Planichloa B. Simon
In reference to the very flattened spikelets.
Sometimes referred to Ectrosia
Habit, vegetative morphology. Erect annual. Culms 12–40 cm high; herbaceous; unbranched above; 1–3 noded (terete). Leaves not basally aggregated; non-auriculate. Sheaths hispid, with tubercle based hairs. Leaf blades linear (hispid); narrow; 1–4 mm wide (to 10 cm long); flat, or folded; without abaxial multicellular glands; without cross venation; persistent; a fringed membrane; 0.2–0.3 mm long.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; contracted to open; when contracted, more or less irregular; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate (the pedicels 0.5–1 mm long, hairy).
Female-fertile spikelets. Spikelets 5–11 mm long (3–6 mm wide); strongly compressed laterally; disarticulating above the glumes (but the glumes falling later); not disarticulating between the florets (the rachilla rigid). Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus absent. Callus short.
Glumes two; very unequal; shorter than the spikelets; shorter than the adjacent lemmas; hairless; scaberulous on the margins and keel; pointed; awnless; carinate; similar (lanceolate, acuminate, usually mauve). Lower glume 1 nerved. Upper glume 3 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets awned. Spikelets without proximal incomplete florets.
Female-fertile florets 2–8. Lemmas rigid, flattened, yellowish green or the apices infused with mauve, dark-pigmented on the lateral nerves; similar in texture to the glumes (leathery); not becoming indurated; entire; pointed; awnless (acute to acuminate), or awned (the awns increasingly emphasized acropetally in the spikelet). Awns 1; median; apical; non-geniculate; hairless (scabrous); much shorter than the body of the lemma to about as long as the body of the lemma; persistent. Lemmas hairless; scaberulous on the keel and margins; carinate; without a germination flap; 5 nerved, or 7 nerved (the laterals more or less grouped together). Palea present; conspicuous but relatively short (about half the lemma length, ‘comma shaped’); awnless, without apical setae; hyaline, with leathery and scaberulous margins; not indurated; 2-nerved; 2-keeled. Palea keels winged; scabrous. Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Anthers about 0.5 mm long (mauvish red). Ovary glabrous. Stigmas 2; pale yellow, plumose.
Fruit, embryo and seedling. Fruit small (about 1.4 mm long); ellipsoid; slightly compressed laterally, or not noticeably compressed. Hilum short. Pericarp fused. Embryo large (about half the length of the caryopsis).
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals smaller and narrower); of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type. Microhair apical cell wall thinner than that of the basal cell and often collapsed. Microhair basal cells 21 microns long. Microhair total length/width at septum 5. Microhair apical cell/total length ratio 0.5. Stomata common. Subsidiaries triangular (predominantly), or dome-shaped. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs (a few only, with crescentic silica bodies), or not paired (mostly solitary and unsilicified); mostly not silicified. Intercostal silica bodies absent, or imperfectly developed. Costal short-cells predominantly paired. Costal silica bodies present throughout the costal zones; saddle shaped (a very small version, predominating), or tall-and-narrow to crescentic (intergrading with the saddles); not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheath outlines uneven. PCR sheaths of the primary vascular bundles interrupted; interrupted abaxially only. PCR sheath extensions present. Maximum number of extension cells 2–3. Mesophyll with radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size (low). Midrib fairly conspicuous (via a widish, flat abaxial keel and the larger bundle); with one bundle only. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups (the groups very large, one in each furrow); in simple fans (these predominating, the median cells large and deeply penetrating), or associated with colourless mesophyll cells to form deeply-penetrating fans (these infrequent). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (nearly all the bundles); forming ‘figures’ (nearly every bundle with an ‘I’ or an ‘anchor’). Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Taxonomy. Chloridoideae; main chloridoid assemblage.
Distribution, ecology, phytogeography. 1 species; restricted to the Cook pastoral district of northern Qld. Mesophytic to xerophytic; species of open habitats; glycophytic. In sandy soils.
Australian. North and East Australian. Tropical North and East Australian.
References, etc. Morphological/taxonomic: Simon 1986. Leaf anatomical: this project.
Illustrations. • Spikelet. • Lemma
Cite this publication as: Watson, L., and Dallwitz, M. J. (1992 onwards). ‘Grass Genera of the World: Descriptions, Illustrations, Identification, and Information Retrieval; including Synonyms, Morphology, Anatomy, Physiology, Phytochemistry, Cytology, Classification, Pathogens, World and Local Distribution, and References.’ http://biodiversity.uno.edu/delta/. Version: 18th August 1999. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993 onwards, 1998), and Watson and Dallwitz (1994), and Watson, Dallwitz, and Johnston (1986) should also be cited (see References).
