Study On Drought Tolerance Of Sinocalycanthus Chinensis Seedlings

For seeking cultivation measures of Sinocalycanthus chinensis seedlings,the responsemechanism of it was studied,from morphology,biomass,physical indicator,photosyntheticindicator,chlorophyll fluorescence indicator and anatomical structure of organelle,under fourwater supply levels through complete randomized test of single factor.The main results are asfollows:(1)As drought intensified,Sinocalycanthus chinensis seedlings suffered a series ofwilting,searing or death.The growth of which stayed in mild drought could be maintained,whilethem under moderate and severe drought were restrained seriously especially root’s.(2)As drought intensified,relative water content of Sinocalycanthus chinensis seedlingsleaves dropped evidently,and the synthesis of chlorophyll was restrained.The chlorophyll contentof seedlings under both moderate and severe drought increased evidently in middle of droughtstress for which relative water content dropped evidently,but it continued dropped under milddrought.The ratio of Chla and Chlb under drought stress trended to be"up-down".It indicated thatSinocalycanthus chinensis could adapte to mild drought or short-term drought through adjustingChla/Chlb.In addition,the activities of enzyme integrated cooperately to tolerate droughtstress,and there was a great relevance between them and content of malondialdehyde.Osmoticadjustment substances increased evidently during all of stress.(3)The photosynthetic enficiency of Sinocalycanthus chinensis under drought stressdeclined severely.Each seedlings suffered “photosynthetic midday-depress”, and the diurnalvariation curves of net photosynthetic rate turned from double-peak types to single-peak typeswith low peak values under severe stress.The decline of photosynthesis was considered as aresult of stomatal restriction under mild stress,but non-stomatal restriction was the dominantunder moderate and severe stress.And photosynthetic midday-depress was caused by stomatalrestriction.More and more sunlight captured by seedlings was used for heat dissipation notphotosynthesis.(4)Microscopy observations showed that,as drought intensified,anatomical structure oforganelle suffered a series of damage.Chloroplast was more sensitive to drought thanmitochondria.(5)Principle component analysis showed that Sinocalycanthus chinensis could endure milddrought not moderate or severe drought.In eastern China,Sinocalycanthus chinensis as gardenplants should be paid attention on irrigation in drought season. And it is effectual to control waterproperly for preventing excessive growth in non-drought season.