Oryza longistaminata A. Cheval. & Roehr.

Family: Poaceae,  Tribe: Oryzeae

Common names:  red rice

Disseminule 

Fertile floret with two glume-like sterile florets; disarticulation above the glumes (below the glume-like sterile lemmas).

Description

Disseminule (floret with 2 sterile lemmas) oblong, ca. 7-12 mm long, 2-3 mm wide. Callus smooth, oblique. Sterile lemmas similar, glume-like, linear, glabrous, 2-4.5 mm long. Rachilla internode pronounced below fertile lemma. Fertile lemma and palea strongly laterally compressed, keeled, cartilaginous, surface scaberulous and tuberculate in a grid pattern; lemma 5-nerved, its margins inrolled, interlocking palea margins, lemma with apical awn 26-150 mm long, straight, antrorsely barbed. Caryopsis lanceolate or oblong, 5-7 mm long, laterally compressed, reddish, hilum linear, as long as caryopsis.

Identification remarks

The wild red rices (O. longistaminata, O. punctata and O. rufipogon) can be distinguished from O. sativa L. (cultivated rice) by their red caryopses, although it may be difficult to differentiate the wild red caryopses from commercial rice cultivars with red grains.

The spikelets of O. rufipogon and O. longistaminata are difficult to differentiate morphologically. However, the two species are distinct geographically; O. rufipogon is not found in Africa, while O. longistaminata is found mostly in Africa.

Similar species

Oryza punctata Kotschy ex Steudel

Oryza rufipogon Griff.

Distribution

Tropical Africa, South Africa and Madagascar.

Native to tropical Africa.

Habitat

Deep water, standing or running water, salt marshes, dry, sandy fields.

General information

Oryza longistaminata is a rhizomatous perennial grass, to 120 cm tall. This species is believed to be the wild progenitor of O. glabberrima Steud., the African cultivated rice. The evolution of O. glabberrima parallels that of O. sativa L. See comments about the weediness of the wild red rices in the O. rufipogon fact sheet.

Florets in side view

Florets and caryopses

photo by Mark Thurmond

A, Floret; B, caryopsis in side view showing embryo

drawing by Lynda E. Chandler