Life Processes — Part 3: Transport in plants and excretion: visual lesson, CBSE Class 10 Science

Lesson

Transport in plants and excretion

Part 3 — how water climbs to the top of a tall tree, how food travels around a plant, and how kidneys clean our blood.

In this lesson you will

Explain the transport of water by xylem (transpiration pull) and of food by phloem (translocation)
Describe the structure and function of the nephron
Explain the principle of dialysis
List ways in which plants get rid of wastes

Concept

Two transport tissues in plants

Plants have two conducting tissues. Xylem carries water and minerals from the roots upwards. Phloem carries food made in the leaves to all parts. Plants need less energy than animals, so their transport systems can be slower.

Table comparing xylem and phloem by what they carry, direction, driving force and cells
	Xylem	Phloem
Carries	Water and dissolved minerals	Food (mainly sucrose), amino acids and other substances
Direction	Upwards, from roots to leaves	Up or down, to wherever it is needed
Driving force	Mainly transpiration pull; root pressure	Uses energy from ATP
Cells	Vessels and tracheids	Sieve tubes and companion cells

Diagram

Water up, food everywhere

Blue arrow: xylem (upwards). Green arrow: phloem (food moves to wherever it is needed, up or down).

Water and minerals enter the root hairs and rise through xylem. Phloem carries food from the leaves to storage organs and growing parts. Water is lost from the leaves as vapour: transpiration.

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