Proline on the induction of tolerance of sour passion fruit seedlings to salt stress

Abstract

Water sources in the Brazilian semi-arid region commonly contain high levels of dissolved salts in their composition, standing out as one of the abiotic stresses that limit the expansion of irrigated fruit growing, especially salt stress-sensitive crops such as sour passion fruit. Thus, the use of elicitors, such as proline, can be an effective alternative to mitigate salt stress in plants. In this context, the objective of this study was to evaluate the effects of foliar application of proline on chlorophyll fluorescence, growth, quality and tolerance of sour passion fruit irrigated with saline water during the seedling formation phase. The experiment was conducted from July to October 2022, under greenhouse conditions in Campina Grande, PB, Brazil, using a completely randomized 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 replicates and two plants per plot. Water salinity from 0.6 dS m-1 reduces the maximum fluorescence, variable fluorescence, quantum yield of photosystem II and growth of ‘BRS GA1’ sour passion fruit seedlings. Foliar application of proline at concentrations ranging from 6 to 8.05 mM increases the growth in plant height, stem diameter and leaf area of sour passion fruit seedlings. The sour passion fruit genotype ‘BRS GA1’ is sensitive to water salinity, with a salinity threshold level of 0.6 dS m-1 and a reduction per unit increase in electrical conductivity of 10.49%.