Rosa rugosa Thunb. ex Murray
2005; Wiley; Volume: 93; Issue: 2 Linguagem: Inglês
10.1111/j.1365-2745.2005.01002.x
ISSN1365-2745
Autores Tópico(s)Plant and animal studies
ResumoRosaceae, Rosoideae, Rosa L.; subgenus Eurosa Focke; section Cinnamomeae (DC.) Rehder. Japanese Rose. Rhizomatous multi-stemmed erect deciduous shrub, strongly suckering, mature clones forming impenetrable thickets. Rhizomes woody, with orange-brown cortex and triangulate scale leaves. Rhizome branches and suckers emerge from axillary buds subtended by scale leaves. In addition, suckers may arise from buds on the roots. Stems erect, sometimes arching, to 1.5(−2) m, often much branched, tomentose when young, densely prickly. Cortex light yellowish brown. Prickles subulate, slender and straight, of all sizes down to acicles. Larger prickles tomentose, at least near the base, and usually glabrous in the apical part. Leaves alternate with (5–)7–9 leaflets contiguous on the rachis. Leaflets nearly equally sized, 2–5 × 1.5–3 cm, leathery and robust, widely elliptical, acute, with broadly cuneate or rounded base. Adaxial side dark green, conspicuously bullate or rugose, rather shiny. Abaxial side green-grey, tomentose to pubescent, with sessile pale glands, and with reticulate nervation. Leaf margin bluntly and simply crenate-serrate, involute, edge of teeth often deflexed. Petiole and rachis densely pubescent, and with many unequal subulate prickles. Stipules pale green, densely pubescent, 2.5 × 1–1.5 cm, divergent, the free part broadly ovate or deltoid. Flowers usually solitary or few together, 6–9 cm across, fragrant, nectarless. Sepals 2–3 cm, entire, with a broad, expanded tip, appressedly pubescent, aciculate and glandular (sometimes with stipitate glands), erect on the hip, persistent. Petals five, bright purplish-pink, sometimes white (R. rugosa f. alba (Ware) Rehder). Stamens 200–250 per flower, and styles often more than hundred. Styles pilose; stigmas in a large, domed head, sunk in the narrow, concave disc; disc 2.5–4 mm across; orifice large, at least half the diameter of the disc. A hypanthium (hip) encloses the achenes. It is depressed globose, 1.5–2 cm long and 2–2.5 cm wide, with a distinct neck below the sepals, dull green to orange when unripe, becoming glossy and brilliant red when ripe, most often smooth. Pedicel of the same length as the hip, tomentose, often with gland-tipped acicles, erect in flower, curved in fruit so that the hip points downwards. Achenes with a woody-bony pericarp enclosing the seed. Achenes broadly ovoid, obtusely angular, 4.0–6.0 mm long and 2.0–2.6 mm wide and 1.8–2.2 mm thick, with a distinct suture on both ventral and dorsal sides, hilum basal. Achene surface more or less lustrous, orange-brown. Mean seed (achene) mass is 6.6 mg. The albumen is oily. No subspecies of R. rugosa have been recognized in the British Isles. Despite the many cultivated varieties of the species, mainly forms close to the wild type are seen naturalized. However, naturalized clones may be confused with R. × hollandica (syn. R. × kamtchatica). This taxon differs morphologically from R. rugosa by having soft-textured, dull leaflets, without prominent veins, less prickly stems, conspicuously glandular sepals, and smaller flowers and hips (Rutherford 1990). Taxonomic position: Rosa L., subgenus Eurosa Focke (syn. subgen. Rosa), section Cinnamomeae (DC) Rehder (syn. sect. Rosa; sect. Cassiorhodon Dumort.). Section Cinnamomeae is central in the subgenus Eurosa, which contains all but four of the approximately 150 Rosa species in the world. The diploid species of this section, including R. rugosa, are probably basal in the reticulate evolutionary series from diploid species to irregular polyploid species within this genus (Erlanson 1938; Grossi et al. 1998). Originally introduced as a garden and landscape ornamental, and widely used as rootstock for other cultivated roses, R. rugosa can be found in many different cultivated settings. Now a well-established naturalized alien occurring scattered throughout Britain and invasive in fixed dunes and other coastal habitats. Rosa rugosa has a wide distribution in the British Isles, from southernmost England to Shetland, albeit rare or absent from upland areas of Wales, northern England and Scotland, and, in