Salicylic acid and irrigation with water of different cationic compositions on ‘Paluma’ guava seedlings

ABSTRACT The occurrence of water sources with high concentrations of salts in the semi-arid region of Northeastern Brazil limits the expansion of irrigated agriculture. Therefore, it is extremely important to look for strategies capable of mitigating the effects of salt stress on plants. The objective of this study was to evaluate the effects of foliar application of salicylic acid in inducing tolerance of guava seedlings irrigated with water of distinct cationic composition. The experiment was carried out under greenhouse conditions using a randomized block design in a 5 × 5 factorial arrangement, with five cationic compositions of irrigation water (S1 - Control tap water, S2 - Na++Ca2++Mg2+, S3 - Na++Ca2+, S4 - Ca2++Mg2+, and S5 - Na++Mg2+), so as to have equivalent ratios of 7:2:1 relative to Na++Ca2++Mg2+ and 1:1 relative to other combinations, respectively maintaining electrical conductivity - ECw at 3.0 dS m-1, and five concentrations of salicylic acid (0, 0.8, 1.6, 2.4, and 3.2 mM), with three replications and two plants per plot. Electrolyte leakage, succulence, and chlorophyll a fluorescence signals increased in guava seedlings irrigated with water up to 3.0 dS m-1. Water with ECw of 3.0 dS m-1 can be used to produce guava seedlings with acceptable quality for transplanting to the field, regardless of its constitution. In the absence of salicylic acid, water salinity negatively affected the chlorophyll a and b contents of seedlings, regardless of the cationic nature of the water.