Alectra spp.

Name and classification

Alectra Thunb.
Family Scrophulariaceae

Disseminule

seed

Description

Note: this description is primarily based on the morphology of six species.

Fruit a loculicidal capsule with numerous seeds. Testa of seeds a membranous envelope separate from and enclosing rest of seed. Seed with testa linear to wedge shaped, sometimes curved, truncate at ends; transparent to opaque; straw-colored to light brown, delicately reticulate; 0.5–1.4 mm long, 0.3–0.5 mm wide. Central 'nucleus' (seed without testa) obovate or cone-shaped, amber to nearly black; 0.1–0.3 mm long, 0.05–0.18 mm wide. Embryo dwarf-spatulate, cotyledons poorly developed.

Identification considerations

Seeds may be encountered with testa envelope lacking.

Distribution

tropical Africa, Asia

General information

Alectra are annual or perennial root parasites, up to 75 cm tall. Seeds germinate in response to host root exudate and the seedlings must contact the host root immediately after germinating. The genus comprises about 40 species, 10 of which are native to South Africa. Alectra vogelii Benth. is known as a parasite of cowpeas, peanuts, soybeans and bambara nut. This species reduces crop yields or may cause total destruction of crops.

Alectra arvensis (Benth.) Merr. seeds

Alectra arvensis (Benth.) Merr. seeds

Alectra arvensis seeds, detail

Alectra arvensis seeds, detail

Alectra arvensis seeds without testa envelope

Alectra arvensis seeds without testa envelope

Alectra aspera  (Cham. & Schlecht.) L.O. Williams seeds

Alectra aspera (Cham. & Schlecht.) L.O. Williams seeds

Alectra aspera seeds, detail

Alectra aspera seeds, detail

Alectra fluminensis  (Vell.) Stearn. seeds

Alectra fluminensis (Vell.) Stearn. seeds

Alectra fluminensis seeds, detail

Alectra fluminensis seeds, detail

Alectra melampyroides  (Rich) Kuntz. seeds

Alectra melampyroides (Rich) Kuntz. seeds

Alectra melampyroides seeds, detail

Alectra melampyroides seeds, detail

Alectra stricta Benth. A, seed; B, longitudinal section of seed showing embryo; C, transection of seed; drawing by Lynda E. Chandler

Alectra stricta Benth. A, seed; B, longitudinal section of seed showing embryo; C, transection of seed; drawing by Lynda E. Chandler