Influence of Nitrogen on Plant Growth

Roles of Nitrogen in Plants

Nitrogen is an integral component of many essential plant compounds. It is a major part of all amino acids, which are the building blocks of all proteins, including the enzymes, which control virtually all biological processes. Other critical nitrogenous plant components include the nucleic acids, in which hereditary control is vested and chlorophyll, which is the heart of photosynthesis. Nitrogen is also essential for carbohydrate use within plants. A good supply of nitrogen stimulates root growth and development as well as the uptake of other nutrients.

Plants respond quickly to increased availability of nitrogen, their leaves turning deep green in color. Nitrogen increases the plumpness of cereal grains, the protein content of both seeds and foliage, and the succulence of such crops as lettuce and radishes. It can dramatically stimulate plant productivity, whether measured in tons of grain, volume of lumber, carrying capacity of pasture, or thickness of lawn. Healthy plant foliage generally contains 2.5 to 4% of nitrogen, depending on the age of the leaves and whether the plant is a legume.

Deficiency of Nitrogen in Plants

Plants deficient in nitrogen tend to have a pale yellowish green color (chlorosis) and have a stunted appearance and develop tin, spindly stems. In a nitrogen deficient plant, the protein content is low and the sugar content is high, because there is insufficient nitrogen to combine with all the carbon chains stemming from sugars that wold normally be used to make proteins. Nitrogen is quite mobile within the plant and when plant uptake is inadequate, supplies are transferred to newest foliage, which causes the older leaves to show pronounced chlorosis. The older leaves of nitrogen-starved plants are therefore the first to turn yellowish, possibly becoming prematurely senescent and dropping off. Nitrogen deficient plants often have a low shoot to root ratio and they mature more quickly than healthy plants. The negative effects of nitrogen deficiency on plant size and vigor are often dramatic.

Nitrogen deficiency - Soil fertility - Plant Growth

Nitrogen Deficiency - Plant Growth Problem

Oversupply of Nitrogen in Plants

When too much nitrogen is applied, excessive vegetative growth occurs, the cells of the plant stems become enlarged but relatively weak and the top-heavy plants are prone to falling over with heavy rain or wind. High nitrogen applications may delay plant maturity and cause the plants to be more susceptible to disease especially fungal disease and to insect pests. These problems are especially noticeable if other nutrients such as potassium are in relatively low supply.

Nitrogen Toxicity in Plants

An oversupply of nitrogen degrades crop quality, resulting in undesirable color and flavor of fruits, and low sugar and vitamin levels of certain vegetables and root crops. Flower production on ornamental plants is reduced in favor of abundant foliage. An oversupply can also cause the buildup of nitrates that are harmful to livestock in case of foliage and to babies in the case of leafy vegetables. Besides the leaching of excess nitrates from the soil can lead to environmental degradation of downstream water basins and we will post about it later.