Effects of salinity fluctuation on photosynthetic physiology and growth of two tropical seagrass species
Seagrasses that grow in the intertidal zone is adaptable to salinity fluctuations.However,considering that extreme weather and human activities may cause intensification of coastal seawater salinity fluctuation,the adaptation thresholds of seagrasses to the salinity fluctuation and the physiological mechanism are worth exploring.In this context an experiment was made with controllable salinity fluctuation amplitudes of seawater,and two seagrass species,Cymodocea rotundata and Thalassia hemprichii,were planted in the seawater with different salinity fluctuation amplitudes from 0 to 10.The changes of seagrass growth indicators related to photosynthesis were determined.The results showed that with the increase of salinity fluctuation amplitudes,average leaf area,photosynthetic products,photosynthetic pigments of the two seagrass and leaf growth rate of C.rotundata increased first and then decreased,except for the leaf growth rate and the content of Chl-a for T.hemprichii that increased continuously.Fv/Fm,Fv/Fo,qP and Y(Ⅱ)of the two seagrass species increased first and then decreased,while Y(NPQ),Y(NO)and qN decreased first and then increased.Salinity fluctuation amplitudes,species and their interactions had significant influence on average leaf area,leaf growth rate,contents of starch,soluble sugar,soluble protein,Chl-a,Chl-b,carotenoids,Fv/Fm,Fv/Fo,qP,qN,Y(Ⅱ),Y(NPQ),Y(NO)and maximum electron transport rate(ETRmax)(P<0.05).These results showed that the water environment with salinity fluctuations of 2～6 and 2～10 could promote the photosynthesis and growth of C.rotundata and T.hemprichii,respectively.These ranges of salinity fluctuation are optimum for both the two seagrass species,while other ranges of salinity fluctuation was not conducive to the physiological growth and photosynthesis of the two seagrass species.
NETL
NSTL
万方数据
