Effects Of Three Plant Growth Regulators On The Growth And Physiological Characteristics Of Liquidambar Formosana Seedlings

Plant growth regulators are synthetic organic compounds which are widely used in agroforestry and have regulating effects on plants.Liquidambar formosana is a extremely potential subtropical greening and ornamental tree.It is of guiding significance to study the growth of Liquidambar formosana seedlings under the action of plant growth regulators for the seedling cultivation of Liquidambar formosana.With annual Liquidambar formosana as the experiment object,the effects of GA₃,IAA and PP₃₃₃at different concentrations（0 mg/L（CK）,40 mg/L,80 mg/L and 120mg/L）on the growth and physiological characteristics of Liquidambar formosana seedlings were explored to measure its growth,physiological and photosynthetic indexes,and then the indexes are comprehensively evaluated by analysis of variance,multiple comparison analysis,correlation analysis,principal component analysis and quality comprehensive evaluation of seedlings,the action mechanism of growth regulators on Liquidambar formosana was explored,and the optimum concentration and combination for promoting the differentiation and growth of Liquidambar formosana were selected,thus providing reference and theoretical support for the cultivation and management of Liquidambar formosana seedlings.The main results were as follow:（1）The results of growth index analysis showed that three plant growth regulators with different concentrations all can effectively regulate the growth of Liquidambar formosana seedlings,and IAA has the best effect on promoting the growth of Liquidambar formosana seedlings at 40 mg/L.In terms of growth regulators,GA₃can significantly promote the branch growth of Liquidambar formosana seedlings,IAA can significantly promote the increment of seedling height,and its performance in shoot-root ratio is better than that of GA₃and PP₃₃₃,and PP₃₃₃has inhibitory effect on the increment of seedling height.One-way ANOVA showed that the performance of multiple growth indexes at the concentration of 40 mg/L was better than that of 80mg/L and 120 mg/L.IAA at 40 mg/L has the best performance in increment of ground diameter,leaf area,seedling height increment,biomass and stem-root ratio.GA₃at 40mg/L has the most obvious promotion effect on the number of branches,and has a significant difference with other treatment groups.PP₃₃₃at 120 mg/L has significant inhibition effect on seedling height increment and leaf area,and has highly significant difference with CK.（2）The results of physiological index analysis showed that three plant growth regulators with different concentrations had significant effects on the physiological characteristics of Liquidambar formosana seedlings,among which IAA at 40 mg/L and 80 mg/L have the most effective regulation.After the plant growth regulator treatment,soluble protein,soluble sugar and root activity of Liquidambar formosana seedlings were all improved in different degrees,among which the soluble sugar content increased significantly,and they were very significant different from CK,while IAA has a prominent role in promoting root activity;Compared with CK,the MDA content,SOD activity and POD activity of Liquidambar formosana seedlings treated with growth regulators decreased to varying degrees,and the MDA content of Liquidambar formosana seedlings treated with GA₃decreased most significantly.IAA40 mg/L significantly increased the soluble protein content and root activity of Liquidambar formosana seedlings,and was the best in reducing SOD and POD activities.（3）The results of photosynthetic index analysis showed that three plant growth regulators with different concentrations had different effects on the photosynthetic characteristics of Liquidambar formosana seedlings,and PP₃₃₃at 120 mg/L has a inhibitory effect on the photosynthesis of Liquidambar formosana,which may be that the reduction of leaf area of Liquidambar formosana under the action of PP₃₃₃leads to reduction of photosynthetic efficiency.And the photosynthetic characteristics of other treatment groups were all improved compared with CK,but there was no significant difference,while GA₃at 40 mg/L had the best performance in the total chlorophyll content,Pn,Gs,Tr and Ci.（4）To sum up,IAA at 40 mg/L has the best promoting effect on the growth and physiological characteristics of Liquidambar formosana seedlings.Although its promoting effect on photosynthetic indexes was not the best,there was significant improvements compared with CK.The results of principal component analysis and seedling quality index analysis also showed that IAA at 40 mg/L had the best promoting effect on the growth of Liquidambar formosana seedlings,and the quality of Liquidambar formosana seedlings after plant growth regulator treatment was better than CK.