Efeitos antagônicos de auxinas e sacarose exógenos sobre o amadurecimento do melão amarelo cv. eldorado não climatérico.

Abstract

Studies have been performed with melon aiming to understand the maturation of climacteric and non-climacteric fruits since this Cucurbitaceae is a model plant among the cultivated plants, presenting these two patterns of maturation. Therefore, this work aimed at evaluating the effects of exogenous application of auxins, sucrose, sorbitol, naphthylphthalamic acid and 2,3,5- triiodobenzoic acid on non-climacteric yellow melon cv. Eldorado. For this purpose, the experimental design adopted was entirely randomized and two experiments were performed: the first one consisted of the application of sucrose and indolbutyric acid, both at 200, 250 and 300 mM and naphthylphthalamic acid (NPA) at 0.025 mM with the application of water and lanolin as a control. The second experiment was composed of indoleacetic acid at 60 mM, sucrose and sorbitol at 200 mM and 2,3,5-triiodobenzoic acid (TIBA) at 0.02 mM. Six repetitions were used in the 2019/2020 harvest season and four repetitions in the 2020/2021 harvest season with 1 fruit per plot. The variables evaluated were: accumulated degree-days (ADD), color parameters, firmness (N), soluble solids (oBrix), titratable acidity, ratio and pH. Considering ADD among the stages evaluated, in both experiments the final period of fruit development showed higher thermal requirements with no influence from the treatments. On the other hand, the ripening time of the fruits was influenced by the treatments applied in the two implemented harvests where the auxin concentrations delayed ripening together with the TIBA. However, the sucrose concentrations along with sorbitol anticipated it and the NPA didn’t influence it in less days than the previous hormone. In Experiment I, auxin increased firmness and titratable acidity contents and decreased soluble solids, ratio and pH. In Experiment II, auxin and sucrose showed the same antagonistic behavior in the ripening of melons. The color’s fruit parameters showed no significant difference between the treatments in the two years of study. Thus, it can be concluded that the use of auxin retarded ripening and sucrose accelerated it. These physiological results reinforce the antagonistic action between this hormone and sugar in the ripening of the fruits, in which the former delays while the latter accelerates it.