Morphology of Flowering Plants

Study Notes

The Root

Roots are cylindrical, underground structures essential for plant stability and nutrient absorption.
They exhibit positive geotropism (growing downwards) and negative phototropism (avoiding light).
There are three types of root systems:
Tap root system: Consists of a primary root that grows deep into the soil, with lateral roots of various orders (e.g., carrots, turnips).
Fibrous root system: Characteristic of monocots, where the primary root is short-lived and replaced by numerous fine fibrous roots (e.g., wheat).
Adventitious root system: Roots that develop from parts of the plant other than the radicle, such as grass and banyan trees.

Main Functions of Roots

Absorb water and minerals from the soil for plant nutrition.
Anchor the plant firmly in place.
Store reserve food materials.
Synthesize plant hormones to regulate growth.

Regions of the Root

Root cap: A multicellular structure protecting the root tip as it penetrates the soil.
Region of meristematic activity: Contains actively dividing cells for root growth.
Region of elongation: Responsible for the increase in root length through cell elongation.
Region of maturation: Cells differentiate into various tissue types; root hairs form here to enhance absorption surface area.

Modifications of Roots

Roots can undergo modifications for specific functions:
Storage roots: Enlarged primary tap roots or adventitious roots for food storage (e.g., carrots, sweet potatoes).
Respiratory roots: Pneumatophores, which emerge above ground to absorb oxygen, typically in swampy areas (e.g., mangroves).
Prop roots: Arise above ground from stems for structural support (e.g., banyan tree).
Stilt roots: Support the plant from lower nodes, growing obliquely into the soil (e.g., sugarcane).

The Stem

The stem is the aerial part of the plant that supports leaves, flowers, and fruits and plays a critical role in nutrient transport.
Functions of the stem include:
Support for leaves and flowers.
Transportation of water and minerals from roots to other plant parts.
Distribution of food manufactured in leaves.

Modifications of Stems

Stems can adapt through various modifications:
Underground stems: Such as rhizomes for food storage and vegetative propagation (e.g., ginger).
Tuber: The swollen end of an underground stem for food storage (e.g., potato).
Corm: A vertical swollen stem that stores food (e.g., gladiolus).
Bulb: A reduced stem with fleshy leaves for food storage (e.g., onion).
Stem tendrils: Modified axillary buds that support climbing (e.g., grapevine).
Stem thorns: Modified axillary buds that protect the plant from herbivory (e.g., citrus).

Sub-aerial Modifications of Stems

Offsets: Lateral branches of aquatic plants that grow aerially and root when touching the ground (e.g., Pistia).
Suckers: Lateral branches that emerge from the main stem below ground and grow upwards (e.g., banana).
Runners: Long, prostrate branches that root at nodes (e.g., grasses).
Stolons: Slender branches that grow horizontally and arch down to touch the soil (e.g., mint).

Aerial Stem Modifications

Phylloclade: Flattened or cylindrical stems that perform photosynthesis in arid environments (e.g., Opuntia).
Cladode: Modified stems resembling leaves for photosynthesis (e.g., asparagus).

Important Terminologies

Terminal bud: Bud located at the tip of the stem.
Axillary bud: Bud located in the axil formed by leaf and stem.

These notes encapsulate the morphology of flowering plants' roots and stems while highlighting their key features, functions, and modifications adapted to various environmental conditions.

Description

Explore the fascinating morphology of roots in flowering plants. This quiz covers various aspects of root systems, their characteristics, and classifications. Test your knowledge on the main root and lateral branches as well as their growth patterns.