Sexual Reproduction In Flowering Plants

Step 1: Location.
Microsporangia are pollen sacs present in the anther of a flower. Each anther has four microsporangia.
Step 2: Structure.
1. Wall layers (from outside to inside):
- Epidermis
- Endothecium
- Middle layers
- Tapetum (nourishes pollen grains)
2. Inside → Microspore mother cells (diploid) undergo meiosis.
3. They form haploid microspores, which develop into pollen grains.
Step 3: Conclusion.
Thus, microsporangium is the pollen sac that produces pollen grains through meiosis of microspore mother cells.

Step 1: Definition.
Double fertilization is a unique feature of angiosperms in which two fusions occur inside the embryo sac.
Step 2: Process.
1. One male gamete fuses with the egg cell → forms diploid zygote (syngamy).
2. Second male gamete fuses with two polar nuclei → forms triploid primary endosperm nucleus (PEN).
Step 3: Significance.
- Zygote develops into embryo.
- PEN develops into endosperm, which nourishes the embryo.
Step 4: Conclusion.
Double fertilization ensures formation of both embryo and nutritive endosperm in angiosperms.

Autogamy.
Autogamy is a form of self-fertilization in which an organism fertilizes its own eggs with its own sperm. It is common in certain plants and hermaphroditic animals. For example:
1. Plants: Some plants are capable of self-pollination, where the pollen from a flower fertilizes the same flower or another flower of the same plant.
2. Hermaphroditic Animals: Certain animals, like earthworms, can mate with themselves, as they possess both male and female reproductive organs.
Conclusion.
Implantation is a vital process in pregnancy, ensuring the embryo receives nutrients from the mother.

Step 1: Structure of grass seed.
Grass seeds (monocot seeds) have a single cotyledon called the scutellum.
Step 2: Function.
Scutellum helps in absorption of nutrients from the endosperm during germination.
Step 3: Conclusion.
Hence, scutellum in grass seeds is the cotyledon.

Step 1: Structure of egg apparatus.
The egg apparatus in embryo sac consists of one egg cell and two synergids, along with filiform apparatus present in synergids.
Step 2: Antipodal cells.
Antipodal cells are present at the chalazal end of the embryo sac and are not part of the egg apparatus.
Step 3: Conclusion.
Therefore, the part not associated with egg apparatus is Antipodal cells.

Step 1: Male gametophyte development.
The pollen grain (microspore) has two cells: the vegetative cell and the generative cell.
Step 2: Division of generative cell.
The generative cell undergoes mitotic division to form two male gametes (sperms), which take part in double fertilization.
Step 3: Conclusion.
Thus, the cell that divides to form two male gametes is the Generative cell.

Step 1: Vegetative propagation in plants.
Vegetative propagation involves formation of new plants from vegetative parts like stems, roots, and leaves. Structures such as offset, bulb, and rhizome are examples.
Step 2: Special case of gemmules.
Gemmules are internal buds found in sponges (Porifera), not plants. They help in asexual reproduction in animals, not vegetative propagation in plants.
Step 3: Conclusion.
Thus, gemmules are not responsible for vegetative propagation of plants.

Step 1: Structure of microsporangium.
A microsporangium has 4 wall layers: Epidermis, Endothecium, Middle layers, and Tapetum. These surround pollen mother cells.
Step 2: Understanding micropyle.
Micropyle is a small opening in the ovule, not a part of microsporangium.
Step 3: Conclusion.
Therefore, the part not belonging to microsporangium is Micropyle.