Morphology of Flowering Plants's Question 23 | Biology XI | NCERT Exemplar Questions

Botany

The Living World Biological Classification Plant Kingdom Morphology of Flowering Plants

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Draw diagrams of a typical monocot and dicot leaves to show their venation pattern.

Explanation

Venation is the pattern of distribution of veins and veinlets in the lamina of leaf. It's pattern is different in monocot and dicot leaf.

Monocot leaf	Dicot leaf
The veins run parallel to each other within a lamina. It is called parallel venation. Parallel venation, e.g., grasses, wheat, maize, etc., (usually found in monocots).	Veins and veinlets form a network in the lamina. It is called reticulate venation. Reticulate venation, e.g., Hibiscus, bean, pear etc., (usually found in dicots).

A typical angiosperm flower consists of four floral parts. Give the names of the floral parts and their arrangements sequentially.

Explanation

The four floral parts of typical angiospermic flower are

Calyx It is the outermost whorl of the flower and members are called calyx or sepals. These are usually green and are protective in function (in bud stage).

Corolla It is composed of petals, usually bright coloured to attract insects for pollination.

Androecium It is composed of stamens, the male reproductive organ. Each stamen has stalk or filament and anther (containing pollen sac and pollen grains).

Gynoecium It is the female reproductive part and made up of one or more carpels. Each carpel has stigma, style and ovary.

Given below are a few floral formulae of some well known plants. Draw floral diagrams from these formulae.

(i) $\oplus \quad \mathrm{K}_{(5)} \mathrm{C}_{(5)} \quad \mathrm{A}_5 \mathrm{G}_\underline{(2)}$

(ii) $\mathrm{K}_{(5)} \mathrm{C}_{1+2+2} \mathrm{~A}_{(9)+1} \mathrm{G}_\underline{1}$

(iii) $\oplus \mathrm{K}_5 \mathrm{C}_5 \quad \mathrm{~A}_{5+5} \mathrm{G}_{(5)}$

Explanation

(i) Floral Formula $\oplus \quad \mathrm{K}_{(5)} \mathrm{C}_{(5)} \quad \mathrm{A}_5 \quad \mathrm{G}_\underline{(2)}$ represents flowers of Solanaceae family.

(ii) Floral Formula $\% \quad K_{(5)} C_{1+2+2} \quad A_{(9)+1} \quad G_\underline{1}$ represents flowers of Fabaceae family.

(iii) Floral Formula $\oplus \underset{+}{\bigodot} \mathrm{K}_5 \mathrm{C}_5 \quad \mathrm{~A}_{5+5} \quad \mathrm{G}_{\underline{(5)}}$ represents flowers of Malvaceae family.

Reticulate venation is found in dicot leaves while in monocot leaves venation is of parallel type. Biology being a 'Science of exceptions', find out any exception to this generalisation.

Explanation

Reticulate venation is a characteristic of dicots and parallel venation is of monocots. But few exceptions are also seen in this generalisation parallel venation is also found in dicot plants, e.g., Calophyllum, corymbium, etc., and reticulate venation is also found in monocot plants such Alocasia, Smilax, etc.

You have heard about several insectivorous plants that feed on insects. Nepenthes or the pitcher plant is one such example, which usually grows in shallow water or in marsh lands. What part of the plant is modified into a pitcher? How does this modification help the plant for food even though it can photosynthesise like any other green plant?

Explanation

In insectivorous plant, e,g., Nepenthes, the leaf lamina gets modified in the form of pitcher and anterior part of petiole coils like tendril which keeps the pitcher in a vertical direction. Posterior part of the petiole remains flattened like a leaf. The apex of lamina forms a lid. Pitcher contains digestive enzyme which digest the trapped insects.

All these modifications and adaptation are developed to make up the nitrogen deficiency in the plant because these plants are found in $\mathrm{N}_2$ deficient soil, (marshy/swamp soils)

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