H. van Gelder

Reconsideration of the use of deionized water as vase water in postharvest experiments on cut flowers

Abstract The relevance of deionized water as a control treatment in vase life experiments and the effects of major tap water components on cut flower water balance were investigated. Chrysanthemum ( Dendranthema x grandiflorum Tzvelev cv. Cassa) was used in all experiments. Deionized water gave a sharp decrease in fresh weight of the cut flowers after 1–3 days. This decrease was absent in tap water. After 4 days in deionized water, hydraulic resistance in the basal part of the stem was ∼50 times the value of fresh cut flowers and seven times the value in tap water. Change in fresh weight during vase life in a solution containing combinations of CaCl 2 , NaHCO 3 and Cu 2+ at concentrations commonly present in tap water was similar to that in tap water. However, none of the minerals tested by themselves gave fresh weight results similar to those from using tap water. In the combined solution, hydraulic resistance in the basal part of the stem after 4 days was comparable to that in tap water. A minimal amount of Cu 2+ (>0.30 mg·l −1 ) enhanced fresh weight, probably by reducing bacterial growth in the cut open vessels. Calcium chloride (>0.7 mM) delayed the increase in hydraulic resistance in the stem (not including the basal 3 cm) compared to deionized water, and at a high concentration (10.7 mM), substantially decreased the transpiration rate. Sodium bicarbonate (1.5 mM) neither affected hydraulic resistance nor transpiration rate, but positively influenced fresh weight change during vase life when combined with CuSO 4 and as compared to deionized water. Results strongly question the appropriateness of deionized water as a control solution in vase life experiments.

Effect of time since harvest and handling conditions on rehydration ability of cut chrysanthemum flowers

Abstract Fresh cut chrysanthemum (Dendranthema x grandiflorum ‘Cassa’) flowers rehydrated fully after rapid water loss over 1 h at 20°C, 60% relative humidity (RH), and 14 μmol·m−2·s−1 light, the water loss being 5% of their fully saturated fresh weight. For rehydration after desiccation, it proved important that flowers were cut at a minimum distance above soil level. The water status of cut flowers dry-stored in darkness for 24 h at 20°C with minimal water loss (∼1%) decreased sharply during the first days of subsequent vase life. Flowers stood for 3–4 h in 20°C water and at low light intensity (14 μmol·m−2·s−1) followed by ‘desiccation’ did not rehydrate after the desiccation, but decreased further in fresh weight when returned to water. Rehydration ability of these flowers was restored, however, when the stem ends were trimmed by 7 cm under water after desiccation. Recutting in air did not restore rehydration ability. After periods of 4 or 24 h at 20°C in 5°C water at low light intensity followed by desiccation, flowers regained their water status during subsequent vase life. Flowers stood for 24 h in 20°C water and at high light intensity (187 μmol·m−2·s−1) followed by desiccation rehydrated almost fully when returned to water. It is proposed that an undefined ‘rehydration-inhibiting’ process starts after harvest, which is not due to dehydration of xylem walls or other stem tissue, or to the growth of microorganisms.

Reconsideration of the use of deoonized water as vase water in postharvest experiments on cut flowers (corrected version)

The relevance of deionized water as a control treatment in vase life experiments and the effects of major tap water components on cut flower water balance were investigated. Chrysanthemum (Dendranthema x grandiflorum Tzvelev cv. Cassa) was used in all experiments. Deionized water gave a sharp decrease in fresh weight of the cut flowers after 1–3 days. This decrease was absent in tap water. After 4 days in deionized water, hydraulic resistance in the basal part of the stem was ∼50 times the value of fresh cut flowers and seven times the value in tap water. Change in fresh weight during vase life in a solution containing combinations of CaCl2, NaHCO3 and Cu2+ at concentrations commonly present in tap water was similar to that in tap water. However, none of the minerals tested by themselves gave fresh weight results similar to those from using tap water. In the combined solution, hydraulic resistance in the basal part of the stem after 4 days was comparable to that in tap water. A minimal amount of Cu2+ (>0.30 mg·l−1) enhanced fresh weight, probably by reducing bacterial growth in the cut open vessels. Calcium chloride (>0.7 mM) delayed the increase in hydraulic resistance in the stem (not including the basal 3 cm) compared to deionized water, and at a high concentration (10.7 mM), substantially decreased the transpiration rate. Sodium bicarbonate (1.5 mM) neither affected hydraulic resistance nor transpiration rate, but positively influenced fresh weight change during vase life when combined with CuSO4 and as compared to deionized water. Results strongly question the appropriateness of deionized water as a control solution in vase life experiments.

Water relations and keeping-quality of cut Gerbera flowers. V. Role of endogenous cytokinins☆

Abstract The objective of the present work was to investigate if differences in internal water relations, due to differences in membrane permeability, between Gerbera petals of inflorescences ageing in a vase and on the plant could be ascribed to differences in cytokinin activities. Moreover, cytokinin activities in petal-extracts of 3 cultivars, differing in their keeping-quality, were compared. Cytokinin activities (“free” and “bound”) in petals decreased during the first 6 days of the experiment (both in the vase and on the plant). On Day 8, a very high activity was found in almost all the R f -fractions of the chromatogram. After Day 8, the activity decreased again. For young inflorescences, developing on the plant, a peak level was reached for “free” cytokinins at a very early bud stage and for “bound” cytokinins when the petals were just fully expanded. There were no correlations between petal-cytokinin activities at day of harvest of 3 Gerbera cultivars and their keeping-quality. It is concluded that changes in membrane permeability, which occur during ageing of petals of cut Gerbera inflorescences, are not triggered by changes in cytokinin activities.