The Plants in ambient conditions are subject to dealing with biotic and abiotic stresses. Water deficit, being an abiotic stress, causes changes in plants that make them respond in several ways, such as reduced growth, leaf senescence and lower fruit growth rate, production of Reactive Oxygen Species (ROS), caused by a deficiency in the dissipation of energy due to impaired photosynthesis. The application of silicon becomes an alternative to mitigate the effects of this stress on plants, being deposited in the cell wall, providing rigidity, and increasing the plant's defense enzymes. The study aimed to understand the morphological, physical, and post-harvest responses of mini watermelon according to different soil humidity associated with the foliar application of silicon. The study was conducted in a greenhouse using the mini watermelon cv. Sugar Baby. The experimental design was in randomized blocks, in a 3x2 factorial scheme, with three water tensions in the soil (-35 kPa without water deficit, -50 kPa moderate water deficit, and -65 KPa severe water deficit) and two doses of foliar Si (0 and 1.5 g L-1), with four repetitions. The variables plant length, stem diameter and shoot dry mass, root dry mass, total soluble carbohydrates, proline, gas exchange, and post-harvest analyses were analyzed. There was a significant difference for the variables (p>0.05), but there was no interaction between tension and Si. Proline levels were not statistically significant. The water deficit promoted shorter plant length, aerial part dry mass, root dry mass and Si provided greater stem diameter. For biochemical variables, water deficit caused a higher carbohydrate content in the leaf and lower gas exchange rates. Si influenced skin thickness and average fruit weight. Thus, SI proves to be a strategy for cultivating mini watermelon in conditions of deficient water application.
