नमस्कार मित्रांनो इयत्ता बारावी Biology या Subject च्या Practical मध्ये PART - B: Demonstration Experiments (Spotting) हा भाग Practical Exam च्या दृष्टीने फार महत्त्वाचा आहे. या Blog Post मध्ये आपण Spotting Practical Number 5: Study of V.S. of anatropus ovule through a permanent slide/relevant chart ह्या Practical Experiment चे Answer पाहणार आहोत. खाली दिलेल्या उत्तरांमध्ये काही अडचण असल्यास आम्हाला comment करा किंवा तुमच्या संबंधीत विषय शिक्षकांशी चर्चा करा.
B. DEMONSTRATION EXPERIMENTS (Spotting)
5. Study of V.S. of anatropus ovule through a permanent slide/relevant chart.
Ovule (megasporangium) is enclosed in the ovary. There may be one or many ovules in an ovary.
Aim :- Study of anatropous ovule and functions of its various parts.
• The ovule in which micropyle, chalaza and funicle are not in one straight line and integuments run parallel to funicle is called as anatropus ovule. It is also called as inverted ovule and is the most common type of ovule, in angiosperms.
• The ovule shows two main parts as: - body and funicle.
• The body shows two integuments originating from base of ovule reaching-up to the tip of ovule. The tip shows a small a cleft, left by two integuments called as micropyle.
• The integuments enclose a mass of fertile, parenchymotous, diploid cells called nucellus. There is only one fertile cell located more or less in the centre of nucellus but towards micropylar end of ovule this is called megaspore mother cell. It finally develops into only one female gametophyte (embryo sac).
• In monosporic Embryo sac, the female gametophyte.) It is 8-nucleated and 7-celled structure.
• Female gametophyte consists of egg apparatus, 2-polar nuclei and 3-antipodal cells.
• The egg apparatus is located closer to the micropylar end of embryo see. It consists of central haploid egg cell and 2 supporting laterally placed haploid synergids.
• In mature female gametophyte, the 2 polar nuclei fuse to form the diploid secondary nucleus (definitive nucleus).
Figure :-
Sketch Figure :-
Comment on the special features of anatropus ovule and embryo sac :
1. The anatropous ovule is characterized by its micropyle being directed toward the stalk, making it the most common type of ovule in angiosperms.
2. The ovule consists of two main parts: the stalk, known as the funicle, and the body. In an anatropous ovule, the funicle is largely attached to the ovule's body, forming a ridge called the raphe.
3. The point where the funicle attaches to the ovule's body is known as the hilum.
4. The ovule body comprises several components: the nucellus, chalaza, integuments, micropyle, and the embryo sac.
5. The body of the ovule is covered by two integuments, which originate from the base of the ovule and do not completely encase the nucellus, leaving a small opening at the tip known as the micropyle.
6. The nucellus serves as the megasporangium of the ovule.
Questions
1. What is ovule?
Ans :- The ovule is a structure in seed plants that contains the female reproductive cells. After fertilization, it develops into a seed.
2. Enlist the functions of the micropyle prior to fertilization and after fertilization in the ovule of angiosperms.
Ans :- The micropyle is a small opening at the apex of the ovule in angiosperms. Prior to fertilization, it allows the entry of the pollen tube for the delivery of sperm cells. After fertilization, the micropyle facilitates the diffusion of respiratory gases necessary for the developing embryo.
3. What is the double fertilization?
Ans :- Double fertilization is a complex mechanism in angiosperms involving two male gametes. One sperm cell fertilizes the egg cell to form a diploid zygote, while the other sperm cell fuses with two polar nuclei to create a triploid endosperm, which provides nourishment to the developing embryo.
4. Give functions of:
a. Integuments
Are protective coverings of the ovule that enclose the nucellus.
b. Nucellus
Nucellus protects the embryo & also provides nourishment to the embryo.
c. Funicle
funicle attaches the ovule to the placenta.
d. Synergid cells
Fill form apparatus of synergid cell guide the pollen tube towards the egg.
e. Antipodal cells
Antipodal cells help in the nutrition of the endosperm.
5. Distinguish between female and male gametophytes in angiosperms.
Ans :-
*PDF Link - Click Me :) or Click on Download Button Below:
