\nhotosynthesis is a chemical reaction that is fundamental to life. In this video we are going to have a look at the factors that affect the rate of photosynthesis. There are 3 main factors: light intensity, carbon dioxide concentration...\nhotosynthesis is a chemical reaction that is fundamental to life. In this video we are going to have a look at the factors that affect the rate of photosynthesis. There are 3 main factors: light intensity, carbon dioxide concentration and also temperature. These factors are called limiting factors. Light is essential for photosynthesis, as it provides the energy to split the water and therefore enable carbon dioxide and water to react. No light, no photosynthesis. Increasing the light intensity, increases the rate of photosynthesis… until a point, when the rate is at it’s maximum. In fact, plants spread out their leaves to maximise the amount of light falling on them, and to ensure the lower leaves are not shaded by the ones above. Some woodland plants are known as shade plants because they can photosynthesis more efficiently in dim light than other species. If there is insufficient carbon dioxide in the air, then photosynthesis cannot occur at the maximum rate. Light intensity and carbon dioxide concentration are both obvious limiting factors, as they are both inputs into the reaction. However, just like us, plants are sensitive to temperature too. Too hot and they cannot photosynthesise. Too cold and their productivity slows down to zero. This is because there are enzymes involved in photosynthesis, and so above 40 degrees celsius the enzymes start to denature and so the rate of photosynthesis slows down. And then as it gets colder, the enzymes move around more slowly and hence the rate of reaction drops. Different types of plants have different optimum temperatures for photosynthesis; plants that live in colder climates have an optimum rate at a lower temperature. These are the three main limiting factors, however there are some others such as chlorophyll concentration, water and pollution. Farmers and horticulturists can use the knowledge of these limiting factors to increase crop growth in greenhouses. They can use artificial lights to extend the daylight hours or increase the light intensity, they can increase the concentration of carbon dioxide by burning paraffin lamps, and they can control the temperature inside the greenhouse. Unsurprisingly, many crops such as tomatoes and lettuces give much higher yields when grown in greenhouses. Another fantastic bonus of photosynthesis is that because it needs carbon dioxide, we can pump waste carbon dioxide from our factories straight into greenhouses.\n
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