Effect of Plant Growth Regulators on Shoot Growth of a Columnar Type Apple Tree

Abstract

We investigated the effects of plant growth regulators on shoot growth of a columnar type apple tree. The shoot growth of ‘Trajan’ differed from that of normal type trees and it's growth stopped in June, but then continued until early October. The shoot growth was inhibited in ‘Trajan’ when treated with NAA and MH, but promoted with BA, BA + MH and BA + GA₃. However, the number of shoots was greater when treated with BA than with NAA, and the response to BA alone was greater at 600 ppm than at 300 ppm. In addition, the effects of applying BA plus MH or GA₃ had an interactive effect on ‘Trajan’. It is evident from the above results that cytokinins, auxin, and gibberellins affect shoot growth of the columnar type.