How to Control the Climate in your Hydroponics Grow Room...
...And Why You Really Should Bother.
Despite what the marketing departments of manufacturers of nutrients tell us, the real key to spectacular growth and abundant yields lies in control of the environmental factors within your grow room.
You see, to a plant, photosynthesis is what it's all about. It's how a plant feeds, and for this to proceed at pace the temperature and humidity must be absolutely spot on at all times.
The key to maximising growth and therefore maximising yield is to:
Achieve and sustain the maximum rate of photosynthesis.
But what exactly is Photosynthesis?
Photosynthesis (photo - light, synthesis - generate) is a special reaction that occurs within many plant cells. It takes place in miniature 'biological factories' called chloroplasts that are found in great abundance within leaf 'palisade cells' and is what causes them to appear green in colour (red and blue wavelengths are absorbed).
Photosynthesis is the reaction that's responsible for plants ability to convert light (energy) into sugar (energy store). To proceed at its maximum rate the cell needs to be supplied with a constant, uninterrupted supply of light, water and Carbon Dioxide; as well as many macro and micro nutrients.
You may be wondering what all this has to do with the climate inside your grow room or tent. Everything as it turns out. The byproducts, waste products from the plants perspective, from photosynthesis are Water and Oxygen. These must both be able to escape the leaf surface in order to make space for the next reaction. When this isn't possible the reaction essentially stops. So what can prevent the water and oxygen molecules escaping? It's all down to special structures in the leaf surface called stomata (little mouths).
The process of water molecules escaping the leaf surface is called transpiration and it's this that is controlled by the opening and closing of the stomata.
Unlike animals, plants are essentially stationary. They cannot run away to escape unfavourable conditions such as being eaten by a predator or too hot or cold conditions. Instead they have to react to these conditions in other ways. In the case of temperature and humidity changes the plant deals with suboptimal conditions by opening and closing it's stomata in order to increase or decrease the transpiration rate.
Transpiration is a passive process in essence, being driven by evaporation. As the temperature increases so the evaporation rate does. The only means the plant has over this evaporation rate is to open or close it's stomata, although this is also passively controlled by temperature. Luckily, evaporation requires energy, so when a molecule of water evaporates from the surface of a leaf it takes energy from the plant in the form of heat. This loss of heat translates to a cooling effect on the plant.
So, when the temperature rises, the plants stomata open encouraging the loss of water and the cooling of the plant. A Negative feedback loop entails, the more water evaporates, the cooler the plant gets which then causes the stomata to close again reducing the transpiration rate to normal.
When transpiration rates are too low, photosynthesis slows considerably. When they are too high, transpiration accelerates to its maximum rate, above which the plant is powerless to compensate for higher temperatures and big problems start to appear.
To the indoor gardener, these issues will appear to be nutrient burn. This is because the plant is drawing water up through it's roots as fast as it can to satisfy the demand for evaporation. Unless they've been given plain water, this will be laden with a rich blend of nutrients causing overdose, the knock on effect of which is nutrient burn to the leaves.
So, to wrap up, photosynthesis is the process by which plants convert light to sugar which is then used by the plant for growth and life support systems. For photosynthesis to proceed at its maximum rate it must be able to get rid of the waste products, oxygen and water. This is controlled by the plant through a process known as transpiration and in order for transpiration to be optimised the temperature and humidity need to be spot on. When they aren't photosynthesis and transpiration rates are severely effected.
The lesson for the indoor grower here is clear, controlling the temperature and humidity in the grow room is essential if maximum yields are to be achieved.