addition, most of Ireland (Reynolds 2002) (Fig. 1). Its distribution has increased strikingly between the publication of the most recent distribution maps, from 333 10 × 10 km mapping quadrats (Graham & Primavesi 1993) to 947 quadrats approximately 10 years later (Preston et al. 2002), but part of the apparent increase may be attributed to better recording in the latter mapping. Rosa×hollandica is found mainly in urban areas of England and southern Scotland. It has been recorded from 94 10 × 10 km mapping squares (Preston et al. 2002) (Fig. 2). The distribution of Rosa rugosa in the British Isles. (○) Pre-1950; (•) 1950 onwards. Each dot represents at least one record in a 10-km square of the National Grid. Mapped by Henry Arnold, Biological Records Centre, Centre for Ecology and Hydrology, mainly from records collected by members of the Botanical Society of the British Isles. The distribution of R. × hollandica in the British Isles. (○) Pre-1950; (•) 1950 onwards. Each dot represents at least one record in a 10-km square of the National Grid. Mapped by Henry Arnold, Biological Records Centre, Centre for Ecology and Hydrology, mainly from records collected by members of the Botanical Society of the British Isles. Rosa rugosa has been recorded as an established garden escape in 16 European countries between the latitudes c. 46° and 68° N, and is naturalized in parts of northern, western and central Europe (Fl. Eur. 2) (Fig. 3). It is considered an invasive species along the coasts of the Northern Atlantic, the North Sea and the Baltic Sea, including the Netherlands (Christenhusz & van Uffelen 2001), Germany (Hegi Fl. ed. 3, 4, p. 50), Denmark (Pedersen 1965; Andersen 1995), Norway (Fremstad 1997), Sweden (Nilsson 1967; Milberg 1998), and Lithuania (Eringis & Apalia 1976; Gudžinskas 2000). In North America R. rugosa is reported from 19 states in the USA, from New England to Missouri and in Washington (USDA, NRCS 2002), and from six provinces in Canada, from Ontario to Newfoundland (Darbyshire 2003). The distribution of Rosa rugosa in Europe. Reproduced from Atl. Fl. Eur. 13 by permission of the Committee for Mapping the Flora of Europe and Societas Biologica Fennica Vanamo. The native range of Rosa rugosa includes northern Japan (Hokkaido and Honshu south to 35° N; Ohwi 1965), the Korean Peninsula (Ohwi 1965), north-east China (on the coast and islands of southern Liaoning province and eastern Shandong province, classified as an endangered species; Fu 1992), and the Russian Far East (Kamchatka north to 55° N, Sakhalin, Kuriles, Khabarovsk region, and Primorye region; Sokolov et al. 1980). In its native range, R. rugosa mainly inhabits stabilized dunes, as well as rocky shores and species-rich meadows, always near the coast, and thus at low elevations. However, in Britain R. rugosa occurs at a maximum altitudinal limit of 435 m at Landdewi Brefi, Cardiganshire, Wales (Pearman & Corner 2004). Rosa rugosa seems to encounter no limitations to growth along the coasts of the British Isles, from southern England to Shetland. It mainly occurs in dry coastal habitats, such as fixed dunes and shingle beaches. In addition, it is found as a garden escape inland, but appears to grow less vigorously there. It is never found in upland habitats. Climatically and topographically its favoured habitat in Britain, and in most of its exotic range, closely resembles its native habitat in eastern Asia. Rosa rugosa most often occurs in sandy or gravelly soils, occasionally on other well-drained substrates. It appears to be absent from highly acid soils, but otherwise has little specificity with regard to soil acidity. In Denmark, it occurs on soil with pH from 4.7 to 7.7 (Table 1). In Japan, Yamane (1990) found that the pH of the topsoil in natural stands of R. rugosa varied between 5.1 and 7.6 (median 6.4) and that the pH of a deeper soil horizon (45–50 cm below surface) varied between 5.4 and 8.5 (median 6.9). In the British Isles, R. rugosa is found in natural communities in sand dunes, shingle beaches, and on sea cliffs, and in addition in hedgerows, on road verges and waste ground. Little information on the composition of plant communities including R. rugosa in the British Isles is available, and the species is not mentioned by Rodwell (2000). On the coasts of