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Reproductive Structures and Seed Formation 33oiAiioiBiioiCiioiDiioi iinuEoi ii nuFcp ratbcotscendoiGHpalhgc pc endIFIGURE 2.13 Development and structure of seed coat in Brassicaceae and Fabaceae. A toD, Brassica campestris var. yellow sarson. A to C, Ls portions of seed coat at various stagesof ovule and seed development showing disintegration of layers of the inner integument andthe development of characteristic thickenings in inner epidermis of outer integument in C.D, Ls part of mature seed coat. E to I, Crotalaria varrucosa. E, Ls micropylar part of ovuleat organized embryo sac stage. F, Ls part of developing seed coat. G, H, Ts developing andmature seed coat showing palisade cells and hourglass cells. I, Ts mature seed with rim aril,counter palisade, and tracheid bar in the hilar region. (Abbreviations: cot, cotyledon; cp,counter palisade layer; end, endosperm; es, embryo sac; hgc, hourglass cells; ii, inner integument;oi, outer integument; pal, palisade layer; pc parenchyma cells; ra, rim aril; sc, seedcoat; tb, tracheid bar.) (A to D, From Rathore, R.K.S. and Singh, R.P. 1968. J. Indian Bot.Soc. 47: 341–349; E to I, From Pandey, A.K. and Jha, S.S. 1988. Flora 181: 417–426.)
34 Histopathology of Seed-Borne Infections2.9.3 HIBISCUS AND GOSSYPIUMThe outer integument is three-layered in H. ficulneus and four- to six-layered inGossypium (Figure 2.14A, B, H). It is nonmultiplicative. The inner integument isinitially three-layered and multiplicative, becoming seven- to nine-layered in Hibiscus(Figure 2.14C, D) and eight- to fifteen-layered in Gossypium (Figure 2.14H). Boththe integuments form the seed coat. The cells of the outer epidermis of the outerintegument elongate tangentially and lose their contents, but hair initials remainsquarish and finally undergo radial enlargement into hairs (Figure 2.14H). Stomata(Figure 2.14F, G) are found in the epidermis of the entire organism, but they areaggregated more in the chalaza. The middle layers are almost squeezed in Hibiscus,but they are differentiated into an outer zone of pigmented cells and an inner zone ofcolorless cells in Gossypium (Figure 2.14I). The cells in the inner epidermis elongateradially, lose their contents, and develop thickenings on the inner tangential and radialwalls in H. ficuleuns (Figure 2.14E), but they remain thin-walled in Gossypium.The inner integument differentiates into four zones. The cells of the outerepidermis enlarge radially and become thick-walled, forming the main mechanicallayer (Figure 2.14E, I). The cells of four or five subdermal layers enlarge, becomethick-walled, and accumulate tanniferous contents. The remaining middle layersremain thin-walled, lose their contents, and are partially digested, forming thecolorless zone (Figure 2.14C, D, and I). The cells of the inner epidermis stretchtangentially and accumulate tanniferous contents in Hibiscus (Kumar and Singh,1990), but the inner epidermis develops characteristic thickenings in Gossypium,called the fringe layer (Joshi, Wadhwani, and Johri, 1967).The development of the seed coat in Gossypium is similar to Hibiscus, but thelint and fuzz hairs are distributed all over the surface of the seed.2.9.4 CUCURBITA AND SECHIUMThe ovules are bitegmic, and the two- to four-layered inner integument (Figure2.15A, F) is absorbed during ontogeny. The seed coat develops from the outerintegument, which shows localized multiplication. By two successive periclinaldivisions the outer epidermis forms three layers, which are designated e, e≤, and e¢,from outside to inside (Figure 2.15B, G). The second division does not take placethroughout the surface in Sechium. The subepidermal layer e is, therefore, discontinuousin Sechium (Figure 2.15H). The cells in e divide only anticlinally to keeppace with the growing seed and later on enlarge tangentially and become thickwalled(sclerotic), forming the main mechanical layer in Cucurbita. The cells of eand e≤ divide periclinally and the outermost derivatives enlarge radially, formingseed epidermis. The remaining layers become thick-walled and lignified, formingthe hypodermis (Figure 2.15C to E).The cells of the ovular hypodermis divide once or twice periclinally, enlarge,become stellate, and develop prominent air spaces to form aerenchyma. They becomethick-walled and lignified in Cucurbita. The cells of other layers enlarge and those onthe outer side develop air spaces while those on the inner side remain compact, forminga chlorenchymatous or parenchymatous zone. This tissue at maturity is separated fromthe outer hard coat and forms the inner coat (Singh and Dathan, 1972).
Page 2 and 3: Histopathology ofSeed-Borne Infecti
Page 4: PrefaceThe book deals with only one
Page 8 and 9: The AuthorsDalbir Singh, Ph.D., for
Page 10 and 11: ContentsChapter 1 Introduction ....
Page 12 and 13: 4.3.2 Routes for Infection from Ova
Page 14: 8.4 Survival in Seed ..............
Page 17 and 18: 2 Histopathology of Seed-Borne Infe
Page 19 and 20: 4 Histopathology of Seed-Borne Infe
Page 22 and 23: 2Reproductive Structuresand Seed Fo
Page 24 and 25: Reproductive Structures and Seed Fo
Page 26: Reproductive Structures and Seed Fo
Page 29 and 30: 14 Histopathology of Seed-Borne Inf
Page 47: 32 Histopathology of Seed-Borne Inf
Page 62 and 63: 3Structure of SeedsThe seed habit i
Page 64 and 65: Structure of Seeds 49(1971) of usin
Page 66 and 67: Structure of Seeds 51is found in as
Page 68 and 69: Structure of Seeds 53dry seed of Ly
Page 70 and 71: Structure of Seeds 553.3.2 SEED COA
Page 72 and 73: Structure of Seeds 57Endosperm: One
Page 74 and 75: Structure of Seeds 59scendembepsmuA
Page 76 and 77: Structure of Seeds 61Endosperm: Sca
Page 78 and 79: Structure of Seeds 63Chalaza simple
Page 80 and 81: Structure of Seeds 65stystypmerA Bc
Page 82 and 83: Structure of Seeds 67epsent endCADB
Page 84 and 85: Structure of Seeds 69perhscendembpe
Page 86 and 87: Structure of Seeds 71eposgepi′epo
Page 88 and 89: Structure of Seeds 73(Zea and Sorgh
Page 90 and 91: Structure of Seeds 75Baker, D.M. an
Page 92 and 93: Structure of Seeds 77Maheshwari Dev
Page 94: Structure of Seeds 79Vries, M.A. de
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84 Histopathology of Seed-Borne Inf
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TABLE 5.6Location of Mycelium of St
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7Seed Infection by VirusesViruses a
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Seed Infection by Viruses 201TABLE
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Seed Infection by Viruses 205Unlike
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Seed Infection by Viruses 2073. The
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Seed Infection by Viruses 209Wilcox
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Seed Infection by Viruses 213floret
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Seed Infection by Viruses 215ptowvv
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Seed Infection by Viruses 2177.4.2
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Seed Infection by Viruses 219seed(s
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Seed Infection by Viruses 221AMV fo
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Seed Infection by Viruses 223REFERE
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Seed Infection by Viruses 225Hunter
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Seed Infection by Viruses 227Wolf,
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