NH₃ is first stable product of nitrogen fixation. N₂ is form in which nitrogen naturally exists. NO₃^– is form of nitrogen taken up by plants. NH₄⁺ is toxic form of nitrogen which gets accumulated in plants.

Usually source is understood to be that part of plant which synsises food, i.e., leaf, and sink, part that needs or stores food. But, source and sink may be reversed depending on season or on plant?s needs.

The chief sinks for mineral elements are growing regions of plant such as apical and lateral meristems, young leaves, developing flowers, fruits and seeds, and storage organs.

The enzymes for nitrogen fixation are found exclusively in prokaryotes. Rhizobium bacterium is known for its symbiotic relationship with roots of legumes. Rhodospirillum, Bacillus, Azotobacter are or bacteria having nitrogen fixing capability.

Hydroponics is process of growing plants in artificial nutrient media by providing required conditions for its proper growth. It was demonstrated by Julius Von Sachs in 1860. Melvin Calvin is an American biochemist who received 1961 Nobel Prize for Chemistry for his discovery of chemical pathways of photosynsis. The Hoagland solution developed by Hoagland and Snyder provides every nutrient necessary for plant growth and is appropriate for growth of a large variety of plant species. It was corrected by scientist Arnon.

Amides contain more nitrogen than amino acids. They are transported to or parts of plant through xylem vessels. Phloem tissue has no function in relation to translocation of amides.

Cu deficiency leads to Exanma in Citrus. P deficiency leads to poor growth of leaves. B deficiency leads to heart rot of beets. Zn deficiency leads to Khaira disease of rice.

Fe is element that activates enzyme catalase. Plants obtain iron in form of ferric ions. Na is responsible for C4 metabolism. Co is essential for nitrogen fixation by nitrogen-fixing bacteria associated with legumes and or plants. Si improves health of plants.

Food, primarily sucrose, is transported by vascular tissue phloem from a source to a sink. Food in phloem sap can be transported in any required direction.

Mineral ions are moved from mature organs to younger organs of plants before senescence. In deciduous plants, elements are removed to or parts before all leaves fall.