GROWTH OF GUAVA TREE CULTIVARS UNDER SALINITY STRESS CONDITIONS

Abstract

Guava tree (Psidum guajava L.) is a rustic fruit crop that can be used in areas with marginal soils. This research evaluated the response of guava tree to saline stress during the growth stage. The plants were obtained from rooted cuttings of the Calvillo Siglo XXI and Merita cultivars. The experiment was conducted under a floating root hydroponic system, in 50 % Steiner solution. Five salinity conditions were evaluated, and the electrical conductivity was adjusted with NaCl to 2.0, 2.5, 3.0 and 3.5 dS m^-1, and the control to 1.2 dS m^-1 without NaCl. The experimental design was completely randomized with five replications. The evaluated variables were number and length of sprouts, number of leaves per sprout, average leaf lifespan, transpired water volume, chlorophyll content, leaf area, root length, fresh and dry matter in leaves, stem and root. Additionally, leaf and root concentration of P, Ca, K and Na, and density and longitudinal diameter of stomata were determined. Calvillo Siglo XXI cultivar outperformed Merita in chlorophyll content (36.35 vs 32.74 SPAD units); in contrast, Merita presented higher concentration of P (0.1306 vs 0.1106 %) and Ca (1.0514 vs 0.7463 %) in leaf. Salinity decreased the average leaf lifespan from 74 to 42 d. Leaves contained, on average, a higher K concentration than roots (2.372 vs 0.966 %). At 3.5 dS m^-1 EC, the K concentration decreased by 31.8 % in leaves and 55.5 % in roots, and the Na concentration in leaves increased by 68.6 % compared to the control. The capacity of the two cultivars to maintain high K concentration in leaves, as well as the transport of Na to leaves, increased their salinity resistance at the evaluated levels. Salinity had no significant effect on the growth of guava plants.