ASCORBIC ACID ANTIOXIDANT ACTIVITY AGAINST LEAF BLACKENING OF PROTEA

Abstract

Some cultivars of the genus Protea develop an important postharvest disorder, which manifests as a blackening of the foliage, only a few days after harvest. This blackening usually initiates in the leaves closest to the flower bud, which subsequently decreases the monetary value of the cut flower, and therefore limits the marketability of these cultivars. In a previous assay, antioxidant activity of ascorbic acid decreased the phenols and polyphenols associated with this kind of blackening, which led us to perform a subsequent experiment. In November, cut flowers of the cultivars ‘Pink Ice’ and ‘Susara’, which are both susceptible to leaf blackening, were collected and subjected to three treatments: the Control (TC) where flowering stems were kept in water as a vase solution; Treatment 1 (T1) where flowering stems were kept in a 5 g L-1 ascorbic acid vase solution, and Treatment 2 (T2), where flowering stems were kept in water as a vase solution, but were sprayed with 5 g L-1 ascorbic acid on a 24 h basis. ‘Susara’ flowering stems sprayed with ascorbic acid presented significantly less blackening in comparison to the control stems throughout the 13 days vase life period. On the contrary, a delay of 11 days in the development of blackening symptoms was only observed in ‘Pink Ice’ kept in the 5 g L-1 ascorbic acid vase solution when compared to the control.