Sucrea Soderstrom
Named for Dimitri Sucre.
Habit, vegetative morphology. Perennial; rhizomatous and caespitose. Culms 30–100 cm high; herbaceous; unbranched above. Culm nodes hairy, or glabrous. Culm sheaths persistent. Plants unarmed. Leaves mostly basal, or not basally aggregated; without auricular setae. Leaf blades broadly ovate; broad; 25–100 mm wide; pseudopetiolate; cross veined; rolled in bud; ligule present, or absent.
Reproductive organization. Plants monoecious with all the fertile spikelets unisexual; without hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; female-only and male-only. The male and female-fertile spikelets segregated, in different parts of the same inflorescence branch (the female spikelets terminal, the males below). The spikelets overtly heteromorphic.
Inflorescence. Inflorescence paniculate; open (terminal); spatheate (the terminal sheath constituting a spathe); not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes paniculate; persistent. Spikelets not secund; pedicellate (the pedicels of female spikelets thickened apically); not in distinct ‘long-and-short’ combinations.
Female-sterile spikelets. Male spikelets without glumes; lemma membranous, 3-nerved; palea membranous, 2-nerved; lodicules 3, fleshy; stamens 3, free, non-penicillate. Rachilla of male spikelets terminated by a male floret. The male spikelets without glumes; without proximal incomplete florets; 1 floreted. Male florets 1; 3 staminate. The staminal filaments free.
Female-fertile spikelets. Spikelets 6.5–10 mm long; disarticulating above the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent. Callus absent.
Glumes two; more or less equal; long relative to the adjacent lemmas (exceeding them); hairy (finely pubescent); pointed (ovate-acuminate to shortly subulate); shortly awned (with a terminal scabrid subule); non-carinate; similar (with cartilaginous margins, twisting with age, tessellate). Lower glume 5 nerved. Upper glume 3 nerved. Spikelets with female-fertile florets only.
Female-fertile florets 1. Lemmas fusiform, completely embracing the palea; decidedly firmer than the glumes; pitted; becoming indurated (leathery when young); awnless; hairless; glabrous; non-carinate; having the margins inrolled against the palea; without a germination flap (apparently); 5 nerved (tessellate). Palea present; relatively long (slightly shorter than the lemma); entire; awnless, without apical setae; textured like the lemma; indurated; 2-nerved (? ‘2 strong nerves and transverse veinlets’). Lodicules present; 3; free; fleshy; glabrous; heavily vascularized. Stamens 0 (3 staminodes). Ovary glabrous. Styles fused (the ovary attenuate into one long style). Stigmas 2.
Fruit, embryo and seedling. Hilum long-linear. Embryo small; waisted.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present. Intercostal papillae not over-arching the stomata; several per cell (round, thick walled, in 2–3 irregular rows on long-cells and interstomatals, the costals with mostly only one row). Long-cells markedly different in shape costally and intercostally (the intercostals much broader); of similar wall thickness costally and intercostally (quite thin walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls (coarsely so). Microhairs present; panicoid-type; (45–)48–51(–54) microns long; 5.4–6.3 microns wide at the septum. Microhair total length/width at septum 7.1–10. Microhair apical cells 19.5–25.5 microns long. Microhair apical cell/total length ratio 0.43–0.5. Stomata common; 21–24 microns long. Subsidiaries mostly high dome-shaped. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs (mostly). Costal short-cells conspicuously in long rows. Costal silica bodies saddle shaped, oryzoid, and ‘panicoid-type’ (forming an almost continuous series); the panicoid form cross shaped; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with adaxial palisade; with arm cells; with fusoids. The fusoids external to the PBS. Leaf blade adaxially flat (except for the midrib). Midrib conspicuous; having a conventional arc of bundles (a large median, and a small one on either side); with colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups (these wide); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with most of the main bundles); forming ‘figures’ (most of the main bundles with I’s or ‘anchors’).
Cytology. Chromosome base number, x = 11. 2n = 22. 2 ploid.
Taxonomy. Bambusoideae; Oryzodae; Olyreae.
Distribution, ecology, phytogeography. 3 species; Brazil. Shade species. In forest.
Neotropical. Central Brazilian.
References, etc. Morphological/taxonomic: Soderstrom 1981c. Leaf anatomical: this project.
Illustrations. • Transverse section of leaf blade. Sucrea maculata.
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).
