Effects Of Light Treatment On Growth And Physiological Characteristics Of Rhododendron Trefoil

Syzygium grijsii belongs to the genus Syzygium and Myrtaceae.It has a small plant and is suitable for making bonsai with high ornamental value.At the same time,it also has high medicinal value,which can treat edema and clearing heat and detoxification,so it has a very broad market prospect.In order to make sustainable use of this resource,the effects of different temperature and gibberellin concentration on seed germination were studied.Five low light gradients of 100μmol·m-2·s-1,40μmol·m-2·s-1,20μmol·m-2·s-1,100μmol·m-2·s-1 and 2μmol·m-2·s-1 were simulated in the artificial climate chamber.Five shading treatments of 1000μmol·m-2·s-1,800μmol·m-2·s-1,600μmol·m2·s-1,400μmol·m2·s-1 and 200μmol·m-2·s-1 were set through shading nets on the roof.To explore the response mechanism of physiological characteristics to different light treatments,and to provide theoretical basis for breeding and garden application of Chennan triloba.The main findings show that:(1)The seeds could germinate at 15-25℃,but the germination rate and germination potential increased with the increase of temperature,and the optimal germination temperature was 25℃.(2)The germination time of the seeds was increased under three different gradient gibberellin concentrations(50mg/g,100mg/g,150mg/g),and the germination rate and germination potential were significantly increased under 100mg/g.(3)The leaf area and plant height of C.triloba treated with low light increased to varying degrees,and the growth rate decreased with the weakening of light intensity,and the leaf color became lighter.Under 2μmol·m-2·s-1 light,the growth of C.triloba was hindered,the leaf yellowed,dried and dropped,and gradually died after 40 days.Under 40-100μmol·m-2·s-1 light,the growth state of C.trifolia was good,the values of Fv/Fm,qP and ETR increased,the Fo decreased,the chlorophyll content increased,the accumulation of photosynthates increased,and the activity of MDA increased significantly.However,under 10-20μmol·m-2·s-1 light,the active oxygen content of C.triphosa after 20 days of treatment did not accumulate seriously,the chlorophyll content still increased in a short time,and the SOD content showed a trend of decreasing first and then increasing,but with the elongation of time,the physiological indexes showed a certain stress resistance under 1Oμmol·m-2·s-1 light.The MDA activity,soluble protein and soluble sugar contents were significantly lower than those in the initial stage of stress,but the normal growth could be maintained.(4)The growth and physiological activity of C.triloba under shade treatment could maintain normal during the whole stress period.Under the light of 1000μmol·m-2·s-1,the leaves turned green and red,and still continued to grow.When the light was lower than 600μmol·m-2·s-1,the growth condition was good,the leaf area and plant height increased significantly,the leaf color was dark green,the chlorophyll content showed an overall upward trend,the photosynthetic products were significantly higher than the initial stage of stress,and the MDA content continued to decrease.When the light intensity was 400μmol·m-2·s-1,SOD activity and soluble protein content increased significantly,Fv/Fm,qP,ETR values increased,Fo decreased.When the light intensity increased at 800-1000μmol·m-2·s-1,the leaf color gradually became yellow-green with the increase of light intensity,the branches were obviously dry,the MDA content increased,the SOD activity was lower than the initial stage of stress,the relative water content of the leaves changed little,and the membrane permeability gradually decreased with the decrease of light intensity.(5)The principal component analysis of physiological indicators showed that under low light stress,the comprehensive score of C.triphyllum was the highest under 100μmol·m-2·s-1 light intensity,indicating that the growth condition was the best under 100μmol·m-2·s-1 light.Other light gradients were as follows:40μmol·m-2·s-1>20μmol·m-2·s-1>10μmol·m-2·s-1;In the shade treatment test,the comprehensive score was the highest under 400μmol·m-2·s-1 light intensity,indicating that the growth condition was the best under 400μmo·m-2·s-1 light.Other rankings were as follows:200μmol·m-2·s-1>600μmol·m-2·s-1>800μmol·m-2·s-1>1000μmol·m-2·s-1.