Mineral Elements, Micro

The micro elements included in culture media and their metabolic role include the following. 

Boron (B): Boron is essential in enzyme activity in lignin biosynthesis and metabolism of phenolic acids. Boron deficiency inhibits cell division and elongation in both root tip and shoot tip meristems. In culture media, boron is supplied as boric acid. 

Cobalt (Co): Cobalt is not considered as an essential element by plant physiologists. However, about 0.1 ìM cobalt is widely used in plant culture media. It may be toxic at higher concentrations. 

Copper (Cu): As a plant nutrient, copper seems to function primarily as a cofactor for a variety of oxidative enzymes. Copper is used in the form of copper sulfate at 0.1 ìM in culture media. Higher concentration may be toxic. 

Iodine (I): The effect of iodine varies depending on plant species. I is not an essential element but added to media to improve growth of roots and callus in culture. 

Manganese (Mn): As a cofactor, manganese is required by some enzyme reactions, particularly in respiration and photosynthesis processes. Usually, 5-30 ìM manganese is added to the medium in the form of manganese sulfate. 

Molybdenum (Mo): Molybdenum is a cofactor with two enzymes involved in transforming nitrate to ammonium. It is supplied as sodium molybdate at 1 ìM in media. 

Zinc (Zn): Zinc is absorbed as the divalent cation Zn₂+ by plants. It is an activator of a large number of enzymes. Typical symptoms of zinc deficiency include shortened internodes and smaller leaves. Zinc sulfate is the most common form added to culture media at 5-30 ìM.