Vol. 72 No: 1

Title:
The Dwarfing Effect of a Single Application of Growth Inhibitors to the Root-Stem Connection—"the Collar Tissue"—of Five Species of Fruit Trees

Authors:
MARIA J. GROCHOWSKA and MALGORZATA HODUN

pp: 83-92

Abstract:
Five species of one year old potted fruit trees (plum, sour and sweet cherries, apricot and pear) were treated once only, with two growth inhibitors at two doses, or with benzyladenine, (BA) at the surface of the collar (the vascular transition region) and at the mid-stem, to diminish growth and enhance fruiting. Paclobutrazol P, (15 mg per tree) and 2,3,5-triiodobenzoic acid, TIBA (3.5 mg per tree) significantly reduced shoot length in all five and two fruit species, respectively, over three consecutive years. The plum trees cv. Early Prune and sour cherry trees cv. Ujfehertoi Furtos were most responsive to P and TIBA applications to the collar. The length of the shoots was reduced to almost one third with P and to half with TIBA compared with the controls in both species. Fruiting of the plum trees treated with P on the collar increased four-fold. When calculated on the basis of tree size, fruiting was still higher compared with that of larger control trees. Plum and sour cherry trees reduced in size by TIBA treated on the collar also showed similar results. An advance in flowering time in pear trees and an apparent reduction in number of flowers (due to the reduced tree size) were observed in sweet cherry and apricot trees after P application on the collar. The TIBA treatment on the collar at a dose of 7 mg per tree markedly increased flowering of the sweet cherry trees but did not affect that of the apricot and pear trees. Also, treatment with BA did not affect shoot elongation or flowering but extended the growth period of the plum and apricot trees. The growth inhibitors, when applied to the mid-stem, affected neither shoot length nor flowering or fruiting of four fruit species, the exception being the sour cherry trees whose growth was significantly depressed. The results indicate that the collar tissue of fruit trees, especially of plum and sour cherry species, is a sensitive region of the trunk and the most suitable location for influencing tree growth and fruiting. The minute amounts of the growth regulators applied are not hazardous to consumers or to the environment, as they are separated in time and place from fruiting in subsequent years and are applied to the tree not to the soil.

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