Salt-induced changes in photosynthetic in a potential medicinal plant Bishop's activity and growth weed (Ammi majus L.)

Sixty seven-days-old plants of Ammi majus L. were subjected for 46 d to sand culture at varying concentrations of NaCl, i.e. 0 (control), 40, 80, 120, and 160 mM. Increasing salt concentrations caused a significant reduction in fresh and dry masses of both shoots and roots as well as seed yield. However, the adverse effect of salt was more pronounced on seed yield than biomass production at the vegetative stage. Calculated 50% reduction in shoot dry mass occurred at 156 mM (ca. 15.6 mS cm(-1)), whereas that in seed yield was at 104 mM (ca. 10.4 mS cm(-1)). As in most glycophytes, Na(+) and Cl(-) in both shoots and roots increased, whereas K(+) and Ca(2+) decreased consistently with the successive increase in salt level of the growth medium. Plants of A. majus maintained markedly higher K(+)/Na(+) ratios in the shoots than those in the roots, and the ratio remained more than 1 even at the highest external salt level (160 mM). Net photosynthetic (P(N)) and transpiration (E) rates remained unaffected at increasing NaCl, and thus these attributes had a negative association with salt tolerance of A. majus. Proline content in the shoots increased markedly at the higher concentrations of salt. Essential oil content in the seed decreased consistently with increase in external salt level. Overall, A. majus is a moderately salt tolerant crop whose response to salinity is associated with maintenance of high shoot K(+)/Na(+) ratio and accumulation of proline in shoots, but P(N) had a negative association with the salt tolerance of this crop.