Salt tolerance of Hibiscus hamabo seedlings: a candidate halophyte for reclamation areas

In order to evaluate the salinity tolerance of Hibiscus hamabo Siebold & Zuccarini (Malvaceae), a candidate halophyte for reclamation areas, we analyze the effects of NaCl concentration, ranging from 0 to 500 mM, on the morphological, photosynthetic and chlorophyll fluorescent traits of this species. The optimal concentration for the germination of H. hamabo was 25 mM NaCl, and the optimal concentration for the survival and growth of H. hamabo ranged from 5 to 10 mM NaCl. Growth traits of H. hamabo at 25 mM, including the plant height, canopy diameter, number of leaves and width of the largest leaf, showed no statistical differences from the control. Net photosynthetic rate, stomatal conduction, light utilization efficiency, water utilization efficiency, maximal photosynthetic rate, light saturation point and chlorophyll content were the highest at 7.5 mM NaCl. Fv/Fm and Fv/F0 at 5 and 7.5 mM were significantly higher than the others, while F0 was significantly lower. Fm and Fv at NaCl concentrations ranging from 2.5 to 10 mM were significantly higher than the others. Pearson correlation analysis showed that the chlorophyll content, maximal photosynthetic rate and light saturation point were significantly positively correlated with the number of leaves, while F0 was significantly negatively correlated with the width of the largest leaf. Light compensation point was significantly negatively correlated with plant height, leaf number, width of the largest leaf and canopy diameter, and might be a good indicator for the salt tolerance of H. hamabo.