Hypolepis punctata (PROSEA)
Hypolepis punctata (Thunb.) Mett. ex Kuhn
- Protologue: Filic. Afr.: 120 (1868).
- Family: Dennstaedtiaceae
- Chromosome number: n= (c. 92), 98, (c. 104); multiple cytotypes may exist
Phegopteris punctata (Thunb.) Mett. (1864), Nephrodium punctatum (Thunb.) Diels (1899), Dryopteris punctata (Thunb.) C. Chr. (1905).
- Downy ground fern (En)
- Malaysia: paku resam paya.
Origin and geographic distribution
H. punctata is little known and is probably a species complex. In a narrow sense it occurs from north-western India, southern China to Taiwan, Ryukyu Islands and Japan, throughout continental South-East Asia to Peninsular Malaysia, Sumatra and possibly northern Philippines. In a wide sense it extends to New Zealand, Hawaii and other islands of the South Pacific.
In South-East Asia leaves of H. punctata are made into a poultice for boils. The plant is also used in Chinese medicine. It can be grown as an ornamental, but due to its very rapid spreading habit it is not really suitable for a garden.
Three sesquiterpene glycosides of the illudane type, analogues of ptaquiloside, were isolated from H. punctata . They are named hypolosides (hypolepines) A, B and C, and characterized as compounds related to pterosin Z. From the aerial parts the following substances have been isolated: 3(S)-pteroside D, 3(S)-pterosin D, 3(R)-pterosin D, 2(R), 3(R)-pterosin-L-2'-O-β-D-glycoside and 2(S), 3(R)-pterosin-L-2'-O-β-D-glycoside. Hypacrone, a sesquiterpene containing a reactive cyclopropane ring, has also been isolated; it shows anti-tumour activity and similar reactivity with nucleophiles to ptaquiloside.
A terrestrial fern with finely dissected, long-scrambling leaves. Rhizome long-creeping, 1.5-4 mm in diameter, glabrous in the older parts, densely hairy near the apex, hairs up to 2 mm long, pale brown. Leaves 3-pinnate at base, 2-pinnate at apex; petiole 15-75 cm long and 2-4 mm in diameter, adaxially grooved, with hairs up to 2 mm long; lamina broadly ovate in outline, 22-80(-100) cm × 17-70 cm, truncate at base, margin sometimes with very short hairs, apex acute, indeterminate, pale green, papyraceous, with brownish glandular and non-glandular hairs up to 1.5 mm long on the underside, shorter and sparser on upper surface; rachis grooved, with coarse multicellular hairs, their bases remaining as minute prickles; primary pinnae in 15-25 subopposite pairs, narrowly triangular to ovate, 9-50 cm × 3.5-20 cm, basal ones longest; secondary pinnae oblong-subtriangular, 2-11 cm × 1-4 cm; tertiary segments oblong, 0.4-1.9 cm × 0.2-0.8 cm, entire in smaller leaves, divided more than halfway in larger leaves; ultimate segments lobed to crenate to dentate, rounded, with pinnate veins. Sori oval or round, originating away from the margin, naked, not covered with a reflexed marginal flap, without hairs. Spores ellipsoid, (32-)34-39(-43) μm long, pale, monolete, echinate.
Growth and development
The gametophyte of H. punctata consists of three kinds of prothalli: a slow-growing male prothallus loaded with antheridia, and two types of cordate, eventually hermaphrodite prothalli. The cordate propthallus can be a large-sized, generally fast-maturing prothallus with symmetrical broad wings, initially archegonial but later it may bear antheridia, or a relatively smaller prothallus that usually is initially protrandrous and during subsequent archegonial phase bears only few fresh antheridia. H. punctata has an intricate balance between inter- and intragametophytic mating systems. The frequency of intergametophytic mating is relatively higher and correlated with the frequency and duration of the initial archegonial phase on the eventually hermaphrodite prothalli. In H. punctata the growth of the leaf apex is controlled by the lateral pinnae. The leaf apex remains suppressed until the lateral pairs of pinnae uncoil and expand. The process is repeated until the expansion of the terminal pinna is completed. The growth and spreading of H. punctata tends to be very fast.
