Bachelor’s Degree Programme (BSCG) – Plant Anatomy and Embryology Assig. Answer | BBYCT – 135 (Q-7)
7. a) Describe the structure of a mature embryo sac with the help of a well labelled diagram.
b) Trichomes play important role in plants, Justify the statement.
a) The typically mature embryo sac of an angiosperm consists of two ends that are the chalazal end and another one is the micropylar end. At the micropylar end, there are two cells called synergids cells with an egg apparatus.
The two synergid cells contain filiform apparatus like element which helps in guiding the pollen tubes entry in the embryo sac during the event of fertilization. It also helps to stimulate the division and another function of filiform is to produce lots of nectar and also to identify the pollen at the very stage of stigma. Filiform also helps in the transfer absorption of the nutrients from the Nucellus into the embryo sac. In the chalazal end, there is a presence of three antipodal cells. When we see at the middle portion that means the between of the two ends there is a presence of two polar nuclei.
The function of these two polar nuclei is to fuse, which will happen before the fertilization and form the diploid secondary nucleus. So eight nuclei are being present in seven cells that’s why the embryo sac is called 7 celled and eight nucleated.