Saxifraga oppositifolia L.
Purple saxifrage, purple mountain saxifrage, opposite-leafed saxifrage.
Sp. Pl. 1: 402. 1753.
Antiphylla oppositifolia (L.) Fourr.
Saxifraga oppositifolia subsp. grandulisepala Hultén
Plants cushion-like, or with branched or unbranched matted stems (forming mats 20–50 cm in diameter, CAN 395412), or with stems trailing along the ground; 2–5 cm high (rarely to 10 cm high where plants are etiolated). Taproot present (rarely collected). Aerial stems erect (branched and sometimes very highly compacted), or prostrate (with trailing stems); glabrous, or sparsely hairy (when visible). Leaves distributed along the stems (often imbricate, and densely overlapping); opposite (4-ranked); evergreen, or marcescent (the shoots overwinter with new green leaves, which do not turn orange and die until the end of the next growing season). Petioles absent. Blades 0.25–0.4 cm long; 2–3 mm wide; leathery and succulent; obovate; with inconspicuous veins; glabrous. Leaf margins with non-glandular hairs (that are bristle-like). Conspicuous hydathodes present (seen as pores on the thickened, often flat, apex of the leaf; often with white calcium carbonate deposits; illustrated in the image library). Leaf apices obtuse.
Flowering stems 0.5–3(–5.5) cm long; with leaves (that are often more widely spaced, narrower, attenuate at base, and without conspicuous truncate apices or hydathodes, than the leaves of the vegetative stems); hairy. Flowers solitary; medium-sized, 5–15 mm in diameter or length. Calyx sepals 5; green, or purple; glabrous. Petals purple, or pink, or red (pale), or white (rarely); obovate (with narrow bases); unlobed; 6–9 mm long. Stamens 10. Carpels partly fused; 2 (rarely 4–5). Gynoecia partly inferior. Styles 2. Stigmas per style 1. Ovules 50–100 (approx.). Fruit with calyx persisting (corolla persistent); spherical (lower half, with divergent free carpels above); 5–7.5 mm long; 4–5 mm wide; brown, or red (purplish); styles style modified modifying and persisting. Seeds 50–100 (approx.); 0.7–1.1 mm long; brown; smooth, or verrucose (at one end).
Chromosome information. 2n = 26 and 52.
Distribution. Circumpolar. Arctic. Range in the Canadian Arctic Archipelago wide-spread. Common. Arctic Islands: Baffin, Devon, Ellesmere, Axel Heiberg, Parry Islands, Cornwallis, Banks, Victoria, Prince of Wales, Somerset, and King William.
Ecology and habitat. Substrate hummocks (on the sides), around the margins of ponds, along streams, river terraces, lake shores, tundra (raised centres of frost boils, solufluction slopes), slopes (of hermats), sea shore (just above high tide on beach ridges); imperfectly drained, or dry, or moderately well drained; gravel (fellfield, shale, rocky mountain slopes, drumlin surfaces), till, moss; with low organic content (granitic-schist), or with high organic content, or peat. The species characterizes extensive Saxifraga oppositifolia barrens (illustrated in the image library). Plants occasionally grow in moss and in standing water (two observations made at different locations on Ellesmere Island in 1994).
Saxifraga oppositifolia is almost always the earliest "flower" to appear in spring, although sometimes some of the willows will be earlier by a day (Polunin 1940). The flowers overwinter in a well developed condition. One observation was that in December, in Greenland, petals and stamens were already coloured (Warming 1909). In West Greenland, they have been observed to flower as early as late March. Plants from Svalbard to Nova Zemblia are reported to have flowers with a strong scent. Nectar is often secreted abundantly from the base of the ovary. The flower is so widely expanded, that in rain or melting snow it may be filled with water. The flower is initially protogynous and the stigmas mature before the flowers are fully expanded. At first the styles are longer than the stamens, but gradually the anthers become as long as the styles, and gather so closely around them that self-pollination takes place. Staminate flowers occur, in which the gynoecium is very small, but the stamens are of normal length. Such flowers do not set fruit. Pistillate flowers have been observed. In these, the stamens were almost rudimentary or sterile (Warming 1909).
Wagner and Tengg (1993) studied the embyrogenesis and seed development of S. oppositifolia plants growing in European mountains. They found that immediately before the flowers open the ovules are in the post-meiotic state and not ready for fertilization, until the flowers are fully open. After fertilization there is a delay of 2–3 weeks before the development of helobial endosperm begins. The differentiation and ripening of the seeds takes a total of 11 weeks.
Taxon as an environmental indicator. This species is usually indicative of harsh environments where there is little competition from other species. Saxifraga oppositifolia is one of the four species of plants known from the northernmost botanical locality on earth, that is Lockwood Island, 83°24'N, on the north coast of Greenland. It has been collected in Canada on Ward Hunt Island, 83°05'N. (CAN).
Indigeneous knowledge. The flowers, which have a pleasant fresh taste, are often eaten in large quantities when they appear early in the growing season. Too many of the flowers eaten at once can induce diarrhoea.
Notes. The variation in S. oppositifolia was the basis of a study by Teeri (1972) who concluded that distinct forms that had been named as taxa, were merely expressions of a single species that shows remarkable vegetatively phenotypic plasticity with little reliable genotypic basis on which to separate infraspecific taxa. Brysting et al. (1996) studied the purple saxifrage on Svalbard to determine whether there were two taxa or one. They concluded, that the conspicuous variation probably results from local, in situ ecoclinal differentiation, and is without taxonomic significance, but important in the context of arctic conservation biology and the potential impact of global warming on Arctic vegetation. Boris Yutsev (LE) has suggested that there are two taxa within S. oppositifolia in Canada, one with glabrous sepals, the other with glandular hairs on the sepals. In a survey of specimens at CAN plants with glandular sepals were found as were specimens with densely matted hairs on the sepals and others with sparse or few hairs. The type specimen of the name "smalliana" has almost no hairs on the sepals. These observations are thet basis of a study that is currently underway in the year 2000.
