Lesson 4: Air and Ventilation

 

There are three basic reasons why plants need air and/or ventilation:

• photosynthesis - the need for carbon dioxide

• respiration - the need for oxygen

• pollutant removal - the prevention of toxicity and asphyxiation

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Plants use carbon dioxide (CO₂) in the air and return oxygen (O₂) to the air.
The carbon dioxide is an essential requirement for photosynthesis to take place, and the oxygen is a very desirable      by-product of the process, without which our planet would not be inhabitable by us.
Outdoor plants generally have an unlimited amount of carbon dioxide available, which they can readily absorb through their leaves.
Plants that are grown in a confined area with no ventilation can suffer from a lack of carbon dioxide, which can significantly inhibit growth, depending on the degree photosynthesis is hindered.

Source: http://urbanext.illinois.edu/
gpe/case1/c1facts3e.html

Animals and humans need oxygen to burn food in order to grow and sustain themselves. Similarly, plants require oxygen for respiration to burn nutrient sugars that provide the energy for growth and sustenance.

Oxygen enters the plant primarily through leaf (and stem) stomata, but roots also require oxygen. In soil, adequate oxygen is usually available, unless the soil is extremely heavy and/or compacted. However, lack of atmospheric oxygen can be a problem in an enclosed environment.
Again, barring any temperature issues, the solution to the problem is fresh air supplied by appropriate ventilation.

Courtesy of Science Unleashed
www.scienceunleashed.ie

Pollutant Removal

Likely you have heard of "acid rain" causing damage to trees and forests in some parts of the world. Acid rain is really rain water that contacts air pollutants such as sulphur dioxide gases. This forms sulphuric acid that is rained onto plants.

Similarly, ordinary household pollutants can damage plants as follows:

• Household pollutant gases and other air pollutants can combine with water vapours and general atmospheric humidity to form toxic substances harmful to plants.
  

• Dust and smoke particles can settle on plant leaves and clog up leaf openings to hinder the intake of carbon dioxide and/or oxygen gases, thereby essentially asphyxiating (i.e., "choking") a plant. Plant asphyxiation can cause tissue damage on the stem of a plant, which in turn affects the entire plant by weakening its vitality and even causing death.

Once again, the best way to remove such problematic pollutants is by appropriate ventilation of the house or other confined plant area. A gentle cleaning of a plant's leaves can also help significantly.

Washing the leaves of a plant can remove air pollutants that may be clogging up leaf stomata.

Positive Influences of Plants on Air Quality

For confines such as individual rooms without ventilation, plants can contribute significantly to the quality of air within the confined space. Consider the following:

• Plants can help eliminate volatile organic compounds such as benzene, toluene, and xylene. These compounds are removed primarily by soil microorganisms.
  

• Photosynthesis uses up much more carbon dioxide than respiration produces, and respiration uses up less oxygen than photosynthesis produces. The result in a confined area is more oxygen and less carbon dioxide. Carbon dioxide in indoor areas is correlated with lower work performance by humans. Think of this:
  

  • The effect of plants on air quality has been investigated by NASA for use in spacecrafts
    

  • In a classroom of 20 children, there are 20 very efficient pumps (their lungs) that fill the room with carbon dioxide in a short time. Small wonder these children become lethargic! A good supply of plants can help!

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Vertical Forest Buildings

Architect Stefano Boeri came up with the concept of Bosco Verticale, or Vertical Forest, as a way to combine high-density residential development with tree planting in city centres.
The combination of small and large trees, 5,000 shrubs, and 11,000 floral plants will:

•  provide habitats for birds and insects
  
• create a humid micro-climate that produces oxygen
• shade residences from harsh sunlight
• absorb dust in the air, helping to depollute the city