Mineral Nutrition

Anaemia refers to any condition in which there is an abnormally low haemoglobin concentration and/or blood cell count. The most common cause is deficiency of iron which is an essential element of haemoglobin molecule.
Thus, the iron compounds in the diet will help to alleviate the symptoms of anaemia.
Thiamine (vitamin B₁), deficiency causes beri-beri.
Riboflavin (vitamin B₂) deficiency causes cheilosis and skin diseases.

The insectivorous plants grow in nitrogen deficient soil and their nitrogen requirement is fulfilled by capturing and digesting the insects.

Enzyme nitrogenase plays a key role in N, fixations and remains active only during anaerobic condition. It is made up of two protein subunits :

i) non-heme iron protein or Fe-protein or dinitrogen reductase.

ii) Iron molybdenum protein or Mo-Fe protein or dinitrogenase

Ca is essential macronutrient for plant growth. It is constituent of middle lamella, activator of enzymes, connected with chromosome formation and many aspects of metabolism

All the given options are hydrophytes in nature which grow in extremely wet or watery conditions. But among them only in Ceratophyllum roots are completely absent even in embryonic stage. They remain under water completely Nymphaea is a rooted hydrophyte with floating leaves.

Vallisneria is rooted submerged hydrophyte and Sagittaria is rooted emergent hydrophyte.

Plants require nutrients for proper growth and development. There are 16 elements which are required for plant and are termed as essential elements. They are as follows:

Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), Sulphur (S), Potassium (K), Magnesium (Mg), Calcium (Ca), Iron (Fe), Copper (Cu), Boron (B), Zinc (Zn), Manganese (Mn), Molybdenum (Mo) and Chlorine (Cl).

The essential elements are categorised into 2 groups, 

1. Macro- nutrients: These are required by plants in large quantities. eg, C, H, O, N, S, P, K, Ca and Mg.
2. Micro- nutrients: These are required by plants in very small quantities. eg, Fe, Cu, B, Mn, Ni, Mo and Cl.

Hydroponics is a subset of hydroculture, which is a method of growing plants without soil by using mineral nutrient solutions in a water solvent. It is useful in areas having thin, infertile and dry soils. They conserve water. It can regulate pH optimum for a particular crop, control soil borne pathogens, avoid problems of weeding and obtain consistently better yield.

Rhizobium is the nitrogen fixing bacteria present in root nodules of leguminous plants. Roots of a legume secrete chemical attractants flavonoids and betaines. Bacteria collect over the root hairs, release nod factors that causes curling of root hairs around the bacteria, degradations of cell wall and formation of an infection thread enclosing bacteria. The infected cortical cells differentiate and start dividing. It produces swelling of nodules and the infected cells enlarge. Bacteria stop dividing and form irregular polyhedral structures called bacteroids. The host cells develops a pinkish coloured pigment called leghaemoglobin. It is an oxygen scavenger and protects nitrogenase from oxygen. Symbiotic nitrogen fixation requires co-operations of 'Nod' genes of legumes, 'nod' 'nif' and 'fix' genes of bacteria.

Micronutrients are minerals obtained from the soil and present in plant tissues at concentrations usually less than 3 $\mathrm{\mu }$ mol g^-1 dry matter. Copper (Cu), Manganese (Mn) and Iron (Fe) are the micronutrients which affect both photosynthesis and mitochondrial electron transport as they are the main constituents of various electron carriers.

Leghaemoglobin is a pinkish pigment present inside the root nodules of nitrogen fixing plants like legumes. It is an oxygen scavenger and is related to blood pigment haemoglobin. It protects nitrogen fixing enzyme nitrogenase from oxygen. The most important bacteria present inside the nodules is Rhizobium.