EXPLOITING THE RESPONSES TO ABIOTIC CONSTRAINTS TOWARDS A BETTER UNDERSTANDING OF FRUIT PHYSIOLOGY, RIPENING AND QUALITY

Abstract

Environmental constraints are known to have some incidence on nutritional quality and physical characteristics of fruits. Responses of the plant to abiotic stresses are often characterized by changes in its oxidative status. For example, water stress applied on tomato plants enhanced the synthesis of reactive oxygen species (ROS), accompanied by an increase in ascorbate (AsA) content in the fruits. In the same way, an oxidative burst brought about shading leaves of citrus led to an increase in AsA and carotenoid contents in the fruit. These responses observed at the fruit level in planta can also be induced after harvest. So, after harvest and ripening, the activities of catalase and peroxidase were higher in the peel of mango fruit wellexposed to light, compared to fruit inside the canopy. In addition, AsA and carotenoid contents were higher in well-exposed fruits, while sugar content and titratable acidity (TA) remaining similar. Analogous changes were observed for mango fruits stored at different temperatures before ripening, with a graduated ROS response in ripe fruits. Sugar content and TA were similar in all fruits, but the final content of AsA and carotenoids were respectively negatively or positively correlated to storage temperature. These results confirm the role of the oxidative stress in the build-up of some quality criteria, for moderate stress. In addition to the environmental conditions, the maturity stage at harvest affects the postharvest ripening of climacteric fruit. Maturity stage at harvest of mangoes had an incidence in some hormonal balance such abscissic acid and ethylene. So, in addition to their impact on fruit physiology through the oxidative stress, it could be suggested that abiotic constraints could impair ripening metabolism. Therefore, investigations are required for a better understanding in the relationship between hormonal balance and the role of signaling pathways by oxidative stress in ripening metabolism. (Resume d'auteur)