This is one of the common species in the Arctic Archipelago. Polunin (1940) considered it possibly one of the most numerous of all arctic species, as it dominates large tracts of country in the Far North, if the term "dominates" can be used when the total vegetation is extremely sparse and largely limited to occasional tufts of this one species (illustrated in the image library). He considered it possibly the hardiest of all phanerogams, at least to cold-rigour, occurring on the most exposed ridges and hill tops, often where no other vascular plants can grow. This may be because of the unique structure of the leaves.
The internal structure of the leaves led Galloe (1910) to consider this species a xerophyte. The upper epidermal cells have fairly straight lateral walls with numerous pits. The outer walls vary in thickness in different parts of the leaf. Towards the apex they are very thick, and from there become gradually thinner towards the leaf base. The cuticle is distinct and very finely wrinkled. The stomata are mainly parallel to the length of the leaf. They are entirely absent from the tip of the apex where the hydathode is. Immediately behind the apex they occur in a broad band across the leaf and are partially continued along the under-side of the leaf margin. The leaves are usually so close together that for the greater part they overlap. Only the part of the leaf that is covered with neighbouring leaves bears stomata, while the light-exposed surface is almost without them. This was regarded as protection against excessive transpiration by Lazniewski (1896). Galloe (1910) considered that the distribution of the stomata represent a primitive form of bud-protection in developing leaves, in a species where bud scales are absent. The pallisade cells of the leaves at the exposed apex are very distinct and occur on both the upper and lower surfaces.
Polunin (1940) remarked that "S. oppositifolia ... before and after flowering is among the most squalid-looking of plants, forming untidy brownish mats or tussocks in barren and often dusty situations. When it blooms it must be reckoned among the world's greatest beauties, especially as it stands out in its usually bleak and desolate surroundings. Unfortunately, few ever see it at its best, which is surely in the Far North, for it is so quickly over that the vast majority of the ever-increasing band of summer visitors to arctic parts come too late".
Illustrations. • Habitat. Saxifraga baren where purple colour is that of flowering plants of purple saxifrage. Nunavut, Ellesmere Island, Alexandra Fiord at the top of a mountain. L.J. Gillespie. • Habitat. Adjacent plants growing in the water of a small run-off stream, on a seepage slope of rock and silt. Two morphological forms growing within 20 cm of each other. The more compact form had leaves growing above the surface of the water. Nunavut, Ellesmere Island, Franklin Pierce Bay, 79°25.94° N, 75°37.86 W. S.G. Aiken 98–030a. CAN. Photograph by Mollie MacCormac. • Plant habit. PURPLE SAXIFRAGE, PURPLE MOUNTAIN SAXIFRAGE, OPPOSITE-LEAFED SAXIFRAG: loosely clustered plant with opposite leaves that have long trichomes on the margins. Note flower born singly, hairs on the sepals, five 'purple' petals, 10 pink stamens with small purple anthers, and two adjacent carpels. Nunavut, Ellesmere Island, Alexandra Fiord, L.J. Gillespie. • Plant habit. Compact cushion-like plants in full flower, growing in saxifraga barren. Nunavut, Ellesmere Island, Alexandra Fiord, L.J. Gillespie. • Line drawing of plant habit. Fig. A flowering stem that is leafy to just below the flower. Fig. B, opposite leaf arrangement. Fig. C elongated fruiting stem. Fig. D trailing growth form and E, compact growth form that has been distinguished by some authors using the name 'smalliana'. • Leaves with hydathodes. Note small leaves with large trichomes on the margins, borne opposite each other and hydathodes (white arrow) on the triangular ends of the fleshy leaves. Many hydathodes have white calcite deposits at leaf tip. Hydathodes are small openings on the leaf blades which exude water. Leaves also have a ciliated leaf margins. Nunavut, Cornwallis Island, Resolute Bay. Each stem of leaves about 0.7 cm across. • Close-up of flower. Close-up of flower with sepals that have hairs on the surface, five petals, ten stamens that have robust filaments tipped with tiny purple anthers, and two orangy-pink carpels that are fused at the base but separate for most of the length before diverging towards the purple stigmas. Nunavut, Ellesmere Island, Alexandra Fiord. L. J. Gillespie, s.n. • Plant in fruit. Flowers with carpels in fruit. Note glandular hairs on the sepals, seen in upper flower to the left of centre, withered dark purple petals, yellow dots of remnant anthers, seen on upper flowers to the right of centre, and swollen, dark red carpels that diverge towards the apex. Nunavut, Ellesmere Island, Vendom Fiord, plants growing in sand of a flood plain. • Plant in fruit. Note long peduncles and hairs on the sepals, seen in the left-hand specimen, dishisced anthers that have persisted and dark red diverging carpels. Nunavut, Cornwallis Island, Resolute Bay. CAN. August, 1998. Photograph by Mollie MacCormac. • Arctic Island Distribution.
Cite this publication as: ‘C.L. McJannet, S.G. Aiken, M.J. Dallwitz, L.J. Gillespie and L.L. Consaul. 1997 onwards. Saxifragaceae of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 28th November 2000. http://www.mun.ca/biology/delta/arcticf/’. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993, 1995, 2000), Aiken, Dallwitz et al. (1999), and Aiken, Dallwitz, McJannet, Gillespie, and Consaul (1998) should also be cited (see References).
