Proline accumulation is associated with inhibition of rice seedling root growth caused by NaCl

The effects of NaCl on changes in the proline level in roots and root growth of rice seedlings were investigated. NaCl was effective in inhibiting root growth and in increasing proline accumulation in roots. Mannitol was also effective in inhibiting root growth, but proline accumulation was observed only at the concentration iso-osmotic with 150 mM NaCl. Accumulation of proline in roots preceded inhibition of root growth caused by NaCl. The inhibition of root growth and accumulation of proline in roots by NaCl are reversible. Exogenous L-proline and gabaculine, which were found to enhance in an accumulation of proline in roots, inhibited root growth of rice seedlings. The relationship between growth inhibition of roots caused by NaCl and changes in the proline level in roots is discussed.