Morphology of Flowering Plants's Question 29 | Biology XI | NCERT Exemplar Questions

Botany

The Living World Biological Classification Plant Kingdom Morphology of Flowering Plants

Zoology

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How can you differentiate between free central and axile placentation?

Explanation

Placentation is the arrangement of ovules on the walls of ovary with the help of special kind of tissue called placenta. Plants show different types of placentation, central and axile are among them.

They have the following differences

Free Central Placentation	Axile Placentation
Ovary contains only one chambers the placenta bearing. The ovules are borne on the central axis and less free inside the ovary. The septa are absent.	Ovary is syncarpous and multi-carpellary, i.e., contain many chambers. Placenta arise from the central axis where the septa fuse to form axile column to which ovules are attached.

Tendrils are found in the following plants. Identify whether they are stem tendrils of leaf tendrils.

(a) Cucumber (b) Peas (c) Pumpkins (d) Grapevine (e) Watermelon

Explanation

(a) Cucumber (Cucums sativus), have stem tendril from axillary bud.

(b) Peas (Pisum sativum) leaf gets modified into tendril for climbing.

(d) Grape wine (Vitis), stem tendril from axillary bud.

(e) Water melon (Citrullus lanatus), stem tendril from axillary bud.

Why is maize grain usually called as a fruit and not a seed?

Explanation

The maize grain is usually known as fruit because it is infact a ripend ovary which contains a ripened ovule, e.g., a single seed. This fruit is known as caryopsis in which the pericarp is fused with the seed coat. The maize grain occurs attached to a thick cob or peduncle.

Tendrils of grapevines are homologous to the tendril of pumpkins, but are analogous to that of pea. Justify the above statement.

Explanation

Homologous Organs are organs that have similar origin but they differ functionally. Axillary bud of stem gives rise to tendril of both grapevine and pumpkins so they have same origin, i.e., homologous, whereas analogous organs are organs having different origin, but perform same function. The tendril of pea arises from the leaf and helps the plant to climb. Hence, the origin of pea tendril is different but, its function is similar to the tendrils of grapevines.

Rhizome of ginger is like the roots of other plants that grows underground. Despite this fact ginger is a stem and not a root. Justify.

Explanation

Rhizome of Ginger is a type of underground modification of stem which grows horizontally underground and bear nodes, internodes and scaly leaves and buds, which gives rise to aerial shoots. The adventitious root arises from the lower surface of nodes. It is not a root because root does not have nodes and internodes. Further the rhizome donot perform the function of roots, i.e., anchorage and absorption, rather serves as resevoir for storage of food. All these characteristics support the fact that ginger is a stem and not a root.

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