Plants That Kill: Apocynaceae

Adapted from page 52 of Plants That Kill:

The dogbane family is one of the larger families of flowering plants, and is today considered to contain more than 5,000 species in 366 recognized genera, including those that have, at times, been placed in their own family, Asclepiadaceae. The almost globally distributed Apocynaceae (only northern regions lack native species) has adapted to almost all environments and contains a large diversity of plant forms. 

Species grow as herbs, climbers and lianas, succulents or trees. The flowers are often showy or conspicuous in form or smell, and many species have evolved special structures for pollen dispersal, such as pollinia, coherent masses of pollen grains that are transferred to the next plant by sticking to insect pollinators. These structures are especially elaborate in milkweeds (Asclepias spp.), waxflowers (Hoya spp.) and their relatives, constituting a feature that allows easy placement of these plants within the family (although deciding on the actual genus and species can be quite difficult).

Elephant vine (Strophanthus amboensis) is found from Zaire to Namibia and contains cardioactive steroids. The petals are fused to form a cup at the base and there are five spreading, elongated lobes.

The large number of species and wide geographical distribution of the dogbane family makes it easy to understand why so many plants are used by humans. The showy, waxy flowers of frangipani (Plumeria spp.) have found a place as a constituent in Polynesian lei garlands, the fibres from dogbane (Apocynum cannabinum) have been used to make cloth and string, some species are used in religious rituals, and some genera, such as Landolphia, were briefly important as sources of rubber in the late nineteenth and early twentieth centuries. Several plants in the family have been used as arrow poisons or in traditional medicinal systems, and the Madagascar periwinkle (Catharanthus roseus) is the source of an important cancer drug. 

It seems that most plants in the dogbane family are toxic to some degree, but the reason for this differs between groups of species. Some groups produce cardioactive steroids as the toxic principle, while others produce monoterpene indole alkaloids. Accordingly, the family presents several toxidromes, the combined picture of symptoms in poisonings, with some presenting as acute heart failure with arrhythmias and others giving signs of detrimental effects on the nervous system – for example, seizures, paralysis and hallucinations. As members of the dogbane family are widely distributed and many produce fatal intoxications, the use of these plants in suicides and poisonings is not uncommon in certain regions of the world.

Plants That Kill: A Natural History of the World’s Most Poisonous Plants
By Elizabeth A. Dauncey & Sonny Larsson

This richly illustrated book provides an in-depth natural history of the most poisonous plants on earth, covering everything from the lethal effects of hemlock and deadly nightshade to the uses of such plants in medicine, ritual, and chemical warfare.

Featuring hundreds of color photos and diagrams throughout, Plants That Kill explains how certain plants evolved toxicity to deter herbivores and other threats and sheds light on their physiology and the biochemistry involved in the production of their toxins. It discusses the interactions of poisonous plants with other organisms–particularly humans—and explores the various ways plant toxins can target the normal functioning of bodily systems in mammals, from the effects of wolfsbane on the heart to toxins that cause a skin reaction when combined with the sun’s rays. This intriguing book also looks at plants that can harm you only if your exposure to them is prolonged, the ethnobotany of poisons throughout human history, and much more.

A must for experts and armchair botanists alike, Plants That Kill is the essential illustrated compendium to these deadly and intriguing plants.

  • Provides an authoritative natural history of the most poisonous plants on earth
  • Features hundreds of color illustrations throughout
  • Looks at how and why plants produce toxins
  • Describes the effects of numerous poisonous plants, from hemlock and deadly nightshade to poppies and tobacco
  • Explains poisonous plants’ evolution, survival strategies, physiology, and biochemistry
  • Discusses the uses of poisonous plants in medicine, rituals, warfare, and more
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