THE EFFECT OF GERMICIDES ON THE LONGEVITY OF CUT FLOWERS

The effect of DICA (50 mg.liter-1), BCDMH (12 mg available chlorine/liter), and HQC (250 mg-liter-1) on the longevity of 14 popular cut flower species was assessed. Longevity was significantly extended in: Rosa hybrida L. 'Gabrielle' and Scilla campanulata L. Squill. by all germicides; Lilium parkmannii L. 'Nepal', Gerbera jamesonii L. 'Mercy', and Narcissus tazetta L. 'Fortune' by DICA and BCDMH; Gypsophila paniculata L. 'R22' by DICA and HQC; and Freesia hybrida Eckl. ex Klatt 'White Bergunden' by BCDMH. No effect on longevity was found in Dendranthema grandiflora (Ramat) Kitamura. 'Horim', Dianthus caryophyllus L. 'Medea', Dianthus barbatus L., Iris hollandica L. 'Pearl', and Gerbera jamesonii L. 'Double Delight'. Longevity was significantly reduced by DICA in Alstroemeria aurantiaca L. 'Mona Lisa' and Tulipa hybrida L. 'Apeldoorn'. Analysis of microbial concentrations showed that proliferation was effectively controlled by DICA and BCDMH, but not by HQC. Levels of up to 10(6) cfu.ml-1 Were detected in water, indicating that species not affected by germicides can tolerate these microbial quantities. Fresh weight and solution uptake data indicated that germicides acted primarily by improving solution uptake. Longevity was significantly reduced in R. hybrida 'Gabrielle' and D. caryophyllus 'Medea' flowers placed in solutions containing high counts of microorganisms (>10(8) cfu.ml-1) isolated from D. caryophyllus or R. hybrida. Chemical names used: 1-bromo-3-chloro-5,5-dimethylhydantoin (BCDMH); sodium dichloroisocyanuric acid (DICA); 8-hydroxyquinoline citrate (HQC).