|
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 3
|
|
|
| 1 |
Sessile spikelets male or barren, hard, involucrelike, awnless; pedicelled spikelets fertile, long awned. |
|
197 Germainia |
| + |
Sessile spikelets fertile, often awned; pedicelled spikelets male, barren, or suppressed |
|
(2) |
| |
|
|
|
| 2 (1) |
Racemes borne on an elongate central axis or its branches, axis longer than lowest raceme, not supported by spathes |
|
(3) |
| + |
Racemes solitary, paired or subdigitate, often supported by spathes |
|
(7) |
| |
|
|
|
| 3 (2) |
Rachis internodes and pedicels without a purple translucent median line |
|
(4) |
| + |
Rachis internodes and pedicels with a purple translucent median line |
|
(6) |
| |
|
|
|
| 4 (3) |
Lower glume of sessile spikelet laterally compressed; raceme often reduced to a triad. |
|
200 Chrysopogon |
| + |
Lower glume of sessile spikelet dorsally compressed; raceme of several spikelet pairs below terminal triad |
|
(5) |
| |
|
|
|
| 5 (4) |
Glumes of sessile spikelet leathery; panicle usually loose, racemes of 2–7 spikelet pairs; lodicules ciliate. |
|
198 Sorghum |
| + |
Glumes of sessile spikelets firmly cartilaginous; panicle dense, racemes of 5–15 spikelet pairs; lodicules glabrous. |
|
199 Pseudosorghum |
| |
|
|
|
| 6 (3) |
Racemes of 1–5(–8) spikelet pairs, often reduced to triads. |
|
202 Capillipedium |
| + |
Racemes of more than 8 spikelet pairs. |
|
203 Bothriochloa |
| |
|
|
|
| 7 (2) |
Rachis internodes and pedicels with a purple translucent median line. |
|
203 Bothriochloa |
| + |
Pedicels and rachis internodes without a translucent median line |
|
(8) |
| |
|
|
|
| 8 (7) |
Lower floret of sessile spikelet staminate, with well-developed palea |
|
(9) |
| + |
Lower floret of sessile spikelet barren, reduced to a lemma, palea absent |
|
(13) |
| |
|
|
|
| 9 (8) |
Pedicel lacking a spikelet, partially fused to lower glume; sessile spikelet broadly truncate, apex with scarious colored band (A. intermedius with pedicelled spikelet). |
|
196 Apocopis |
| + |
Pedicel bearing a spikelet, free from lower glume |
|
(10) |
| |
|
|
|
| 10 (9) |
Ligule a line of hairs; raceme solitary; lower glume of sessile spikelet deeply grooved, apex elongate, scarious. |
|
204 Sehima |
| + |
Ligule membranous; racemes often more than 1; lower glume of sessile spikelet not as above |
|
(11) |
| |
|
|
|
| 11 (10) |
Sessile spikelet laterally compressed, smooth; raceme solitary, reduced to spathate triad, these numerous, crowded into compound panicle. |
|
206 Apluda |
| + |
Sessile spikelet dorsally compressed; racemes (1 or)2 or more, terminal or axillary |
|
(12) |
| |
|
|
|
| 12 (11) |
Rachis internodes and pedicels stoutly linear to thickly clavate; sessile spikelet often rugose or knobbly. |
|
205 Ischaemum |
| + |
Rachis internodes and pedicels filiform to linear; sessile spikelet smooth, grooved along midline. |
|
195 Microstegium |
| |
|
|
|
| 13 (8) |
Awn arising from low down on lemma back; culms slender, often trailing, leaf blades lanceolate. |
|
208 Arthraxon |
| + |
Awn arising from apex of lemma, or from sinus of 2-lobed apex |
|
(14) |
| |
|
|
|
| 14 (13) |
Lower glume of sessile spikelet 2-keeled; callus inserted into hollowed internode apex |
|
(15) |
| + |
Lower glume of sessile spikelet convexly rounded without keels; callus attached obliquely, its apex visible |
|
(17) |
| |
|
|
|
| 15 (14) |
Racemes solitary. |
|
209 Schizachyrium |
| + |
Racemes paired or digitate |
|
(16) |
| |
|
|
|
| 16 (15) |
Leaves not aromatic; racemes not deflexed, borne on unequal terete raceme bases. |
|
210 Andropogon |
| + |
Leaves aromatic; racemes usually deflexed at maturity, borne on subequal flattened raceme bases. |
|
211 Cymbopogon |
| |
|
|
|
| 17 (14) |
Upper lemma 2-toothed, awned from sinus. |
|
212 Hyparrhenia |
| + |
Upper lemma entire, awned from apex |
|
(18) |
| |
|
|
|
| 18 (17) |
Raceme with 2 large homogamous spikelet pairs at base, forming an involucre. |
|
213 Themeda |
| + |
Raceme with or without homogamous spikelet pairs, but not forming an involucre |
|
(19) |
| |
|
|
|
| 19 (18) |
Sessile spikelet with pungent callus. |
|
214 Heteropogon |
| + |
Sessile spikelet with obtuse callus |
|
(20) |
| |
|
|
|
| 20 (19) |
Inflorescence terminal, composed of (1 or)2–8 subdigitate racemes. |
|
201 Dichanthium |
| + |
Inflorescence a small spathate raceme, racemes grouped in bunches on flexuous peduncles, forming a compound panicle. |
|
215 Pseudanthistiria |
|
|
List of Keys
|
List of lower taxa
| Related Links (opens in a new window) |
|
Treatments in Other Floras @ www.efloras.org
Other Databases
|
|
|
|
|
|
|
