Structure <strong>of</strong> <strong>Seed</strong>s 69perhscendembperBscend cotperscend cotAPhFIGURE 3.11 Cypsil structure in Asteraceae. A, Ls cypsil <strong>of</strong> Lactuca longifolia. B, Ts part<strong>of</strong> cypsil <strong>of</strong> Helianthus annuus showing hair, pericarp with phytomelanin layer, seed coat,and cotyledon. C, Ts part <strong>of</strong> cypsil <strong>of</strong> Guizotia abyssinica. (Abbreviations: cot, cotyledon;emb, embryo; end, endosperm; per, pericarp; ph, phytomelanin layer; sc, seed coat.) (A,From Kaul, V. and Singh, D. 1982. Acta Biologica Cracoviensia 24: 19–30; B, C, Vaughan,J.A. 1970. The Structure and Utilization <strong>of</strong> Oil <strong>Seed</strong>s. Chapman & Hall, London.)smooth, shining; hilum inconspicuous at or near marginal notch, micropyle inconspicuous.Internal: <strong>Seed</strong> coats two, exotestal, testa (outer coat) crustaceous, epidermis <strong>of</strong>cuboid or radially elongated cells, thick-walled, thickening as stalactites (long pillarlikeor wedge-shaped projections with pointed ends from the outer tangential wall),stalactites rarely absent (Digeria, Achyranthes, and Alternanthera); mesophyll <strong>of</strong>one or two layers <strong>of</strong> thin-walled cells. Inner coat membranous consisting <strong>of</strong> innerepidermis <strong>of</strong> inner integument, cells narrow, elongated, full <strong>of</strong> pigmented contentsand with bands <strong>of</strong> thickenings on cell walls.Embryo: Peripheral, large, curved-lenticular to annular, rarely tips <strong>of</strong> cotyledonsincurved (Achyranthes), cotyledons two, equal or larger than the hypocotyledonaryaxis.C
70 <strong>Histopathology</strong> <strong>of</strong> <strong>Seed</strong>-<strong>Borne</strong> <strong>Infections</strong>Endosperm: Scanty, remnants around embryo and at the micropylar and chalazalends, cell layers distinct only at ends.Perisperm: Massive, main tissue having reserve food material, enclosed in theconcavity <strong>of</strong> embryo, cells thin-walled, rich in starch grains.3.4.11 CHENOPODIACEAE (FIGURE 3.12A TO G)(Artschwager, 1927; Bhargava, 1936; Taneja, 1981)External: <strong>Seed</strong> small to medium, circular-lenticular to reniform, notched, rarelyovoid and beaked (Saeuda) or flat and narrowly obovate (Kochia), brown to black,shining. Di- and polymorphism <strong>of</strong> seeds known in Atriplex spp. Achenes withattached perianth (seed ball) form planting unit in Beta and Spinacia.Internal: <strong>Seed</strong> coats two, exotestal, seed epidermis radially or horizontallyelongated, usually thick-walled with stalactites, cells with uniformly thickened outertangential and radial walls (Spinacia) or full <strong>of</strong> pigmented material (Beta). Stalactitesabsent in both <strong>of</strong> them. Mesophyll one or two layers, thin-walled, compressed;innercoat membranous formed by inner epidermis, cells narrow tangentiallystretched, full <strong>of</strong> pigmented contents, cell walls with bands <strong>of</strong> thickenings. In Kochiaand Salsola the seed coat is membranous and uniseriate.Embryo: Peripheral, curved-horse-shoe shaped, annular or coiled, large, cotyledonstwo, hypocotyledonary root axis usually longer than the cotyledons.Endosperm: Scanty, remnants <strong>of</strong> one or two layers at micropylar and chalazalends.Perisperm: Massive, enclosed in the concavity <strong>of</strong> embryo; cells thin-walled,full <strong>of</strong> starch grains, main storage tissue. Perisperm absent in seeds <strong>of</strong> Saeuda andSalsola.3.4.12 POACEAE (GRAMINAE) (FIGURE 3.13A TO I)(Kiesselbach and Walker, 1952; Narayanswami, 1953, 1955a,b; Sanders, 1955; Bradburyet al. 1956a,b; Chandra, 1963, 1976)One-seeded indehiscent fruit, caryopsis usually with pericarp and testa fused,form the commercial grain or seed for planting. There is considerable variability inexomorphic and internal features <strong>of</strong> the caryopsis. This account mainly concernscultivated cereals and millets.External: Caryopsis naked (Triticum, Zea, Sorghum, and Pennisetum) or coveredwith lemma and palea, which are chaffy (Hordeum and Avena) or hard horny (Oryzaand Paspalum); pericarp papery, hyaline, white, easily separating and seed coat welldeveloped, tough (Eleusine); elongated-ovate, elliptic, fusiform, rounded or squarish;smooth, faintly or prominently longitudinally striate, rough, pubescent or spinescents,rarely median groove on ventral surface (Triticum); pale white, yellow, variousshades <strong>of</strong> red, brown, purplish, grey or black; basal lateral embryo area distinctiveand easily identified in naked types (Zea, Triticum, Sorghum, and Pennisetum);caryopsis scar basal, opposite embryo on ventral side, inconspicuous or conspicuous,rarely floret stalk (rachilla) attached at the base (Hordeum, Avena, and Oryza); innaked grains at the apical end a blunt pointed outgrowth marks the remains <strong>of</strong> style
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