Phenylalanine ammonia-lyase is the first enzyme of phenylpropanoid pathway and has an important role on plant cell wall lignification. The influence of different concentrations (0, 200 and 400 mM) of NaCl on growth, lignin content and PAL gene expression and activity were investigated at different internode positions (first ,fourth and seventh internodes) in a halophyte grass, Aeluropus littoralis (Gouan) parl. Salt stress inhibited the growth, increased the PAL mRNA level and induced PAL activity as well as lignin deposition. Level of gene expression and activity of PAL changed during internode maturity and decreased basipetally along the stem. Growth inhibition under NaCl stress can be the consequence of incorporation of lignin in the cell wall. The result suggests that A. littoralis with growth retardation, higher PAL gene expression and activity and increment of lignin content could have better tolerance at saline conditions.
