Mudas de maracujazeiro-azedo cv. Rubi do Cerrado sob substratos orgânicos e lâminas de água : nutrição, compostos bioativos, trocas gasosas, status hídricos e crescimento.

Abstract

The supply of water and nutrients are essential factors in the initial growth of passion fruit trees and, consequently, in their production in the field. The aim was therefore to evaluate the influence of organic substrates and water levels on gas exchange, nutrition, bioactive compounds, growth and quality of passion fruit seedlings cv. BRS Rubi do Cerrado. The experiment was conducted in a greenhouse and the treatments were distributed in a completely randomized design in a 5 × 2 factorial arrangement, comprising five substrates (S1 = 100% soil, S2 = 75% soil and 25% cattle manure, S3 = 75% soil and 25% goat manure, S4 = 75% soil and 25% worm humus, S5 = 75% soil and 25% organic compost) and two water levels: L1 50% of water available in the substrate and L2 100% of water available in the substrate, with six repetitions, making up 60 experimental units. At 45 days after transplanting, the water status, gas exchange, nutritional status, bioactive compounds, growth, phytomass and quality of the seedlings were assessed. When the seedlings were irrigated with 100% available water, they showed higher stomatal conductance, transpiration, CO2 assimilation rate and internal CO2 concentration, resulting in greater carboxylation. The passion fruit cv. Rubi do Cerrado is sensitive to water deficit, as this caused a reduction in growth, dry matter production and compromised physiological variables such as transpiration, stomatal conductance and CO₂ assimilation. The substrates that promoted the greatest height of the passion fruit seedlings cv. Rubi do Cerrado were S4 = 25% humus and 75% soil (78.32 cm) and S2= 25% cattle manure and 75% soil (75.80 cm). The best results for the dry mass of the aerial part (8.28 g plant) and the total dry mass (10.13 g plant) were obtained when using S4 with 100% available water in the soil. Passion fruit cv. Rubi do Cerrado seedlings grown in substrates containing 25% cattle manure and 25% worm humus showed better responses to water deficit, as the organic substrates promoted greater water retention. There was an influence of the different substrates and water levels on the leaf levels of macro and micronutrients and, consequently, on the nutritional status of the passion fruit seedlings cv. Rubi do Cerrado. Water deficit negatively affected primary and secondary metabolism, highlighting the sensitivity of the plants.