polyembryony.pdf
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This document discusses polyembryony, the occurrence of multiple embryos in a single seed. It begins by classifying polyembryony into true and false types. True polyembryony results from cleavage or adventive embryos developing within the embryo sac, while false polyembryony stems from aposporic embryo sac development. Embryos can also originate from synergids, antipodals, endosperm or cells outside the embryo sac. The causes of polyembryony are debated but may involve necrohormone signaling or hybridization effects. Polyembryony has several uses for plant breeding, horticulture, and propagation of fruit trees to provide disease-free and genetically uniform seedlings.
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3) Fertilization occurs through double fertilization - one sperm fuses with the egg to form a zygote and another with polar nuclei to form endosperm, providing nutrition for the developing embryo.
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Seed and fruit development involve complex processes including double fertilization, embryo and endosperm development, and fruit ripening. Seed abortion can occur due to failures in fertilization, endosperm, or embryo development. It reduces yields in many crops. Fruit abortion is influenced by environmental and genetic factors and plant hormones. It results from embryo or fruit abscission and diminishes wild blueberry yields despite high initial fruit set. Understanding the causes of seed and fruit abortion can help improve crop productivity and yields.
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This document summarizes the process of sexual reproduction in flowering plants. It discusses sporogenesis, gametogenesis, pollination, fertilization, and embryogenesis. Specifically, it describes:
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3. The process of pollination whereby pollen grains are transferred to the stigma and pollen tubes carry sperm cells to fertilize egg and polar cells
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This presentation provides an overview of sexual reproduction in flowering plants. It discusses the structures and processes involved, including the formation of male and female gametes in flowers. Key events covered are microsporogenesis and megasporogenesis, which produce pollen grains and embryo sacs respectively. The role of pollination and double fertilization in seed formation is also summarized. The development of the embryo and seed from fertilization through maturation is outlined.
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This document discusses triploid production through endosperm culture and somatic embryogenesis. It defines endosperm culture as the in vitro development of isolated mature or immature endosperm tissue to obtain triploid plantlets. Two types of endosperm culture are described: mature and immature. The key steps and factors affecting endosperm culture are outlined. Somatic embryogenesis is defined as the development of embryos from somatic cells in vitro. The document compares somatic and zygotic embryos and describes the two routes of somatic embryogenesis: direct and indirect. The stages of somatic embryogenesis and factors influencing the process are summarized.
Endosperm culture and somatic embryogenesis
This document discusses triploid production through endosperm culture and somatic embryogenesis. It defines endosperm culture as the in vitro development of isolated mature or immature endosperm tissue to obtain triploid plantlets. Two types of endosperm culture are described: mature and immature. The key steps and factors affecting endosperm culture are outlined. Somatic embryogenesis is defined as the development of embryos from somatic cells in vitro. The document compares somatic and zygotic embryos and describes the two routes of somatic embryogenesis: direct and indirect. The stages of somatic embryogenesis and factors influencing the process are summarized.
Embryonic and post-embryonic development in insects :its structure, functions...
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Dinesh apomixis presentation
1. Apomixis is a mode of asexual reproduction where the embryo develops without fertilization, allowing exact genetic copies of the mother plant.
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Different modes of reproduction of fungi and reproductive structure and nutri...
The document discusses different modes of reproduction in fungi including vegetative, asexual, and sexual reproduction. Vegetative reproduction occurs through fission, budding, fragmentation, or sclerotia formation. Asexual reproduction involves the formation of spores such as sporangiospores, oidia, chlamydospores, or conidia. Sexual reproduction involves plasmogamy, karyogamy, and meiosis, resulting in spores like ascospores or basidiospores. Fungi obtain nutrition through saprotrophic, parasitic, or symbiotic means.
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reproduction in organism
The document discusses different modes of reproduction in organisms, including asexual and sexual reproduction. Asexual reproduction involves reproduction by a single parent and produces offspring that are genetically identical clones. Common forms of asexual reproduction include binary fission, budding, fragmentation, sporulation, and vegetative reproduction. Sexual reproduction involves two parents and produces offspring with genetic variation. The life cycle of sexually reproducing organisms includes juvenile, reproductive, and senescent phases. Key events in sexual reproduction are pre-fertilization, fertilization, and post-fertilization.
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polyembryony.pdf
- 2. CONTENTS :- Introduction Classification Origin Causes of polyembryony Importance of polyembryony
- 3. embryo in Introduction :- The occurrence of more than one the seed is known as polyembryony. This phenomenon was initially discovered by Leeuwenhoek (1719). Polyembryony is quite common among conifers both this (Gymnosperms).but many species of dicotyledons and monocotyledons exhibits phenomenon.
- 4. Classification :- • Ernst and schnarf classified the polyembryony into two types. : 1. True polyembryony 2. False polyembryony • True polyembryony may be subdivided into two types. : a) Cleavage polyembryony b) Adventive polyembryony
- 5. 1. True polyembryony :- The production of embryos within or by projecting into a single embryo sac is termedtrue polyembryony.
- 6. a) Cleavage polyembryony :- Where the embryos arise within an embryo sac either by a cleavage of the egg or from the synergids antipodals or endosperms.
- 7. b) Adventives polyembryony :- lieing Where the embryos arise from the tissue outside the embryos sac.
- 8. 2. False polyembryony :- This type includes the cases in which more embryos are formed as result two or of the development of the aposporic embryo sac. nucellus The cells of the but generally they come or the integuments to lie within the embryo sac.
- 9. Origin of embryo from synergids or antipodal cells :- The embryos may also be produced from other parts of the embryo sac such as synergids and antipodal cells.
- 10. In most cases the synergids become egg like to form the embryos with or without fertilization. Production of embryos from antipodal cell is rare.
- 11. Origin of embryos from endosperms :- Treub (1898) in balanophora, Woodworth in Alnus and others have reported the embryos developed from endosperm. Embryo develops normally from the egg. Origin of embryos from cell outside embryo sac :- • The embryos also develop from the cells of the nucellus and integument. • Ex – Citrus , Mangifera
- 12. Origin of embryos from other embryo sac in the ovule :- Sometimes the polyembryony occurs due to the presence of multiple embryo sac within the ovule. They may arise from : 1. The derivatives of the same megaspore mothercell. 2. From two or more megaspore mothercell. 3. From nucellar cells.
- 13. Causes of polyembryony :- Many theories have been proposed to explain the occurence of polyembryony by different workers different times. Some of the important theories are as follows : A) Necrohormone theory : • This theory indicates that the degenerating cells of the nucellus act as source of stimulus for the adjacent cells to divide and form adventive embryos.
- 14. B) Hybridization theory : According to this theory the occurrence of multiple embryo is due to hybridization. The recombination of genes takes place during the process of hybridization, forming a single unit that gives rise to the multiple embryos.
- 15. Importance of polyembryony : Plant breeding and horticulture. embryos are supposed to be free from of the fruit tree, such as citrus and Nucellar disease. Propagation mango. The application of adventive embryos is also important for providing genetically uniform seedlings in fruit trees. Can be used for the development of homozygous diploid. Artificial production of these embryos from the eggs or synergids.
- 16. References :- A Text Book Of Botany - Embryology Of Angiosperms By :- B P Pandey
- 17. Thank you …