Responses of Melaleuca quinquenervia seedlings to flooding

Abstract Studies were conducted on effects of flooding for 15, 30, 60, and 90 days on morphological changes, stomatal aperture, water potential, and growth of seedlings of Melaleuca quinquenervia, a species often planted for reclamation of swamps. Flooding rapidly induced formation of many hair-like adventitious roots as well as a few thick adventitious roots that originated on the original root system. Some adventitious roots also formed on submerged portions of the stem. Melaleuca seedlings were very tolerant of flooding as shown by only slight reduction in dry weight increment of shoots after 30 days of flooding in stagnant water. Although flooding for 60 or 90 days significantly reduced dry weight increment of leaves, dry weight increment of roots was not inhibited by any flooding treatment, reflecting both degeneration of some of the original roots and compensatory growth of adventitious roots. On certain days flooding induced stomatal closure on both adaxial and abaxial leaf surfaces. Extensive production of adventitious roots and some stomatal reopening after a critical period of flooding appeared to be important factors in the flooding tolerance of Melaleuca and are consistent with its aggressiveness and vigorous growth on wet sites.