Question

Explain the terms tenuinucellate and crassinucellate?

Answer 1

Ovule body:

1. The ovule body is made up of parenchymatous tissue which is nutritive in nature called the nucellus.
2. On this basis it is classified into crassinucellate and tenuinucellate.

Crassinucellate:

1. If the layer of the nucellus is thicker inside the ovule it is known as crassinucellate.
2. They have a subhypodermal sporogenous cell layer.
3. They are present in unitegmic ovules like in gymnosperms.
4. This tissue often exists in a single layer.
5. The nucellus is considered well-developed when it appears in numerous layers, and an ovule with such a nucellus is referred to as a crassinucellate ovule.

Tenuinucellate:

1. If the layer of the nucellus is thin inside the ovule it is known as tenuinucellate.
2. They are present in bitegmic ovules like in angiosperms.
3. The sporogenous cell or megaspore mother cell is hypodermal due to the single-layered nucellar epidermis.
4. If the sporogenous cell has a single layer of nucellar tissue surrounding it and is hypodermal, the condition is known as tenuinucellate.
5. Tenuinucellate ovules often have very tiny nucelli.

Source of image: https://i.ytimg.com/vi/xRMltLrWmts/maxresdefault.jpg