Viola (plant)

Viola Description and Characteristics

  • Viola is a genus of flowering plants in the violet family Violaceae.
  • It is the largest genus in the family, containing over 680 species.
  • Most species are found in the temperate Northern Hemisphere.
  • Some species are also found in widely divergent areas such as Hawaii, Australasia, and the Andes.
  • Viola species can be perennial plants, annual plants, or small shrubs.
  • Viola plants typically have heart-shaped or reniform (kidney-shaped), scalloped leaves.
  • Some species have linear or palmate leaves.
  • The leaves are arranged alternately, and acaulescent species produce basal rosettes.
  • Stipules, often leaf-like, are present on Viola leaves.
  • The flowers of most Viola species are strongly zygomorphic with bilateral symmetry.
  • They are solitary but occasionally form cymes.
  • Viola flowers have five petals, with four upswept or fan-shaped petals and one broad, lobed lower petal pointing downward.
  • The shape and placement of the petals, as well as the presence of a spur, define many species.
  • The flowers have five sepals that persist after blooming, and the corolla ranges in color from white to yellow, orange, blue, or violet.
  • After flowering, Viola plants produce fruit capsules that are thick-walled and split open by way of three valves.
  • The capsules contain few to many seeds per carpel.
  • On drying, the capsules may eject seeds with considerable force.
  • The nutlike seeds are typically arillate and have straight embryos, flat cotyledons, and soft fleshy endosperm.
  • Viola seeds are obovoid to globose in shape and have an oily endosperm.

Ornamental Use and Horticultural Uses

  • Many species, varieties, and cultivars of Viola are grown in gardens for their ornamental flowers.
  • Pansy is the term used for multi-colored, large-flowered cultivars raised annually or biennially from seed and used extensively in bedding.
  • The terms viola and violet are reserved for small-flowered annuals or perennials, including the wild species.
  • Viola flowers come in various colors, including white, yellow, orange, blue, and violet.
  • They are known for their distinctive shape and often have a spur on the lower petal.
  • The American Violet Society is the international registration authority for Viola cultivars.
  • Cultivars are described using a coding system for ten horticultural divisions, such as Violet (Vt) and Violetta (Vtta).
  • Violets are stoloniferous perennials with small, highly fragrant, self-colored purple, blue, or white flowers in late winter and early spring.
  • Examples of registered cultivars include Viola Little David (Vtta) and Viola Königin Charlotte (Vt).
  • Violets are popular in horticulture due to their fragrant flowers and ability to bloom in late winter and early spring.
  • Viola cultivars, including pansies, were one of the top three bedding plant crops in the United States in 2005.
  • $111 million worth of flats of Viola were produced for the bedding flower market in the US in 2005.
  • Pansies and violas used for bedding are generally raised from seed.
  • F1 hybrid seed strains have been developed for bedding plants, producing compact plants with consistent flower coloring and appearance.
  • Bedding plants are usually discarded after one growing season.

Geographic Distribution and Genetic Diversity

  • Viola species are found in western and central Asia, northern Iraq to Mongolia.
  • They are also distributed in northern hemisphere regions, including South America (Chile), northeastern Africa to southwestern Asia, and the Mediterranean region.
  • Some species are found in the southern parts of South America.
  • The genus is thought to have originated in South America, particularly the Andes.
  • One of the highest concentrations of Viola species is found in the former USSR.
  • Habitat fragmentation has minimal effect on the genetic diversity and gene flow of Viola pubescens in North America.
  • Viola palmensis, a Canary Island endemic, shows unexpectedly high genetic diversity within its limited range.
  • These violets have high rates of outcrossing, indicating strong competition for pollinators.
  • They produce clonal offspring through cleistogamous flowers, but still maintain high genetic diversity.
  • Pollinators can travel considerable distances between fragmented populations, contributing to gene flow.

Ecology and Habitat Adaptations

  • Viola species are used as food plants by larvae of various Lepidoptera species.
  • They are mainly pollinated by Diptera and Hymenoptera insects.
  • Showy flowers are produced in early spring, while clonal cleistogamous flowers are produced later in the growing season.
  • Violets exhibit two modes of seed dispersal: explosive dehiscence and myrmecochory (dispersal by ants).
  • Some violets form relationships with arbuscular mycorrhizal fungi, allowing them to tolerate contaminated soils.
  • Viola species occupy diverse habitats, including bogs, dry hill prairies, and woodland understories.
  • Some violets are indicators of high-quality habitat, while others can thrive in human-altered landscapes.
  • Zinc violets (V. calaminaria and V. guestphalica) can tolerate soils contaminated with heavy metals.
  • They have the ability to form relationships with arbuscular mycorrhizal fungi, aiding their survival in contaminated soils.
  • Flowering is often profuse and can last throughout the spring and summer.

Medicinal and Cultural Associations

  • Many Viola species contain antioxidants called anthocyanins.
  • Some anthocyanins in Violas show strong antioxidant activities.
  • Violaceae plants, including violas, contain cyclotides with various biological activities, such as anti-H

Viola (plant) - Wikipedia Data Sources

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