One of the most important aspects of plant growth is photosynthesis. It's something that all plants do and it effectively involves taking the available light and transforming it into energy. That's really the basic definition of photosynthesis, but it goes a lot further than that. The plants receive light through various pigments on their exterior. Chlorophyll is the most abundant pigment in cannabis and most other green plants and so it is largely responsible for bringing in light energy. In that way, cannabis leaves almost work like solar panels by extending the area that the plant can take in light. More leaves essentially represent more power producers because you have more energy entering into the plant. When the energy is taken into the plant, it is stored in chemical compounds like adenosine-triphosphate (ATP) and nicotinamide-adenine-dinucleotide-phosphate (NADPH2). These are compounds that are built to transfer energy throughout the plant. ATP is integral in the creation of carbohydrates and NADPH2 is integral in the synthesis of carbohydrates. Of course, the plants need to work with something in order to create these carbohydrates. The name alone lets you know that carbohydrates have some mixture of carbon and hydrogen. In marijuana plants, they get those both of those elements from carbon dioxide (CO2) and water (H2O). Obviously, CO2 is found in the atmosphere and water is generally provided by the grower (or other means in a natural environment). Want to know more about growing marijuana? Plants can absorb CO2 from the atmosphere or from the soil. Water is, of course, absorbed through the roots and transferred into the plant itself. So, the light energy (in the form of ATP and NADPH2) comes together with CO2 and H2O to create carbohydrates (CH2O). As a result of this transaction, there is a spare O2 molecule that gets released into the air. Marijuana absorbs and utilizes all of the items required for photosynthesis and then releases oxygen into the atmosphere. Once the carbohydrates have been created, they are utilized as food energy and "building material" for the plant. One of the things that carbohydrates create is a sugar called glucose (CH2O)6, which is essentially a string of 6 carbohydrate molecules. Glucose is then strung together itself to create cellulose which then accounts for about 4/5 of the plant cell structure. Cellulose is one of the most important and prevalent organic compounds on the planet, and its creation in the marijuana plant is due in large part because of photosynthesis. Carbon dioxide is a naturally-occurring gas, but you can add more CO2 if you're growing in a grow room. Most air has a concentration of about .03% carbon dioxide which perfectly safe for you to breathe and great for your plants. But, marijuana plants can actually handle about .15% carbon dioxide in the atmosphere. Having a higher concentration of CO2 correlates to more growth in the plant. More light will also produce more growth. This is obviously because of the way photosynthesis works. If you are consistently providing light energy and CO2 to the plant, it will respond by making more carbohydrates and eventually more cellulose (among other compounds). It should also be noted that the same can't be said about water. Unless you're using a hydroponic system, a constant stream of water will act as a deluge that will drown the roots. That is to say, adding extra water won't produce bigger plants; it will just weaken them (and maybe even kill them). While water is a necessary component to the life of the plant, you should never overuse it. This is largely because the roots also need oxygen to "breathe." If you drown the plant in water and don't let the soil create natural holes for oxygen infusion, then you will start to notice a severely enervated plant.