January, 2020

• 11 January

  Identification Of Ascomycetes: The Sac Fungi

  In the kingdom Fungi, there are two major phyla- Ascomycota and Basidiomycota. These two together form a subkingdom of fungi named as Dikarya. They together were named such as members of both phyla maintain most part of their life cycle in dikaryotic stage meaning each cell contains two genetically different …

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• 11 January

  Experimental Embryology: Bringing Embryology Under Human Control

  

  Modern embryology seems to comprise three main disciplines. The first, or descriptive embryology, is a study of the various developmental processes that take place in a plant from the initiation of the sex organs to the maturation of the embryo. The second, or phylogenetic embryology, attempts to evaluate these data …

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• 10 January

  Polyembryony: Multiple Embryos in a Seed

  

  The phenomenon of polyembryony, i.e., the occurrence of more than one embryo in a seed, has attracted much attention ever since its initial discovery in the orange (Citrus sinensis) by Leeuwenhoek (1719). Ernst (1918) and Schnarf (1929), who have reviewed the older literature, classify it into two types—”true” and “false”—depending …

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• 10 January

  Apomixis: A Subistitution for Sexual Reproduction

  

  Apomixis maybe defined (Winkler, 1908, 1934) as the substitution for sexual reproduction (amphimixis) of an asexual process which does not involve any nuclear fusion. For the sake of convenience it may be subdivided into four classes. Non-recurrent apomixis Recurrent apomixis Adventive embryony Vegetative propagation Non-recurrent apomixis In the first, or …

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• 7 January

  Steps of Fertilization

  

  Fertilization is the union of male and female gametes to produce a zygote. There are several steps of fertilization. They are described below. Germination of Pollen. The course of the pollen tube. Entry of pollen tube into the ovule. Entry of pollen tube into the embryo sac. Gametic fusion. Germination …

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• 7 January

  Female Gametophyte: The Embryo Sac with Its Types

  

  The angiosperm female gametophyte is critical for plant reproduction. It contains the egg cell and central cell that become fertilized and gives rise to the embryo and endosperm of the seed, respectively. Female gametophyte development begins early in ovule development with the formation of a diploid megaspore mother cell that …

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• 7 January

  Nemec Phenomenon: Embryo Sac Like Pollen Grain

  

  In 1898, Nemec noted that in the petaloid anthers of Hyacinthus orientalis, the pollen grains sometimes form large eight-nucleate structures showing a surprising resemblance to embryo sacs. He believed that they arose as the result of a degeneration of the generative nucleus and three divisions of the vegetative nucleus of …

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• 7 January

  Discovery about the Male, Female Gametophytes & Syngamy

  

  Among early students of the development of pollen, Hofmeister (1848) presented some surprisingly good illustrations of the process of tetrad formation (microspore tetrad), and Reichenbach, Hartig and several other workers noted the presence of two nuclei in whole mounts of the mature pollen grains of several angiosperms. Discovery of nature …

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• 7 January

  Pollen Tube Discovery by G. B. Amici

  

  A pollen tube is a tubular structure produced by the male gametophyte (pollen grain) of seed plants when it germinates at the top of the stigma. It’s elongation is an integral stage in the plant life cycle as it brings the sperm nuclei towards the ovule and causes to happen fertilization. …

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• 6 January

  Biosystematics: Steps and Categories

  

  The steps in the biosystematic investigation are as follows A sampling of taxon and its population and cytological study of the chromosome of many populations within geographical races, species, and genera; differences in chromosome number, morphology, and behavior of meiosis indicated genetic differences. Determination of the ability of the different …

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