Histopathology of Seed-Borne Infections - Applied Research Center ...

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Reproductive Structures and Seed Formation 37In Sechium edule, the cells of e, e≤ (wherever present), and e¢ get packed withstarch grains, but remain unlignified (Figure 2.15H). The remaining layers becomeaerenchymatous and acquire starch grains (Singh, 1965). The fruit in Sechium isone-seeded, and the seed shows many uncommon features, i.e., leathery testa, vivipary,and hypogeal germination.2.9.5 LYCOPERSICONThe single integument is multiplicative and differentiates into three zones — theouter epidermis, the mesophyll, and the inner epidermis, which forms the endothelium(Figure 2.16B to D). During the advanced stages of seed development, thecells of the outer epidermis undergo enormous radial elongation. Their inner tangentialand radial walls become thick, thickening and tapering from inside to outsideon radial walls. The outer wall remains thin and readily separates at maturity (Figure2.16E). The middle layers develop lysigenous cavities and are gradually absorbed.Only a few hypodermal layers persist. The cells of endothelium (Figure 2.16D, E)are flattened and accumulate pigmented contents (Saxena, 1970).A succulent envelope (arillode) surrounds the mature seed. The primordium forthe envelope originates in the placenta around the funiculus within 72 to 96 hoursof pollination (Figure 2.16A). It grows rapidly and gradually surrounds the seed.Finally, the seed is completely surrounded (Figure 2.16F, H). The cells of the arillodeare initially polygonal with prominent nuclei, but subsequently enlarge and acquirechloroplasts and starch grains (Figure 2.16 G). At maturity they lose their contentsand their cell walls gelatinize.2.9.6 LACTUCAThe cypsil, dry, one-seeded, indehiscent fruit, forms seed. The pericarp constitutesthe protective covering, and the seed coat is thin when present, or it may be completelyobliterated. Thus the integument and ovary wall both participate in formingthe seed cover.In Lactuca, the integument is six- or seven-layered, multiplicative, and differentiatesinto three and finally four zones (Figure 2.17A to C). The inner epidermisforms the endothelium, and three or four layers adjacent to it constitute the periendothelium(Figure 2.17C). All the layers except the epidermis and the hypodermisare absorbed. The cells of the periendothelium undergo gelatinization before absorption.The epidermal cells develop cellulose thickenings on the radial walls (Figure2.17E, F).The ovary wall comprises eight or nine layers, and its cells stretch tangentiallyduring development. The epidermal cells show pronounced gliding growth, formingspinescent structures. At maturity the pericarp is sinuate and in carinal (ridge)position bears a fibrovascular bundle (Figure 2.17D, E). Other components of thepericarp are the epidermis and one or two layers of narrow tangentially elongatedsclereids (Figure 2.17F, H). The size of the epidermal cells, the amount of tannin,and the ratio of their body and spinescent region (Figure 2.17G) vary in differentLactuca species (Kaul and Singh, 1982).
38 Histopathology of Seed-Borne InfectionsarlpovAmlepoentBepoomlomlCimlimlententDespomlEseedarlarlFGHFIGURE 2.16 Development and structure of seed of Lycopersicon esculentum. A, Ls ovuleat four-celled endosperm stage with arillode primordium (arlp). B to D, Ls part of integumentand developing seed coat showing absorption of cells in outer middle layers. E, Ls part ofimmature seed coat comprising epidermal cells with inner tangential and radial walls lignified;reduced number of middle layers and the persistent endothelium. F, Ls developing seed withthe arillode. G, Arillode cells from whole-mount preparation at green fruit stage. H, Diagramof fresh seed on graph to show the relative proportion of seed and arillode. (Abbreviations:arl, arillode; arlp, arillode primordium; ent, endothelium; epo, outer epidermis; eps, seedepidermis; iml, inner zone of middle layers; ml, middle layers; oml, outer zone of middlelayers; ov, ovule.) (From Saxena, T. 1970. Ph.D. thesis, University of Rajasthan, Jaipur, India.)
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 51: 36 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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88 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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