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

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Reproductive Structures and Seed Formation 252.8.1 ENDOSPERMThe primary endosperm nucleus divides mitotically, and depending on the mannerof wall formation during its development, three main types of endosperms arerecognized. (1) If the first few divisions are not followed by wall formation andnuclei lie free in the cytoplasm, the endosperm is of the nuclear type (Figure 2.9A,B). (2) If the first and subsequent nuclear divisions are followed by cell wallformation, the endosperm is of the cellular type (Figure 2.9C, D). (3) It is in theintermediate type, in which the first nuclear division is followed by cell wallformation, that two unequal chambers are usually formed. The micropylar chamberis larger, and its nucleus divides repeatedly without wall formation. In the smallchalazal chamber, the nucleus may undergo a few free nuclear divisions or it mayremain undivided. This endosperm is of the helobial type. During further development,cell wall formation takes place in the micropylar chamber. Nuclearendosperms also ultimately become cellular. The endosperm development is of thenuclear type in most of the food plants (Brassicaceae, Malvaceae, Tiliaceae,Fabaceae, Cucurbitaceae, Apiaceae, Solanaceae, Asteraceae, and Poaceae) and cellularin Sesamum (Pedaliaceae).The female gametophyte remains sac-like, and food material is translocated intoit from the surrounding tissue. In several families, portions of endosperm in thechalazal and/or micropylar regions undergo tubular elongation to form endospermhaustoria, which function to draw nutrition. Endosperm haustoria have been reportedin the nuclear as well as the cellular types of endosperms. Among the families offood plants, some genera of Fabaceae, Cucurbitaceae, and Pedaliaceae (sesame)develop haustoria. In Cucurbitaceae and Fabaceae, a chalazal, tubular, and coenocyticor cellular haustorium with dense cytoplasm, has been reported. The coenocytichaustoria in Cucurbitaceae (Chopra, 1955; Singh, 1957) and Fabaceae (Rau, 1953),when studied in living materials, show protoplasmic streaming. Dute and Peterson(1992), who studied the endosperm development in soybean, have reported thedevelopment of wall ingrowths in the chalazal endosperm haustorium, providingevidence that the haustorium functions to absorb nutrients from the surroundingnucellar tissue that shows lysis. Johansson and Walles (1993) report wall ingrowthsalong the whole embryo sac boundary in faba bean (Figure 2.12A).The endosperm tissue is unique to angiosperms. It is rich in food materials, andin many plants almost the entire endosperm is absorbed by the developing embryo(Fabaceae and Cucurbitaceae), while in others it is persistent (Poaceae, Solanaceae,Euphorbiaceae, Sesamum, Linum, Malvaceae). However, little is known regardingthe time when the embryo begins to utilize the endosperm for its nutrition. Recentstudies have shown that the endosperm, during the early stages of development,needs adequate nutrients for its growth, and only in late embryogeny does it havea pool of reserve materials, which are utilized for the growth of embryo (Newcomb,1973; Yeung and Clutter, 1978).
26 Histopathology of Seed-Borne InfectionsptzABcaqcbmqEIciii′mnn′FJmciii′mnn′Gii′mciHcotsiCDKLMFIGURE 2.9 Development of endosperm and embryo. A, B, Arachis hypogaea. Embryo sacswith two and several endosperm nuclei (nuclear type). C, D, Sesamum indicum. Ls embryosac to show initial stages in cellular type of endosperm development. E to K, Developmentof embryo in Viola tricolor. Note the bilateral symmetry in cordate embryo (dicotyledon type).L, M, Late stages from the development of embryo in Najas lacerata (monocot) showingdifferentiation of shoot initials on one side and single cotyledon in terminal position. (Abbreviations:cot, cotyledon; pt, pollen tube; si, shoot initials; z, zygote; the rest are the usualabbreviations used for terms that trace embryo development.) (A, B, From Prakash, S. 1960.Phytomorphology 10: 60–64; C, D, From Singh, S.P. 1960. Phytomorphology 10: 65–82; Eto K, Singh, D. 1963. J. Indian Bot. Soc. 42: 448–462; L, M, Redrawn from Swamy, B.G.L.and Krishnanurthy, K.V. 1980. From Flower to Fruit — Embryology of Flowering Plants.Tata McGraw-Hill, New Delhi.)
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 39: 24 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
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Structure of Seeds 75Baker, D.M. an
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Structure of Seeds 77Maheshwari Dev
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Structure of Seeds 79Vries, M.A. de
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82 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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