Photosynthetic capacity and ion accumulation in a medicinal plant henbane (Hyoscyamus niger L.) under salt stress

A greenhouse experiment was conducted to assess the effect of salt stress on growth of an important medicinal plant henbane (Hyoscyamus niger L.). Sixty seven days-old plants of H. niger were subjected for 46 days to sand culture salinized with varying concentrations of NaCl, i.e., 0 (control), 40, 80, and 120 mmol/L. Increasing salt levels caused a significant reduction in plant fresh and dry masses. The reduction in shoot dry biomass of H. niger at the highest salt level (120 mmol/L) with respect to control was about 66 percent. Na+ and Cl- in both shoots and roots increased, whereas K+ and Ca2+ decreased consistently with the progressive increase in salt level of the growth medium. Plants of H. niger maintained markedly higher K+/Na+ and Ca2+/Na+ ratios in the shoots than those in the roots, and the former ratio was greater than I even at the highest external salt level (120 mmol/L). Proline content in the shoots did not change with increase in external salt level. Net CO2 assimilation rate had a negative association with the growth of H. niger under saline conditions. Overall, H. niger is a salt sensitive crop whose response to salinity is associated with maintenance of high K+/Na+ and Ca2+/Na+ ratios in both shoots and roots, although these ionic ratios showed a negative association with the salt tolerance of the crop.