Rhodamnia

Abstract: A macrofloral fossil assemblage from fluvial Taratu Formation sediments of Waipawan to Bortonian (Early to Middle Eocene) age, near Livingstone, North Otago, New Zealand, is described. The assemblage yielded two indeterminate coniferous taxa, thirteen taxa of angiosperm leaves, including Myrtaceae (aff. Eucalyptus, and aff. Rhodomyrtus/Rhodamnia), Proteaceae (cf. Orites excelsa), Sterculiaceae (Brachychiton populneus), Elaeocarpaceae (Sloanea), probable Lauraceae, possible Passifloraceae and two kinds of Myrtaceae reproductive structures. The original community is compared with extant vegetation in Australia and rainfall may have been seasonal.

Abstract: cinerea, collected by him in Sumatra and the Malay Islands and distinguished from Myrtus by 4-merous flowers and unilocular ovaries with paired, parietal placentas. Jack's new genus was overlooked by taxonomists for several years because of the destruction of most copies of his publications and nearly all of his herbarium by a fire on board ship (Merrill, 1952). His book, Descriptions of Malayan Plants, was republished several times, the first occasion by Hooker (1835), after which his genus was taken up by taxonomists. During the intervening period several new species were described that are now considered to belong to Rhodamnia and these were placed either in Myrtus or in Monoxora Wight (1831), a genus based on Myrtus spectabilis Blume, a species now recognized to be a synonym of R. cinerea. The first treatment of Rhodamnia was by Blume (1850) who recognized seven species, including four new combinations and two new species. Among the new combinations was that based on Myrtus trinervia Sm. from Australia, so establishing the genus in Australia. The species in the Dutch East Indies were reviewed by Miquel (1855), who described one new species. The Australian species were studied by Bentham (1867), who described two new species and who also suggested that R. trinervia (Sm.) Blume might be no more than an extreme form of the widely distributed Asiatic species, R. cinerea. Subsequent authors, such as Kurz (1877), Duthie (1879), King (19o0) and Gagnepain (192 ), misapplied the name R. trinervia to include Malayan and Asian species, especially R. cinerea. Ridley (1922) reinstated R. cinerea as the correct name for the Malayan species while Diels (1922) reviewed Rhodamnia in New Guinea, describing four new species collected in the Sepik region. The Australian species were described in detail by C. T. White (1937) who recognized seven species in Queensland and New South Wales including two new species. The name R. trinervia was shown to apply only to Australian plants which differed from R. cinerea in the racemose inflorescence, while in R. cinerea the flowers are clustered. In this account all specimens cited have been seen unless otherwise stated.

Abstract: We investigated ex situ conservation options for two Australian rainforest species severely affected by myrtle rust in the wild – Rhodamnia rubescens (Benth.) Miq. and Rhodomyrtus psidioides (G.Don) Benth. Both species were successfully initiated into tissue culture though the rate of contamination was high and not significantly improved by the disinfection techniques tested. Explants surviving initiation grew well on Murashige and Skoog medium (MS; pH 6.0) with 30 g L−1 sucrose, 1 µm benzyl adenine and 0.2 µm indole-3-butyric acid. Culture of R. rubescens for eight weeks on MS with 0, 5, 10 or 20 µm indole-3-butyric acid resulted in root production for some plantlets, and successful transfer to potting mix; no significant differences in root production among treatments were detected. Both species were successfully propagated by semi-hardwood cuttings with strike rates of 0–67% for R. rubescens and 0–75% for R. psidioides. For R. rubescens, pretreatment of cuttings with Zaleton® and incubation in Preforma® plugs reduced the time to root development and significantly improved the strike rate (P = 0.001). R. rubescens seed proved to be orthodox and suitable for standard seedbanking; R. psidioides seed proved to be freezing sensitive but suitable for storage at 4°C. As the two species now produce few viable seeds in the wild, however, conservation by seedbanking will first require the establishment of a seed orchard from vegetatively propagated plants. We recommend swift action to conserve species in the Pacific similarly affected by myrtle rust before their growth and reproductive capacity are seriously diminished.

Abstract: The essential oils of the 17 Australian members of the genus Rhodamnia have been determined. R. dumicola, R. pauciovulata, R. rubescens and R. sp. (McIlwraith Range, L. J.Webb+9527) contained relatively large amounts of α-pinene. R. australis, R. blairiana, R. costata, R. dumicola, one chemotype of R. argentea, R. whiteana and R. sp. (Cape York, L. S. Smith 12538) contained significant amounts of α-, β-, and γ-eudesmol as well as significant amounts of α- and β-pinene. R. glabrescens, another chemotype of R. argentea, R. sessiliflora, and R. spongiosa contained as principal components the sesquiterpenes β-caryophyllene, globulol, viridiflorol and spathulenol. R. maideniana and R. sp. (Calliope, N. Gibson 1335) contained significant amounts of the previously mentioned sesquiterpenes as well as five as yet unidentified oxygenated sesquiterpenes. One notable point about the essential oils of all the species of Rhodamnia examined was the almost complete absence of 1,8-cineole. In all the samples examined it was never present at levels greater than 0.1%. The oil yield on the whole was at a trace to low in most species, the highest being approximately 1% in R. whiteana and R. sp. (Callipe, N. Gibson 1335). © 1997 John Wiley & Sons, Ltd.