Purple Foxglove (Digitalis purpurea)
Description
“Pet poisonous” – Toxic parts: leaves Digitalis purpurea (foxglove, common foxglove, purple foxglove or lady's glove) is a species of flowering plant in the plantain family Plantaginaceae, native to and widespread throughout most of temperate Europe. It is also naturalised in parts of North America and some other temperate regions. The plants are well known as the original source of the heart medicine digoxin (also called digitalis or digitalin). Digitalis purpurea is an herbaceous biennial or short-lived perennial plant. The leaves are spirally arranged, simple, 10–35 cm (3.9–13.8 in) long and 5–12 cm (2–5 in) broad, and are covered with gray-white pubescent and glandular hairs, imparting a woolly texture. The foliage forms a tight rosette at ground level in the first year. The flowering stem develops in the second year, typically 1–2 m (3.3–6.6 ft) tall, sometimes longer. The flowers are arranged in a showy, terminal, elongated cluster, and each flower is tubular and pendent. The flowers are typically purple, but some plants, especially those under cultivation, may be pink, rose, yellow, or white. The inside surface of the flower tube is heavily spotted. The flowering period is early summer, sometimes with additional flower stems developing later in the season. The plant is frequented by bees, which climb right inside the flower tube to gain the nectar within. The fruit is a capsule which splits open at maturity to release the numerous tiny 0.1-0.2 mm seeds. Due to the presence of the cardiac glycoside digitoxin, the leaves, flowers and seeds of this plant are all poisonous to humans and some animals and can be fatal if ingested. The main toxins in Digitalis spp. are the two chemically similar cardiac glycosides: digitoxin and digoxin. Like other cardiac glycosides, these toxins exert their effects by inhibiting the ATPase activity of a complex of transmembrane proteins that form the sodium potassium ATPase pump, (Na+/K+-ATPase). Inhibition of the Na+/K+-ATPase in turn causes a rise not only in intracellular Na+, but also in calcium, which in turn results in increased force of myocardial muscle contractions. In other words, at precisely the right dosage, Digitalis toxin can cause the heart to beat more strongly. However, digitoxin, digoxin and several other cardiac glycosides, such as ouabain, are known to have steep dose-response curves, i.e., minute increases in the dosage of these drugs can make the difference between an ineffective dose and a fatal one.
Taxonomic tree
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Domain: Eukarya
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Kingdom: Plantae
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Phylum: Magnoliophyta
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Class: Magnoliopsida
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Order: Lamiales
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Family: Plantaginaceae
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Genus: Digitalis
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