The Acid Erosion Experiment Of Melliodendron Xylocarpum Seeds And The Response Of Seedling Growth And Photosynthetic Parameters To Light Intensity

This paper explores the suitable conditions for seed germination of Melliodendron xylocarpum and the differences between seedling growth and photosynthetic physiology under different light intensities,aiming at revealing seed germination and seedling growth law of Melliodendron xylocarpum and providing theoretical basis for protection and utilization of Melliodendron xylocarpum.In this study,Melliodendron xylocarpum collected in Hangzhou Botanical Garden of Zhejiang province and Shaoguan garden of Guangdong Province were used as research materials,determination of contrast analysis of morphological characteristics,life force and the water absorbability,fruit to different concentration of sulfuric acid and then distilled water（0,10%,20%,30%,40%）,different immersion time（20 min,40 min,1 h）acid etch,research the acid corrosion effect on the seed germination;Four kinds of light intensity treatments（shading rate 0（L0）,40.50%（L1）,78.08%（L2）and 95.54%（L3））were used to compare and analyze the effects of different light intensity treatments on seedling growth and photosynthetic characteristics.The results are as follows:1.The variation coefficient of Melliodendron xylocarpum morphology was higher than that of Hangzhou Botanical Garden provenance.The seed viability of the two provenances was 98%,and the water absorption was 50%.Acid etching treatment can improve the seed germination rate of Melliodendron xylocarpum in both of the two sources,both with sulfuric acid concentration of 20%and soaking for 1 h,the seed germination rate of Melliodendron xylocarpum in Patio Forest Farm is higher than that in Hangzhou Botanical Garden,and the average seed germination rate of Melliodendron xylocarpum was 50%higher than that of Hangzhou Botanical Garden.2.With the decrease of light intensity,the growth of seedling height and ground diameter of Melliodendron xylocarpum seedling increased first and then decreased,The maximum seedling height and ground diameter growth occurred in The L2 treatment in summer,while in the L1 treatment in autumn.In summer,all light control treatment inhibited the growth of Melliodendron xylocarpum seedlings,and L3 treatment also reduced the growth of Melliodendron xylocarpum seedlings.3.The Pn process of Melliodendron xylocarpum seedlings under different light intensities was‘bimodal’type,and the phenomenon of‘siesta’was obvious,which was caused by non-stomatal limiting factors.Pn,Gs,Tr and WUE all showed a trend of first increasing and then decreasing with the decrease of light intensity,and the maximum value appeared in summer and autumn at L2treatment,while Ci and LUE showed a trend of first decreasing and then increasing,showing‘W’and‘U’type variation characteristics respectively.4.With the decrease of light intensity,Pmax,AQY and LSP of Melliodendron xylocarpum seedlings showed a trend of first increasing and then decreasing,and the maximum value appeared in L2 treatment.The LCP keeps going down.The variation range of LCP was 1.652μmol·m^-2·s^-1-39.742μmol·m^-2·s^-1,and the variation range of LSP was 372.8μmol·m^-2·s^-1-1588.267μmol·m^-2·s^-1,indicating that they had strong light preference and shade tolerance.5.With the decrease of light intensity,F_V/F_M and F_V/Fo of Melliodendron xylocarpum seedlings showed a trend of first increasing and then decreasing,and the maximum values in summer and autumn appeared in L2 and L1 respectively,indicating that the seedling growth was best under L2treatment in summer and L1 treatment in autumn.