B8 Xylem and Phloem

IGCSE biology

State the functions of xylem as well as its direction and location

Function: transport of water and mineral ions, and support

Direction: Up and down

Location: Inside

State the functions of phloem as well as its direction and location

Function: transport of sucrose and amino acids

Direction: bidirectional

Location: outside

What are the root hair cells, and how are they adapted?

Specialised extensions of the roots found on the surface of plant roots that have long hair-like structures. They are adapted to absorb water and mineral ions from the soil. They are meant to increase SA for nutrient absorption.

Describe the pathway of water

Root hair cells: water and mineral ions are absorbed

Root cortex: water moves here from the root hair cells

Xylem: water moves from the root cortex into the xylem stem

Leaves: water moves from the xylem to the mesophyll of the leaves, where it is used for photosynthesis

Soil-->root hair cells-->root cortex-->xylem ->mesophyll cells

What is transpiration?

Transpiration is one of the processes that ensures that water used from the Earth is replaced

What two things happen when water reaches the leaves?

1. Evaporation of the surfaces of the spongy mesophyll to form water vapour

2. Loss of water vapour from the leaf by difussion through stomata

What factors affect transpiration?

An increase in temperature results in a higher rate of transpiration

Wind sweeps water vapour from the leaf by diffusion through the stomata

Define translocation

The active transport of organic substances through the plant's phloem tissue from regions of production (sources) to regions of storage or utilization (sinks)

What movement does translocation involve?

The movement of surcrose and amuno aicds through the phloem

What is a source in terms of translocation?

A region of production in a plant

What can a sink be in translocation

A region of storage and one of use in respiration or growth

What does the xylem tissue consist of?

Two hollow tubes

What does the phloem tissue consist of?

Living cells