Manipulation of oleander growth, development and foliage colour by paclobutrazol and ethephon

The effect of different doses of paclobutrazol (1, 5, 10, 20, 40 and 80 mg per plant) and ethephon (0.1, 0.5, 1, 2, 3 and 5 g per plant) on the growth , development and leaf colour of oleander seedlings (Nerium oleander L. cv. Ajauque) was studied in order to evaluate the use of these plant growth re tardants in the pot cultivation of this plant. The length of time which the effect of such treatment lasted was evaluated by studying the above parame ters, four months and one year after treatment. At the first evaluation pac lobutrazol (greater than or equal to5 mg) and ethephon (greater than or equ al to0.1 g) were seen to have inhibited plant growth since plant height, in ternode length and the aerial part dry weight were substantially reduced. E thephon (greater than or equal to0.5 g) significantly increased the number of shoots per plant compared with the control, while paclobutrazol did so a t all the doses assayed. Paclobutrazol (greater than or equal to 20 mg) and ethephon (greater than or equal to0.5 g) reduced the leaf blade area. Pacl obutrazol (greater than or equal to 40 mg) gave the leaves a more elliptic shape, while ethephon had no effect in this respect. Paclobutrazol (greater than or equal to5 mg) imparted a slightly darker green colour to the leave s while ethephon (greater than or equal to2 g) had the opposite effect. The latter compound at a dose ! 3 mg imparted a slightly yellowish colour to t he leaves. At the second assessment, the plants treated with both paclobutr azol and ethephon continued to show restricted growth but any effect on fol iage colour had disappeared. The degree to which plants were affected depen ded on which parameter was being analysed (internode length was the most af fected by paclobutrazol and leaf blade area by ethephon) and Von the partic ular doses (the higher doses had a stronger effect).