Abstract
To prolong their vase life, cut flowers are commonly kept in holding solutions. These must include a biocide to retard bacterial growth. In this study, the effect of nanosilver (NS) on certain aspects of senescence in cut garden cosmos (Cosmos bipinnatus) flowers was compared to that of the commonly used 8-hydroxyquinoline citrate (8-HQC). In combination with sucrose, both biocides prolonged cosmos vase life but did not prevent the occurrence of stem blockages. NS was more effective in limiting a reduction in endogenous soluble carbohydrates. The malondialdehyde (MDA) contents increased in senescing ray florets, both in intact and control cut flowers held in water. Both biocides were comparably effective in limiting this effect. The hydrogen peroxide content tripled in intact flowers but dropped in flowers held in water or the 8-HQC solutions; in flowers kept in NS solutions its increase was moderate. Also, the catalase activity increased in intact flowers but dropped in all cut flowers. Both biocides had similar effects on the enzyme activity, in both pure solutions and with sucrose. Most of these parameters were not significantly correlated with vase life. Overall, the effect of nanosilver on senescence in cut cosmos flowers was similar to that of 8-HQC.
Highlights
To prolong their vase life, cut flowers are commonly kept in holding solutions
The overall goal of this study was to compare the effects of NS to those of the routinely used 8-hydroxyquinoline citrate (8-HQC) on the longevity of cut cosmos flowers, formation of blockages in stem vessels and on some aspects of senescence occurring in ray florets, such as changes in the relative water content, total glucose, MDA and H2O2 levels and the catalase activity
In pure solutions neither of the biocides had any effect on the longevity of cut flowers
Summary
To prolong their vase life, cut flowers are commonly kept in holding solutions. These must include a biocide to retard bacterial growth. The malondialdehyde (MDA) contents increased in senescing ray florets, both in intact and control cut flowers held in water Both biocides were comparably effective in limiting this effect. Diversity of forms and colors make the species popular among florists and customers but its postharvest longevity is short, usually 4–6 days[1] This longevity can be doubled by making use of the so-called flower food, i.e. holding solutions containing a biocide and a sugar[2]. Sucrose is taken up from the holding solution and metabolized, serving as a respiratory substrate and increasing the osmoticum, improving the water balance and petal turgidity The latter positively affects cell membranes which normally lose their properties during senescence, due to the lipid peroxidation. Sugar-containing preservatives reduced the electric conductivity of the cell sap relative to water control[19]
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