Abstract:

In order to carry out trunk extension by lateral buds, the laws of branching and trunk extension from lateral buds were investigated in 1-year-old seedlings of Paulownia tomentosa × P. fortunei 33 under natural conditions. The results were as follows: 1)The rate of individuals with characteristics of false dichotomous branching was 42% in seedlings of Paulownia tomentosa × P. fortunei 33 under conditions of high density and extensive management. They could not extend their trunks. However other individuals could do it with features of sympodial branching and false monopodial branching (Close to monopodial branching that terminal buds can extend their trunks). These 3 types of branching all could be called branching of false axis; 2)The form quotients of extended trunk were larger but individuals which could vertically extend their trunks were only 14%, individuals of 86% could not straightly extend in the second year, improving their straight degrees needed for 2～3 years; 3)The lengths and diameters of branching were smaller and smaller, but the angles from branching up to trunk were larger and larger, to the fourth lateral branches the angles reached to the largest, then smaller and smaller from upper lateral buds to down lateral buds among individuals of extended trunks. All branches under the fourth lateral branches were dead.

Key words: Paulownia tomentosa ×, P. fortunei 33;sprouting of lateral buds;branching;trunk extension