Role of Ascorbate on the Fruit Physiology of Pepper (Capsicum annuum L.)

Ascorbate (vitamin C) is essential for cell metabolism, and its supply to the human diet derives basically from the consumption of fruits and vegetables. Several biosynthetic pathways of ascorbate have been reported in plants, the major physiological one being the so-called Smirnoff-Wheeler pathway. Ascorbate is a powerful antioxidant in plants, although it also plays an important role in hormone synthesis, cell signalling, gene expression, cell division and growth, and programmed cell death. Based on this multiplicity of functions, nowadays it is considered that ascorbate works as a redox buffer in the plant cell. Bell pepper (Capsicum annuum L.) is the second most consumed vegetable worldwide, and its fruit is one of the richest sources of vitamin C. In our laboratory, we have analysed a number of enzymatic and non-enzymatic antioxidants in fruits from different pepper cultivars under distinct developmental and environmental conditions. Unlike the majority of parameters determined, total ascorbate levels underwent few changes during the fruit ripening process. Likewise, under certain stress situations, provoked by environmental variations, total ascorbate remained practically invariable, and only the ascorbate/dehydroascorbate ratio was modified. Therefore, ascorbate seems to play a relevant role in the physiology of pepper fruit, possibly functioning as a regulator of processes which imply important metabolic alterations, thus contributing to the stability of fruits, a typical feature of peppers which commonly display a long life-span after harvest. _____________________________________________________________________________________________________________