the North Sea, R. rugosa is predominantly found in yellow dune vegetation of the class Ammophiletea arenariae. This vegetation is dominated by Ammophila arenaria, and to less extent Leymus arenarius. Rosa rugosa is mostly confined to dunes with moderate sand accumulation, where Carex arenaria and Corynephorus canescens also occur. An example from the North Frisian island of Amrum, Germany (Türk 1995), which resembles British vegetation, is given in Table 2. However, once invaded by R. rugosa, the dune plant communities are altered to monospecific stands (Härdtle & Vestergaard 1996; Isermann 2003). Schepker (1998) gives three examples of dune vegetation dominated by R. rugosa and adjacent natural communities from the East Frisian island of Borkum (Table 3). The only species that seems to benefit from R. rugosa encroachment is the bryophyte Hypnum lacunosum. According to Schubert et al. (2001), R. rugosa has become a character species of dune scrub of the alliance Salicion arenariae, naturally consisting of Rosa pimpinellifolia, Salix repens ssp. arenaria, and Hippophaë rhamnoides. In addition, R. rugosa is found in fixed dunes with no sand accumulation and in species-rich sand grasslands of the class Armerion elongatae. Türk (1995) gives two examples of such communities from the North Frisian island of Amrum (Table 2). The invasion of R. rugosa presents a threat to populations of the rare species Silene otites and Dianthus carthusianorum, which occur in these grasslands. The invasion by R. rugosa of other coastal plant communities may be due to clonal spread From originally planted individuals. This is probably the case with coastal Empetrum-heath on the German Wadden Sea coast (Schepker 1998). On the coasts of the Baltic Sea, R. rugosa is found in similar communities, i.e. dune vegetation dominated by Ammophila arenaria,×Ammocalamagrostis baltica, Leymus arenarius and Carex arenaria, and with subordinate species such as Artemisia campestris, Corynephorus canescens, Eryngium maritimum, Festuca polesica, Festuca rubra ssp. arenaria, Hieracium umbellatum, Lathyrus japonicus ssp. maritimus and Phleum arenarium (Gravesen & Vestergaard 1969; Apalia 1976; Vestergaard 1991; Eigner 1992). In addition, R. rugosa is invading grassy coastal slopes of sandy or clayey till, there completely replacing the species-rich grassland vegetation. In dense R. rugosa stands, only a few competitive herbaceous species may thrive, e.g. Elymus repens and Epilobium angustifolium in southern Sweden (Agropyro-Rosetum rugosae; Olsson 1993). In inland Southern Scandinavia and in Central Europe, R. rugosa is found in forest fringes and along road and railway embankments (e.g. Brandes 2003). In continental parts of Central Europe R. rugosa may be found in xerothermic grasslands (Hensen 1997), but to what degree it is invasive there is unknown. In its native range R. rugosa is predominantly found in dune scrub, dune grassland communities and shingle beaches, less frequently in tall-herb meadows. In Hokkaido, thickets of R. rugosa are widespread along the coast line. Under natural conditions these thickets occupy only a narrow fringe between the sandy beach and the dune forest, but under conventional forest use and grazing thickets expand at the expense of Quercus forest (Ishizuka 1974; Miyawaki & Suzuki 1993). Both regarding vegetation structure and taxonomic composition the Japanese dune scrub is strikingly similar to European dune scrub communities (Ohba et al. 1973). Many of the codominant species, or close relatives of them, also occur in European and North American dune communities invaded by R. rugosa, e.g. Dianthus superbus, Elymus mollis, Lathyrus japonicus and Festuca rubra. Japanese dune communities including R. rugosa have been described in detail by Ohba et al. (1973) and Nakanishi & Fukumoto (1987, 1990, 1993, 1994), and Korean ones by Jung & Kim (2000). In Korea it may spread along roads, brought in with deicing beach sand, along with other coastal species, e.g. Lathyrus japonicus (Kim et al. 1997). In inland habitats, Rosa × hollandica is found in much the same habitats as R. rugosa, i.e. in hedgerows and on road verges and waste ground. Rosa rugosa seems to be excluded from pastures. However, once established its armoured branches render it highly resistant