Osmolyte accumulation in different rape genotypes under sodium chloride salinity

Abstract

Physiological mechanisms of two rape (Brassica napus L.) genotype adaptation to chlorine salinity were investigated. The plants of two cultivars (Olga and Westar) differing in
salt tolerance were grown in the pots filled with Perlite on the Hoagland and Snyder’s medium under controlled conditions.
At a stage of 3–4 true leaves, the plants experienced 7-day-long salinity induced by a single addition of NaCl to the nutrient
medium in order to attain desired final salt concentration (from 50 to 400 mM). The obtained results showed that a greater
salt tolerance of cv. Olga plants (as compared with cv. Westar) could be accounted for by a capability of their root cells
to uptake water under high salinity (300–400 mM NaCl), which is evident from a greater content of water in the tissues of
cv. Olga. This was ensured by a sharp fall of the osmotic potential of the cellular contents (down to −2.3 MPa) at a low water
potential of nutrient solution owing to more active uptake of Na+ (57–61 µeq/g fr wt) and K+ (210–270 µeq/g fr wt) as well as active accumulation of proline (30–50 µmol/g fr wt). The latter is caused by a reduced activity
of proline dehydrogenase and retarded degradation of this osmolyte. It is important that, in contrast to less tolerant genotype,
the rape plants of salt-resistant cultivar were able to maintain the K+/Na+ ratio at a rather high level at salinity of different degree, which made it possible to preserve ionic homeostasis under
adverse conditions.