Absorption of nutrients.
The absorption of nutrition, and the included dissolved nutrient salts, occurs via the roots of the marijuana plant. This process is done through osmosis. Osmosis is a physical process in which substances move from one fluid, which is separated by a semi-permeable wall (the plant cell), to another fluid. This is done from the side with the highest concentration of nutrients to the side with the lowest concentration of nutrients. This movement of ions is called osmotic pressure.
The same goes for all plants, which consist of about 80% water. So the kind and the amount of substances on the cell wall is important. We're going to keep it simple for a while and assume that the liquid in a marijuana plant and the water on the outside solely contain N (nitrogen), P (phosphorus) and K (potassium) ions.
Did the marijuana plant use nitrogen ions? Then the concentration in the plant is lower than the water outside of that. New nitrogen ions are then absorbed from the water. Does the plant have sufficient potassium ions? In other words, is the concentration on both sides of the cell wall the same? Then the K-molecules do not move and they stay where they are. If there's more P-ions present in the plant than the liquid outside of that, then the phosphorus is extracted from the plant and there will be a shortage in the plant itself.
Transport of nutrients - the blood circulation of a marijuana plant
The salts and oxygen in the water put pressure on the roots; the water with the nutrients wants to go inside. This process is further enhanced because the leaves make the water evaporate which causes pressure in the plant. Due to the root pressure, and the suction in the leaves, moisture and nutrients are transported upward through the marijuana plant.
Even if all the right nutrients are present in the water, then a high humidity can reduce the evaporation (suction force) of the leaves. This makes the plant absorb less nutrients. The availability of water, nutrients, and humidity of the marijuana plant determine if a plant gets the right nutrition in the right place.
Temperature can have the same effect. The evaporation of water via the stomata in the leaves also has another function. Evaporation requires heat. If the temperature is too high, the pores may open to evaporate even more water. This can happen if the light is too close to the plant.
If it's cold, the marijuana plant holds on to warmth by closing the pores and evaporates less water. This mechanism has no immediate influence to the growth or the bloom of the plant but assists in keeping the factory optimally going; this is how everything works very close together in the world of marijuana plants. When you make sure there's a constant and correct temperature in your growing space, the plant doesn't have to sweat as much and it's able to put the energy to more important use.
Converting food into nutrients
During the assimilation process, materials in the marijuana plant are converted to energy and nutrients. These nutrients are needed to maintain existing plant cells and for the formation of new ones. The plant mainly produces leave and stem cells during the growth period. For this, somewhat different raw materials are needed than for the generation of buds. This explains why you need to use different fertilizers during the growing and flowering period.
Just like with all chemical processes, the temperature affects the speed of the processes. The same goes for marijuana plants: too warm means burning, and if it's too cold the process isn't going to sufficiently occur. For marijauna plants the desired assimilation temperate, which occurs during the day, is between 68ºF (20ºC) and 77ºF (25ºC). At night, when dissimulation occurs, a temperature around 59ºF (15ºC) will suffice.