The outermost and innermost wall layers of microsporangium in an anther are respectively: (a) Endothecium and

NCERT Exemplar · Q5

Q. The outermost and innermost wall layers of microsporangium in an anther are respectively:

(a) Endothecium and tapetum

(b) Epidermis and endodermis

(d) Epidermis and tapetum

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Concept understanding — Male And Female Gametophyte

Let’s start with something you already know. Think of a plant like a mango tree. It produces flowers, and those flowers eventually turn into mangoes. How does that happen? The flower is the plant’s reproductive organ, and inside it, two tiny but crucial structures are made: the male gametophyte and the female gametophyte. These are not the “male” and “female” parts of the flower themselves (like the stamen and pistil) — they are the microscopic, single-generation cells that actually carry the genetic material to form the next plant.

The everyday intuition

Imagine you are baking a cake. The male gametophyte is like the packet of dry yeast — it’s small, mobile, and needs to be added to the mixture. The female gametophyte is like the bowl of flour, eggs, and sugar — it’s larger, stationary, and provides the environment where the yeast works. Without the yeast reaching the bowl, no cake rises. Without the bowl, the yeast has nothing to act on. In a flower, the male gametophyte (pollen grain) must travel to the female gametophyte (embryo sac) for fertilisation to happen.

The precise meaning

In NCERT biology, the male gametophyte is the pollen grain. It develops inside the anther (the top part of the stamen). A mature pollen grain contains two cells: a tube cell and a generative cell. The tube cell will grow a long tube down the style of the pistil, and the generative cell will divide to form two sperm cells. So the male gametophyte is not the whole stamen — it’s the tiny, single-celled (or two-celled) structure that carries the male genetic material.

The female gametophyte is the embryo sac. It develops inside the ovule, which is located in the ovary of the pistil. The embryo sac is a seven-celled, eight-nucleate structure (though you don’t need to memorise numbers for a prose subject — just know it’s a small, organised sac). It contains the egg cell (the female gamete) and other cells that help in fertilisation and nourishment. The female gametophyte is not the whole pistil — it’s the microscopic sac inside the ovule.

Important

The male gametophyte (pollen grain) is haploid — it has only one set of chromosomes. The female gametophyte (embryo sac) is also haploid. When they fuse during fertilisation, they form a diploid zygote, which grows into the seed. This is why both are called “gametophytes” — they produce gametes (sperm and egg).

Why it matters …

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The microsporangium in an anther is surrounded by four distinct wall layers, with the epidermis forming the outermost boundary and the tapetum being the innermost layer.

To understand the structure of the microsporangium, we first need to place it within the context of the anther, which is the fertile part of the stamen responsible for producing pollen. A typical anther is bilobed, and each lobe contains two microsporangia, making it dithecous. These microsporangia are the sites where microspores, which develop into pollen grains, are formed.

A transverse section of a mature anther reveals that each microsporangium is surrounded by a protective and nutritive wall, which is crucial for the development of pollen. This wall is composed of four distinct layers, arranged concentrically from the outside inwards:

Epidermis: This is the outermost layer of the microsporangium wall. It is a single layer of cells that provides overall protection to the developing anther. Its primary role is to safeguard the internal tissues from mechanical injury and desiccation.
Endothecium: Lying just beneath the epidermis, the endothecium is typically a single layer of radially elongated cells. A characteristic feature of these cells is the presence of fibrous thickenings, usually made of alpha-cellulose, on their inner and radial walls. These thickenings are hygroscopic, meaning they can absorb and release water. This property is vital for the dehiscence (splitting open) of the anther, which allows for the release of pollen grains.
Middle Layers: These layers are situated below the endothecium. There are usually two to three layers of cells that are relatively thin-walled. These layers are generally ephemeral, meaning they often degenerate or get crushed as the anther matures, contributing to the space available for pollen development. Along with the epidermis and endothecium, the middle layers also contribute to the protective function of the anther wall. …

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Q.The outermost and innermost wall layers of microsporangium in an anther are respectively:

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