Growth, gas exchange, water relations, fresh and dry matter partitioning in young fig (Ficus carica L.) plants irrigated with saline water

Background - Salinity tolerance of Ficus carica L. is still poorly quantified. Objectives - We subjected container-grown fig plants (cv. 'Dottato') to salt stress to determine survival, growth, biomass distribution, leaf gas exchange, and water relations. Methods - In a typical experiment plants were irrigated with saline water at either 50, 100, or 200 mM NaCl concentration for seven-eight weeks. In year 1 we added two additional concentrations: 300 (then adjusted after one week to 250 for the remaining six weeks) and 400 mM NaCl. Results - Salinity rapidly modified plant water status. Leaf photosynthetic rate (A) and stomatal conductance (g(s)) decreased as salinity was increased beyond 50 mM NaCl after 18 days of stress in both years. Leaf chlorophyll concentrations were unaltered by salinity. Shoot growth stopped after two weeks of salinization at 100 mM NaCl and beyond. Leaf area and number decreased significantly for the 200 mM-treated plants starting from five weeks after the beginning of salinization due to extensive leaf drop. Plant dry weight for the 50, 100, and 200 mM NaCl ranged 91-92%, 63-80%, 52-60% of the controls, respectively. The canopy-to-root ratio (both fresh and dry weight) did not change over the 0-100 mM NaCl range. Conclusions - Our study expands the interval of safe growth beyond previously reported thresholds. There are good perspectives to grow fig trees under saline conditions provided tolerant cultivars are planted.