total biomass distribution of Myrica rubraspecies seedling. The seedling height, ground diameter and total biomass all significantly decreased,while their root/shoot ratio significantly increased.(2) Under moderate drought stress, SOD and CAT activities increased, and then their activitiesdecreased with increasing drought stress level; the proline content increased, soluble protein contentwas not very consistent between each Myrica rubra species and different treatments.(3) Under drought stress, the whole trend of leaf relative electrolyte conductivity, MDA and H2O2content of three Myrica rubra species saplings increased; while leaf RWC significantly decreased.(4) Chlorophyll a, chlorophyll b, chlorophyll a+b and carotenoids all decreased under droughtstress, photosynthetic indexes such as Pn, Gs, Tr and fluorescent indexes Fv/Fm, Fv/Fo, qP alldecreased, while NPQ increased, chlorophyll a/b ratio and Ci were not very consistent between eachMyrica rubra species and different treatments.(5) Through exogenously applied salicylic acid under drought stress, indexes such as seedingheight increment, ground diameter increment, total biomass, root/shoot ratio, leaf RWC, proline content,soluble protein content, SOD and CAT activities, chlorophyll and carotenoids content all increased,Photosynthetic capacity and fluorescence ability enhanced, relative electrolyte conductivity, MDA andH2O2content decreased.(6) According to the comprehensive evaluation of drought resistance for three Myrica rubra species, the results showed that: under moderate drought stress and severe drought stress, the range ofdrought resistance from strong to weak could be: Biqi> Wandao> Shenhong.Considering all the above, here are some suggestions: Biqi appeared to be the most resistantspecies, Wandao was second and Shenhong was the most sensitive to drought conditions in seedling;and exogenously applied certain concentration of salicylic acid could ameliorate damage of droughtstress to plants.