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Sources of minerals for plants are atmosphere, water and soil. Minerals are classified based on their quantity, mobility and functions. Macro nutrients (C, H, O, N, P, K, Ca, Mg and S) are required in higher concentration and micro nutrients (Fe, Mn, Cu, Zn, B, Mo, Cl and Ni) are required in lesser concentration. Minerals like Sodium, Cobalt, Silicon and Selenium are required by some plants for specific functions and such minerals are grouped as unclassified minerals. Actively mobile elements are N, P, K, Mg, Cl, Na, Zn and Mo. The deficiency symptoms for these minerals first appear on old and senescent leaves due to active movement of minerals to younger leaves. Relatively immobile elements are Ca, S, Fe, B and Cu. In such minerals, deficiency symptoms first appear on young leaves due to immobile nature. Minerals and their deficiency symptoms include chlorosis (loss of chlorophyll pigments), necrosis (death of tissue), anthocyanin formation, die back of shoot, exanthema, hooked leaf tip, whiptail and so on. A concentration at which 10% of dry weight is reduced is considered as critical concentration. Minerals used in excess concentration become toxic.
Soil less cultivation alleviates problems due to mineral deficiency. It includes hydroponics and aeroponics. Hydroponics is a method of growing plants in a nutrient solution. Aeroponics is the technique in which roots are suspended over the nutrient medium in air and nutrient sprayed over the roots by motor driven rotor. Nitrogen is an important requirement for normal growth and functioning of a plant. Nitrogen fixing organisms fix nitrogen from atmosphere naturally through symbiotic and non-symbiotic modes. Special modes of nutrition are seen in plant which grew in nutrient deficient soils and the character becomes permanent.
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