What is the Orobanchaceae plant family?

The Orobanchaceae , or broomrape family, is a family of parasitic flowering plants with around 100 genera and 2,300 species. They can be found worldwide, especially in Africa, Madagascar, and the warm north temperate zone, and can be serious agricultural pests. Most Orobanchaceae are annual or perennial herbaceous plants, but some are small shrubs. Nearly all are parasitic, using haustoria to connect to and parasitize other plants' roots. Some are hemiparasites, with green foliage that allows them to photosynthesize while also siphoning nutrients from hosts. Others are holoparasites, lacking chlorophyll and relying entirely on their hosts for nutrition, often with reduced, scalelike leaves and a succulent form.

Where are Orobanchaceae plants usually found?

Orobanchaceae, commonly known as the broomrape family, includes around 2,300 species of parasitic plants that can be found nearly worldwide. They are especially common in Africa, Madagascar, and warm areas of the north temperate zone. While most are annual or perennial herbaceous plants, some species of Orobanchaceae are small shrubs. Many members of this family are serious agricultural pests that attack a variety of crops.

What do Orobanchaceae plants look like?

Orobanchaceae, or the broomrape family, consists of about 100 genera and 2,300 species of parasitic plants found worldwide. The vast majority are annual or perennial herbaceous plants, though some are small shrubs. Nearly all Orobanchaceae are parasitic, using specialized root connections called haustoria to tap into other plants. Some are hemiparasites, possessing green foliage for photosynthesis but still drawing nutrients from hosts, often indicated by opposite leaves and glandular hairs. Holoparasites, on the other hand, lack chlorophyll and depend entirely on their host plants, often displaying reduced scalelike leaves and a succulent form. Flowers of Orobanchaceae are bilaterally symmetrical, with fewer stamens than petals. The corolla often has two lips, and they produce capsular fruits filled with numerous seeds.

How do Orobanchaceae plants get their nutrients?

Orobanchaceae plants, also known as broomrapes, are mostly parasitic herbaceous plants . They use haustoria, which are specialized root connections, to parasitize other plants and get nutrients. Some Orobanchaceae are hemiparasites, meaning they have green foliage and can photosynthesize, but they also siphon nutrients from host plants. Others are holoparasites, lacking chlorophyll and relying entirely on their hosts for nutrition. The haustorium penetrates the host's tissues to absorb nutrients and water, forming a vascular union between the plants. Some species have mechanisms to detect specific host plants through chemical signals, triggering seed germination and haustorium growth.

How do Orobanchaceae plants affect other plants and their environment?

The Orobanchaceae family contains about 2,300 species of parasitic plants that impact other plants by attaching to their roots via haustoria to siphon nutrients. Some species, known as hemiparasites, can photosynthesize but still steal products of photosynthesis from their hosts, while others, called holoparasites, lack chlorophyll and rely solely on their host plants for nutrition. Several Orobanchaceae species are agricultural pests that can detect specific host plants through chemical signals. For example, witchweeds (Striga) attack cereal crops, and broomrapes (Orobanche and Phelipanche) attack broadleaf crops, causing significant yield losses. These parasites can devastate crops by seemingly arresting their growth.

Orobanchaceae

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Orobanchaceae

plant family

Also known as: broomrape family

Written by

Melissa Petruzzello

Fact-checked by

Britannica Editors

History

Physical description

The vast majority of the members of the family Orobanchaceae are annual or perennial herbaceous plants, though some are small shrubs. Nearly all are parasitic and have specialized root connections known as haustoria that parasitize other plants. Many species are hemiparasites; that is, they have green foliage and are photosynthetic but supplement their nutritional needs by siphoning the products of photosynthesis from their hosts. Such plants usually have opposite leaves and commonly feature glandular hairs. Other members of the family are holoparasites and have little or no chlorophyll; these obligate parasites rely exclusively on their host plants for nutrition. Given their inability to photosynthesize, these species usually have greatly reduced scalelike leaves, and many are succulent in form.

lousewortLousewort (*Pedicularis lanceolata*).

Like other plants of the order Lamiales, most Orobanchaceae species have bilaterally symmetrical flowers (irregularly shaped corollas with only one plane of symmetry), with fewer stamens than petals. In many species the corolla has two lips, the upper lip being composed of two petals and the lower of three. The number of petals in each lip is sometimes not obvious. Lips may be the same size, or one may be markedly larger. The flowers form capsular fruits, often filled with numerous, sometimes dustlike seeds. Perhaps the record for seed production in the family goes to Boschniakia rossica, a small parasitic plant that produces more than 300,000 seeds. The seeds of certain broomrapes (Orobanche) can be less than 0.3 mm (0.01 inch) long.

Major genera and species

The Angiosperm Phylogeny Group IV (2016) considerably expanded Orobanchaceae from its former delimitation based on molecular data. Instead of about 15 genera and 210 species of entirely parasitic plants, the family now includes many hemiparasitic species that were formerly placed in Scrophulariaceae. These include genera such as Indian paintbrush (Castilleja), with about 200 species, lousewort (Pedicularis), with as many as 800 species, and a number of smaller genera, including Agalinis, Buchnera, and Euphrasia.

The completely parasitic members of the family include broomrape (Orobanche), with 150 species, Euphrasia, with as many as 350 species, and the small genera Bartsia, Rhinanthus, and beechdrops (Epifagus), which are found only on roots of beech trees (Fagus species).

Root parasite Witchweed (*Striga bilabiata*), an obligate root parasite. Witchweeds commonly parasitize cereal crops, and their tiny seeds can persist in agricultural fields for many years.

Some of the genera are serious agricultural pests. The broomrapes and the related Phelipanche attack broadleaf crops in the Mediterranean, Middle East, and elsewhere and are a major constraint to the production of legumes, oilseed crops, and solanaceous crops (e.g., tomatoes, peppers, potatoes, and eggplants). Aeginetia and Christisonia infest sugarcane. Witchweeds (Striga species) and the closely related plants of the genus Alectra attack corn (maize), sugarcane, rice, sorghum, millet, peanuts (groundnuts), soybeans, and tobacco and are particularly problematic in Africa. The common name reflects the dramatic effect it has on crops, seeming to magically arrest host growth and devastate yields.