Plant growth, water relations and proline content of three vetch species under water‐limited conditions

Vetch species (Vicia narbonensis, V. sativa and V. villosa) are widely used for fodder production in Tunisia. This study aims to investigate vetch strategies involved in drought resistance through morphological and physiological criteria. Plants were sown in pots and subjected to four soil-water levels: 100% (control), 80, 60 and 40% of field capacity (FC). After 133 d of water treatment, and under well-watered conditions, V. narbonensis showed the largest plant height and shoot and root dry matter and the highest leaf relative water content and water potential (Ψw), whereas V. sativa had the greatest leaf area (LA). At the 40% FC treatment, V. narbonensis showed smaller decreases in plant height and LA, and the greatest reduction in Ψw (140%). Thus, it shows better adaptation and a more equilibrated water balance, despite having accumulated less proline than the two other species. Vicia sativa and V. villosa showed a similar behaviour under water stress with a superiority of the latter. Vicia sativa was the species most affected in terms of its growth and water-status parameters. Vetch species mainly used avoidance mechanisms to withstand drought, with V. narbonensis showing the highest tolerance.