Post fertilization structures in plants.

endosperm, seed, fruit formation in plants..

1. POST-FERTILISATION : STRUCTURES AND EVENTS Dasari . Sreekanth . M.Sc., NET, TS/AP-SET, ( Ph.D ). Department of Botany, Osmania University, Hyderabd . Email id: [email protected]

2. POST-FERTILISATION : STRUCTURES AND EVENTS PEN  Endosperm (3n) Egg  Zygote (2n) Embryo Ovule  seed Ovary  Friuit .

3. Coconut water: free-nuclear endosperm White kernel: cellular endosperm Endosperm Development PEN Free nuclear divisions cell wall formation Cellular endosperm

4. Embryo Development

5. Embryo Dicot embryo Monocot embryo

6. The Seed

7. Fertilised ovule Non- Albuminous or Albuminous Perisperm : persistent nucellus Seed Dormancy The Seed

8. Seed formation Endospermic & Non-Endospermic Monocots & Dicots

9. Seed Formation The zygote grows repeatedly by mitosis to form an embryo An embryo consists of a plumule (future shoot), a radical (future root) and cotyledons (food stores needed for germination) 3N endosperm nucleus 2N Zygote

10. Endospermic Seed Formation The endosperm nucleus (3N) divides repeatedly to form the endosperm in endospermic seeds. This endosperm acts as a food store for the developing seed e.g. maize 3N endosperm nucleus 2N Zygote

11. Non endospermic Seed Formation In non-endospermic seeds the endosperm is used up in the early stages of seed development so the food is stored in the cotyledons e.g. bean 3N endosperm nucleus 2N Zygote

12. Endosperm Food store for developing embryo Embryo Plumule, radicle, cotyledons Integuments, becomes the seed coat Seed Formation

13. If all the endosperm is absorbed by the developing embryo the seed is a non endospermic seed e.g. broad bean Non endospermic Seed Formation

14. If all the endosperm is not absorbed by the developing embryo the seed is an endospermic seed e.g. Maize Endospermic Seed Formation

15. Seed types and structure Seed embryo Plumule (immature shoot) Radicle (immature root) Cotyledon (food supply or seed leaf) endosperm Food store All seeds In some seeds

16. Endosperm Seed coat (testa) Cotyledon Plumule – will develop into a new shoot Radicle – will develop into a new root Endospermic Seed e.g. Maize

17. Seed coat (testa) Cotyledon Plumule Radicle Non-Endospermic seed e.g. Broad Bean

18. e.g. Broad Bean e.g. Maize Plumule Radicle Cotyledon Endosperm Non–endospermic and Endospermic seed

19. Development of the seed and fruit Dicot embryos develop two cotyledons Monocot embryos develop a single cotyledon Fig. 38.8

20. micropyle –opening in ovule where pollen tube attached, sperm entered hilum –scar where ovule attached to ovary radicle –embryonic root Seedling

21. Part of the Seed Function Embryo Whole dormant immature plant inside the seed Radicle Part of the embryo which will become the roots of the plant after germination Plumule Part of the embryo which will become the shoots (stems, leaves etc.) of the plant after germination Cotyledon This is a “leaf” of the embryo which can be a food reserve (in non-endospermous seeds) or absorb nutrients from the endosperm for growth of the during germination (in endospermous seeds) Testa Protective coating of the seed, formed from the integuments of the ovule. Functions of the Parts of the Seeds

22. more dependable dispersal to new habitats sufficient food reserves The hard seed coat: Protection Variations Seed: Advantages

23. Fruit Formation

24. Fruit Formation The ovule becomes the seed The ovary becomes the fruit

25. Fruit Formation A fruit is a mature ovary that may contain seeds The process of fruit formation is stimulated by growth regulators produced by the seeds

26. Seedless Fruits Can be formed in two ways Genetically Either naturally or by special breeding programmes e.g. seedless oranges

27. Seedless Fruits Growth regulators e.g. Auxins If large amounts of growth regulators are sprayed on flowers fruits may form without fertilisation e.g. seedless grapes

28. 28 How do seedless fruits form? May be a genetic variety and occur naturally e.g. some bananas & cucumbers. Spray flowers with auxin or gibberellin (growth regulators) and fruits form without fertilisation taking place. Gibberellin may also cause bigger fruit to form. Ethene is used to ripen fruit and de-green skins of oranges, lemons and grapefruit .

29. Fleshy fruit/Dry fruit Fruit wall- Pericarp Pericarp - Epicarp , Endocarp, Mesocarp False fruits/True fruits Parthenocarpic fruits: developed without fertilisation Fruits

30. Seed development without fertilisation Diploid egg  Embryo Nucellar cells protrude into the embryo sac and develop into the embryos Polyembryony Apomixis

31. POLYEMBYONY:- It is the phenomenon of formation of more than one embryo during the development of seed. Rao (1965) has found polyembryony to develop during seed germination in vandal caused by cleavage of apical promeristem of single embryo. Polyembryony was discovered by Leeuwenhoek(1719) in case of citrus . Polyembryony is of three types I] Simple- eg . Poa , Casuarinas, Citrus II] Cleavage polyembryony - eg . Pinus , orchids III] Adventitive polyembryony-eg . Citrus, opuntia ,Onion, Mangifera , Trillium,Groundnut .

32. The end POST-FERTILISATION : STRUCTURES AND EVENTS