A hidroponic greenhouse experiment was conducted, in the Universidade Federal do Ceará, from September to December 1999, with the objective of studying the response of guava plants (Psidium guajava L.) to increased levels of NaCl concentrations. The plants were treated with seven levels of NaCl concentrations in the nutrient solution (0, 25, 50, 75, 100, 125 and 150 mmol L-1). Plant height, leaf number, leaf area per plant and unit leaf area were measured at 50 days after stress (DAS). Relative growth rate (RGR) was determined between 30 and 50 DAE. Leaf conductance; transpiration; water potential and relative water content (RGR) were determined at 20, 30, 40 and 50 DAS. The leaf area per plant was the most susceptible among the variables studied, with a reduction of 92% when submitted to the highest salinity level (150 mmol L-1). The stomatal conductance, the leaf transpiration, the relative water content and the water potential decreased with increasing time and level of saline stress. The young guava plants were susceptible to salinity with a threshold salinity of 1,2 dSm-1. The rate of plant survival was reduced by 75% when the plants were submitted to 150 mmol L-1 up to 50 days after stress.
Salinity; water relations; Psidium guajava L.
