Electronic Flora of South Australia Species Fact Sheet

Ruppia megacarpa Mason 1967: 525, fig. 3.

Phylum Magnoliophyta – Subphylum Seagrasses – Class Liliopsida – Subclass Alismatidae – Order Potamogetonales – Family Potamogetonaceae

Selected citations: Green 1981: 5. Sainty & Jacobs 1981: 394 (figs), 395.

Synonym

Ruppia maritima sensu Aston (in part) 1973: 290, fig. 116 a,b,d-f.

Rhizomatous robust perennial herb (Figs 14A, 15D); rhizomes 1–1.5 (–2.5) mm in diameter. Stems 0.5–1 (–2) mm in diameter, 20–30 cm (and up to 2.5 m) long, branched, flexuous. Turions absent. Leaves filiform; sheath 1–3 (–5) cm long with 2 short rounded auricles (Fig. 15F); blade 5–10 (–25) cm long, 0.4–0.5 (–1) mm broad; apex (Fig. 15E) mostly bidentate, sometimes truncate, finely serrulate. Prophylls (Fig. 15F, G) (4–) 6–10 mm long, lanceolate, often conspicuous. Squamules (Fig. 15H) 0.2–0.5 mm long, ovate. Inflorescence (Fig. 15D) 2-flowered, at first enclosed in the enlarged sheaths of two sub-opposite leaves; peduncle at first rigid, erect, becoming lax and flexuose, elongating rapidly to reach the water surface where fertilisation occurs (peduncle length very variable depending on water depth and often to 1 m long). After anthesis the peduncle (Figs 14A, 15D) becomes tightly spirally coiled withdrawing the inflorescence below the surface. Pollen grains (Fig. 151, J) elongate-reniform, adhering in chains. Carpels (2–) 4 (–6) at first sessile, after fertilisation the base elongating into a podogyne (Fig. 15K, L) 2–4 (–5) cm long, about 0.3 mm in diameter, attached to the fruit by a broad base about 0.8 mm across. Fruit (Fig. 15M) asymmetric, usually 3–4 mm long with a distinct stylar beak up to 0.5 mm long; podogyne persistent in the mature fruit after the exocarp has decayed; endocarp dark-brown, rough, with a deltate perforation on each side.

Type from Taumutu, Lake Ellesmere, New Zealand (J. Clarke, 9.ii.1966); in CHR, 150818A.

Selected specimens: Coodanup, Peel Inlet, W. Aust., 0.5 m deep (Carstairs, 12.ix.1982; ADU, A53397). West Lakes, Adelaide, S. Aust., 1.5–2 m deep (Thomas & P. Womersley, 22.xii.1975; ADU, A46713). Coorong, S. Aust., (Womersley, 17.ii.1974; ADU, A50543). Pelican Point, St Georges Basin, near Jervis Bay, N.S.W., 0.5 m deep (Roberts, 8.x.1979; ADU, A53232).


Distribution map based
on current data relating to
specimens held in the
State Herbarium of SA

Distribution: W. Aust., S. Aust., Victoria and New South Wales in permanent water bodies such as estuaries, coastal salt-lakes and inland lakes, brackish to hypersaline with salinities up to 46‰. New Zealand.

Taxonomic notes: The marine material of R. megacarpa is from depths up to 2 m in sheltered areas influenced by the tides but not continuously in contact with the open sea.

R. megacarpa and R. tuberosa grow sympatrically in some localities but are reproductively isolated as flowering times do not overlap (Brock 1982a).

References:

BROCK, M.A. (1982a). Biology of the salinity tolerant genus Ruppia L. in saline lakes in South Australia. 1. Morphological variation within and between species and ecophysiology. Aquat. Bot. 13, 219–248.

GREEN, J.W. (1981). Census of the Vascular Plants of Western Australia. (Western Australian Herbarium: South Perth.)

MASON, R. (1967). The species of Ruppia in New Zealand. N.Z. .1. Bot. 5, 519–531.

SAINTY, G.R. & JACOBS, S.W.L. (1981). Water Plants of New South Wales. (Water Resources Commission of New South Wales: Sydney.)

The Marine Benthic Flora of Southern Australia Part I complete list of references.

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (31 May, 1984)
The Marine Benthic Flora of Southern Australia
Part I
©Board of the Botanic Gardens and State Herbarium, Government of South Australia


Illustrations in Womersley Part I, 1984: FIGS 14A, 15 D–M.

Figure 14 image

Figure 14   enlarge

Fig. 14. A. Ruppia megacarpa (ADU, A46713). Habit, plant with mature fruits. B–D. Ruppia tuberosa. B. Habit, plant with mature fruits on short stiff peduncles (ADU, A52729). C. Habit, plant with young inflorescence on short peduncle (arrowed) and older inflorescences with young fruits on elongate flexuose peduncles (ADU, A51909). D. Vegetative plants showing turions (ADU, A53621).

Figure 15 image

Figure 15   enlarge

Fig. 15. A–C. Ruppia polycarpa (ADU, A53396). A. Leaf apices. B. Inflorescence of two flowers soon after fertilisation. Note short podogynes (po.). C. Mature fruits with elongated podogynes (po.). D–M. Ruppia megacarpa. D. Portion of plant showing one young inflorescence with short peduncle and one inflorescence after anthesis with spirally coiled peduncle. Note pollen sacs (p.s.) and carpels (ca.). E. Leaf apices. F. Prophyll (p.) in leaf axil embracing young branch (b.). (Leaf sheath with auricles (a.) pulled to one side). G. Prophyll removed from leaf axil. H. Squamules. I. Pollen grains adhering in a chain. J. Pollen grain. K. Young fruits showing podogynes (po.), unfertilised carpels (ca.) and dehisced pollen sacs (p.s.). L. Older fruits showing podogynes (po.). M. Endocarp of ripe fruit, after decay of exocarp. (D–J from ADU, A50543. K–M from ADU, A46713.)


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