Effects of Postharvest Treatments with Nanosilver on Senescence of Cut Lisianthus (Eustoma grandiflorum (Raf.) Shinn.) Flowers

Abstract

Lisianthus is among the most popular cut flowers. Regarding the postharvest losses, these experiments were designed to compare the effects of a nanosilver (NS) based preservative to the standard preservative containing 8-hydroxyquinoline citrate (8-HQC) and sucrose (S). Additionally, the effect of 24 h conditioning in the NS solution on the postharvest longevity and the general condition of lisianthus (Eustoma grandiflorum ‘Mariachi Blue’) was tested. The vase life of flowers on conditioned and non-conditioned stems was extended by the preservatives, more so by NS + S than by 8-HQC + S (44–54% versus 13–23%). Conditioning had no detectable effect on longevity. Daily water uptake showed alternative peaks and drops, with a general tendency of the uptake rate to decrease over time. The highest uptake intensity and the highest transpiration rate were in stems in the NS + S solution while the lowest was in 8-HQC + S. Conditioning negatively affected the average fresh weight of the flowering stems in all holding solutions with stems in preservatives being heavier than those in water. Preservatives did not induce accumulation of the total soluble or reducing sugars in petals; such accumulation was promoted by conditioning, but only in the upper flowers. The free proline content increased in senescing lower flowers on non-conditioned stems; conditioning limited this increase in flowers in preservatives. In the upper flowers, free proline increased in both water controls while the preservatives and conditioning generally reduced the proline contents below the initial level. Conditioning lowered the hydrogen peroxide contents in senescing lower flowers, relative to the initial level and the non-conditioned stems. The catalase activity kept dropping during the vase life in both the lower and upper flowers, in conditioned and non-conditioned stems, with the exception of flowers from water where the activity remained the highest from all three treatments. It appears that the NS preservative with sucrose improves the overall condition of lisianthus flowers and extends their vase life.