to grazing. Thus, probably only the seedling and juvenile stages are sensitive to grazing and browsing. In relation to herbaceous plant species, such as species typical of grasslands and dunes, R. rugosa is highly competitive. Where thickets establish, few other plant species can persist. Even the native dune shrub species Rosa pimpinellifolia and Salix repens ssp. arenaria are competitively inferior to R. rugosa (Türk 1995; Schepker 1998). Rosa rugosa often forms dense stands due to its creeping rhizomes from which suckers arise. In natural stands in its native habitat a shoot density of c. 10 m−2 has been reported (Tsuda et al. 1999), but much denser stands occur both in its native and exotic ranges. Dense thickets can cover several hectares (Nezhevenko 1967; Didriksen 1999), but probably originate from several coalescent clones. In dunes, emergence and survival of seedlings appears to be better in dwarf-shrub dominated communities with much bare sand than in dwarf-shrub heath with a dense cover of lichens and bryophytes as well as in grass dominated communities (Fig. 4). Seed germination and seedling survival in five dune plant communities from sowing of pretreated seeds in May 2003 to September 2004 in north-west Denmark (50 seeds per plot, 100 20 × 20 cm plots per plant community, averages shown). Maximum seed germination percentage was attained after 2 months. The summer of 2004 was much drier than that of 2003, causing elevated mortality of seedlings. The plant communities were: A, Calluna dominated vegetation (> 10% bare sand); B, Corynephorus dominated vegetation; C, vegetation dominated by Ammophila and other graminoids; D, Empetrum dominated vegetation with > 20% cover of bryophytes and lichens and < 10% bare sand; and E Empetrum dominated vegetation with < 20% cover of bryophytes and lichens and < 10% bare sand. Unpublished data of L. Frederiksen, J. Kollmann, H. H. Bruun and P. Vestergaard. The growth response of R. rugosa in various habitats was studied by Apalia (1979) by field planting experiments in Lithuania. Plants grew to normal height (c. 150 cm) or taller in sandy or gravelly slopes facing south-west, south or east, but protected from the wind, and having comparatively fertile soils, neither very acidic nor calcareous (pH 4.7–6.9). Low or pulvinate bushes (20–50 cm) formed on dry south-facing dune slopes, with either acid (pH 4.1–4.8) or somewhat calcareous sand (pH c. 7). Fruit production was unrelated to shrub height and habitat. Rosa rugosa is more sensitive to fungal pathogens and herbivorous insects in inland and garden settings than in coastal habitats (e.g. Kovalev 1965). Rosa rugosa is renowned among horticulturalists for its hardiness and its great tolerance of frost, heat, drought and salt. It is highly resistant to chilling (i.e. exposure to temperatures near freezing), both as assessed by traditional visual methods and by chlorophyll fluorescence (Hakam et al. 2000; but see Ohlweiler 1912). Rosa rugosa can maintain turgor under severe drought. In a garden experiment, Augéet al. (1990) showed that plantlets subjected to several drought cycles had a higher leaf water potential and symplastic osmolality than had well-watered plantlets. Despite being stunted and chlorotic, drought-stressed plantlets receiving no additional nitrogen had the highest full saturation turgor pressure and symplastic osmolality of all treatments. Thus, nitrogen deficiency causes an increased drought resistance in R. rugosa. The normal rooting depth in dune sand is 0.5–1 m, occasionally 2 m (Schlätzer 1974). Rosa rugosa is sensitive to flooding and waterlogged soils. When planted in dune slacks it forms a root mat in the shallow upper soil horizon not subjected to waterlogging (Schlätzer 1974). Rosa rugosa is highly tolerant of saline soils. Two-year-old R. rugosa seedlings subjected to salinization (daily watering with 250 mL of 0.25 N NaCl) showed no symptoms of injury in a pot experiment (Dirr 1978). Sodium did not accumulate in the leaves, whereas chloride did (see also phytochemistry). The effect of salt deposition directly on the leaves is unknown, but probably R. rugosa is comparatively tolerant. It has been reported to spread along winter-salted roads and motorways in Scandinavia (Nilsson 1999) and Germany (Brandes 2000). Being