Résumé:
In arid and semi arid areas, soil salinization is a major ecological constraint. Unlike salt tolerant halophytes, most plants are stored in the group of glycophytes, whose physiological and biochemical processes are affected in the presence of salt. Soils rich in sodium chloride are characterized by an abundance of Na
+
and Cl-. Na ions disrupt the absorption of cations ((Na+, K+, Mg2+ et Ca2+), so that the excessive accumulation of chlorine reduces the absorption of anions ((Cl-, SO42-, HCO3- CO32-) essential for growth and development of plants in particular, nitrates, nitrites and sulfates. without bentonite soils irrigated with nutrient solution and saline, have a high content of sulfates 50 meq.l-1 (NaCl + CaCl2).
The impacts of salinity on development and yield of plants are many and difficult to prioritize. Sodium and chloride ions enter the plants through the roots and are transported via the xylem to the stems and leaves. Here they are either stored, type plants "includes" or just selected and revéhiculés by the phloem to the roots of plants such as "excluder". These mechanisms of tolerance or sensitivity are experimentally investigated on a local variety (Phaseolus vulgaris L.) grown under increasing salt diet (50-100-200 meq.gl-1 NaCl+ CaCl2) on sandy soil with or without bentonite.
Salinity causes an increased accumulation of proline. The levels of this amino acid increases with as the salt concentration increases and also depending on the organ and stage of growth. This accumulation of nitrogen compound is more evident in the leaf parts in the parts root. Thus the production of proline is particularly significant that the intensity of treatment is important and that the leaves are young in under conditions of intense cell multiplication.
Changes in proline content change in proportions varying according to the low soil types and the station studied.
The data show that exposure of seedlings of (Phaseolus vulgaris L.), salinity led to a fall in growth mainly from the aerial part, but with a bentonite amended soil, seedlings of the three stations show a high adaptability. The effect of salinity is not uniform for all organs. This depressive effect on growth was accompanied by changes cationic. The accumulation of compatible solutes also induces a decrease in water potential and thus allows the absorption of water from the environment.
