Crop Plants: Glasshouses & Polythene Tunnels (Edexcel IGCSE Biology)

Crop Plants: Glasshouses & Polythene Tunnels

Limiting factors and the growth of crop plants

• The knowledge about limiting factors and how they affect the rate of photosynthesis can be used by farmers to improve crop yields 

• Growing crops outside does not allow farmers to control any of these factors

• Glasshouses and polythene tunnels provide an enclosed environment in which farmers can, to some extent, control the climate inside and increase their crop yields

Glasshouses

• In a glasshouse, several conditions can be manipulated to increase the rate of photosynthesis, including:

  • Artificial heating (enzymes controlling photosynthesis can work faster at slightly higher temperatures - only used in temperate countries such as the UK)

  • Artificial lighting (plants can photosynthesise for longer)

  • Increasing carbon dioxide content of the air inside (plants can photosynthesise quicker)

  • Regular watering

• When considering the use of glasshouses and manipulating conditions like this, farmers need to balance the extra cost of providing heating, lighting and carbon dioxide against the increased income

• In tropical countries where temperatures are much hotter, glasshouses may still be used to control other conditions however they may need to be ventilated to release hot air and avoid temperatures rising too high, which could cause the denaturation of the enzymes controlling the photosynthesis reaction

Polythene tunnels

• More commonly called polytunnels, these are large plastic tunnels that cover crops

• They can protect crops grown outside from the effects of the weather, including excessive wind, rain and extreme temperatures

• They also increase the temperature slightly inside the tunnel

• They can prevent the entry of pests that can damage plants or diseases that can kill plants