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FOC | Family List | FOC Vol. 22 | Poaceae

28. Poaceae Tribe ANDROPOGONEAE

高粱族 gao liang zu

Authors: Shou-liang Chen, Bi-xing Sun, Sylvia M. Phillips & Stephen A. Renvoize

Annual or perennial. Leaf blades linear, rarely lanceolate or filiform; ligule membranous, rarely ciliate. Inflorescence composed of fragile (infrequently tough) racemes, these arranged in a terminal panicle with elongate central axis, or more frequently subdigitate, paired or solitary, often axillary, subtended by spathes and spatheoles and gathered into a compound panicle. Racemes usually bearing paired spikelets (with a terminal triad), rarely spikelets single or in threes, usually one spikelet of a pair sessile and the other pedicelled, infrequently both pedicelled; rachis fracturing at maturity beneath each spikelet pair. Spikelets of a pair alike or more often dissimilar in shape and sex, when dissimilar sessile spikelet bisexual or female, pedicelled spikelet male or barren, rarely pedicelled spikelet vestigial or absent and sessile spikelet then apparently single; sometimes 1 or more of lowermost pairs in raceme infertile, resembling pedicelled spikelets, persistent (homogamous pairs); rachis internodes and pedicels filiform, linear or thickened, sometimes very stout and partially enclosing spikelet, falling with adjacent sessile spikelet, pedicelled spikelet falling separately; callus at base of sessile spikelet obtuse to pungent. Sessile spikelet with 2 florets, usually dorsally compressed; glumes enclosing florets, hardened, lower glume facing outward, very variable, convex or 2-keeled, upper glume boat-shaped, fitting between internode and pedicel; lower floret male or barren, lower lemma hyaline, 2-keeled, lower palea suppressed when floret barren; upper floret fertile, upper lemma hyaline, narrow, entire or 2-toothed, awnless or bearing a geniculate awn with twisted column, upper palea short or absent. Pedicelled spikelet usually lanceolate, papery, often smaller than pedicelled spikelet; pedicel resembling rachis internode, rarely absent or fused to internode. Leaf anatomy Kranz MS. x = 5, 9.

About 85 genera and ca. 1000 species: throughout the tropics, extending into warm-temperate regions; 41 genera (one or two introduced) and 204 species (42 endemic, seven or eight introduced) in China.

Members of this tribe can usually be readily recognized by their fragile racemes bearing paired spikelets, one sessile and the other pedicelled. The dispersal unit is thus composed of sessile spikelet, rachis internode, and pedicel (the pedicelled spikelet falls separately), all of which contribute to the protection of the seed and are frequently ornamented or modified.

In the more primitive members both spikelets of a pair are alike and fertile and are arranged in a terminal panicle. In most genera, however, the pedicelled spikelet has lost its fertility and differs in shape and texture from the sessile one. In some genera the pedicelled spikelet is much reduced, and in extreme cases its pedicel is reduced to a vestige or fused to the adjacent internode. The sessile spikelets then appear single, but the fragile rachis gives a good clue to the correct tribe.

Another trend apparent throughout the tribe is the reduction of the large, terminal inflorescence to a few digitate or paired racemes, often arising from the axils of specialized leaves with inflated sheaths and reduced blades (spathes). In the most complex genera the ultimate unit is a boat-shaped sheath without a blade (spatheole) subtending 1 or 2 short racemes, and by repeated branching many of these units are gathered into a leafy compound panicle.

The spikelets contain 2 florets, but this is not obvious as the florets are delicate and usually reduced. However, it is seldom necessary to dissect the spikelets in order to identify a member of Andropogoneae. The apex of the upper lemma and position of the awn are sometimes important for identification. If the awn is gently drawn out, the small lemma at its base can be examined with a lens.

See the drawings of Andropogoneae features on page 3 of this volume.

Key 1

1 Spikelets all unisexual, separated in different inflorescences or in different parts of the same inflorescence   (2)
+ Spikelets all bisexual, or at least the sessile spikelet of a pair, male and female not separated   (5)
2 (1) Male and female spikelets in different inflorescences, the female in sheathed axillary “cobs” (cultivated maize).   226 Zea
+ Male and female spikelets in different parts of same inflorescence   (3)
3 (2) Female spikelets enclosed in a beadlike, bony utricle.   223 Coix
+ Female spikelets not enclosed in a bony utricle   (4)
4 (3) Female spikelets conspicuously transversely constricted; racemes all solitary, in spathate axillary clusters.   224 Chionachne
+ Female spikelets not transversely constricted; racemes digitate, at least the terminal.   225 Polytoca
5 (1) Spikelets single, without an accompanying vestigial spikelet or pedicel (if spikelets awnlesss and rachis internodes stout, see Key 4)   (6)
+ Spikelets paired, but sometimes pedicelled spikelet vestigial or represented only by the pedicel   (8)
6 (5) Inflorescence of many racemes on an elongate central axis.   186 Spodiopogon
+ Inflorescence of solitary or digitate racemes   (7)
7 (6) Leaf blades linear; raceme rachis tough.   207 Dimeria
+ Leaf blades lanceolate; raceme rachis fragile.   208 Arthraxon
8 (5) Rachis internodes and pedicels slender, filiform to linear, or if widened upward the upper lemma awned   (9)
+ Rachis internodes and pedicels stout, angular, columnar or widening upward, internode and pedicel sometimes joined; upper lemma awnless.   Key 4
9 (8) Spikelets of a pair similar in shape, usually both fertile.   Key 2
+ Spikelets of a pair different in shape and sex (rarely pedicelled spikelet vestigial or reduced to pedicel).   Key 3

List of Keys

  • List of lower taxa


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