光强和土壤含水量对云南蓝果树幼苗生长及光合特征的影响

Effects of Light Intensities and Water Conditions on Growth and Photosynthetic Characteristics of Nyssa yunnanensis Seedlings

采用盆栽室内受控试验的方法,研究不同光强水平(100%光照、60%光照和20%光照)和不同土壤含水量(100%WHC、91.68%WHC、82.85%WHC、60.00%WHC、41.86%WHC和21.28%WHC)(田间持水力,WHC)对云南蓝果树幼苗生长和光合特征的影响。结果表明:随着土壤相对含水量的降低,云南蓝果树幼苗的叶片数目、叶总面积、株高、地下部分生物量、地上部分生物量、净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)都显著降低。高光强水平(100%光照)和深度遮阴(20%光照)均不利于云南蓝果树幼苗的生长及光合作用,适度遮阴(60%光照)最利于幼苗的个体发育。而且,当土壤含水量充足时,光合指标在不同光强水平处理间的差异不显著;当土壤干旱时,不同光强水平处理间的差异显著,其中60%光照处理下其光合指标均高于其他两种光强水平处理。综合评价得分结果表明,60%光照和土壤含水量充足条件下各指标的综合评价得分都最大,进一步证明了适度遮阴可以促进云南蓝果树的幼苗生长,而光强水平过高或过低,都不利于其生长发育。建立的二元线性回归方程表明,对于云南蓝果树生长指标来说,土壤含水量对云南蓝果树幼苗的影响要高于光强的影响;而对于云南蓝果树光合指标来说,光强的贡献率更高。因此,充足的土壤含水量(100%WHC)和中等光强水平(60%光照)最适合云南蓝果树幼苗的生长。

In this study,controlled pot experiment was carried out to study impacts of different light intensities(100%light,60%light and 20%light)and different water conditions(100%,91.68%,82.85%,60.00%,41.86%,and 21.28%WHC)(water holding capacity,WHC)on growth and photosynthetic characteristics of N.yunnanensis seedlings.Measurements were taken after 6 months of seedlings treated.Both growth parameters,including leaf area,plant height,root biomass and aboveground biomass,and photosynthetic characteristics,including Pn,Tr and Gs of N.yunnanensis seedlings were decreased with the decrease of soil relative water content.Intense light irradiation(100%light)and deep shade(20%light)were detrimental for the growth and photosynthesis of N.yunnanensis seedlings,but moderate shade(60%light)was most conducive to the individual development of seedlings.When the soil moisture were sufficient,differences in photosynthetic indexes among different light intensity treatments were not significant;however,differences were significant under drought stress conditions.The photosynthetic indexes of 60%light treatments were higher than those of the other two light intensity treatments.The results of comprehensive evaluation demonstrated that the comprehensive evaluation scores of all indexes were the largest in 60%light and soil moisture conditions treatments.The moderate shade could promote growth of N.yunnanensis seedlings,but both the too high or too low of the light intensity were bad for their growth and development.Established linear regression equation of two variables demonstrated that the effects of soil moisture were more important than that caused by light on seedling growth,whereas the contribution rate of light intensity was greater for photosynthetic indexes.Therefore,adequate soil relative water content(100%WHC)and moderate light intensity(60%light)were best suited for the growth of N.yunnanensis seedlings.