Crop Plants: Glasshouses & Polythene Tunnels

Glasshouse

Enclosed structure that controls environmental conditions for crops

Polythene tunnel

Long plastic tunnel used to control temperature and humidity for crops

Controlled environment

Conditions such as temperature, light, CO₂ and humidity are regulated

Increased temperature

Speeds up enzyme activity and photosynthesis

Increased CO₂

Increases rate of photosynthesis and plant growth

Increased light

Allows more photosynthesis, especially in winter

Humidity control

Reduces water loss from leaves

Pest control

Enclosed space reduces pests and diseases

Fertiliser use

Provides minerals for healthy growth

Why are glasshouses warm?

Sunlight enters and is trapped as heat, raising temperature

Why is higher temperature useful?

Speeds up photosynthesis and growth

Why is CO₂ added to glasshouses?

To increase photosynthesis rate

Why is extra light used?

To extend daylight hours and increase photosynthesis

Why is humidity controlled?

Prevents excessive transpiration and wilting

Why do crops grow faster in glasshouses?

Optimal conditions for photosynthesis and enzyme activity

Why are polythene tunnels cheaper?

Made from plastic, easier to build and maintain

What is a disadvantage of polythene tunnels?

Less durable and less controlled than glasshouses

Why are pests reduced in glasshouses?

Enclosed environment prevents entry of insects

Why are fertilisers used?

Replace minerals removed from soil by crop growth