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