Eco-physiological Studies On Branching And Trunk Extension Sprouted From Terminal And Lateral Buds In Paulownia Trees

Eco-physiological studies on branching and trunk extension sprouted from terminal and lateral buds was investigated in order to carry out trunk extension by lateral buds and resolve the problem of large crown and lower trunk in paulownia. The results were as follows: ①Paulownia tomentosa ×P. fortunei 33 began to make natural trunk extension in 4 years and couldn't make it successively; Under the conditions of high density and extensive management, there were three typess of branching sprouted from the upper lateral buds: false monopodial branching, sympodial branching and false dichotomous branching, respectively accounting for 44%, 14% and 42%. There was only 10% false monopodial branching between the second-year and the third -year. So natural trunk extension was little, and lead tolarge crown and lower trunk. ②The death reason of terminal buds and the first pair of lateral buds was itself ecological adapting strategy, not the injury of early frost and freezing; The lateral buds 2,3 and 4 had obtained the feature of winter dormancy, and could survive in cold winter, and widen its possible temperature range of sprouting to lower temperature by experiencing winter chilling; They could sprout at the same time in spring, but it was difficult to sprout to other lateral buds; The sprouting of upper lateral buds could restrict the sprouting of lower lateral buds at 25℃, but not at 15℃. ③The regularity of the lateral buds sprouting and branch feature of Paulownia tomentosa × P. fortunei 33 wasn't completely false two fork branches, most of all have forms of only one strong fork branch or it almost seemed more like this, trunk extension behaves good growing condition in nature. At the same time, the condition of trunk extension by terminal bud was related with the account and length of the following ones to some extent. So heredity improvement of stem form to raise its wood production should put emphasis on how to make sure of the second year trunk extension growing well. After trunk extension by the terminal bud, all other buds from the firth to end could be cut off, certain sum of buds could make the trunk extension effects better. ④The difference of length extension among natural trunk extension, no trunk, 40cm trunk, 80cm trunk and 120cm trunk was not obvious, to width extension, no trunk were better. ⑤There were differences of branching and trunk extension sprouted from terminal and lateral buds among different provenances in paulownia.