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photosynthesis in greenhouses

The unique process of Photosynthesis

Life on earth (in form that we know it) would be impossible without the process of photosynthesis. It is responsible for the oxygen we breath and food we eat. Also, most of the materials we use and the fossil fuels we consume are the result of photosynthesis.

Photosynthesis is the process by which green plants transform light energy into chemical energy. In photosynthesis, light energy is captured and used to convert water, carbon dioxide and minerals into oxygen and sugars.

Photosynthesis and greenhouse cultivation

The very concept of greenhouse cultivation is based on stimulating and controlling growth of plants. As crop growth is dependent of photosynthesis, we generally strive to achieve increased photosynthesis in greenhouses. By creating the ideal circumstances for the crops to grow, and thus for photosynthesis to occur, production and quality can be increased. Because light is a key ingredient for the photosynthesis, greenhouses are designed in such a way that light interception is as low as possible. All technical installations also influence photosynthesis in one way or the other. This can be supplementing on limiting factors (mostly light & CO2) or controlling the rate of photosynthesis with the greenhouse temperature and available light.

Ingredients for photosynthesis

One of the materials a plant needs for it to grow is sugar. Sugar is created by the plant itself through the process of photosynthesis. For this to occur, the plant needs carbon dioxide, water and light as ingredients.

Through small openings (stomata) on the surface of (primarily) the bottom of the leaves, carbon dioxide is able to enter the plant cells. In these plant cells, there are green pigment cells called chlorophyll. It is in these cells that a reaction takes place between carbon dioxide (CO2) and water (H2O), under influence of light. The product of this reaction is a sugar (C6H12O6) and oxygen (O2). This very reaction is what we call photosynthesis.

CO2 + H2O + Light  →  C6H12O6 + O2

In order for the photosynthesis to occur, light is needed. The light provides the energy required to combine CO2 and water into sugars. A larger photosynthesis activity allows a plant to grow faster as more new cells can me made. The process of photosynthesis can be influenced by temperature, light and CO2. In the simplified chemical equation, water is also mentioned. The water is not sourced through the air, but from water of the plant cells. With a proper irrigation system in the greenhouse, the quantity of water supply won’t be of any influence on the photosynthesis process.

Usage of the sugars

The sugars created through photosynthesis are used for two purposes. The first is as a construction agent for new plant cells. Sugars are used in another way for respiration. In this process, sugar serves as fuel.

Construction agent

The sugars are mainly created in the green parts of the leaves. From the leaves, the sugars are transported to the growing-points, where new cells are formed. Sugars are used as raw-material for the construction of plant cells.
After really sunny days, the plant has created so much sugars, that in the night the creation of cells can continue. With a high photosynthesis-rate, the sugar concentration in the leaves increases, which slows down the creation of new sugars. Plants are then able to store the excessive sugar in the form of starch. At a later moment, the starch can be turned back to sugar and can still be used.

Respiration

Like humans, plants are living organisms which implicates that plants breathe. This breathing /respiration of a plant burns sugars. For the creation of these sugars, light energy was needed, with respiration this energy is released again. This energy is used for all living processes of the plant. The respiration takes place throughout the plant, even in the roots to take in water. With respiration the photosynthesis process occurs in reversed order.