Chemical Stress - Mineral composition
The living systems make use of several mineral ions that they might have encountered at the very origin or during evolution, particularly for transformation of matter involving proteins and nucleic acids. These elements continue to remain essential requirements for life. The nitrogen, phosphorus, calcium, potassium and magnesium are familiar major requirements for plant growth besides carbon, hydrogen and oxygen.
Apart from these, many other micronutrients such as manganese, iron, zinc, cobalt and molybdenum are required for healthy plant growth in much smaller quantities. Availability of these elements in the environment in quantities smaller than required causes deficiency symptoms while a surplus may cause toxicity leading to stunted growth, necrosis, abnormal development of vegetative and reproductive parts.