The Study Of The Relationship Between The Content Of Water Soluble Carbohydrate And Competitive Ability Of Wetland Plants Under Different Environmental Conditions

Competition is the process that plants compete for the resources,and competition ability is an indicator to reflect the ability of the plant to capture resources,including two aspects: competitive response and competitive effect.The competitive response reflects the ability of plants to resist competition pressure,and the competitive effect reflects the ability of plants to inhibit competitors' growth.At present,researches on competitive ability mostly focus on changes in external morphology,such as plant height,root shoot ratio,and so on.There are few studies on internal physiological changes.Water soluble carbohydrates are energy sources of plant life metabolism.When under environmental stress,the content and distribution of water soluble carbohydrates will change accordingly to support the plants to resist and adapt to the changes in the external environment.Recently,the research on the response of water soluble carbohydrates to external environmental factors is mainly focused on abiotic factors such as light and nutrition,and so on.However,there are fewer studies on the effects of biotic stress,such as competition,on soluble carbohydrate content.The analysis of the changes in the content of soluble carbohydrates in the process of competition and their relationships with the competitive ability might help to develop new approaches to deeply reveal the mechanism of competition and improve the theories of plant competition.Meanwhile our finding also could provide theoretical basis for developing and applying technologies for the restoration and reconstruction of degraded vegetation.Six plants in peatland,Eleocharis valleculosa,Saussurea amurensis,Lysimachia davurica,Geranium erianthum,Carex angustior and Comarum palustre,were selected as target species,which competing with Carex angustior,the competing species,respectively.Under the outdoor conditions,we set up two nutrient conditions(high and low soil nutrients)and two light conditions(full sunshine and shading).The total biomass,contents of water soluble sugar and starch were measured.The effects of different environmental conditions and competitive factors on the plant biomass and soluble carbohydrate(water soluble sugar and starch)were analyzed.The relationship between plant competition ability(including competition response and competitive effect abilities)and plant soluble carbohydrate contents were discussed.The main conclusions are as follows:(1)The competition results showed species-specificity when C.angustior competed with the six species of wetland plants.When C.angustior competing with E.valleculosa,the growth of both sides were suppressed.When competing with S.amurensis,the competition improved the growth of C.angustior,while the result was opposite when competing with G.erianthum that the growth of the target plant was improved.however when competing with Comarum palustre and Lysimachia davurica,the results of competition were influenced by environmental conditions.(2)Nutrient,light,and competition treatments had different effects on plant biomass in the six competitive combinations.In most cases,full sunshine and high soil nutrients promoted the accumulation of plant biomass,and competition generally leaded to a decline in plant biomass.However,due to the differences of characteristics among species,the effects of nutrient,light and competition treatments on plant biomass were opposite in some conditions.(3)In different competitive combinations,the specific response of soluble sugar and starch content in root or leaves of plant to nutrient,light and competition might be related to the morphological structure and resource acquisition ability of plants,which directly affected the final results of competition.(4)The relationships between the ratio of soluble carbohydrates and competitive ability of different parts of plants under competition stress is significantly influenced by environment.The relationship between soluble carbohydrate content ratio and competitive response in leaves was significant,and influenced by light conditions,which was significantly negative under full sunshine condition.The ratio of soluble carbohydrate content in roots significantly related with the competitive effect,and was strongly influenced by nutrients.Under low nutrient conditions,the significant negative correlation became into positive when the light intensity increasing.