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

Modification of root refers to the alteration in the structure of a root from its typical form to perform specialized functions beyond anchorage and absorption. These functions can include food storage, mechanical support, or aeration.

The types of root modifications found in the given examples are:

1. Banyan tree: The Banyan tree (Ficus benghalensis) exhibits prop roots. These are adventitious roots that grow downwards from the branches, providing massive pillar-like support to the tree's extensive structure.
2. Turnip: The Turnip (Brassica rapa) shows storage roots. The primary taproot becomes swollen and fleshy due to the accumulation of stored food, aiding in the plant's survival during unfavorable conditions. Other examples include carrots and radishes.
3. Mangrove trees: Mangrove plants, which grow in saline, waterlogged, and poorly aerated soils, develop pneumatophores. These are specialized roots that grow vertically upwards, emerging from the soil surface to facilitate gaseous exchange (absorption of oxygen) for the submerged root system.

1. Underground parts of a plant are not always roots: While many underground plant parts are roots, some are modified stems or leaves. For instance:
   • Rhizomes: Underground stems like those found in ginger and banana are swollen with stored food and exhibit nodes and internodes.
   • Corms: Underground stems like in Colocasia and Elephant foot yam are condensed, vertical stems storing food.
   • Tubers: The swollen tips of underground stems, such as in potatoes, store food and bear 'eyes' which are axillary buds.
   • Bulbs: Modified leaves storing food, like in onions.
   • Geocarpy: In groundnuts, the pedicel elongates after fertilization and pushes the ovary into the soil for fruit and seed development.
2. A flower is a modified shoot: A flower originates from a shoot apical meristem. During the transition to flowering, the shoot apical meristem transforms into a floral meristem. The stem axis (which is typically elongated in a shoot) becomes condensed, with internodes shortening. Instead of leaves, various floral appendages (sepals, petals, stamens, carpels) arise in a specific sequence from the nodes. This structural transformation clearly indicates that a flower is a highly specialized, condensed, and modified shoot, adapted for reproduction.

The difference between pinnately compound and palmately compound leaves lies in the arrangement and attachment of their leaflets:

Phyllotaxy refers to the specific pattern of arrangement of leaves on the stem or branch of a plant. This arrangement is crucial for maximizing sunlight exposure for photosynthesis. There are three main types of phyllotaxy:

1. Alternate Phyllotaxy: In this type, a single leaf arises at each node, and the leaves are arranged alternately along the stem. This is the most common type. Examples include Sunflower (Helianthus annuus), Mustard (Brassica species), and Peepal (Ficus religiosa).
2. Opposite Phyllotaxy: Here, two leaves arise at each node, positioned opposite to each other on the stem. Examples include Guava (Psidium guajava) and Jamun (Syzygium cumini).
3. Whorled Phyllotaxy: In this arrangement, three or more leaves arise from a single node, forming a whorl around the stem. This type is less common. An example is Alstonia (Alstonia scholaris).