IGCSE Revision- Biology
Chapter 8- Transport in plants
8.1 Xylem and phloem
PLANT TRANSPORT SYSTEMS
- Plants absorb water through their roots, and this has to be transported to the leaf
- The transport system that does this is made of tissues called xylem
- Phloem tissues transport sucrose and amino acids from the leaves to the rest of
the plant
XYLEM
- A xylem vessel is like a long drainpipe
- It is made of many hollow, dead cells, joined end to end
- The end of the walls have disappeared, so a long, open tube is made
- Xylem vessels contain no cytoplasm or nuclei, so they help keep the plant upright
- Lignin: A hard, strong, waterproof substance that forms the walls of xylem
vessels (advantages on p150)
VASCULAR BUNDLES
- Xylem vessels and phloem tubes are usually found close together
- A group of xylem vessels and phloem tubes is called a vascular bundle
- In a root, vascular tissues is found in the centre
- In a stem, vascular bundles are arranged in a ring near the outside edge
- Vascular bundles are also found in leaves. They help support the leaves, holding
them out flat to capture sunlight
8.2 Transport of water
WATER UPTAKE
- Plants take water from the soil, through their root hairs
- At the very tip of a root hair, there is a protective cap, to protect the root as it
grows through the soil
- The rest of the root is covered with a layer of cells called the epidermis
- The root hairs are formed from some of the cells in the epidermis
- The root hairs starting growing behind the tip
- Each root hair is a long epidermal cell
- Root hairs do not live for very long
- As the root grows, they get damaged by the soil particles, and are replaced by
new ones
- The function of root hairs is to absorb mineral ions and water from the soil
- Water moves into root hair by osmosis
- The cytoplasm and cell sap inside the root hair are quite concentrated solutions.
The water in the soil is usually a more dilute solution. Water therefore diffuses
Chapter 8- Transport in plants
8.1 Xylem and phloem
PLANT TRANSPORT SYSTEMS
- Plants absorb water through their roots, and this has to be transported to the leaf
- The transport system that does this is made of tissues called xylem
- Phloem tissues transport sucrose and amino acids from the leaves to the rest of
the plant
XYLEM
- A xylem vessel is like a long drainpipe
- It is made of many hollow, dead cells, joined end to end
- The end of the walls have disappeared, so a long, open tube is made
- Xylem vessels contain no cytoplasm or nuclei, so they help keep the plant upright
- Lignin: A hard, strong, waterproof substance that forms the walls of xylem
vessels (advantages on p150)
VASCULAR BUNDLES
- Xylem vessels and phloem tubes are usually found close together
- A group of xylem vessels and phloem tubes is called a vascular bundle
- In a root, vascular tissues is found in the centre
- In a stem, vascular bundles are arranged in a ring near the outside edge
- Vascular bundles are also found in leaves. They help support the leaves, holding
them out flat to capture sunlight
8.2 Transport of water
WATER UPTAKE
- Plants take water from the soil, through their root hairs
- At the very tip of a root hair, there is a protective cap, to protect the root as it
grows through the soil
- The rest of the root is covered with a layer of cells called the epidermis
- The root hairs are formed from some of the cells in the epidermis
- The root hairs starting growing behind the tip
- Each root hair is a long epidermal cell
- Root hairs do not live for very long
- As the root grows, they get damaged by the soil particles, and are replaced by
new ones
- The function of root hairs is to absorb mineral ions and water from the soil
- Water moves into root hair by osmosis
- The cytoplasm and cell sap inside the root hair are quite concentrated solutions.
The water in the soil is usually a more dilute solution. Water therefore diffuses