Other botanical information
The name H. punctata has been extensively misapplied and this species has been erroneously published under several other names in a complex nomenclatural history that reflects the variability of the species complex. The review of Brownsey (1987) is a valuable addition to the existing literature but a revision of the genus is badly needed to solve all problems (estimated number of species is 40, distributed pantropically). No certainty can be acquired about the correct identification of the specimens involved in the indicated uses and properties. H. punctata Beddome (syn. H. beddomei Nair & Ghosh) is not identical with H. punctata (Thunb.) Mett. ex Kuhn but refers to H. pallida (Blume) Hook., a species from Taiwan, Indo-China, Peninsular Malaysia, Java and perhaps also in Borneo and the Philippines (main difference is that sori of H. pallida are protected by a well-developed reflexed membranous flap (indusium), while sori in H. punctata are unprotected). However, for both species a similar medicinal use has been recorded.
H. punctata is usually found in open locations and clearings in mountainous forest areas at 750-1500 m altitude. Although the plant can produce huge leaves, it is often much smaller and sometimes quite dwarf, but still fertile. The larger leaves straggle through forest edges. Young leaves are less sticky under less favourable environments.
Propagation and planting
The most suitable way to propagate H. punctata is by planting rhizome cuttings, but it also easily grows from spores. Under glasshouse conditions dispersal by spores is often spontaneous and can become a nuisance.
H. punctata can be raised indoors at day temperatures of 21-26°C, at night of 10-15°C, with relative humidity of at least 60%. It requires bright light and moist but well-drained soil.
Genetic resources and breeding
H. punctata is a common species complex reproducing sexually in its natural area. It is not known at present to what extent the constituting minor taxa and cytotypes may be threatened. Germplasm collections or breeding programmes are not known to exist.
As long as the identity of taxa within the H. punctata complex remains unknown it is impossible to formulate clear prospects. The anti-tumour activity of the complex may deserve further investigation and might be interesting.
- Brownsey, P.J., 1987. A review of the fern genus Hypolepis (Dennstaedtiaceae) in the Malesian and Pacific regions. Blumea 32: 227-276.
- Hayashi, Y., Nishizawa, M., Harita, S. & Sakan, T., 1972. Structure and synthesis of hypolepin A, B, C, sesquiterpenes from Hypolepis punctata Mett. Chemistry Letters (1972): 375-378.
- Hayashi, Y., Nishizawa, M. & Sakan, T., 1973. Structure of hypacrone, a novel seco-illudoid, possible biological precursor of pterosins in Hypolepis punctata Mett. Chemistry Letters (1973): 63-66.
- Hayashi, Y., Nishizawa, M. & Sakan, T., 1975. The synthesis of hypacrone, a novel seco-illudoid sesquiterpene from Hypolepis punctata Mett. Chemistry Letters (1975): 387-390.
- Hayashi, Y., Nishizawa, M. & Sakan, T., 1977. Studies on the sesquiterpenoids of Hypolepis punctata Mett. 1. Isolation and structure determination of hypacrone, a new seco-illudoid. Tetrahedron 33: 2509-2511.
- Hayashi, Y., Nishizawa, M. & Sakan, T., 1977. Studies on the sesquiterpenoids of Hypolepis punctata Mett. 2. The total synthesis of hypacrone. Tetrahedron 33: 2513-2519.
- Potter, D.M. & Baird, M.S., 2000. Carcinogenic effects of ptaquiloside in bracken fern and related compounds. British Journal of Cancer 83(7): 914-920.
- Saito K., Nagao T., Takatsuki S., Koyama K. & Natori, S., 1990. The sesquiterpenoid carcinogen of bracken fern, and some analogues, from the Pteridaceae. Phytochemistry (Oxford) 29(5): 1475-1480.
- Verma, S.C., Kaur, A. & Sharma, S.S., 1987. Gametophyte ontogeny, sex expression and mating system in Hypolepis punctata. Phytomorphology 37: 53-68.
W.P. de Winter & Bambang Hariyadi