Friday, July 3, 2020

Morphology of Flowering Plants - Notes | Class 11 | Part 1: The Root

5. MORPHOLOGY OF FLOWERING PLANTS


Morphology is the study of external forms of organisms.

A flowering plant (Angiosperm) has 2 parts: 
  • Root system (underground part) 
  • Shoot system (portion above the ground).

THE ROOT

It is the underground part formed from radicle of embryo.


Root systems are 3 types:
  • Tap root system: It consists of primary roots (tap root) and its branches (lateral roots such as secondary roots, tertiary roots). Seen in dicots. Primary root is elongated from radicle. E.g. Mustard plant.
  • Fibrous root system: In monocots, primary root is short lived and is replaced by many roots. They originate from the base of stem to form fibrous root system. E.g. Wheat.
  • Adventitious root system: Roots that arise from parts other than radicle. E.g. Grass, Monstera and banyan tree.
Regions of the Root


  • Root cap: It is the covering at the apex of root. It protects the tender apex of the root.
  • Region of meristematic activity: Seen above the root cap. Here, the cells are very small, thin-walled and with dense protoplasm. They divide repeatedly.
  • Region of elongation: Region just above the meristematic region. Here, cells undergo rapid elongation and enlargement. Helps in growth of the root in length.
  • Region of maturation: It is proximal to elongation zone. Here, the cells differentiate and mature.
  • Root hairs: Very fine, delicate, thread-like structures formed from epidermal cells in region behind region of elongation. They absorb water and minerals from the soil.

Modifications of Root

In some plants, roots are modified to perform functions other than absorption and conduction. E.g.

  • Swollen roots for food storage: E.g. Tap roots of carrot, turnips and adventitious roots of sweet potato.
  • Prop roots: Hanging structures that support banyan tree.
  • Stilt roots: The supporting roots coming out of the lower nodes of the stem. E.g. maize & sugarcane.
  • Pneumatophores: The roots that come out of the ground and grow vertically upwards to get oxygen for respiration. E.g. Rhizophora growing in swampy areas.

Functions of root

  • Absorption of water and minerals from the soil.
  • Provide a proper anchorage to the plant parts.
  • Storage of reserve food material.
  • Synthesis of plant growth regulators.

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