Postharvest characteristics of cut flowers of selected members of the family Myrtaceae : a thesis presented in fulfilment of the requirements for the degree of Master of Philosophy at Massey University, New Zealand

Abstract

Stages of floral development were described for Eucalyptus ficifolia and Metrosideros collina 'Tahiti' flowers (Myrtaceae) attached and detached from plants. Vase solution treatments were applied to promote bud opening of cut flowers and to prevent postharvest stamen wilting and abscission in both species. Water uptake and mass of harvested flowers in both species declined rapidly when the pedicels were placed in water (control). Some flower buds did not open after harvest. The decline in water uptake and flower mass was greatly reduced by a vase solution treatment containing 2% sucrose, and 200 ppm hydroxyquinoline citrate (HQC) adjusted to pH 4 using citrate buffer. Vase solutions containing higher sucrose concentrations (more than 6%) and of greater acidity (pH<4) were not beneficial for vase life of both species. Cut flowers of both species held in the standard solution (2% sucrose, 200 ppm HQC adjusted to pH 4 using citrate buffer) were treated with ethephon (0-10,000 ppm) following pre-treatment with silver thiosulphate (STS) (0-2.0 mM). Ethephon treatments significantly induced stamen wilting, but had no effect on stamen or petal abscission in both species. Pre-treatment with 2 mM STS had no effect on the rate of stamen wilting, but significantly reduced stamen or petal abscission in both species. Cut flowers of M. collina 'Tahiti' held in the standard solution were treated with ethylene (0-5 ppm). Exogenous ethylene significantly promoted abscission of stamens and petals in M. collina 'Tahiti'. Treatment with 0.5 and 5 ppm ethylene also induced flower abscission. Ethylene emanation from untreated cut flowers from plants grown in two environments (greenhouse and outside) was also measured. Untreated cut flowers harvested from plants grown outside produced more endogenous ethylene than those from plants grown in the greenhouse. The abscission of M. collina 'Tahiti' probably results from a relatively high sensitivity to ethylene.