Effects of gibberellin on the growth and the flowering of several evergreen ornamental trees and shrubs

Abstract

Experiments were carried out in order to investigate the effects of gibberellin on growth, flowering and cold-resistance of several evergreen ornamental trees and shrubs. Gibberellin was applied to the plants by spraying asaqueous solution and single or monthly repeated applications (from August to October) were made. Concentration of sprayed solution of gibberellin were 50 and 100 ppm. Comparison was made between treated plants and non-treated control plants.
The results obtained are as follows:
(1) Growth of them were generally more increased in high concentration or in repeated application of gibberellin solution than in other cases. The effect of growth-increase was in order from “Otometsubaki (Camellia japonica L. var. rosacea MAKINO)”, “Winter Daphne (Daphne odora THUNB.)”, “Evergreen Spindle-tree (Euonymus japonicus THUNB.)” to “Cape Jasmine (Gardenia jasminoides ELLIS forma grandiflora MAKINO)”
(2) Flowering of Winter Daphne was rema kable hastened by spraying of gibberellin solution. The higher concentration or the more repeated application of gibberellin solution the more hastened the flowering of Winter Daphne. The remarkably hastened flowering was about five months earlier than the normal flowering.
(3) Cold-resistance of Cape Jasmine was weakened by spraying of gibberellin solution. The higher concentration or the later spraying of gibberellin solution the more weakened the cold-resistance of them. Eew of them were dead.