EFFECTS OF 3 PLANT-GROWTH REGULATORS ON GROWTH, MORPHOLOGY, WATER RELATIONS, AND FROST-RESISTANCE IN LEMONWOOD (PITTOSPORUM-EUGENIOIDES CUNN,A)

Pittosporum eugenioides is a native ornamental species with a wide dis tribution throughout New Zealand. The effects of the application of tw o plant hormones (gibberellic acid and abscisic acid) and a gibberelli n biosynthesis inhibitor (paclobutrazol) on the growth and development , frost resistance, and water loss on two-year old seedlings of P. eug enioides were studied. Gibberellic acid increased plant growth, stem d iameter, and shoot succulence, while also inducing leaf hyponasty and vegetative bud break of apices. Abscisic acid induced growth suppressi on while being effective in promoting leaf epinasty and inhibiting bud break. Paclobutrazol induced growth suppression, promoted epinasty, d ecreased shoot succulence, inhibited bud break in apices, and increase d foliar frost resistance. The effects of paclobutrazol were also over come by the addition of gibberellic acid. The results are compared wit h those gained from species not native to New Zealand, and indicate th e potential for the application of plant growth regulators to a New Ze aland species of ornamental value.