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corn, cultivated corn

Habit Plants annual. Plants annual or perennial; synoecious, monoecious, or dioecious; primarily herbaceous, habit varied.
Culms

(0.5)1-3(6) m tall, (0.5)1-5 cm thick.

annual, usually solid, sometimes somewhat woody, sometimes decumbent, often branched above the base.

Leaves

distichous;

sheaths usually open;

auricles usually absent;

abaxial ligules usually absent, occasionally present as a line of hairs;

adaxial ligules membranous, sometimes also ciliate, or of hairs, sometimes absent;

blades sometimes pseudopetiolate;

mesophyll radiate or non-radiate;

adaxial palisade layer absent;

fusoid cells usually absent;

arm cells usually absent;

kranz anatomy absent or present;

midribs usually simple, rarely complex;

adaxial bulliform cells present;

stomata with triangular or dome-shaped subsidiary cells;

bicellular microhairs usually present, with a long, narrow distal cell;

papillae absent or present.

Blades

mostly 30-90 cm long, 2.5-12 cm wide.

Inflorescences

ebracteate (Paniceae) or bracteate (most Andropogoneae) panicles, racemes, spikes, or complex arrangements of rames (in the Andropogoneae), usually bisexual, sometimes unisexual;

disarticulation usually below the glumes, frequently in the secondary and higher order axes of the inflorescences.

Spikelets

bisexual or unisexual, frequently paired or in triplets, the members of each unit usually with pedicels of different lengths or 1 spikelet sessile.

Glumes

usually 2, equal or unequal, shorter or longer than the adjacent florets, sometimes exceeding the distal florets;

florets 2(-4), usually dorsally compressed, sometimes terete or laterally compressed;

lower florets sterile or staminate, frequently reduced to a lemma;

upper florets usually bisexual;

lemmas hyaline to coriaceous, lacking uncinate hairs, often terminally awned;

awns single;

paleas of bisexual florets well-developed, reduced, or absent;

lodicules usually 2, sometimes absent, cuneate, free, fleshy, usually glabrous;

anthers 1-3;

ovaries usually glabrous;

haustorial synergids absent;

style branches 2, free and close or fused at the base.

Caryopses

concealed in fruitcases (wild taxa) or exposed (domesticated taxon);

fruitcases of wild taxa distichous, triangular in side view; domesticated taxon without fruitcases, glumes reduced and shallow or collapsed and embedded in the rachis.

hila usually punctate;

endosperm hard, without lipid;

starch grains simple;

embryos large in relation to the caryopses, usually waisted;

epiblasts usually absent;

scutellar cleft present;

mesocotyl internode elongated;

embryonic leaf margins usually overlapping, rarely just meeting, x = 5, (7), 9, 10, (12), (14).

Pistillate

inflorescences rames or spikes, usually shortly pedunculate (sometimes sessile), solitary, 4-30(40) cm long, (0.5)1-10 cm thick, with 2 or more rows of paired spikelets, hence the spikelets 4 or more ranked, rarely terminating in an unbranched staminate inflorescence.

Staminate

panicles 10-25+ cm, with 1-60(235) branches, internodes 1.5-8.2 mm;

spikelets 9-14 mm long, 2.5-5 mm wide;

lower glumes rounded dorsally, flexible, translucent, papery, loosely enclosing the upper glumes, the 2 lateral veins subequal to the others, not winged.

2n

= 20.

Zea mays

Poaceae subfam. panicoideae

Distribution
from FNA
AL; AR; AZ; CA; CO; CT; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; NE; NH; NJ; NM; NV; NY; OH; OR; PA; RI; SC; TN; TX; UT; VA; VT; WA; WI; WV; WY; PR; ON; QC; Virgin Islands
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[BONAP county map]
Discussion

Of the five subspecies of Zea mays, only the domesticated subspecies, Z. mays subsp. mays, is widely grown outside of research programs. Three wild subspecies are treated here, albeit briefly, because of their importance as genetic resources for Z. mays subsp. mays.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

The subfamily Panicoideae is most abundant in tropical and subtropical regions, particularly mesic portions of such regions, but several species grow in temperate regions of the world. Within the Flora region, the Panicoideae are represented by 59 genera and 364 species. They are most abundant in the eastern United States (Barkworth and Capels 2000). Photosynthesis may be either C3 or C4. All three pathways are found in the subfamily, but the PCK and NAD-ME variants appear to have evolved only once, while the NADP-ME pathways seems to have evolved several different times (Giussani et al. 2001).

