Study On Response Of Rhizophora Stylosa And Bruguiera Gymnorrhiza To Nitrogen,Phosphorus And Potassium Formula Fertilization Under Different Environment

Mangrove forests refer to woody plant communities that grow in tropical and subtropical estuaries and are dominated by mangrove plants.Mangrove ecosystems provide many important ecological services,such as purifying seawater,maintaining biodiversity,sequestering carbon,mitigating coastal erosion,and mitigating sea level rise.Since mangroves grow in the intertidal zone and are periodically submerged,their living environment is extremely harsh.Most of the seedlings cannot adapt to the harsh environment in the intertidal zone,while the big seedlings have more advantages.Fertilization can provide nutrients needed by plants and promote the growth and development of seedlings.This study was conducted to investigate the effects of nine nitrogen,phosphorus,and potassium fertilizer combinations on the growth and physiology of Rhizophora stylosa and Bruguiera gymnorrhiza,using two cultivation environments: freshwater and half-seawater(salinity is about 15 ‰).Through three factor and three level orthogonal experiments,their morphological and physiological indicators were measured,and the effects of nine nitrogen,phosphorus,and potassium fertilizer combinations on the growth and physiology of Rhizophora stylosa and Bruguiera gymnorrhiza were investigated to summarize the best nitrogen,phosphorus,and potassium fertilizer application techniques,with a view to providing technical guidance for seedling cultivation of Rhizophora stylosa and Bruguiera gymnorrhiza.The conclusion is as follows:(1)In freshwater environment,N,P and K ratio fertilization promoted the morphological indexes of both mangrove plants.When the ratio of N,P and K was1:2:2,the growth rate of plant height was the highest;when the ratio of N,P and K was 2:3:1,the growth rate of base diameter and leaf length was the highest;when the ratio of N,P and K was 3:1:3,the growth rate of leaf width was the highest;when the ratio of N,P and K was 3:3:2,the growth rate of leaf thickness was the highest;SOD activity and chlorophyll content were increased,while CAT activity was decreased.When the ratio of N,P and K was 2:3:1,the growth rate of plant height,leaf width and leaf thickness was the highest;when the ratio of N,P and K was 3:1:3,the growth rate of base diameter was the highest;when the ratio of N,P and K was 2:1:2,the growth rate of leaf length was the highest;when the ratio of N,P and K was 3:3:SOD activity increased first and then decreased,CAT activity and chlorophyll content increased.(2)Under half-seawater environment,all treatments significantly promoted plant height,but significantly inhibited base diameter.The growth rate of plant height was the highest when the ratio of N,P and K was 3:1:3,and the growth rate of base diameter was the highest when the ratio of N,P and K was 2:3:1.It had no significant effect on SOD activity,promoted CAT activity first and then inhibited it,and promoted chlorophyll and photosynthetic indexes mostly in the later stage.All treatments significantly promoted plant height,base diameter,leaf width and leaf thickness.When the ratio of N,P and K was 3:2:1,the growth rate of base diameter was the highest when the ratio of N,P and K was 3:1:3,and the growth rate of leaf width and leaf thickness was the highest when the ratio of N,P and K was 3:3:2.CAT activity increased significantly,and promoted SOD activity,chlorophyll content and photosynthetic index in the final stage.(3)Compared with freshwater and half-seawater environment,half-seawater environment was more conducive to the growth of plant height,base diameter,leaf width and leaf thickness,while freshwater environment was more conducive to the growth of leaf length.half-seawater environment was more conducive to the growth of plant height and base diameter,while freshwater environment was more conducive to the growth of leaf length,leaf width and leaf thickness.(4)In production,according to the different needs of seedling height and diameter thickening,the nursery environment can be adjusted by gradually diluting water and diverting sea water to promote the growth of seedlings.In the fresh water environment,the fertilization ratio of Rhizophora stylosa was: urea: superphosphate:potassium chloride = 1:2:2,and that of Bruguiera gymnorrhiza was 2:3:1.In the half-seawater environment,the fertilization ratio of Rhizophora stylosa was 3:1:3:superphosphate: potassium chloride = urea,and that of Bruguiera gymnorrhiza was 3:2:1.