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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 4

1 Inflorescence terminal, racemes solitary, subdigitate or spread along an elongate axis   (2)
+ Inflorescence of axillary racemes from the upper leaf axils   (4)
2 (1) Sessile spikelet with pectinate, often spinose margins, or margins tuberculate; raceme solitary.   220 Eremochloa
+ Sessile spikelet without pectinate margins; racemes solitary to many   (3)
3 (2) Pedicel joined to rachis internode; pedicelled spikelet absent.   218 Mnesithea
+ Pedicel free; pedicelled spikelet present.   216 Phacelurus
4 (1) Sessile spikelets alternating on raceme in 2 opposite rows; pedicelled spikelets absent; pedicel joined to rachis internode.   222 Ophiuros
+ Sessile spikelets all on one side of raceme; pedicelled spikelets well developed to vestigial; pedicel free or partially or completely joined to rachis internode   (5)
5 (4) Spikelets of a pair similar (if 2 sessile ornamented spikelets at each node, see Mnesithea); racemes tough or tardily disarticulating; rachis articulation line usually oblique without central peg.   217 Hemarthria
+ Spikelets of a pair different; racemes easily disarticulating; rachis articulation line ± straight with central peg   (6)
6 (5) Sessile spikelet globose, reticulately ornamented.   221 Hackelochloa
+ Sessile spikelet not globose, smooth or with longitudinal slits or grooves between the veins   (7)
7 (6) Lower floret of sessile spikelet staminate, its palea well developed; spikelets smooth.   219 Rottboellia
+ Lower floret of sessile spikelet barren, its palea reduced or absent; spikelets with 2–7 longitudinal slots or grooves between the veins, rarely smooth.   218 Mnesithea

List of Keys

  • List of lower taxa


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