Salinity affects growth, yield and elemental concentration of fennel

Abstract

'Monte Bianco' and 'Everest' fennel (Foeniculum vulgare Mill.) were grown in 157-L plastic pots and irrigated with water containing NaCl at 0, 0.25, 0.5, 1.0, 1.5, 2.0, or 2.5 g·L-1. The salt-tolerance threshold for yield was expressed as electrical conductivity of irrigation water (ECi) and saturated soil extract (ECe). ECi was 1.15 dS·m-1 for both cultivars and ECe was 1.51 and 1.47 dS·m-1 for 'Monte Bianco' and 'Everest', respectively. The thresholds for plant fresh weight were the same as yield. Below the threshold the average bulb yields were 265 g/plant in 'Monte Bianco' and 284 g/plant in 'Everest'. Relative yields were reduced 18.9% and 17.8% for ECi and 15.7% and 14.3% for ECe for each unit increase above the threshold in 'Monte Bianco' and 'Everest', respectively. Sodium concentration was higher in bulbs in comparison with other tissues at all salinities. Bulb Na concentration increased to 3 dS·m-1, reaching 1835 and 1866 mmol·kg-1 dry weight in 'Monte Bianco' and 'Everest', respectively. Chloride concentration had similar tissue distribution and trend as Na. Potassium concentration in bulbs decreased with increasing Na concentration, while it remained constant in the other organs. Calcium concentration was not affected by salinity. Thus, fennel is sensitive to salt stress, lacking mechanisms for controlling inn influx into plant tissues, and is unable to cope with saline sodic environments.