adapted to life in sand dunes, R. rugosa tolerates a moderate annual sand covering. Moreover, experiments by Belcher (1977) varying planting depth with 2-year-old R. rugosa showed that it not only tolerates, but rather seems to benefit from, an annual sand cover of 30 cm. Compared to plantlets planted at 0 cm and 15 cm below normal planting depth, those planted at 30 cm below normal planting depth expanded their leaves earlier and survived the dry growing season better. The general tolerance of R. rugosa to destruction of its above-ground tissue renders it tolerant to burning. Tsuda et al. (1999) investigated the effect of prescribed autumn burning of thickets of R. rugosa in its native habitat – fixed dunes in Hokkaido, Japan. They found that the number of shoots per m2 increased from 8.9 before burning to 23.3 in the second growing season after the fire, and then gradually decreased again. At the same time, the average height of the shoots first decreased from 32 cm to 24 cm, and then increased linearly. In the fifth growing season after the fire, shoots were both higher and stood more densely than before (Fig. 5). Similar results were obtained in a study of chemical control of the species (Didriksen 1999). Even when all above-ground tissue was destroyed, vigorous shoot growth appeared the year after. However, glyphosate applied in August appeared to damage rhizomes and roots as well. Mowing of R. rugosa stands twice or three times a year for two years appeared to reduce plant vitality, but only in the short term (Eigner 1992), whereas a larger-scale use of excavator and riddles to remove all rhizomes from the soil is very drastic and costly, and still requires subsequent digging of resprouts from root fragments (Kowarik 2003). Response of a Rosa rugosa stand to experimental burning in its native habitat, fixed dunes in Hokkaido, Japan (from Tsuda et al. 1999). (a) Number of sterile (white) and flowering shoots (black) per 25 m2 in the year prior to burning and in five subsequent years. (b) Average height of all shoots (black squares), and shoots in cohorts from each year following the burning (year 4–5 pooled). No data available for 1995. Furst (1984, 1986) studied the anatomical development of the first-year stems of various rose species that differed in winter hardiness in Moscow, Russia. The stems of R. rugosa, among the winter-hardy species, in the first season grew only to a height of 29.8 cm, partitioned into 10 internodes. The shoot extension growth was completed 2–4 times more rapidly than in non-hardy species. Stems had suberized collenchyma which replaced the periderm, and had high sugar content and little or no starch in the autumn. The annual lateral growth of first-year stems has been estimated to be approximately 0.4 mm, with little lateral growth in subsequent growing seasons. Wood anatomy was also described by Furst (1984, 1986). Xylem vessels have a tangential diameter of 35 µm, and fibrous tracheids a tangential diameter of 11 µm with 2 m thick walls. The vessels contain very high amounts of F-lignin, but no M-lignin, whereas the fibrous tracheids contain high amounts of both lignin types. It has later been discovered that the xylem of R. rugosa contains perforated ray cells (Eom & Chung 1995). These are secondary xylem cells derived from ray initials, but with perforation plates and lateral wall pitting like vessel elements, and being much larger than the surrounding ray cells. Leaves are leathery and robust, having a leaf thickness of 186.7 µm (SD = 31.1) (Ueda et al. 2000). Specific leaf area for whole leaves including rachis and stipules is 7.59 m2 kg−1 (SD = 1.33). It is slightly higher (11.0 m2 kg−1) for fully expanded but still light green leaves. For single leaflets mean specific leaf area is 9.02 m2 kg−1 (SD = 1.13), but significantly varying with position on the rachis. The terminal leaflet has a lower specific leaf area than basal leaflets (r2 = 0.16, P = 0.007, n = 40). The chlorophyll content has been estimated as 0.80 mg g−2 fresh weight (SD = 0.016) (Ueda et al. 2000). The ratio of chlorophyll a : b is 75 : 25 (Percival & Fraser 2002). Leaf nervation is reticulate, with each vein ending in two tracheids (Strain 1933). Stomata are absent from adaxial leaf surface, and are not easily seen on the