2.What type of Megagametogenesis is utilized?
3.Describe the Double Fertilization that occurs in the Mature Embryo Sac and Indicate the results of such Fertilization.
1.The production of mature embryo sac or the female gametophyte via the process of the magagametogenesis refers to the unique process of Angiosperm. In this process, the megaspore develops into the embryo sac that is known as the gametophyte (Xi et al., 2014). This is one of the important stage of the life cycle of the vascular plants. The megasporocyte undergoes the meiotic cell division and forms the haploid. Among the four haploids, three die and the remaining one develops megaspore. After the enlargement of the megaspore, the nucleus undergoes mitosis for three times. As a result, eight nuclei are formed and arranged in two rows. The groups of the rows send the nucleus to centre and form the polar nuclei. The microploar becomes the egg and apparatus. This is formed with the egg and the two synergids. This entire structure with the eight nuclei is known as embryo sac (Fellenberg & Vogt, 2015).
2.The functional megaspore can develop the female gametophyte. According to Ao et al., (2016), the improvement of female gametophyte in the angiosperm is endosporous. However, the megasporogenesis has variation and forms four separate megaspore cells that does not develop usually. When the four megaspores develop, it is called the monosporic as it develops from the single megaspores. For example, in the oenothera, the improvement of the megaspore is monosporic. However, only four nuclei form rather than eight nuclei. In this case, the antipodals are eliminated. There is variation in appearance of the gametophytes. For example, Peperomia have only one nucleus and there is no polar nucleus (Augusto et al., 2015).
3.In case of angiosperm, both the zygote and the endosperm are formed via the double fertilization. In such case, one of the sperm fuses with the egg cells and the other fuses with the polar nuclei. In such way the zygote and the endosperm form. In first stage of embryonic development, the zygote is divided in two cells, develops the suspensor, and gives rise to the proembryo (Qu et al., 2015). In second stage, due to the presence of cotyledons, the embryo becomes heart shaped. With the growth of the embryo, it begins to bend to fill the seeds and helps it for the dispersal. The suspensor provides the nutrition to the embryo and helps to grow (Xi et al., 2014).
Augusto, L., De Schrijver, A., Vesterdal, L., Smolander, A., Prescott, C., & Ranger, J. (2015). Influences of evergreen gymnosperm and deciduous angiosperm tree species on the functioning of temperate and boreal forests. Biological Reviews, 90(2), 444-466.
Ao, C. Q., Wang, L. Y., Sun, H., Lin, J. T., Chai, Y., & Chen, C. C. (2016, June). Megasporogenesis and Megagametogenesis in Zephyranthes candida (Amaryllidaceae), with Special Notes on the Behavior of the Synergids, the Central Cell and the Antipodal Cells. In PHYTON-ANNALES REI BOTANICAE (Vol. 56, No. 1, pp. 91-101). WIENER STRASSE 21-23, A-3580 HORN, AUSTRIA: FERDINAND BERGER SOEHNE.
Fellenberg, C., & Vogt, T. (2015). Evolutionarily conserved phenylpropanoid pattern on angiosperm pollen. Trends in plant science, 20(4), 212-218.
Qu, L. J., Li, L., Lan, Z., & Dresselhaus, T. (2015). Peptide signalling during the pollen tube journey and double fertilization. Journal of experimental botany, 66(17), 5139-5150.
Xi, X., Guo, L., Xu, W., Zhang, J., & Li, B. (2014). Megasporogenesis, megagametogenesis, and induction of 2n eggs with colchicine in poplar section Aigeiros. Scandinavian Journal of Forest Research, 29(6), 527-536