Plant Transport Systems

Study Notes

Overview

Plant transport systems are responsible for the movement of water, minerals, and sugars throughout the plant.
There are two main types of transport systems in plants: xylem and phloem.

Function: transports water and minerals from roots to leaves.
Components:
- Tracheids: dead, hollow cells that form the xylem vessel.
- Vessel elements: living cells that form the xylem vessel.
- Xylem parenchyma: living cells that store water and minerals.
Transport Mechanism:
- Root pressure: pushes water into the xylem vessel.
- Transpiration pull: pulls water up the xylem vessel due to evaporation from leaves.
- Cohesion-tension theory: water molecules stick together, creating a continuous column.

Function: transports sugars and amino acids produced by photosynthesis from leaves to rest of the plant.
Components:
- Sieve cells: living cells that form the phloem vessel.
- Companion cells: living cells that provide energy for transport.
- Phloem parenchyma: living cells that store sugars and amino acids.
Transport Mechanism:
- Active transport: sugars and amino acids are loaded into phloem vessel using energy from companion cells.
- Mass flow: sugars and amino acids are transported down a concentration gradient.

Transpiration Stream: the flow of water from roots to leaves through the xylem.
Source-Sink Relationship: the relationship between the source of sugars (leaves) and the sink (rest of the plant) in phloem transport.
Apoplast-Symplast Transport: the movement of substances across the plant cell membrane and cell wall.

Xylem transports water and minerals from roots to leaves.
Components of xylem include tracheids, vessel elements, and xylem parenchyma.
Tracheids are dead, hollow cells that form the xylem vessel.
Vessel elements are living cells that form the xylem vessel.
Xylem parenchyma are living cells that store water and minerals.
Root pressure pushes water into the xylem vessel.
Transpiration pull pulls water up the xylem vessel due to evaporation from leaves.
Cohesion-tension theory explains how water molecules stick together, creating a continuous column.

Phloem transports sugars and amino acids produced by photosynthesis from leaves to the rest of the plant.
Components of phloem include sieve cells, companion cells, and phloem parenchyma.
Sieve cells are living cells that form the phloem vessel.
Companion cells provide energy for transport.
Phloem parenchyma are living cells that store sugars and amino acids.
Active transport loads sugars and amino acids into phloem vessel using energy from companion cells.
Mass flow transports sugars and amino acids down a concentration gradient.

Transpiration stream is the flow of water from roots to leaves through the xylem.
Source-sink relationship refers to the relationship between the source of sugars (leaves) and the sink (rest of the plant) in phloem transport.
Apoplast-symplast transport refers to the movement of substances across the plant cell membrane and cell wall.