Hypericum punctatum

Hypericum punctatum
Scientific classification
Kingdom:Plantae
Clade:Angiosperms
Clade:Eudicots
Clade:Rosids
Order:Malpighiales
Family:Hypericaceae
Genus:Hypericum
Section:Hypericum sect. Graveolentia
Species: H. punctatum
Binomial name
Hypericum punctatum
Synonyms[1]

Hypericum punctatum, or spotted St. John's wort, is a perennial herb native to North America.[2] The yellow-flowered herb occurs throughout eastern North America into southern Canada. The process of microsporogenesis carried out by this plant is prone to errors in chromosomal segregation. Insects are attracted to the plant's pollen and the hypericin in the plant's leaves is toxic to mammals.

Description

Hypericum punctatum is seldom branched and grows to 50–100 cm (20–39 in) in height. The leaves of the herb are 2–6 cm (0.79–2.36 in) long and are situated opposite on the glabrous stem, either sessile or with very short petioles. The leaves vary in shape from oblong to elliptic or ovate, have rounded points at their apex, and taper towards their base. The inflorescence is crowded with many yellow flowers that measure 0.8–1.5 cm (0.31–0.59 in) in width. The flowers are star-like in shape and have five petals. The sepals and petals are spotted with dark dots, especially on their underside, with the petals about twice as long as the oblong and acute sepals.[3] Each flower has twenty stamens or more. In the center of the flower a flask-like pistil is surrounded by many yellow anthers. The capsule is ovoid and 0.4–0.6 cm (0.16–0.24 in) long.[4][5] The root system consists of a branching taproot and several short rhizomes from which vegetative colonies of the herb can grow.[6]

The herb flowers from July to August.[2] It fruits from early September to October.[7]

Microsporogenesis of H. punctatum is abnormal in many ways. Rather than pair at diakinesis the chromosomes link together in a chain and during the first metaphase the chromosomes tend to separate and alternate members move to opposite poles. Irregularities often occur such that at second metaphase the haploid number is seven or nine rather than the usual eight for the species. During the first division, chromosomes may lag behind and become lost from the spindle apparatus. Extra nuclei are occasionally formed during meiosis. During the second division the extra chromosomes tend to form their own spindle apparatus and divide. Megasporogenesis is similar to microsporogenesis in the tendency to form chains and in the alternation of chromosomes in the first metaphase.[8]

Habitat and distribution

Hypericum punctatum is common in floodplains, roadsides, moist fields, and thickets.[4]

It can be found throughout the American Midwest and the Atlantic coast and into Canada in Nova Scotia, Ontario, and Quebec.[9]

Ecology

The herb is valuable to bees, attracting both bumblebees and sweat bees.[9] Though they pollinate to a lesser extent, beetles and hoverflies also visit the flowers. Flowers do not produce nectar, instead the insects are attracted by the pollen. Gray hairstreak caterpillars feed on the seed capsules and gray half-spot caterpillars feed on the leaves. Though insects eat the plant, foraging mammals seldom feed on the foliage as leaves contain hypericin which, in mammals, can blister skin and irritate the digestive tract.[6]

References

  1. ↑ "Hypericum punctatum". The Plant List. 2013. Retrieved 15 August 2018.
  2. 1 2 Robert H. Mohlenbrock (2013). Vascular Flora of Illinois: A Field Guide (4th ed.). SIU Press. p. 248. ISBN 9780809332090.
  3. ↑ Merrit Lyndon Fernald (1970). R. C. Rollins, ed. Gray's Manual of Botany (Eighth (Centennial) – Illustrated ed.). D. Van Nostrand Company. p. 1010. ISBN 0-442-22250-5.
  4. 1 2 Ann Fowler Rhoads, Timothy A. Block (2007). The Plants of Pennsylvania: An Illustrated Manual (illustrated ed.). University of Pennsylvania Press. p. 553. ISBN 9780812240030.
  5. ↑ Melanie Choukas-Bradley (2004). An Illustrated Guide to Eastern Woodland Wildflowers and Trees: 350 Plants Observed at Sugarloaf Mountain (illustrated ed.). University of Virginia Press. p. 75. ISBN 9780813922515.
  6. 1 2 Dr. John Hilty (2017). "Spotted St. John's Wort". Illinois Wildflowers. Retrieved 15 August 2018.
  7. ↑ New Jersey State Museum (1911). Annual Report of the New Jersey State Museum. MacCrellish & Quigley. p. 555.
  8. ↑ Hoar, Carl Sherman (1931). "Meiosis in Hypericum punctatum". Botanical Gazette. The University of Chicago Press. 92 (4): 396–406.
  9. 1 2 "Hypericum punctatum NPIN". Lady Bird Johnson Wildflower Center. The University of Texas at Austin. Retrieved 15 August 2018.
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