Thanks to: diels alder
Note: diels alder was instrumental in helping turn this very technical subject into something much easier to understand. This is by no means a complete, technical explanation of Botany, rather it’s an understanding of the basic principles.
Many times I’ve seen in posts that “roots grow during the dark.”. If this were true, the 24/0 photoperiod would result in a plant with a tiny root structure, if one at all! We know this is not the case - so how does it actually work?
To simplify things, lets use an analogy. Try to think of a plant as a building… one constantly under construction. The plant needs raw materials, (fertilizers and water), and energy (light) in order to “build itself”. The raw materials are the “bricks and mortar” of the building. The energy is the workers, vehicles and power tools used to assemble the building.
The Plant is capable of storing some raw materials and some energy for use later, but the amount is limited...think of a warehouse and a battery.
During the day however, the plant is not as efficient at building itself, as it is at night (lights OFF.) It can build itself, but not as quickly.
The bad news: since there is no light energy, the plant must rely on energy it stored while the lights were ON (its stored energy). (Essentially, the plant is running on batteries, and using raw material from the warehouse.)
There is no light energy to collect. Since the plant needs energy to absorb more raw materials, it is easier for the plant to use raw materials that it stored during the day than it is to absorb raw materials through its roots.
One last thing to remember is the fact that a plant will always strive to maintain a balance between the size of its roots and the size of its canopy (Leaf mass.) The roots must be big enough to supply as much raw materials as the canopy can use, and the canopy must be big enough to provide the energy required to store those raw materials….
If you actually measured them several times daily over several days, you’d notice that they actually DO get bigger at night, but roots and canopy at the same rate, unless either has been trimmed, and as long as the “batteries” hold out.