Interactive effects of boron and salinity on greenhouse tomato grown in closed soilless system.

Tomato (Solanum lycopersicum L. ‘Caramba’) plants were grown in semi-closed perlite culture under the typical climatic conditions of Mediterranean region from late winter to summer and using two NaCl (2.0 and 10.0 mol m-3) and B (27.8 and 185.0 mmol m-3) concentrations in the irrigation water. The quality of irrigation water did non affect significantly the uptake of water and mineral elements apart from that of Na and B, which increased in the plants irrigated with NaCl- and B-enriched water. B toxicity resulted in an evident chlorosis and necrosis of leaf margins. The use of saline water resulted in higher frequency of the discharge of recirculating nutrient solution; as a consequence, B concentration in the root zone was lowered and this alleviated the severity of leaf damages in plants grown with B-enrich water. In all treatments, a considerable difference in B content was found between the marginal and central areas of the leaves, the latter remaining active also in conditions of severe B toxicity, as indicated by the determination of chlorophyll content and fluorescence. No or minor effects of NaCl and B concentrations were found on leaf area evolution, shoot biomass accumulation, crop yield and fruit quality.