Nanosilver as a novel biocide for control of senescence in garden cosmos

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. Growing consumer interest in new cut flower species drives field production of seasonal, locally grown flowers 1. Garden cosmos-also known as lace cosmos because of its delicate pinnate foliage-is gaining popularity not only as a garden or a bedding plant but also as cut flowers. Diversity of forms and colors make the species popular among florists and customers but its postharvest longevity is short, usually 4-6 days 1. However, 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. These two components are crucial in extending the vase life as they delay flower senescence. Senescence usually occurs faster in cut flowers than in those left on mother plants. This was clearly illustrated by de Stigter 3 on cut and intact hydroponically grown 'Sonia' roses observed under the same environmental conditions and confirmed by subsequent studies on rose 4 , lilac 5 , clematis 6 and peony 7. The processes of senescence are accelerated mainly by water stress caused by improper water balance in cut stems. Such stems, even when held in water, are unable to absorb sufficient amounts of water to compensate for the transpiration losses. Vessels in cut stems become obstructed by blockages of various nature, with the presence of microbes in vase water being the most common 8. For this reason, biocides in holding solutions are crucial for the postharvest longevity of cut flowers. For over a half a century the esters of 8-hydroxyquinoline have been used as potent biocides, in mixtures with sucrose. This is called the standard preservative 9. Nanosilver [NS] has emerged as a new biocide for cut flowers after the use of toxic silver nitrate had been outlawed 10. Though it was enthusiastically accepted in ...

Do Eco-Friendly Floral Preservative Solutions Prolong Vase Life Better than Chemical Solutions?

“…Holding solutions, which contain a combination of carbohydrates (usually sugar), plant growth regulators, germicides, ethylene inhibitors, mineral salts, and organic acids are used to extend the vase life of cut flowers [55,77]. Each flower species and cultivar is adapted to various constituents and concentrations in the holding solution [55,78]. The sugar provides energy for plant respiration, and the germicides affect and kill harmful bacteria, and its action prevents plant tissue plugging [49,79].…”

“…A number of germicide solutions have been used to extend the vase life of cut flowers, including the silver compounds: STS [12,103] and AgNO 3 [103]); chlorine compounds (sodium hypochlorite, sodium dichloroisocyanurate, and ClO 2 [5]), and certain other compounds, such as 8-HQS [12], 8-Hydroxyquinoline citrate (8-HQC) [104], salicylic acid (SA) [105], calcium [106], calcium nitrate [107], aluminum sulfate [108,109], isothiazolinone [49], and quaternary ammonium chloride [110]). To prevent microbial growth, a sugar solution is always added to a biocide solution [78]. In cut flower roses, germicide treatments preserve the hydraulic conductance of the cut flower stems [92].…”

Effect the Different Concentrations of Hydrogen Peroxide and Addition Soil Amendments on Growth and Nutrient Balance in Ranunculus Asiaticus L. Grown under Salinity Conditions

“…Also, spraying with hydrogen peroxide, which is considered an antioxidant, protects cells and cell membranes and delays aging, as well as the accumulation of nutrients and sugars and an increase in dry matter in flowers. All of these factors lead to an improvement in the characteristics of floral growth [23].…”

Organoleptic test on the quality of cut roses (Rosa hybrida L.) due to the effect of various types of natural preservative solutions and immersion times

“…Preservation of cut flowers using solutions containing a combination of carbohydrates (sugars), growth regulators, germicides, ethylene inhibitors, mineral salts, and organic acids is used to extend the life of cut flowers. Each type of solution and the concentration used is adjusted to the flower species and cultivar [4]. Sugar produces energy for respiration in plants, and germicides play a role in inhibiting bacterial growth to prevent blockage of plant tissue [5].…”