Growth and ion accumulation in seedlings of Handroanthus serratifolius (VAHL.) cultivated in saline solution

Abstract

Salinity is an environmental problem in several biomes and many plants have to overcome its effects in order to survive. However, some native species are not able to cope with such environment and this must be known. This work evaluated the salt tolerance of Handroanthus serratifolius, a well known pioneer species in reforestation. Fifteen days old seedlings of Handroanthus serratifolius were grown for 45 days in nutrient solution and NaCl treatments of -0.1, -0.2, -0.3, -0.4, -0.8 and -1.5 MPa osmotic potentials. Sodium accumulation was quantified in whole seedlings by flame photometer and chloride by titration. The evaluated variables were: root, stem and leaf dry biomass as well as leaf area, and these were used to calculate the growth parameters: relative growth rate, net assimilatory rate and root:shoot ratio. Stomata density was evaluated on the leaves’ abaxial face. Statistical analysis was performed in one-way anova with five replicates. Seedlings survived only at -0.1 (92% of survival), -0.2 (56% of survival) and -0.3MPa (32% of survival) and in the control group (100% of survival). Seedlings dry biomass declined in all saline treatments compared to the control group. Salinity promotes a decrease in relative growth rate and in net assimilatory rate. Leaf area and stomata density were reduced in all saline treatments. All saline treatments increased the root:shoot ratio. Seedlings accumulated sodium proportionally with the saline solutions but chloride accumulate only to 0.41 MPa in the -0.1 MPa solution without differences in the lower osmotic potential solutions. Therefore, Handroanthus serratifolius can not survive in severe saline environments, and seedling development is only possible up to an osmotic potential of -0.3 MPa.