Formação de mudas de maracujazeiro-azedo irrigado com águas salinas e aplicação de prolina.

Abstract

In semi-arid areas of the Brazilian Northeast, the occurrence of water sources with high levels of dissolved salts is common, standing out as an abiotic stress factor for crops sensitive to saline stress, such as passion fruit. In this context, the search for strategies capable of enabling irrigation with saline water in irrigated fruit growing is essential to ensure the need for food production. In this context, the objective of this study was to evaluate the effects of proline concentrations on the physiology, growth, quality and tolerance of sour passion fruit irrigated with saline water in the seedling formation phase. The research was conducted under greenhouse conditions belonging to the academic unit of agricultural engineering at the Federal University of Campina Grande, in Campina Grande - PB, using a completely randomized experimental design, in a 5 × 4 factorial scheme, with five levels of electrical conductivity of irrigation water ECw - (0.6; 1.2; 1.8; 2.4 and 3.0 dS m-1) and four concentrations of proline (0,5, 10 and 15 mM) with four repetitions and two plants per plot, totaling 160 experimental units. Water salinity from 0.6 dS m-1 reduced relative water content, gas exchange, maximum variable fluorescence, photosystem II quantum efficiency and growth, and increased electrolyte leakage and initial fluorescence in BRS GA1' sour passion fruit plants. Irrigation with water with electrical conductivity between 1.3 and 1.8 dS m-1 stimulated the biosynthesis of photosynthetic pigments in the passion fruit 'BRS GA1'. Foliar application of proline at concentrations ranging from 4.5 and 6.5 mM increased stomatal conductance, transpiration, CO2 assimilation rate, instantaneous carboxylation efficiency, chlorophyll contents and growth of sour passion fruit. Water with an electrical conductivity of up to 3.0 dS m-1 enabled the formation of passion fruit seedlings with acceptable quality for transplanting in the field. The 'BRS GA1' sour passion fruit genotype is sensitive to water salinity, with a threshold salinity level of 0.6 dS m-1 and a reduction per unit increase in electrical conductivity of 10.49%.