Effects of Commensalism on the Physiological and Growth Characteristics of Thalassia hemprichii and Cymodocea rotundata
There are few researches about commensalism—an important ecological phenomenon,existing widely in the plant kingdom—in marine plant,such as seagrass.The phenomenon of highly overlapping distribution of Thalassia hemp-richii and Cymodocea rotundata in the seagrass meadows of Hainan Island having been discovered,a simulation experi-ment was conducted by separate and mixed planting of the two seagrass species,so as to evaluate the influence of the commensalism environment on the physiological and growth conditions of Thalassia hemprichii and Cymodocea rotundata,and explore the symbiosis mechanism of the two seagrasses.It was found that the symbiotic environment could improve the primary productivity of Cymodocea rotundata,which showed that the leaf growth rate and average leaf area of Cymodocea rotundata was improved.Besides,the symbiotic environment could effectively promote the accumulation of nitrogen and phos-phorus elements in the leaves of Cymodocea rotundata.The commensalism with Thalassia hemprichii could increase the pho-tosynthetic pigments contents of Cymodocea rotundata,such as Chl-a,Chl-b and carotenoid.The contents of photosynthates—starch,soluble sugar and soluble protein,which are important for cell permeation—were significantly(P＜0.05)or extreme significantly(P＜0.01)increased,which could be taken as the evidences of enhancing the photosynthesis and stress resis-tance of Cymodocea rotundata.In the underground part,the root activity of the Cymodocea rotundata also increased signifi-cantly in the symbiotic environment.However,symbiotic environment had no significant effect on the physiological and growth characteristics of Thalassia hemprichii.Therefore,co-growing with Thalassia hemprichii,a favorable and partial com-mensalism for the Cymodocea rotundata,could enhance the physiological and growth activities of Cymodocea rotundata.
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