Learn Unit 2: Structural Organisation in Animals and Plants with Top Tutors

Justification of Statement on Underground Parts of Plants: The statement "Underground parts of a plant are not always roots" can be justified based on external features. For example, in plants like ginger and turmeric, the underground parts are actually modified stems known as rhizomes. These rhizomes have nodes, internodes, and buds, which are characteristic of stems, rather than roots. Similarly, in plants like potatoes, the underground part is a modified stem called a tuber. Tubers also possess eyes, which are the dormant buds, indicating their stem origin.

Difference Between Pinnately and Palmately Compound Leaves:

• Pinnately compound leaves have leaflets arranged on both sides of a common central axis, resembling a feather, whereas palmately compound leaves have leaflets arranged like the fingers of a hand, radiating from a common point at the tip of the petiole.
• Example of pinnately compound leaf: Neem (Azadirachta indica)
• Example of palmately compound leaf: Horse chestnut (Aesculus hippocastanum)

Types of Phyllotaxy: Phyllotaxy refers to the arrangement of leaves on the stem. Different types include:

• Alternate phyllotaxy: Leaves are arranged singly at each node, alternating along the stem. Example: Mango (Mangifera indica)
• Opposite phyllotaxy: Leaves are arranged in pairs at each node, opposite each other along the stem. Example: Guava (Psidium guajava)
• Whorled phyllotaxy: Leaves are arranged in groups of three or more at each node. Example: Oleander (Nerium oleander)

Definition of Aestivation and Placentation:

• Aestivation: Aestivation refers to the arrangement of floral parts (sepals, petals, etc.) in a flower bud before it opens. It can be valvate, twisted, imbricate, or vexillary.
• Placentation: Placentation refers to the arrangement of ovules within the ovary of a flower. It can be marginal, axile, parietal, or basal.