Résumé:
In arid and semi-arid regions, soil salinity is a major environmental stress.
Conversely halophytic tolerant salts, most plant species are classified in the group of
glycophytes, whose physiological and biochemical processes are assigned in the presence
of salt. Soils rich in sodium chloride are characterized by an abundance of Na+ and Cl-ions.
The Na+ ions disturb absorption of cations (Na+, K+, Mg2+ and Ca2+), so that excessive
accumulation of chlorine decreases absorption of anions, essential for the growth and
development of plant particularly nitrates, nitrites and sulfates.
The impact of salinity on the development and yield of plants are numerous and
difficult to prioritize. The sodium and chloride ions enter the plants via the roots and are
conveyed by the conductive tissues. These mechanisms of tolerance or sensitivity are
experimentally investigated on radish, grown under increasing salt diet (50 et 100 meq.gl-
1 NaCl) on a sandy soil with 07 % and 10 % bentonite.
The salinity causes an increased accumulation of proline. The levels of this amino
acid increases gradually as the salt concentration increases and also as the member and
the stage of growth. Thus the production of proline is more marked as the intensity of
treatment is important and that the leaves are young ie under conditions of intense cell
multiplication.
Changes in proline content evolve in a greater or less weak according to different
soil types and the station studied.
The data show that the exposure of seedlings (Raphanus sativus L.), salinity
resulted in a fall in growth especially of the aerial part, but with an amended soil
bentonite, seedlings of three stations show great adaptability. The effect of salinity is not
uniform for all organs.
This depressive effect on growth was accompanied by cationic modifications. The
accumulation of compatible solutes also induces a decrease in the water potential and
thereby allows the absorption of water from the environment.
