Nitrogen (N) is one of the crucial necessities a plant needs. It is an important part of proteins, chlorophyll (leaf green), vitamins, hormones and DNA. Because it is a component of enzymes, nitrogen is involved in all enzyme reactions and plays an active role in the plant’s metabolism.
Nitrogen is mainly absorbed by the plant in the form of nitrate (NO3-) and ammonium (NH4+). Nitrogen can also be absorbed through small organic molecules. It is important that the balance between nitrate and ammonium is correct in the feeding otherwise the pH in the rhizosphere (the environment immediately surrounding the roots) will become too high or too low. Plants with nitrate as their source of nitrogen have a higher organic acid content. This has an influence on the taste and preservation of the crop.
Nitrate is converted into ammonium in the plant by the nitroreductase enzyme. Ammonium is then assimilated into organic molecules. Nitrogen has a positive influence on the plant’s growth. The plant gets bigger leaves, more branches and the vegetative period is extended. This phenomenon is often used in practice by reducing the nitrogen dosage during cultivation, which causes the plants to flower earlier. Earlier flowering is a consequence of increased production of abscisic acid, a plant hormone.
When a Nitrogen shortage is the case you will find your plant going through the next cycle:
Nitrogen deficiency slows down protein synthesis which prevents the plant from performing optimally. In order to continue to meet its nitrogen requirements the plant breaks down its own proteins. This breakdown produces a carbohydrate surplus which causes leaf stalks and the stem to turn purple. The chlorophyll is also broken down eventually which leads to the typical bleached green to white-yellow leaf color and finally the leaves wither and fall off.
Mild forms of nitrogen deficiency can occur during fast growth under full light. Due to the increased rate of photosynthesis and the formation of new cells, the demand for nitrogen at this time is more than the roots can provide. The nitrogen deficiency is generally corrected when growth stagnates. Nitrogen deficiency can also be caused by incorrect feeding, mostly when giving feeding that contains insufficient nutrient elements. This could be the case when using a nutrient developed for a certain type of substrate but applying it to another one.
Certain diseases that affect the plant’s transport system, such as Fusarium, can cause nitrogen deficiency symptoms to arise. These are however, accompanied by the base of the stalk becoming woody and rotting and by roots turning brown. Substrates that contain a lot of fresh organic material can cause nitrogen deficiency because microorganisms bind the nitrogen. A lot of nitrogen can be bound, particularly in the first weeks; this is released later but it is generally too late.