abaxial surface, which is densely tomentose. Pollen grains are tricolpate (tricolporate), inoperculate, 30–50 µm along the polar axis, 15–39 µm along the equator (Ueda & Tomita 1989). According to Naruhashi & Toyoshima (1979) the mean length and breadth of pollen grains are 29.9 µm and 21.9 µm, respectively. The pollen exine is striate with clear fingerprint-like ridges interspersed with prominent perforations (Ueda & Tomita 1989). As the hypanthia ripen, the chloroplasts in their tissue develop into chromoplasts. When fully developed, these are packed with microtubules, which contain high amounts of carotenoids (Wuttke 1976). Epidermis cell patterns of outer and inner surface of unripe hips were studied by Bernsen (1961). Cell walls are relatively thin and without pits, cells being only slightly larger in the inner epidermis than in the outer, and the cell layer immediately below the inner epidermis containing irregularly dispersed star-shaped druses. These characters enable discrimination between hips of R. rugosa and R. canina (L.) Crépin, even when the tissue has been pulverized. The achene micromorphology was described by Jessen (1958), Starikova (1975), Grigas (1986) and Anderberg (1994). The achene pericarp consists of a small-celled epidermis (or exocarp), a 0.6-mm thick mesocarp, and a thin small-celled endocarp. The mesocarp is a spongy parenchyma consisting of relatively large, almost isodiametric cells, with thin, pored walls. The testa is thin, less than 0.02 mm. In dry achenes, the spongy tissue functions as an aerenchyma, allowing the achenes to float for a considerable period (see Seed dispersal). No information on mycorrhizal status is given by Harley & Harley (1987). However, experience with succession in barren dunelands in New England suggests that R. rugosa is likely to be dependent upon mycorrhiza for establishment (Gemma & Koske 1997), and mycorrhizal infection has been found in seedlings in natural dune areas (Koske & Gemma 1997). Entoloma clypeatum (Basidiomycota, Agaricales) has been recorded twice from R. rugosa scrub in Britain. This species is always associated with rosaceous shrubs, mostly hawthorn (Crataegus), and may form mycorrhiza with these (cf. Kobayashi & Hatano 2001). Rosa rugosa is a clonal shrub (phanerophyte, over-wintering buds in shoot tips both above-ground and underground). An annual shoot turnover rate within stands of c. 0.2 has been reported from a natural population in sand dunes on Hokkaido, Japan (Tsuda et al. 1999). Individual shoots may become more than 5 years old. Tsuda et al. (1999) found that 20% of the shoots in a stand were flowering, and these shoots were generally the tallest in the stand. Extension of clones is effectively achieved by rhizome growth. Extension with a closed front (phalanx mode) is predominant, but single shoots interspersed in herbaceous vegetation (guerrilla mode) are also common. By examination of aerial photographs of a coastal heath in Denmark, Didriksen (1999) found that R. rugosa had spread from a few clones to a more or less contiguous area of 3.5 ha in less than 50 years, most likely by means of clonal growth. Artificial vegetative propagation is easily achieved with cuttings of rootstocks (Butkenë 1975). 2n = 2x = 14 (Blackburn & Heslop Harrison 1921; Hurst (1931), both for British material). The same chromosome number has been reported for material from the species' native range (Nishikawa (1985) for Japan; Volkova & Melnikova (2001) for the Primorye region, Russia) and elsewhere (Täckholm 1922; Małecka & Popek 1984; Liu & Li 1985; Ma et al. 1997). One chromosome pair is heteromorphic, showing differences in length and staining patterns (Akasaka et al. 2003). The chromosomes are very small, with an average length of 1.46 µm (Ma et al. 1997). A DNA 2C value of 0.98 pg per cell (equals 473 Mb/1C) was reported for R. rugosa f. alba by Yokoya et al. (2000), and a slightly higher value of 1.10 pg was reported for R. rugosa by Rajapakse et al. (2001). Meiosis was first reported to be completely regular (Blackburn & Heslop Harrison 1921; Klášterská 1971). However, the occurrence of a B chromosome has later been observed (Price et al. 1981). A single nuclear organizer region for the whole genome was observed on the short arm of one submetacentric chromosome pair (Ma et al. 1997; Fernández-Romero et al. 2001). The pollen grains are binucleate and the plastid DNA is inherited maternally (Corriveau & Coleman 1988). Little information exists. Ueda et al. (2000) investigated the photosynthetic response to temperature and light using R. rugosa shoots grafted onto R. multiflora rootstock. Photosynthetic rate was estimated to reach a maximum of 13 µmol m−2 s−1 at 13 °C when irradiance (photosynthetic photon flux density) was kept constant at 360 µmol m−2 s−1. Leaves were fully light-saturated at an irradiance of 750 µmol m−2 s−1 (at 24 °C). The maximum photosynthetic rate was 16.8 µmol m−2 s−1 under this temperature and light regime. The light compensation point was 40 µmol m−2 s−1. The phytochemistry of R. rugosa is well-studied. The following overview is based on the thorough review by Hashidoko (1996), unless otherwise stated. Much of the phytochemical work has used cultivated R. rugosa, but the amount and composition of secondary metabolites seems to show little variation between garden and wild plants (Hashidoko 1996). Hashidoko (1996) tentatively concluded that the secondary metabolites of R. rugosa first developed in response to environmental conditions is its coastal habitat, and, fortuitously, some of these compounds provided resistance to insect herbivores and microbial diseases attacking members of the genus Rosa. Phenolic compounds are the dominant secondary metabolites in both below-ground and aerial parts. Of these, condensed tannins and their oxidized derivatives are the major secondary metabolites in rhizomes and roots, constituting up to 10–20% of the fresh weight of tissue (after defattening). Also catechin derivatives, low molecular weight phenolic compounds, are important secondary metabolites (Pankov & Safronova 1975; Hashidoko 1996). In addition, roots contain flavonoids and triterpenoids. The catechol group is siderophilic, and hence iron-mobilization in the rhizosphere has been suggested as a function of catechin derivatives. Roots also contain flavonoids and triterpenoids. Rosa rugosa has been found to accumulate pollutants such as heavy metals, e.g. copper and zinc (Hashidoko 1996), trace elements, e.g. neodymium, lanthanum and caesium (Kovács et al. 1982), and hydrogen sulphide (Syarheichyk & Sanko 1982). The leaves of R. rugosa contain a wide array of structurally different secondary metabolites. Flavonoids, i.e. flavonols and their glycosides, and 2-phenoxychromones have been isolated from leaves. A number of cinnamoyl esters have been isolated from R. rugosa leaves. The photochemical properties of these compounds suggest that they may function as light sensors or UV protectors of cell or chloroplast membranes. Some steroid substances have been isolated from aerial plant parts. In comparison with Rosa species that are more susceptible to fungal pathogens, R. rugosa has relatively low steroid levels. Thus, low steroid levels may be a feature in its resistance to harmful fungi. Tocopherols and carotenes, e.g. γ-tocopherol (Vitamin E) and β-carotene, are abundant in the leaves. Levels of some carotenoids, viz. xanthophyll epoxides, increase as leaves senesce. Young leaves contain small, but significant, levels of odorant monoterpenes and aromatic oils that contribute to leaf fragrance. Large amounts of the phenolic compounds pyrogallol and pyrocatechol are released upon leaf damage. These compounds have significant antimicrobial activity against saprophytic and phytopathogenic fungi and bacteria (Hashidoko et al. 2002). Carotane sesquiterpenes (see below) have also been isolated from damaged leaves. Glandular trichomes actively exude chemically distinct syrup-like droplets from the tip (c. 10–15 g kg−1 fresh leaves). The main components of the exudate are sesquiterpenes (incl. sesquiterpene acids) of the carotane, bisabolane and acorane classes. Among the Rosaceae, only members of the genus Rosa produces sesquiterpenes, and carotanes are known to occur only in R. rugosa and some of its hybrids (Hashidoko et al. 2001). Twenty-eight carotane sesquiterpene compounds, most of which are, so far, unique to R. rugosa (e.g. rugosal A and rugosic acid A) have been identified. Rugosal A has been shown to have substantial anti-microbi
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