Paramètres agronomiques liés à la tolérance au sel chez le haricot (Phaseolus vulgaris L.)

Agronomical traits associated with salinity-tolerance in common bean (Phaseolus vulgaris L.). Identifying multiple agronomical parameters associated with salinity-tolerance is important for evaluating common bean (Phaseolus vulgaris L.) cultivars and improving their tolerance to salinity. Six cultivars were grown in soil, under glasshouse conditions and exposed to three salinity levels (control, 25 and 50 mM NaCl) to evaluate their tolerance using their biomass and the relative salt-susceptibility index: I.S.R.S. = D.R.B./I.I.S. (D.R.B.: relative biomass deficit and I.I.S.: salinity intensity index). On the other hand, a comparative field trial was conducted at four experimental stations of INRAT (Ariana, Oued Beja, Oued Meliz and Sejnane) during three consecutive years with sixteen cultivars to determine their grain yield stability, grain size and precocity. Results showed that tolerant cultivars are colour-seeded, early and presented yield stability and medium grain size. By contrast the susceptible cultivars are late, white-seeded and characterized by a less stable yield and small to medium grain size

Endurcissement à la sécheresse et accumulation de glucides solubles et d'acides aminés libres dans les phyllodes d'Acacia cyanophylla Lindl

Drought hardening, soluble carbohydrates and free amino acid accumulation in Acacia cyanophylla Lindl phyllodes. Two plots of 8-month-old plants of Acacia cyanophylla Lindl grown in the greenhouse have been subjected to two contrasting water feedings. The first was nearly maximum evapotranspiration (D) and the second was D/6. Three plants of each water feeding were subjected to a drying cycle by water withholding after 1, 3, 5 and 13 months in order to allow the emergence of adaptive mechanisms in hard drought. At the beginning of each drying cycle, water potential component had been measured at 1 Pm in order to evaluate the effect of drought preconditioning duration on the D/6 plants. At the end of each cycle, marked by zero turgor, the same measures had been made and the remaining phyllodes were used to determine the concentration of free amino acids, soluble sugars and starch. We noted at the beginning of the cycles that D plants had a slight decrease in osmotic potential and a slight increase in the turgor; these variations seemed to be related to age. The response of D/6 plants varied with the duration of preconditioning. After 1 month, at the beginning of the cycle, their turgor was less than that of D plants. At the end of the cycle, they had a less negative osmotic potential and lower contents of free amino acids as compared to D plants. This suggests that a 1 month preconditioning to D/6 treatment was insufficient to induce hardening mechanisms. After 3 months and at the beginning of the cycles, we noted a higher turgor and a lower osmotic potential in the D/6 plants with an increasing difference in osmotic potential between D and D/6 over time (from 0.15 to 0.47 MPa). At the end of the fourth cycle, D/6 plants maintained a positive turgor at water potentials near -4.50 MPa. The difference of osmotic potential between D and D/6 plants was significant (from 0.40 to 1.60 MPa) and was accompanied by an increasing accumulation of soluble sugars and free amino acids, especially proline. Concomitantly, a reduction in starch concentration was observed. This could in part explain the accumulation of soluble sugars. These results attest to an acquired hardening by D/6 plants subsequent to a preconditioning of more than 3 months. This hardening was expressed at the end of the drying cycles by increasing osmotic adjustment ability over time.Deux lots d'Acacia cyanophylla Lindl cultivés en pots, sous serre, ont été soumis à l'âge de 8 mois à deux alimentations hydriques très contrastées : une dose d'irrigation proche de l'évapotranspiration maximale (D) et D/6. Au bout de 1, 3, 5 et 13 mois, trois plants de chaque lot ont été soumis à un cycle de dessèchement par privation d'eau afin de permettre aux mécanismes adaptatifs de s'exprimer en condition de sécheresse extrême. Au début de chaque cycle, les composantes du potentiel hydrique du phyllode ont été mesurées à 13 heures, afin d'évaluer l'effet de la durée du préconditionnement à la sécheresse sur les plants D/6. À la fin de chaque cycle, marquée par une turgescence nulle, des mesures analogues ont été effectuées et les phyllodes restants ont servi à la détermination des acides aminés libres, des sucres solubles et de l'amidon. Chez les plants D, on a noté au début des cycles une légère baisse du potentiel osmotique et une légère augmentation de la turgescence au cours du temps; ces variations semblent être liées à l'âge. La réponse des plants D/6 a varié selon la durée du préconditionnement. Après 1 mois, leur potentiel de turgescence, au début du cycle, a été inférieur à celui des plants D; à la fin du cycle, ils ont eu un potentiel osmotique moins négatif et des teneurs plus faibles en acides aminés libres en comparaison avec les plants D. Cela semble indiquer que 1 mois de préconditionnement à la dose D/6 a été insuffisant pour induire des mécanismes d'endurcissement. À partir du troisième mois, on a noté, au début des cycles, une turgescence plus élevée et un potentiel osmotique plus bas chez les plants D/6 avec une différence de potentiel osmotique entre D et D/6 croissante dans le temps (de 0,15 à 0,47 MPa). À la fin du quatrième cycle, les plants D/6 ont conservé une turgescence positive à des potentiels hydriques voisins de -4,50 MPa. La différence de potentiel osmotique entre D et D/6 s'est accentuée (de 0,40 à 1,60 MPa) et a été accompagnée d'une accumulation croissante de sucres solubles et d'acides aminés libres, essentiellement de proline. Parallèlement, on a enregistré une diminution de la teneur en amidon qui n'explique qu'en partie l'accumulation des sucres solubles. Ces résultats témoignent d'un endurcissement acquis par les plants D/6 suite à un préconditionnement de 3 mois ou plus. Cet endurcissement s'est traduit à la fin des cycles de dessèchement par une capacité d'ajustement osmotique croissante au cours du temps

On the distribution and subspecific variation of the Tunisian – Algerian endemic Delphinium sylvaticum (Ranunculaceae)

The morphology and biogeography of the Tunisian–Algerian endemic Delphinium sylvaticum Pomel has been studied in Tunisia. As presented here, this study resulted in an enlargement of the known distribution and in the description of two new subspecies: D. sylvaticum subsp. ichkeulianum El Mokni, Domina, Sebei & El Aouni and D. sylvaticum subsp. purpureum El Mokni, Domina, Sebei & El Aouni native to Tunisia in Mogods and in the northeast regions, respectively. Besides ecological features and clearly separated distribution, the two new subspecies show very well differentiated morphology. An updated distribution map and a diagnostic key of the studied taxa are provided

Chemical composition and antioxidant activity of essential oil from aerial parts of Teucrium flavum L. subsp. flavum growing spontaneously in Tunisia

The objectives of this study were to chemically characterise and evaluate the antioxidant potential of the essential oil from Teucrium flavum L. subsp. flavum growing spontaneously in Tunisia. The volatile oil was extracted by hydrodistillation of the aerial parts in a Clevenger type apparatus. Forty constituents were identified via GC and GC-MS analysis. β-caryophyllene (32.5%) and α-humulene (17.8%) were the most abundant components. The evaluation of free radical scavenging activity using stable DPPH free radical showed that the volatile oil exhibits a moderate antioxidant activity and reduces DPPH to 50% at EC50 value of 1230 μg mL− 1