Salinity tolerance of Rhizophora mucronata Lam. from Gujarat coasts of India

Greenhouse experiments were conducted to assess the effects of soil salinity on germination, growth, water status, proline content and mineral accumulation of seedlings of Rhizophora mucronata (Rhizophoraceae). NaCl was added to the soil and salinity was maintained at 0.2, 2.5, 5.1, 7.7, 10.3, 12.6, 15.4, 17.9, 20.5, 23.0 and 25.6 psu. This plant is highly salt tolerant at the germination stage. Growth of seedlings was significantly promoted by low salinity and optimum growth was obtained at 20.5 psu. Moreover, higher salinities inhibited plant growth. Water potential of tissues became significantly more negative with increase in salinity. Proline content in tissues significantly increased as salinity increased. The concentration of Na in tissues increased, whereas K, Ca, N and P content decreased with increase in salinity. We discuss changes in tissues and whole-plant accumulation patterns of other nutrients, as well as possible mechanisms for avoidance of Na toxicity in this plant in response to salinity.