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12. Poaceae Tribe AVENEAE

燕麦族 yan mai zu

Authors: Zhen-lan Wu, Sheng-lian Lu, Shou-liang Chen, Wenli Chen & Sylvia M. Phillips

Annual or perennial. Leaf blades linear to setaceous; ligule membranous. Inflorescence an open, contracted, or spikelike panicle. Spikelets all alike, somewhat laterally compressed, with 1 to several fertile florets; rachilla usually disarticulating below each floret, occasionally strictly 3 florets with lower 2 staminate or barren and of different appearance from upper fertile floret, then disarticulating above glumes and florets falling together; glumes persistent, often equal to spikelet or at least longer than first floret, commonly membranous with broad, shining, hyaline margins; floret callus bearded; lemmas hyaline to leathery, 3- to several-veined (Coleanthus 1-veined), apex entire or denticulate, awned from back, rarely awnless; awn usually geniculate with twisted column; palea hyaline, subequaling or much shorter than lemma. Lodicules 2, rarely absent. Stamens (2 or)3, rarely 1 (Cinna). Caryopsis mostly ellipsoid; hilum round or oval, endosperm sometimes soft or liquid. Starch-grains compound. Chromosomes large; basic number 7 (5 in Anthoxanthum). Leaf anatomy:non-Kranz, microhairs absent, silica-bodies oblong.

About 60 genera: temperate and cold regions of the world, extending to mountains in the tropics; 20 genera, one hybrid genus, and 144 species (40 endemic, 11 or 12 introduced) in China.

Recent molecular studies show the tribes Poeae and Aveneae to be closely related and to some extent interleaved, with certain genera traditionally placed in one tribe ordered at a molecular level within the other. On this account the tribes are sometimes united into a broadly defined Poeae. However, most genera can be easily assigned to one or other tribe on morphological characteristics, and therefore the traditional treatment is maintained here.

1 Spikelets with 2 or more fertile florets   (2)
+ Spikelets with 1 fertile floret   (8)
2 (1) Ovary hairy; spikelets large, 7–45 mm   (3)
+ Ovary glabrous or almost so; spikelets small, 2.5–10 mm   (4)
3 (2) Perennial; glumes unequal, 1–7-veined.   75 Helictotrichon
+ Annual; glumes subequal, 7–11-veined.   77 Avena
4 (2) Lemmas keeled   (5)
+ Lemmas rounded on back   (6)
5 (4) Lemmas awned from back.   78 Trisetum
+ Lemmas awnless or with a subapical awn-point.   79 Koeleria
6 (4) Annual; florets arising at about same level; rachilla extension absent.   82 Aira
+ Perennial; florets separated by an internode; rachilla extension present   (7)
7 (6) Panicle glistening; lemma apex erose.   80 Deschampsia
+ Panicle not glistening; lemma apex 4-toothed.   87 Deyeuxia
8 (1) Inflorescence of several racemes along a central axis.   92 Beckmannia
+ Inflorescence a panicle, sometimes spikelike   (9)
9 (8) Fertile floret accompanied by staminate or sterile florets   (10)
+ Fertile floret solitary, with or without a rachilla extension   (13)
10 (9) Spikelets with 2 florets   (11)
+ Spikelets with 3 florets, the 2 lower staminate or barren (reduced to small scales in Phalaris)   (12)
11 (10) Spikelet disarticulating above glumes; lower floret staminate.   76 Arrhenatherum
+ Spikelet disarticulating below glumes; upper floret staminate.   81 Holcus
12 (10) Lower lemmas rudimentary; plants without coumarin.   83 Phalaris
+ Lower lemmas well developed; plants scented with coumarin.   84 Anthoxanthum
13 (9) Spikelets in compact umbellate clusters; glumes absent.   85 Coleanthus
+ Spikelets in an open, contracted or spikelike panicle; glumes present   (14)
14 (13) Spikelets falling entire   (15)
+ Spikelets disarticulating above glumes   (19)
15 (14) Spikelets shed with a basal stipe.   89 Polypogon
+ Spikelets shed without a basal stipe   (16)
16 (15) Panicle open   (17)
+ Panicle spikelike or capitate; stamens usually 3   (18)
17 (16) Glumes indistinctly 3-veined; lemma with awnlet; stamen 1.   90 Cinna
+ Glumes prominently 3-veined; lemma awnless; stamens 3.   91 Cyathopus
18 (16) Lemma awned from back.   93 Alopecurus
+ Lemma awnless.   94 Phleum
19 (14) Glumes slightly shorter than floret.   87 Deyeuxia
+ Glumes equaling or longer than floret   (20)
20 (19) Glumes mucronate.   86a ×Agropogon
+ Glumes acute to acuminate   (21)
21 (20) Spikelets usually less than 5 mm; callus glabrous or shortly hairy; lemma hyaline.   86 Agrostis
+ Spikelets often more than 5 mm; callus bearded, hairs 1/3 as long as to longer than floret (if shorter, penicillate rachilla extension present); lemma membranous to firm   (22)
22 (21) Lemma at least 3/4 as long as glumes, usually firm; callus hairs almost as long as to clearly shorter than floret; rachilla extension present, penicillate   87 Deyeuxia
+ Lemma 1/2–2/3 as long as glumes, membranous; callus hairs often much exceeding floret; rachilla extension absent, or if present glabrous or shortly hairy.   88 Calamagrostis

  • List of lower taxa


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