Biological Attributes of The Canopy-held Melaleuca Seeds in Australia and Florida, U.S

The paperbark tree Melaleuca quinquenervia (Cav.) S.T. Blake (melaleuca) is invasive in southern Florida, U.S., but benign in its native range (eastern Queensland and northeastern New South Wales, Australia). As part of an ongoing study to explain this dual nature, we compared the biological attribu...

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Bibliographic Details
Published in:Journal of aquatic plant management 2002-07, Vol.40 (2), p.87-91
Main Authors: Rayamajhi, M B, Van, T K, Center, T D, Goolsby, JA, Pratt, P D, Racelis, A
Format: Article
Language:English
Subjects:
Australia, New South Wales
Australia, Queensland
Melaleuca quinquenervia
USA, Florida
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Summary:The paperbark tree Melaleuca quinquenervia (Cav.) S.T. Blake (melaleuca) is invasive in southern Florida, U.S., but benign in its native range (eastern Queensland and northeastern New South Wales, Australia). As part of an ongoing study to explain this dual nature, we compared the biological attributes of canopy-held seeds between the two countries by collecting infructescences (capsule clusters) from branches of open-grown trees in dry to seasonally flooded habitats and comparing branch-position cohorts in terms of capsule densities and seed quality. The infructescence lengths were similar in both countries, but gaps (scars from aborted capsules) within infructescence axes were more common on trees in Australia than on trees in the U.S. This difference was associated with high incidences of flower or fruit abortion in Australia. Consequently, capsule density on infructescence axes was three per cm in Australia compared to eight per cm in the U.S. This resulted in 18 and 49 capsules per infructescence in Australia and the U.S., respectively. Each infructescence in Australia contained ca. 5,000 seeds with 1,200 viable. Seed quality also differed with 9% vs. 14% of seeds containing embryos, 39% vs. 63% of embryonic seeds being viable, and 34% vs. 52% of viable seeds being germinable in Australia and Florida, respectively. The proportional viability and germinability of embryonic seeds did not vary consistently among infructescence-position cohorts in Australia, whereas in the U.S., the proportions were greatest in middle-aged and least in youngest and oldest infructescences. Overall quality and quantity of canopy-held seeds were reduced in Australia when compared to the U.S.
ISSN:0146-6623