EXOGENOUSLY SUPPLIED SUCROSE IMPROVES THE POSTHARVEST QUALITY OF GREVILLEA SYLVIA INFLORESCENCES

Short vase life (e.g. 3-7 days) is a problem with inflorescences of Gr evillea used as cut flowers and may be associated with depletion of re spirable substrates. A series of 4 experiments addressing this hypothe sis were conducted with Grevillea hybrid 'Sylvia' inflorescences. In e xperiment 1, the effect of leaf retention on inflorescence stems and a range of sucrose concentrations (0-6% w/v) in vase solutions was inve stigated. In experiment 2, the relationship between inflorescence matu rity (4 stages) and sucrose supply was studied. In experiment 3, the e ffect of sucrose concentration as a short period pulse and pulsing dur ation was determined. In experiment 4, simulated handling and transpor t was undertaken to gauge the practical usefulness of sucrose pulsing to the cut flower industry. These vase life experiments were conducted in a constant temperature room (22 +/- 2 degrees C) at 50-80% relativ e humidity. All vase solutions contained 10 mg chlorine/L to suppress microbial growth. Three percent sucrose (w/v) was found in experiment 1 to be the best vase solution. This treatment gave a mean vase life o f 10.1 +/- 0.2 days, which was 44% longer than the control (no sucrose ) treatment. Inflorescences picked at the 'early looping' stage and pr ovided with 3% (w/v) sucrose had the best overall vase life (12.0 +/- 0 days) and visual appeal in experiment 2. Sucrose pulsing (10% w/v) f or 6-24 h extended vase life by at least 1 day. The presence of leaves shortened the vase life of both sucrose-pulsed and non-pulsed inflore scences by about 1 day in experiment 3. Storage for 5 days at 5 degree s C as handling/transport simulation in experiment 4 did not shorten t he vase life of Grevillea 'Sylvia' inflorescences. Sucrose pulsing (10 % w/v) before simulated handling/transport did not result in a signifi cant increase in the vase life of Grevillea 'Sylvia' inflorescences, a nd is therefore not recommended. To achieve the best floral display, G revillea 'Sylvia' inflorescences should be picked at the 'early loopin g' stage of maturity and then placed in a vase solution containing 3% (w/v) sucrose.