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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.

Plant growth and production are greatly affected by water deficit worldwide and particularly in Tunisia. In this context, a study was conducted to analyse the response of three vetch species (Vicia narbonensis, V. sativa and V. villosa) to four water treatments: 100% (Control), 80%, 60% and 40% of field capacity. Water stress led to important changes of both leaf physiology and anatomy. V. narbonensis kept cells turgor by adjusting the osmotic potential without changes in cell walls elasticity. V. sativa showed the most pronounced reductions of leaf water potential and the lowest osmotic adjustment under water stress although cell walls elasticity has not changed. However, V. villosa kept a higher fraction of apoplastic water over V. sativa that allowed it to maintain cells turgor despite the rigidity of its cell walls. Drought did not affect lamina thickness but increased the palisade parenchyma at the expense of spongy parenchyma. It was characterised by leaf lamina increase and constant thickness of the spongy parenchyma: a strategy to cope with drought. Moreover, stomata were reduced in size but were increased in number in order to avoid water loss.

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The current challenge of agriculture is to get the best yields while overcoming frequent water deficit conditions. The objective of this study was to compare performances of three vetch species (Vicia narbonensis L., V. sativa L., and V. villosa Roth) subjected to water stress. Plants were sown in pots under rainout shelter and submitted to four water regimes: control (100% field capacity [FC]), 80%, 60%, and 40% FC through 3 yr experiment. Results showed that V. narbonensis had the smallest declines in all the studied variables in response to water restriction but the highest water use efficiency (WUE) and stress tolerance index (STI) in both control and water-treated plants. This indicates the greater tolerance of this species to water constraint and its better water use. Vicia villosa was characterized by drastic declines in leaf area and DM yield (75% and 64%, respectively). It had also the smallest WUE and STI suggesting its low adaptation to water stress. Vicia sativa showed severe reductions in seed yield and yield components; accordingly, it was the most sensitive species in terms of seed yield. The three species implied avoidance strategies to cope with water stress. The different levels of drought tolerance explain the species ecological distribution in Tunisia.

Abstract:Responses to salt stress were investigated in three alfalfa varieties (Gabès, Hunterfield, and Hyb.555). Seedlings were submitted to salinity induced by adding NaCl into water at 4 concentrations (0 -2.5 -5 and 10g.l -1

Résumé -Les effets de la durée d'une acclimatation à une alimentation hydrique déficiente sur l'endurcissement à la sécheresse d'Acacia cyanophylla Lindl. ont été recherchés sur un lot de plants âgés de 8 mois, cultivés en pots. Un autre lot irrigué à une dose optimale proche de l'évapotranspiration maximale a servi de témoin. La durée des 2 traitements hydriques a été de 13 mois. Des plants des deux lots ont été soumis après l'expiration de 1, 3, 5 et 13 mois à un dessèchement rapide par privation d'eau afin de permettre aux traits physiologiques de l'acclimatation de s'exprimer. Des mesures de biomasse, de potentiel hydrique minimum (Ψ min), de potentiel osmotique (Ψπ) et de résistance stomatique ont été effectuées au cours des différentes périodes de dessèchement. En conditions de sécheresse extrême, les plants témoins ont révélé une bonne tolérance d'A. cyanophylla vis-à-vis de la sécheresse, exprimée par une turgescence positive et des stomates ouverts à des niveaux assez bas de Ψ min (-2,5 à -3,0 MPa). L'acclimatation au manque d'eau, pendant une durée de 3 mois, n'a pas été suffisante pour induire chez A. cyanophylla l'expression accrue de mécanismes de tolérance à la sécheresse. Les plants stressés ont réagi par une forte baisse de production de biomasse et par une fermeture stomatique précoce à un Ψ min de -1,9 MPa. Pour une durée d'acclimatation supérieure à 3 mois, les plants ont montré des signes d'un endurcissement croissant à la sécheresse, exprimé par le maintien d'un taux de croissance relative comparable à celui des témoins et d'une turgescence positive relativement élevée à des niveaux très bas de Ψ min (-3,2 à -4,7 MPa) résultant d'une régulation stomatique et d'une capacité croissante d'ajustement osmotique.Acacia cyanophylla / conductance stomatique /potentiel hydrique / acclimatation / endurcissement à la sécheresse Abstract -Influence of acclimation duration on the drought hardening of Acacia cyanophylla Lindl. The effects of a acclimation treatment to a severely deficient watering regime on the drought hardening of Acacia cyanophylla Lindl. were studied in a set of 8-month old plants grown in plastic pots. Another set of plants watered with an optimal dose close to the maximum evapotranspiration loss served as a control treatment. The period of both watering treatments lasted 13 months. In addition, plants from both sets were submitted at 1,3, 5, and 13 months to a progressive dehydration by water withholding in order to allow for the expression of adaptive mechanisms under extreme drought conditions. Measurements of biomass, minimum water potential (Ψ min), osmotic potential (Ψ π) and stomatal resistance were taken during different desiccation periods. Under extreme drought conditions, control plants showed signs of a satisfactory drought tolerance illustrated by a positive turgor and open stomata at fairly low levels of Ψ min (-2.5 to -3.0 MPa). The acclimation to lack of water at a severe intensity during a period of 3 months was not sufficient to induce drought tolerance mechanisms in...

Plants are known for their ability to resist or tolerate various types of stress (water and salt stresses, heat, frost, etc.)