In vitro assessment of tolerance of orthosiphon stamineus to induced water and salinity stress

The response of in vitro plantlets of Orthosiphon stamineus to water and salinity stress indicated potential tolerance to both stress, with better tolerance to water-stress detected. Survival and vegetative growth was not severely affected for plantlets under induced water or salinity stress. Tolerance to water and salinity stress might be attributed to the proline and total soluble proteins produced. The levels for both biochemical markers significantly increased and correlated positively to the increasing concentrations of polyethylene glycol (PEG) and sodium chloride (NaCl) used. However, the chlorophyll content in Orthosiphon stamineus were reduced with the increase in concentrations of NaCl. Therefore, Orthosiphon stamineus show better tolerance to water stress than salinity stress, as survival rate, growth (fresh weight), proline level, total soluble protein and chlorophyll content in plantlets under water stress were relatively higher than plantlets challenged with salinity stress.