Biology Class 11 NCERT Solutions: Chapter 5 Morphology of Flowering Plants Part 4

Download PDF of This Page (Size: 751K)

Q: 10. Describe the various types of placentation’s found in flowering plants.

Answer:

Placentation refers to the arrangement of ovules inside the ovary. It is of five basic types.

(A) Marginal placentation:

The ovary in which the placenta forms a ridge along the ventral suture of the ovary and the ovules develop on two separate rows is known to have marginal placentation. This type of placentation is found in peas.

Q 10 A Image of Marginal Placentation

Q 10 a Image of Marginal Placentation

Q 10 A Image of Marginal Placentation

(B) Parietal placentation

When the ovules develop on the inner walls of the ovary, the ovary is said to have parietal placentation.

Q 10 B Image of Parietal Placentation

Q 10 B Image of Parietal Placentation

Q 10 B Image of Parietal Placentation

(C) Axile placentation:

In axile placentation, the placenta is axial and ovules are attached to it. Examples include China rose, lemon, and tomato.

Q 10 C Image of Axilel Placentation

Q 10 C Image of Axilel Placentation

Q 10 C Image of Axilel Placentation

(D) Basal placentation:

The ovary in which the placenta develops from its base and a single ovule is found attached to the base is said to have basal placentation. It is found in marigold and sunflower.

Q 10 D Image of Basal Placentation

Q 10 D Image of Basal Placentation

Q 10 D Image of Basal Placentation

(E) Free Central Placentation

In free central placentation, the ovules develop on the central axis while the septa are absent. This type of placentation is found in Dianthus and primrose.

Q 10 E Image of Free Central Placentation

Q 10 E Image of Free Central Placentation

Q 10 E Image of Free Central Placentation

Q: 11. What is a flower? Describe the parts of a typical angiosperm flower?

Answer:

A flower can be defined as the reproductive unit of any flowering plant (angiosperms). Flowers carry out sexual reproduction in angiosperms. A typical flower is a modified stem with a condensed axis. A flower has four different parts i.e., the calyx, corolla, androecium, and gynoecium. Androecium and gynoecium represent the male and female reproductive organs of a flower (respectively). Bisexual flowers are those which contain both androecium and gynoecium, while unisexual flowers contain either gynoecium or androecium. The corolla and the calyx are generally distinct, but may sometimes be fused (called perianth). A flower that contains all four floral parts is called a complete flower.

Parts of Flowers

Image shows the Parts of Flowers

Image Shows the Parts of Flowers

Image shows the Parts of Flowers

(A) The calyx: forms the outermost whorl of a flower, which contains sepals. They are green, leaf-like structures that cover and protect the flowers during the bud stage. When the sepals of a flower are free, they are called polysepalous, while fused sepals of a flower are called gamosepalous.

(B) The Corolla: of a flower is a layer that lies inside the calyx. It contains beautifully coloured petals, which help in attracting insects for pollination. When the petals are free, they are called polypetalous, while fused petals are called gamosepalous.

(C) The Corolla: or the stamen is the male reproductive part of a flower. It consists of two parts, the filament, and the bilobed anther. The bilobed anther is the site for meiosis and the generation of pollen grains.

(D) Gynoecium represents the female reproductive part of a flower. It consists of an ovary. The ovary is connected by a long tube (called style) to the stigma. The ovary bears numerous ovules attached to the placenta.