Light is an important source of energy which is needed for processes like photosynthesis. Therefore it is essential for the plants metabolism. As long as plants get plenty of light, they will grow in a uniform manner. Unless these conditions are fulfilled the plants grow too quickly with the result of fewer flowers and fruits.
Furthermore the cycle of light and darkness phases is directly related to the seasons. Thereby it controls the different growth phases like vegetative stage or flowering stage.
Water is the central substance for metabolism. It is available in the form of rain, humidity or groundwater. It serves as a transportmedium for nutrients and moisture. Therefore it is one of the key factors for photosynthesis and responsible for the plant growth and the plant stability.
The majority of the water is taken up directly by the roots. But the level of humidity is very important, too. Especially seedlings, which possess a particularly small root network, absorb water from the air through their leaves. Depending on the stage of development, many plants should be provided with a relative humidity of 40-60% to grow as strong and fast as possible.
Like other living beings, plants need constantly fresh and clean air. Especially carbon dioxide is essential for the process of photosynthesis. It is being absorbed through microscobic pores under the leaf.
In terms of plants growth the temperature of the air (and of the plant) is an important physical parameter, too. The average temperature for most plants should be between 18-26°C, whereas the temperature at night should be around 5°C lower than at daytime.
Further moving air has a good influence on plants. It makes them more robust and ensures a denser foliage.
Besides light, carbon dioxid, oxygen and water, plants need different minerals in order to fully develop. The most important are nitrogen, phosphorus, potassium, magnesium, sulfur and calcium. These minerals are either (in soluble form) in the substrate or in the form of a nutrient solution - depending on the method of cultivation.