The Panicoideae were first recognized as a distinct unit by Brown (1814), earlier than any of the other subfamilial taxa of the Poaceae. Its early recognition is undoubtedly attributable to its distinctive spikelets. Recognition of the tribe Gynerieae is recent (Sanchez-Ken and Clark 2001) and its placement in the Panicoideae, rather than the Centothecoideae, should be regarded as tentative.

Spikelets with two florets are found in many other subfamilies, but rarely do they follow the pattern of the lower floret being sterile or staminate and the upper floret bisexual. Development of unisexual florets within the Panicoideae appears to be consistent across the subfamily (LeRoux and Kellogg 1999), but differs from that in the Ehrhartoideae (Zaitcheck et al. 2000).

The Paniceae and Andropogoneae have their conventional interpretation in this Flora, so far as the North American taxa are concerned. Molecular studies, however, while strongly supporting the monophyly of the Andropogoneae, show the Paniceae to be paraphyletic, with two distinct clades. In one of these clades, most taxa have a chromosome base number of x = 9, but some have x = 10, and the taxa are pan-tropical in origin. The taxa in the other clade, with one exception, have a chromosome base number of x = 10 and are American in origin. This latter clade is sister to the Andropogoneae, which also have a chromosome base number of x = 10 (Gomez-Martinez and Culham 2000; Giussanni et al. 2001; Barber et al. 2002).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Key
1. Pistillate inflorescences cylindrical spikes, 2-5(10) cm thick, with 8-24+ rows of spikelets pairs, each inflorescence tightly and permanently enclosed by several leaf sheaths and a large prophyll, not disarticulating at maturity; caryopses 60-1000+, not concealed by the glumes; staminate panicle branches not disarticulating below the sessile spikelets, lacking abscission layers; central axis of the staminate panicles polystichous, much thicker than the lateral branches; obligate domesticate
subsp. mays
1. Pistillate inflorescences cylindrical, distichous rames, less than 1 cm thick, with 2 rows of spikelet pairs, each rame usually enclosed by a single leaf sheath and a prophyll, disarticulating at maturity into fruitcases; caryopses 4-15, each one concealed within a fruitcase; staminate panicles composed of rames that disarticulate below the sessile spikelets and have evident abscission layers; central axis of the staminate panicles similar in width to the rames; in the Flora region, wild taxa are known only from research plantings.
→ 2
2. Staminate spikelets (6.6)7.5-10.5 mm long; fruitcases 6-10 mm long, 4-6 mm wide; staminate panicles with 1-35+ ascending to divergent, rather stiff branches
subsp. mexicana
2. Staminate spikelets 4.6-7.2(7.9) mm long; fruitcases 5-8 mm long, 3-5 mm wide; staminate panicles usually with 10-100(235) divergent to nodding branches.
→ 3
3. Leaves pubescent; staminate panicles with (2)10-100(235) branches
subsp. parviglumis
3. Leaves glabrous or almost so; staminate panicles usually with fewer than 40 branches
subsp. huehuetenangensis
1. Blades of leaves on the lower 1/2 of the culms disarticulating from the sheaths; plants 2-15 m tall, unisexual, without axillary inflorescences; blades with midribs 5-15 mm wide
Gynerieae
1. Blades of most or all cauline leaves remaining attached to the sheaths; plants 0.05-6 m tall, usually bisexual, sometimes with unisexual inflorescences, often with axillary inflorescences; blades with midribs 0.2-5 mm wide.
→ 2
2. Glumes usually conspicuously unequal; lower glumes usually greatly exceeded by the upper florets; upper glumes from subequal to longer than the distal florets; lemmas of the upper florets usually coriaceous to indurate; disarticulation usually beneath the glumes, not in the axes of the inflorescence branches
Paniceae
2. Glumes usually subequal, usually exceeding and concealing the florets; lemmas of the upper florets hyaline to membranous; disarticulation frequently in the axes of the inflorescence branches
Andropogoneae
Source FNA vol. 25, p. 701. FNA vol. 25, p. 351. Author: Grass Phylogeny Working Group;.
Parent taxa Poaceae > subfam. Panicoideae > tribe Andropogoneae > Zea Poaceae
Sibling taxa
Z. diploperennis, Z. luxurians, Z. perennis
Subordinate taxa
Z. mays subsp. huehuetenangensis, Z. mays subsp. mays, Z. mays subsp. mexicana, Z. mays subsp. parviglumis
Name authority L. Link
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