Morphology of Plants | General Awareness for SSC CGL PDF Download

Introduction

• The complex bodies of multicellular plants and animals perform specific functions through the coordination of different cell groups.
• These cells organize into tissues, tissue systems, organs, organ systems, and ultimately form the entire organism.
• Morphology is the branch of biology that studies the form and structure of organisms, including their external features.
• For plants, this includes structures like roots, stems, and leaves.

Root Morphology

• The primary root originates from the radicle of the embryo and develops secondary and tertiary roots from its sides, forming a tap root system.
• In monocots, numerous roots arise from the lower stem, known as the fibrous root system.
• Some plants, such as Monstera, grasses, and banyan trees, develop roots from parts other than the radicle, referred to as adventitious roots.

Root Modifications

• Some roots produce suckers from adventitious buds, which grow into aerial shoots capable of independent existence and help in plant propagation.
• Certain flowering plants act as parasites on other plants by producing haustoria, which penetrate the host's tissues and connect with its vascular system.

Morphology of Stem

• The stem is the ascending part of the plant that develops from the plumule of the embryo.
• Underground Modifications: Underground stems store food and become thick and tuberous, e.g., stem tubers like potatoes, bulbs like onions, corms like gladiolus, and rhizomes like ginger.
• Sub-aerial Modifications: These modifications occur above ground but are not fully developed, e.g., runners in gram, stolons in mint, offsets in water hyacinth, and suckers in roses.
• Aerial Modifications: These modifications are entirely above ground, e.g., stem tendrils in grapes, stem thorns in lemons, phylloclades in cacti, and bulbils in Ruscus.

Morphology of Leaves

• Leaves are flat structures attached to the stem at nodes, where axillary buds may develop into new branches. They originate from the shoot apical meristem and are arranged in acropetal order.
• A leaf consists of the leaf base, petiole, and lamina. Small leaf-like structures called stipules are present at the base.
• The arrangement of veins and veinlets in a leaf, known as venation, can be either reticulate (branched) or parallel.
• Leaves can be simple (with a full lamina) or compound (with leaflets instead of a full lamina).

Morphology of Flower

• A flower is essentially a modified shoot.
• Its arrangement on the floral axis is called inflorescence, which can be racemose (where the main axis continues to grow) or cymose (where the main axis terminates in a flower).

Fruit and Seed

• A fruit is a ripened ovary that develops after fertilization and consists of the pericarp, which can be dry or fleshy.
• Seeds are matureovules that develop post-fertilization. Depending on the number of cotyledons in the seed's embryo, seeds can be dicotyledonous (with two cotyledons) or monocotyledonous (with one cotyledon).