Sexual Reproduction in Flowering Plants — NEET UG practice

Autogamy is self-pollination within the same flower, so the pollen genetically matches the plant it lands on — no new genetic variation is introduced.

Cleistogamous flowers never even open, forcing autogamy, which again means no genetically different pollen is involved.

Geitonogamy is the transfer of pollen from one flower to another flower on the same plant; since both flowers belong to the same plant, the pollen is still genetically identical to the recipient.

Xenogamy is the transfer of pollen from the anther of one plant to the stigma of a genetically different plant of the same species, so it is the only type that actually brings in genetically different pollen.

Hence, the answer is Option B: Xenogamy.

A typical angiosperm anther is bilobed, meaning it is made up of two lobes joined together by a connective.

Each of these two lobes contains two theca, so each lobe is described as being dithecous.

Hence, the answer is Option B: 2.

Microsporogenesis is the process by which haploid microspores are formed from a diploid pollen mother cell through meiosis, and it happens inside the anther in a fixed order of stages.

The process begins with the sporogenous tissue present inside each microsporangium, which is the tissue that eventually gives rise to pollen.

Cells of the sporogenous tissue differentiate into pollen mother cells (PMC), which are the cells that will actually undergo meiosis.

Each PMC then undergoes meiotic division to form a group of four haploid cells called microspore tetrads.

Finally, the microspores of the tetrad separate and mature into individual pollen grains.

So the correct developmental order is: $\text{Sporogenous tissue (B)} \rightarrow \text{Pollen mother cell (D)} \rightarrow \text{Microspore tetrads (A)} \rightarrow \text{Pollen grains (C)}$

Hence, the answer is Option B: B, D, A, C.