Wednesday, 8 February 2012

5.1 Glasshouses and Polythene Tunnels

Describe how glasshouses and polythene tunnels can be used to increase the yield of certain crops.

Glasshouses (a.k.a. greenhouses) are basically a small house but all surfaces are made out of glass - allowing light to penetrate through to the interior of the glasshouse.

First of all, we start with solar radiation, and that is our initial source of energy, in the form of light. The light is able to penetrate through the glass to the internal surfaces. The next feature is that the light is absorbed by surfaces inside the glasshouse, which could be soil, plants etc. These surfaces will then re-emit this energy as heat which warms the hair, raising its average kinetic energy (temperature increases).

  • The warm air which is raising the temperature is trapped and eventually all parts in the glasshouse will be warm, this warm air makes the enzyme reaction speed nearer the optimum temperature, therefore reacting faster and producing more products. 
  • As well as this, glasshouses provide shelter for the plants inside, which allow plants to survive through climatic hazards such as strong storms and winds, allowing plants to be able to mature and be harvested.
  • Since plants are in an enclosed area in the glasshouse, they are most likely to be immune to diseases and pests outside the area which protects the plant and allows it to grow. 
  • Additionally, glasshouses provide a constant temperature all year round which means a constant production which is particularly true in high altitude areas.
  • Glasshouses also prevent a loss of water vapour through transpiration which prevents the plants from drying out.
  • Plants also avoid frost damage, especially seedlings, in the spring.
  • Glasshouses are often warmed by the burning of fossil fuels, this leads to an increase in the carbon dioxide levels in the glasshouse which means more product from photosynthesis.
  • In glasshouses, through incomplete combustion, ethene may form as the product which can help stimulate fruit ripening, particularly with the tomato.

The polythene tunnels, usually a framework with polythene over the surface which also allows light to penetrate through to the interior. Even though, both polythene tunnels and greenhouses provide warm temperature for the growth of plants, polythene tunnels provide less shelter for the plants and may be less effective which may have an effect of the output. Polythene tunnels are more common in developing countries than developed countries because of the cheaper costs but sometimes is more preferred because it is more adjustable and movable.


  1. D. so impressed with your recent work. This is the type of effort that will bring success.

  2. omg ,, thanks to you i think i may get a good grade in biology!! :D

  3. not bad, not bad

  4. Thank you for doing our classwork for us with exactly the same question, word for word. We are very grateful and love you.