Wheat response to interactive effects of boron and salinity

In semiarid regions with irrigated agriculture, excess boron (B) often occurs in association with moderate to high salinity. However, little information is available on plant uptake of B under saline conditions. This greenhouse study was conducted to determine the interactive effects of salinity and varying concentrations of boron on growth, yield and ion relations of wheat (Triticum aestivum L., cv. 'Yecora Rojo'). Plants were grown in sand cultures that were irrigated four times daily with modified Hoagland's nutrient solution. Sixteen treatments were initiated 4 d after planting in a completely randomized factorial experiment with 4 salinity levels (electrical conductivities of the irrigation waters = 1.5, 4, 8, and 12 dS m(-1)) and 4 B concentrations (1, 5, 10, and 15 mg L-1). Salinizing salts were NaCl and CaCl2 (2:1 molar basis). Symptoms of B toxicity were closely correlated with B concentration in the leaves and injury became severe when leaf-B exceeded 400 mg kg(-1). At each concentration of external B, shoot-B was least under nonsaline conditions and increased significantly as salinity increased. Shoot-calcium (Ca) concentration increased with increasing salinity, but was unaffected by applied B. Shoot-magnesium (Mg), and potassium (-K) decreased significantly in response to increases in salinity and substrate B. Salinity and B as well as their combined effects significantly reduced wheat biomass production, yield components, and final grain yield.