The Effects Of Gibberellic Acid On Photoassimilate Reallocation Pattern Of The Poplar Cutting Seedling

Using the methods of physiological,biochemical mensuration and the stable isotope analysis technique,we studied the regulative effects of the exogenous GA₃ on the growth,photoassimilate and sucrose-metabolizing enzymes.The effects of gibberellic acid on photoassimilate reallocation pattern of the Populus×euramericana 'Nanlin895' cutting seedling were explored.The results showed as follows:1.With the increase of GA₃ concentration,exogenous GA₃ promoted the increase of the plant height and ground diameter of the Populus×euramericana 'Nanlin895' cutting seedling.5mg/L and 50mg/L GA₃ had no effects on the number of new increasing leaves,but 150mg/L and 300mg/L GA₃ caused the apical stem to be necrotic,and also leaves on the apical stem were shrinkage or absence.2.Exogenous GA₃ promoted the metabolism of the soluble sugar in the stem. 50mg/L GA₃ was the optimum concentration to promote the production of the chlorophyll,fructose,total soluble sugar in the leaves and photosynthetic capacity of the Populus×euramericana 'Nanlin895' cutting seedling.And 150mg/L GA₃ was the best concentration to the production of sucrose in the leaf.However,50mg/L GA₃ was the best one to the accumulatio?? sucrose in the stem.3.GA₃ promoted the activity of SS and SPS in the leaf or stem.Synchronously, GA₃ inhibited the activity of AI and NI in the stem.However,50mg/L GA₃ was the best to promote the increasing activity of AI and NI in the leaf.4.In the earlier stage of GA₃ treatment,the production and accumulation of the soluble protein of the Populus×euramericana 'Nanlin895' cutting seedling were inhibited respectively.Later on,it could be promoted.Furthermore,with the increase of exogenous GA₃ concentration,endogenous IAA content in the leaf increased,and endogenous GA₃ content was decreased.Besides,endogenous ABA and ZR content were not affected obviously.5.With the increase of GA₃ concentration,theδ¹³C value of leaves decreased,theδ¹³C value of stem increased,and theδ¹³C value of roots initially increased,then reduced.All in all,50mg/L was the best one which affected on carbon fractionation, and enhanced late growth of the Populus×euramericana 'Nanlin895' cutting seedling.