Basic Plant Physiology (Continued)

Respiration in Plants

Carbohydrates produced through photosynthesis are used to store energy.  When these carbohydrates are used by the plant as food, it produces energy necessary to build plant tissue and for plant growth. The process whereby these carbohydrates (sugars and starches) produced during photosynthesis are broken down to produce energy is called oxidation.  During this process, the sugar combines with oxygen to produce carbon dioxide, water, and heat.  When oxidation occurs in the controlled environment of a living cell, it is called respiration.

Respiration results from a series of complex reactions regulated by enzymes.  During the reactions, the stored complex carbohydrates are broken down into simply carbohydrates, carbon dioxide, water, and energy.  The energy produced can be used in many other cell processes and functions.

Respiration occurs all the time in living tissue, even in parts of the plant that have been removed such as during harvest.  This makes storage conditions important for harvested fruits and vegetables. 

The rate at which respiration occurs is dependent primarily on the temperature, but also on the availability of oxygen and carbohydrates.  This rate of respiration doubles every 18° F rise in temperature between 40° and 96° F. 

So, photosynthesis occurs only in sunlight within plant cells that contain chloroplasts.  It uses carbon dioxide and water to produce carbohydrates which get stored for energy.  It releases oxygen as a byproduct.  Respiration is essentially the reverse of photosynthesis.  Respiration occurs 24x7 in all plant cells.  It uses oxygen to break down the stored complex carbohydrates into simple carbohydrates.  It produces carbon dioxide and water and releases energy.