The Effect of Sucrose in a Vase Solution on Leaf Browning of Protea Neriifolia R. Br.

Carbohydrate Depletion and Leaf Blackening in Protea neriljiolia

“…Optimum sugar concentration varies with species, duration of treatment, and stage of floral development (Halevy and Mayak, 1981). Concentrations in the range of 0.5% to 1% are recommended for P. nen.ifolia to enhance inflorescence quality and reduce the onset of leaf blackening (Brink and de Swardt, 1986;Newman et al, 1989). In our study, a vase solution with 0.5% sugar did not delay leaf blackening in darkness (Fig.…”

“…Lack of respiratory substrate can lead to degradation of cellular components in floral tissue, including membranes, to fulfill carbohydrate demand (Coorts, 1973). In cut flower stems of P. neriifolia, carbohydrate reserves in leaves are probably depleted by the strong inflorescence sink, resulting in membrane degradation, polyphenol leakage and oxidation, and leaf blackening (Brink and de Swardt, 1986;Newman et al, 1989). Our results demonstrate that leaves in light actively photosynthesize (Table 2) and contribute to the carbohydrate pool (Fig.…”

“…Many Proteaceous species have become important "cut-flower crops. A major postharvest problem of this genus, in particular Protea neriifolia and P. eximia, is premature blackening of the leaves (Brink and de Swardt, 1986;Ferreira, 1983;Newman et al, 1989;Paull et al, 1980). Leaves of susceptible species begin to turn black within 3 to 7 days after harvest, severely reducing the market value of a flower stem that otherwise has a potential vase life of 3 to 4 weeks.…”

“…Leaves of susceptible species begin to turn black within 3 to 7 days after harvest, severely reducing the market value of a flower stem that otherwise has a potential vase life of 3 to 4 weeks. Leaf blackening appears to be caused by oxidation of the polyphenols and leuco-anthocyanins (Whitehead and de Swardt, 1982) that leak into the cyfosol from the vacuole after rupture of intracellular membranes (Brink and de Swardt, 1986;Ferreira, 1986;Newman et al, 1989). The physiological mechanisms or stresses that initiate rupture of the intracellular membrane and subsequent leaf blackening have not been clearly established.…”

“…However, leaf blackening is known to decrease significantly when the influence of the inflorescence sink is eliminated by girdling the stem immediately below the inflorescence or by removing it (Newman et al, 1989;Paull et al, 1980). Blackening is also reduced by lighted postharvest conditions (Newman et al, 1989) and the addition of external sugar to the vase solution at concentrations ranging from 0.5% to 1.0% (Brink and de Swardt, 1986;Ferreira, 1986;Newman et al, 1989). These observations suggest that depletion of carbohydrates from leaves, caused by translocation to the strong inflorescence sink, may play a role in initiating the cascade of events that leads to leaf blackening.…”