TRANSPORT IN PLANTS

Why do plants need transport systems?

Exchange of substances

Why do small organisms rely on diffusion?

They have a high surface area to volume (SA:V) ratio, so diffusion distances are short.

Why is diffusion insufficient for large plants?

Low SA:V ratio + long distances = diffusion too slow to meet metabolic demands.

How do plants adapt to increase SA:V ratio?

Branching body shape, flat/thin leaves, root hairs.

What is mass transport in plants?

The bulk movement of substances, maintaining diffusion gradients at exchange sites.

What are the two transport systems in plants?

xylem and phloem

Why don't plants need a transport system for gases?

High SA:V ratio allows gas diffusion; chloroplasts produce O₂ and use CO₂.

What are the functions of xylem?

Transports water & minerals, provides structural support, stores food.

Where is xylem located in vascular bundles?

roots (centre), stems (inside vascular bundles), leaves (upper sides of bundles)

What does phloem transport?

Sucrose and other nutrients from source (e.g., leaves) to sink (e.g., roots).

What are the main components of phloem?

Sieve tube elements (transport), companion cells (support), parenchyma (storage), fibres (strength).

Where is phloem located in vascular bundles?

roots (edges of the centre core), stems (outside vascular bundle), leaves (lower side of bundles)