Chapter 5 Embryo

1. Chapter 5 Embryo

3. The Zygote is formed when a Sperm nucleus fuses with the egg nucleus (Syngamy). This will develop into the Diploid Embryo.

4. Stages of growth and development of the embryo.

5. Structure of dicot. seeds.

6. Seeds in a Pod, Arabidopsis sp. (SEM x220).

7. seven、zygote The zygote is a unicellar system which, through a programmed sequence of events, give rise to a multicellar embryo with well-differentiated organ and, as such, embodies within itself the multifarious properties of an adult plant.

8. In angiosperms the zygote is located at the micropylar pole of the embryo sac and presents a characteristic polarized appearance with the micropylar pole vacuolate, while the chalazal pole contains the nucleus and most of its cytoplasm.

9. Eight、Embryogeny 黑穗醋栗精卵融合

12. 黑穗醋栗幼胚 甜菜幼胚

14. 1.The development of embryo in dicot Proembryo the apical cell the basal cell suspensor quadrant octant

15. 荠菜的球形胚 荠菜的心形胚 甜菜的心形胚

16. 荠菜的鱼雷形胚 荠菜的成熟胚

17. 3.The grass embryo Among the monocotyledons, the grasses present some remarkable features in their embryogeny as well as the structure of mature embryo.

18. With in the caryopsis, the mature embryo is placed toward the base on the dorsal side and is relatively small in relation to the endosperm. the scutellum the epiblast the coleorhiza the epidermis leaf primordia shoot apex the coleoptile

19. 1. At 4 wk postpollination flowers. 2. At 8 wk，the pistils begin to swell. 3. At 14 wk，the pistil continued to swell and the spadix became disfigured. 4. At 20 wk. 5. At 24 wk. 6. Zygotic embryo, 4 mm in length, at 24 wk postpollination. Inflorescence of Anthurium after pollination.

20. 7. Week 4 zygote adjacent to a single synergid cell and single-cell-layer nucellus. 8. ovule at week 4. The embryo has undergone a transverse division. 9. Multicellular embryo 6 wk postpollination. 10. Multicellular embryo 8 wk. 11. Chalazal end of 8 wk. 12. embryo 10 wk. 13. embryo 14 wk ，with differentiated shoot apex. 14. Inner and outer integument 14 wk postpollination.

21. 15. embryo 16 wk ~2 mm in length. 16. Shoot apex and leaf primordium in embryo 20 wk. 17. 20 wk. 18. Root apex of embryo 20 wk. 19. Base of embryo with suspensor 20 wk. 20. Starch and protein storage products of the cotyledon and endosperm 20 wk. 21. Calcium oxalate crystal deposits (raphides) in the cotyledon of an embryo 20 wk. 22. Tracheary protoxylem in cotyledon 24 wk.

22. The result of fertilization is the development of the ovule into the seed. By the segmentation of the fertilized egg, now invested by cell-membrane, the embryo-plant arises. A varying number of transverse segment-walls transform it into a pro-embryo.

23. A cellular row of which the cell nearest the micropyle becomes attached to the apex of the embryo-sac, and thus fixes the position of the developing embryo, while the terminal cell is projected into its cavity.

24. In Dicotyledons the shoot of the embryo is wholly derived from the terminal cell of the pro-embryo, from the next cell the root arises, and the remaining ones form the suspensor. In many Monocotyledons the terminal cell forms the cotyledonary portion alone of the shoot of the embryo, its axial part and the root being derived from the adjacent cell.

25. The cotyledon is thus a terminal structure and the apex of the primary stem a lateral one. A condition in marked contrast with that of the Dicotyledons. In some Monocotyledons, however, the cotyledon is not really terminal.

26. The primary root of the embryo in all Angiosperms points towards the micropyle. The developing embryo at the end of the suspensor grows out to a varying extent into the forming endosperm, from which by surface absorption it derives good material for growth.

27. At the same time the suspensor plays a direct part as a carrier of nutrition, and may even develop, where perhaps no endosperm is formed, special absorptive "suspensor roots" which invest the developing embryo, or pass out into the body and coats of the ovule, or even into the placenta.

28. In some cases the embryo or the embryo-sac sends out suckers into the nucellus and ovular integument. As the embryo develops it may absorb all the food material available, and store, either in its cotyledons or in its hypocotyl, what is not immediately required for growth, as reserve-food for use in germination, and by so doing it increases in size until it may fill entirely the embryo-sac.

29. Or its absorptive power at this stage may be limited to what is necessary for growth and it remains of relatively small size, occupying but a small area of the embryo-sac, which is otherwise filled with endosperm in which the reserve-food is stored.

30. There are also intermediate states. The position of the embryo in relation to the endosperm varies, sometimes it is internal, sometimes external, but the significance of this has not yet been established.

31. The early embryo develops into a tubular, three dimensional structure in Monocots and Dicots. Lilium is the model for monocot embryogenesis. Capsella is used for dicots.

32. Both have a Suspensor. Dicots have a suspensor that is a unicellular filament, while Monocots have suspensors which are several cells in width.

33. Early stage in Lily Embryogenesis. note the Nuclei in the periphery of the Endosperm. Cellularization has started but most of the Endosperm is liquid.

34. In both cases, the Suspensor is minute compared to the Embryo. In some plants, like coconut palm the embryo is very small and is surrounded with a large endosperm. Coconut Milk is liquid endosperm and the "meat" is solid endosperm. The endosperm is consumed during seed germination.

35. Nine、Suspensor

36. The fuction of suspensor： 1. Transfer the nutrition to embryo from the tissue around it； 2．Combine and excrete the incretion.