Responses of Barringtonia racemosa to Tidal Flooding

  Objective   Responses of the endangered semi-mangrove Barringtonia racemosa to submergence in tides were studied to determine the adequacy of their planting for urban inland river, lakeside, and wetland restorations or other similar landscape projects.

  Method   Two-year-old B. racemosa seedlings were used in the simulated semi-diurnal tide experiment. Morphology, physiology, biochemistry, and mineral contents of the plants in response to tidal submergence for varied durations were monitored.

  Result   (1) The seedlings survived 250 d under the flooding treatments, but the plant height, leaf count, and leaf area were significantly lower, while the numbers of aerial roots, piercing plants, and lenticels significantly higher, than those of control. (2) The chlorophyll a and total chlorophyll in the leaves decreased continuously under flooding, except the 16 h·d⁻¹ submergence treatment; MDA increased, except the 14 h·d⁻¹ treatment; and, MDA, proline, and soluble sugars became significantly higher than those of CK and peaked under the 10 h·d⁻¹ treatment. (3) The flooding increased the absorption of N, P, and Fe but inhibited that of K and Cu in the leaves.

  Conclusion   The area, the contents of P, total chlorophyll, and soluble protein, and the activities of CAT and POD of leaves as well as the surface area of lateral roots were the major indicators that reflected the responses of B. racemosa to the flooding stress. The plants showed strong tolerance and adaptability to the adversity brought about by the semi-diurnal tides that lasted 20 h·d⁻¹. Thus, B. racemosa could be adequately planted for landscaping at waterfront, lakeshore green belt, and/or freshwater wetland.