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

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Reproductive Structures and Seed Formation 15AngBCpgDEFIGURE 2.5 SEM photographs of ovary surface of Cassia occidentalis. A, Ovary surfaceshowing trichomes. B, Same showing stomata and trichomes. C, Cup-shaped glands on ovarysurface having thick cuticle around globular head. D, Stomata magnified, guard cells witharching cuticular rim. E, Trichomes with pollen grains having reticulate exine. (Abbreviations:ng, nectary gland; pg, pollen grain; st, stomata.) (From Sharangpani, P.R. and Shirke, D.R.1996. Phytomorphology 46: 277–281.)2.3.2.2 StyleThe sterile part of the carpel between the stigma and ovary constitutes the style.Single and free carpels usually have one style, while in syncarpous gynoecia, thestyle may be united or partly or completely free. The style forms the pathway forpollen tubes to reach placentae and ovules. It has a specialized tissue that provides
16 Histopathology of Seed-Borne Infectionsnutrients to the pollen tube and permits it to reach the destination. Arber (1937)called this tissue the transmitting tissue. Based on its distribution, the styles areclassified as hollow and solid. The hollow style, which is common in monocotyledons,is characterized by the presence of a stylar canal, lined entirely or in longitudinalstrips by glandular transmitting tissue. In Lilium longiflorum, the cells of thetransmitting tissue are rich in organelles and contain abundant multivesicular bodies(Rosen and Thomas, 1970; Dashek, Thomas, and Rosen, 1971).The solid styles lack stylar canal and show one or more strands of transmittingtissue, leading to the placentae of ovary. The cells of the transmitting tissue areelongated, rich in cytoplasm, and possess intercellular spaces. The pollen tubes passthrough the intercellular spaces, which, as reported in Lycopersicon, possess aviscous fluid (Cresti et al., 1976). A solid style is common in dicotyledons.A third type of style, half-closed, has been reported in some members of Cactaceae(Hanf, 1935) and Artabotrys (Rao and Gupta, 1951). In these plants the styleis hollow, and the transmitting tissue develops only on one side of the stylar canal.In addition to the transmitting tissue, the style consists of parenchyma withvascular supply. The epidermis may have stomata and is covered by the cuticle.2.3.2.3 StigmaThe distal part of the carpel, having special features to facilitate pollen reception,germination, and penetration of the pollen tube into the closed carpel, is called thestigma. The stigmatic surface is generally papillate or hairy and rarely smooth. InPoaceae and other wind-pollinated plants, the stigmatic surface develops into longbranched hairs. According to Konar and Linskens (1966a), the stigma in Petuniacomprises two zones — an upper secretory zone of epidermis and the lower storagezone. The epidermal cells are covered with the cuticle. Mattson et al. (1974) observedthe presence of an extracuticular proteinaceous layer (pellicle) on the stigma papillaeof many angiosperms. The pellicle remains intact in fresh stigma, but forms cracksand fissures on older stigma through which the cuticle can be seen after stainingwith benzpyrene and observing with a fluorescent microscope.The stigma secretes the stigmatic fluid, which in Petunia consists of oil, sugars,and amino acids (Konar and Linskens, 1966b). The protein contents of the stigmaticexudate are specific recognition factors that interact with proteins released from thepollen. In case of acceptance or compatible reaction, the pollen germinates, forminga tube, which penetrates the cuticle of the stigma, whereas rejection is indicated bythe failure of pollen to germinate. Heslop-Harrison et al. (1975) using fluorochromaticand immunofluorescence methods have concluded that the stigma pellicle isthe site of recognition responses. In compatible reactions, the ejected pollen proteinsbind very quickly to the pellicle, and it is in the binding zone that erosion of thecuticle takes place to facilitate pollen tube entry. In Raphanus (Dickinson and Lewis,1973) and Iberis (Heslop-Harrison, Knox, and Heslop-Harrison, 1974), the rejectionreaction is signified by the deposition of callose in both the pollen tube and thestigma papillae within 4 to 6 hours of pollination. Dickinson and Lewis (1975)observed that in Raphanus the incompatible pollen tubes may penetrate the papillarwall through enzymatic action, but soon after penetration a lenticular callose reaction
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: 14 Histopathology of Seed-Borne Inf
Page 33 and 34: 18 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
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Structure of Seeds 65stystypmerA Bc
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Structure of Seeds 67epsent endCADB
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Structure of Seeds 69perhscendembpe
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Structure of Seeds 71eposgepi′epo
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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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