Salt sensitivity of wheat at various growth stages

Summary

The relative salt tolerance of two wheat species (Triticum aestivum L., cv. Probred and Triticum turgidum L., Durum Group, cv. Aldura) at different stages of growth was determined in a greenhouse experiment. Plants were grown in sand cultures that were irrigated four times daily with modified Hoagland's solution. Salinization with NaCl and CaCl₂ (2:1 molar ratio) provided seven treatment solutions with osmotic potentials (Ψ _s ) ranging from −0.05 to −1.25 MPa (electrical conductivities of 1.4 to 28 dS/m). Salt stress was imposed for 45 days beginning at either 10, 56, or 101 days after planting. The three 45-day stages are referred to here as the vegetative, reproductive, and maturation stages although the first stage included spikelet differentiation. In a separate experiment, seedling growth was measured after 21 days of salt stress (Ψ _s = −0.05 to −0.85 MPa) initiated at 0, 7, 11, and 16 days after planting. Salt stress (Ψ _s = −0.65 MPa) delayed germination by 4 days for both wheats but full emergence occurred. Relative growth response curves of the seedlings were alike regardless of whether salt stress was imposed at planting or at the 1st, 2nd, or 3rd-leaf stage of growth. Salt stress also retarded leaf development and tillering but hastened plant maturity. Grain yields from plants stressed during either the vegetative, reproductive, or maturation stages indicated that both species became less sensitive to salinity the later plants were stressed. Grain yield was reduced 50% at Ψ _s = −0.76, −1.53, and −1.58 MPa for Probred and −0.65, −1.08, and −1.34 MPa for Aldura when salinized during stages 1, 2, and 3, respectively. Salinity reduced grain yield by reducing seed number more than seed weight indicating that salt stress during stage 1 affected spikelet differentiation. Straw yield was significantly reduced by salt stress only during stage 1. Leaf mineral analyses revealed that Aldura readily accumulated Na whereas Probred did not. Both species accumulated Cl but the concentrations were much higher in Aldura. K uptake was severely inhibited by salt stress imposed during the first stage but not when imposed the second stage.