Sexual Reproduction in Flowering Plants

Tapetum

Step 1: The microsporangium wall has four layers — epidermis, endothecium, middle layers, and tapetum. Step 2: The tapetum is the innermost wall layer and it plays a very important role. Step 3: It nourishes the developing pollen grains. Tapetal cells have dense cytoplasm and often more than one nucleus, which supports their nutritive function. Step 4: Epidermis, endothecium, and middle layers mainly provide protection and help in anther dehiscence (opening). Step 5: So, tapetum is the nutritive layer — this is an important exam point.

Microsporogenesis

Step 1: The pollen mother cell (PMC) undergoes meiosis to produce microspores. Step 2: This process of forming microspores from PMC through meiosis is called microsporogenesis. Step 3: Megasporogenesis, on the other hand, is the formation of megaspores from the megaspore mother cell (MMC) — this happens in the ovule, not the anther. Step 4: The result of microsporogenesis is a microspore tetrad — a cluster of 4 microspores. Step 5: Each microspore then matures into a pollen grain (male gametophyte). So, microsporogenesis is the correct term.

Primary Endosperm Nucleus

Step 1: Double fertilisation is a unique feature of angiosperms and involves two fusion events. Step 2: First fusion (Syngamy): One male gamete fuses with the egg cell → produces a diploid zygote → develops into embryo. Step 3: Second fusion (Triple fusion): The second male gamete fuses with the two polar nuclei in the central cell → produces a triploid Primary Endosperm Nucleus (PEN). Step 4: The PEN is triploid (3n) because it results from the fusion of 3 haploid nuclei. Step 5: The central cell after triple fusion becomes the Primary Endosperm Cell (PEC) and eventually develops into the end

Vallisneria

Step 1: Pollination by water is called hydrophily and it is quite rare in flowering plants, limited to about 30 genera. Step 2: Vallisneria is a freshwater plant where the female flowers reach the surface of water through a long stalk, and male flowers or pollen grains are released on the water surface. Step 3: Pollen grains are carried by water currents and reach the female flowers. Step 4: Maize is pollinated by wind (anemophily) — you can see the feathery stigma (tassels) that trap airborne pollen. Step 5: Rose and sunflower are insect-pollinated (entomophily). So Vallisneria is the correct