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Electronic Flora of South Australia Genus Fact Sheet
Phylum Phaeophyta – Order Dictyotales – Family Dictyotaceae – Tribe Zonarieae
Thallus complanate and relatively thin, flabelliform and entire or becoming lacerate often to the base, 2–20 cm long and broad, basally attached by rhizoids. Growth by a marginal row of apical cells with a revolute apical margin, circinnately inrolled to the upper facing surface, segmenting to form a blade 2–8 cells thick, with concentric zones of phaeophycean hairs on one or both surfaces. Phaeoplasts numerous per cell, discoid. Some species with a branched, terete to compressed, slender "Vaughaniella" stage, from which the flabellate thalli arise.
Reproduction: Unilocular sporangia in concentric rows or zones, or in patches, on one or both sides of the thallus, producing four meiospores, or probably apomeiotic in some species. Indusia more or less conspicuous over the sori, or absent, derived from the outer thallus membrane. Sexual plants rare, with oogonia and antheridia in sori in concentric zones.
Life history diplohaplontic and isomorphic, in some species direct from the sporophyte generation.
Type species: P. pavonica (Linnaeus) Thivy in Taylor. Price et al. (1979, p. 3) consider that the correct citation is P. pavonica (L.) Lamouroux.
Taxonomic notes: A genus of some 30 species (see Papenfuss 1977, p. 277), widely distributed in tropical waters and extending into warm (rarely cool) temperate regions. Only one species is common on southern Australian coasts, largely confined to Victoria, but three other species extend from Western Australia to the southern coast. In addition, P. tenuis Bony occurs on the Western Australian coast as far south as Rottnest Island.
The circinnately inrolled apices of the fronds characterise Padina and the inrolled side is normally the upward facing one (referred to below as the upper), with the opposing side being the lower (Trono 1969, p. 33).
References:
ADANSON, M. (1763). Families des Plantes. Part 2. (Paris.)
PAPENFUSS, G.F. (1977). Review of the genera of Dictyotales (Phaeophycophyta). Bull. Jap. Soc. Phycol. 25, Suppl. Mem. Iss. Yamada, 271–287.
PRICE, J.H., TITTLEY, I. & RICHARDSON, W.D. (1979). The distribution of Padina pavonica (L.) Lamour. (Phaeophyta: Dictyotales) on British and adjacent European shores. Bull. Br. Mus. Nat. Hist. (Bot.) 7(1), 1–67.
TRONO, G.C. (1969). The marine benthic algae of the Caroline Islands, II. Phaeophyta and Rhodophyta. Micronesica 5, 25–119.
The Marine Benthic Flora of Southern Australia Part II complete list of references.
Publication:
Womersley, H.B.S. (14 December, 1987)
The Marine Benthic Flora of Southern Australia
Part II
©Board of the Botanic Gardens and State Herbarium, Government of South Australia
KEY TO SPECIES OF PADINA
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1. Thallus 4 cells thick above, becoming | P. gymnospora |
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1. Thallus 2 or 3 cells thick throughout | 2 |
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2. Thallus 3 cells thick throughout | P. fraseri |
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2. Thallus 2 cells thick throughout | 3 |
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3. Thallus with indusiate sori of sporangia on lower surface only | P. sanctae-crucis |
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3. Thallus with indusiate sori of sporangia on upper surface only | P. elegans |
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