Kangaroo paw inflorescences stored dry at 0 to 1°C for 14 days have been found previously to have substantially reduced post-storage vase life. In this project, experiments were conducted to quantify the vase life of dry, stored Kangaroo paw flowers following storage at either 0, 7.5 or 13°C for up to four weeks. the aim of these experiments was to determine a dry storage temperature suitable for commercial use. experiments were carried out using two cultivars of Kangaroo paw, 'Bush Dawn' and 'Big Red'. For each cultivar, vase life was assessed by (1) determining the time taken for each flower to lose 20% of its initial fresh weight and (2) determining the time taken for 10% of the inflorescence to become to discoloured. Vase life studies were carried out a 22°C prior to and following removal from low temperature storage and flowers were weighed, inflorescence colour determined and chlorophyll fluorescence parameters Fo, minimal fluorescence emission, and Fm, maximum fluorescence emission were determined.
The results indicated that ~n general the post-storage vase life of cv. 'Bush Dawn' and 'Big Red' were reduced by 35 and 60% respectively compared to their unstored controls. When the effects of storage temperature and duration of storage were separated for cv. 'Bush Dawn', it was found that both temperature and period of storage had a significant effect on the vase life of this cultivar. The vase life of cv. 'Bush Dawn' ranged from a mean of 6.6 days for flowers stored at 0°C for up to 4 weeks, to 3.5 days after 4 weeks at 13°C. For flowers stored at 0, 7.5 and 13°C for 7 days, the mean vase life was 8.4 days and for flowers stored at these same temperatures for 4 weeks, the mean vase life was 3.4 days. For cv. 'Big Red' the vase life ranged from 7.4 days following storage at 0°C to 2.4 days at 13°C for 2 weeks. For cv. 'Bush Dawn', inflorescence colour measured with a laboratory colour scan showed that the colour parameters, value and chroma (-1.095 to -11.333) differed significantly (p > 0.05) between each storage temperature. The effect of the storage temperature on flower colour that is 'hue' was non-significant. As the duration of storage increased from 1 to 2, 3, and 4 weeks there was a significant change in flower colour. This was seen in the colour parameters, value and hue, which changed from 4.733 to 4.862 and 1.108 to 24.903 respectively during 4 weeks. For cv. 'Big Red' there was no significant difference in any of the colour values during the three storage treatments.
The effect of storage temperature on the chlorophyll fluorescence parameters, Fo and Fm was highly significant (p > 0.01) in the cv. 'Bush Dawn'. Mean Fo values increased by 30.87, 10.48 and -2.31% following flower storage at 0, 7.5 and 13°C respectively for up to 4 weeks and Fm decreased after storage. For cv. 'Big Red' the storage temperature did not affect the value of the Fo and Fm readings. In both cultivars, the Fv/Fm ratio declined from 0.85 to 0.56 in flowers stored at either 0 or 13°C for up to four weeks. The Fv/Fm ratio was unchanged across all periods of storage at 7.5°C. The reduction in Fv/Fm at 0°C was attributed to the inflorescence becoming chill injured, while the marked reduction in Fv/Fm in flowers stored at 13°C for up to four weeks was thought to be due to flower senescence. The poststorage vase life was highly correlated with post-storage Fm values (r = 0.859). The correlation coefficient for post-storage vase life and colour Chroma values was 0.650.
The results clearly demonstrate that Kangaroo paw flowers should not be stored at 0°C or 13°C if a prolonged post-storage vase life is required. Comparative results from flowers kept at the three storage temperatures showed that 7. 5°C was the optimum for prolonging post-storage vase life of this flower. The highly significant correlation (p > 0.01) between post-storage chlorophyll fluorescence maximum (Fm) and vase life (0.859) is a clear and definite indicator for predicting vase life of post-storage cut flowers. Using appropriate regression models for a standard set of cut flowers post-storage Fm values can be used to predict the post-storage vase life of Kangaroo paw flowers. This will have great application at commercial level.