The electrical conductivity (EC) of the nutrient solution in the rooting medium of your plants is a measure of the concentration of the quantity of nutrients. It is generally known that the growth of the plant and the quality of the fruits can be manipulated with the EC. The EC in the soil or the substrate influences the transpiration from the crop, the uptake of the roots, the vegetative and generative growth, the quality and durability of the fruits, etcetera.
The primary effect of the EC is the influence on the water uptake: the higher the EC, the harder it is for the plant to take up water. The internal water management of the plant plays an important role in the creation of these effects.
In order to understand how EC, internal water management and growth are dependent on each other, we first need to get into a little plant physiology. A plant is for the most part nothing more than water. In order to be able to make leaves and fruits therefore, water is needed in the growing tissues. This water has to be tapped from the main stream, which leaves the plant via its roots and suction power vascular system. In order to be able to tap this water, parts of the plant develop a sort of suction power, the 'water potential'. The water that’s taken up leads to a certain pressure in the cells, the so called turgor.
This pressure ensures that cells can grow. In the competition between the evaporation and the suction power of the growing cells the EC plays an important role. If the EC is high, and the water uptake by the roots becomes more difficult as a result, then the growing tissues find it more difficult to get water in them. The turgor then falls and the growth rate decreases. This mostly occurs when thanks to high solar radiation or low air moisture levels the evaporation also draws heavily on the water flow. Often cells can defend themselves against this by developing for themselves a little extra suction power. They do this by making osmotically active substances, such as sugars and acids. This is one of the reasons why the EC has an effect on the taste.
Leaves lose 7% of their turgor for every 1 mS/cm rise in EC. In comparison with an EC of 1 mS/cm, the turgor at 8 mS/cm had fallen by 50%. Obviously this has a negative effect on the size of the leaf and so on the quantity of light intercepted and thus on the speed of growth. The root growth is much less sensitive for rises in the EC. By making relatively more roots the plant tries to counter the negative effect of the EC on the water uptake. It also closes more of the stomata (leaf holes), and in so doing the evaporation from the leaf is reduced.
First and foremost, one should always try to make sure that the bottles and canisters of nutrients and supplements are not allowed to be stored too cold or too hot, since the active substances in the nutrient can be degraded, and thanks to this plant itself could even be damaged by them. The optimal temperature for storage is between 10 and 25 degrees. Furthermore, you need to make sure that the bottles and canisters of nutrient and the supplements are not left in direct sunlight, or right under a high power lamp, as this too can degrade the contents. One should not store made up feed water that is not being kept in circulation by a pump for longer than 24 hours.