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    Efficacy of blue-diode laser exposure on the postharvest quality maintenance of strawberries
    (2024-12-01)
    Cui, Shijiang
    ;
    Supapvanich, Suriyan
    ;
    Xiao, Yinghui
    ;
    Zhang, Weiyan
    ;
    Li, Junbing
    The purpose of this research was to evaluate the impact of postharvest laser irradiation on strawberry visual quality and texture. In preliminary studies, strawberries were exposed to diode laser radiation for 2.5 or 5 min at wavelengths of 405, 450 and 660 nm. The treatment at 450 nm for 2.5 or 5 min kept the visual appearance without deterioration after storage at 20 °C, 70% RH, for 4 d. The diode laser at 450 nm was selected to screen the exposure duration, and 2 min of exposure preserved a desirable visual appearance without decay during storage at 20 °C, 70% RH, for 6 d. Subsequently, the impacts of a diode laser at 450 nm for 2 min on the quality and softening of strawberries during storage at 4 °C for 14 d were observed. The laser treatment delayed strawberry softness and visual fungal development and maintained total acidity level, but had no effect on the total soluble solids content and BrimA value during storage. The membrane degradation of the laser-treated fruits was retarded, due to the inhibitions of the increases in malondialdehyde levels, phospholipase-D (PLD) activity and FaPLD gene expression. The activities of cell wall hydrolases such as polygalacturonase (PG) and β-galactosidase (β-Gal) activity and the expressions of FaPG1 and Faβ-Gal1genes were suppressed by the laser treatment. The laser treatment had no effect on the cellulase activity. These findings show that diode laser irradiation is a promising postharvest approach for efficiently preventing strawberry softness and deterioration.
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    Ethylene-sensitive and ethylene-insensitive abscission in Dendrobium: Correlation with polygalacturonase activity
    (2011-04-01)
    Bunya-atichart, Kanokpon
    ;
    Ketsa, Saichol
    ;
    van Doorn, Wouter G.
    We previously showed that the abscission of floral buds of the orchid Dendrobium cv. Miss Teen was absent in controls but highly promoted by ethylene, whilst open flowers also did not abscise without ethylene but were not responsive to ethylene. Here, we determined the activities of three enzymes in the abscission zone (AZ): polygalacturonase (PG), β-1,4-glucanase (cellulase), and pectin methylesterase (PME). In the AZ of floral buds an increase in PG activity coincided with the ethylene-induced abscission. A small increase was found in the AZ β-1,4-glucanase (cellulase) activity, shortly after the end of ethylene treatment of the flower buds and a few days before the onset of abscission. The activity of pectin methylesterase (PME) in the AZ of floral buds was not affected by ethylene. In the AZ of flowers that had just opened no increase in enzyme activity was observed after ethylene treatment. The data indicate a role of PG, and possibly of β-1,4-glucanase, in abscission. The data also suggest that the reason for the decrease in ethylene sensitivity of the abscission zone, during flower opening, lies upstream from the induction of enzyme activity in the AZ. © 2010 Elsevier B.V.