SRM - 1 - Vascular System in Plants

Vascular system in plants consists of complex interconnected tissues, known as vascular tissues, essential for water transportation.
This system allows water to move upward against gravity through two main types of tissues: xylem and phloem.

Origin of the term: Derived from the Greek word ‘xylon’ meaning 'wood'; introduced by Swiss botanist Carl Nageli in 1838.
Function: Transports water and dissolved minerals from roots to the rest of the plant in a unidirectional manner (bottom to top).
Cells involved:
- Tracheary elements: Main components including tracheids (less specialized, water moves through pits) and xylem vessels (conduct water with minimal obstruction).
- Tracheids: Dead cells with thin perforated walls allowing water movement.
- Xylem vessels: Also dead cells, designed for efficient water transport through perforations (pits).
- Xylem fibres: Non-living support cells situated between tracheids and vessels.
- Xylem parenchyma: Living, thin-walled cells involved in storage of nutrients.

Primary Xylem: Arises from dividing cells at growing root and shoot tips.
Secondary Xylem: Forms as plants increase in girth, contributing to the woody structure.
Older xylem cells die, creating a supportive skeleton; only the external layers contribute to water conduction.
Heartwood: Inner part of the trunk composed of dead primary xylem; tree age can be determined by counting annual rings of xylem.

Origin of the term: Derived from the Greek word “phloos” meaning 'bark'; also introduced by Carl Nageli in 1838.
Function: Responsible for the conduction of organic food synthesized in leaves to all parts of the plant, with bidirectional flow (leaves to other parts and vice versa).
Cells involved:
- Sieve tubes: Specialized cells forming the main conduits for nutrient transport.
- Companion cells: Assist sieve tubes in transport function and support.
- Phloem parenchyma: Living cells involved in storage and transfer of nutrients.
- Phloem fibres: Provide structural support to the phloem tissue.

Composed of interconnected tissues termed vascular tissues, aiding water transport against gravity.

Derived from Greek "xylon," meaning wood; named by Swiss botanist Carl Nageli in 1838.
Function: Transports water and minerals from roots upward, in a unidirectional manner.
Composed of specialized water-conducting cells known as tracheary elements, including tracheids and xylem vessels.
Tracheids: Dead, less specialized cells that facilitate water movement through pits in cell walls.
Xylem Vessels: Main cells for water conduction in angiosperms, also dead, allowing unobstructed water flow through perforations (pits).
Additional components of xylem include:
- Xylem Fibres: Non-living support cells located between tracheids and vessels.
- Xylem Parenchyma: Living, thin-walled cells that store substances.

Begins with primary xylem from actively dividing cells at root and shoot tips.
Secondary xylem forms in woody plants, developing as the plant grows in girth, encasing primary xylem.
As primary xylem cells die, they form a supportive skeleton, with only older secondary xylem conducting water.
Heartwood consists of dead primary xylem, while the age of a tree can be determined by counting annual xylem rings.

Originates from Greek "phloos," meaning bark; also named by Carl Nageli in 1838.
Function: Conducts organic food from leaves to other plant parts, with bidirectional flow.
Composed of specialized cells, including:
- Sieve Tubes: Main conduits for food transport.
- Companion Cells: Assist sieve tubes in function.
- Phloem Parenchyma: Store substances.
- Phloem Fibres: Provide structural support.