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Evaporation and Leaf Temperature
Climate control is more than lighting, temperatures, watering, ventilation, EC and pH. In fact, humidity is the number one factor in maintaining level temperatures.
With a low humidity, around 40 per cent, your grow room will derive a lot of water from the leaves. Think of this as the cooling process. A lot of water has to be supplied from the roots because, as the water in the leaves runs out and the water supply stops, the leaf stomas, at the tip of the leaves, will start to close. This is considered curling leaves. In the growth phase the leaves usually curl down wherein the bloom phase they will curl up. This curling is not directly related to nutrients, a common misbelief among gardeners. In fact, the leaf just becomes too hot and by curling it is essentially protecting itself against the light and the temperature. Remember, lamps are not only sources of light; they are sources of heat as well and they will create heat in the leaves of your plants. When you don’t take action in this period, the leaves will start to curl on all sides and eventually they will burn.
Water Supply and Humidity
Water supply via the roots and humidity should go hand in hand. When the leaves are no longer cooled, the production of energy stops, and your crops will no longer produce. This process is very similar to human perspiration.
These problems often take place in the few final hours of daily growth and because most growers will be sleeping at that time and not checking their plants, the problem goes unnoticed. The result is that the plant may stop production for as long as three hours, thus reducing the yield.
Example: If the temperature is 86°F and you’re sitting on the beach without any fluids, your skin will start to burn. Your body is no longer being cooled because your water supply has sweated out and no additional fluids are being taken in.
It is best to check on your plants a few hours before the lamps are turned off as checking your plants when the lights are turned on only shows the leaves at their best. As your plants bring up new coolant, or water, in the dark period the leaves curl up so curling will not be visible under the lights. During the night the root will ensure the battery on top is recharged or filled with coolant. The root cannot supply coolant to the leaves when:
Your growth medium has no water
When the substrate is too cold
When there is no oxygen in the growth medium (may be too wet)
When the EC value of the substrate is too high (the root can’t supply water to the leaves, which can also lead to curling leaves.)
It is clear that curling leaves has to do with the cooling process of the leaves. Working with the proper humidity is beneficial and essential for climate control. By keeping the room a little more humid, you demand less from the sweating or evaporation of the plant. Water supply via the root does not have to be as quick. In this way, everything will proceed more gradually meaning that the plant can produce for 12 hours instead of 10.
Everything is a little easier for the plant and a mistake every now and then has fewer consequences because you are not growing near the maximum cooling capacity of the leaves.
To get the right humidity values, you will have to use a humidifier, which is available in all sorts and sizes. In warm periods always use a humidifier that provides a cold mist, even in the summer period the temperature of the grow room can lowered by as much as 41°F.
In winter when the temperatures are low, a warm mist is best. A humidifier is essential for successful yields; even the professional horticulturist invests a lot of money in humidifiers. Growth is more controlled and a higher yield is realized. Once you have climate control perfected, nutrient additives becomes the next important step in your success. In part two of we will talk about methods you can implement to maintain climate control.