Minerals and Nutrients

A magnesium-deficient crop will tend to have a pale overall colour. The earliest specific symptom of magnesium deficiency is interveinal chlorosis of older leaves. Chlorosis generally progresses to yellowing and necrosis of the oldest leaves. Therefore, without sufficient amounts of magnesium, plants begin to degrade the chlorophyll in the old leaves. This causes the main symptom of magnesium deficiency, interveinal chlorosis, or yellowing between leaf veins, which stay green, giving the leaves a marbled appearance.

Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite and chlorapatite, with high concentrations of $OH^{-},F{-},Cl{-}$ respectively, in the crystal. Proteins in plants and animals have nitrogen. Chile saltpetre and Indian saltpetre are $NaNO _3$ and $KNO _3$ respectively.

The nitrogen which exists free in nature which is made up of 78% of Earth atmosphere and naturally found in mineral deposits, soil and organic compounds.

Since proteins form components of cytoplasm, therefore it is responsible for growth and repair.

Proteins are the primary structural components of cells and tissues, often referred to as body-building foods because they are essential for growth and repair.

Nitrate reductase is a critical enzyme involved in nitrogen assimilation in plants and is classified as a molybdenum-containing protein, requiring molybdenum as a cofactor for its catalytic electron-transfer function.

Cellulose waste can be converted into single-cell protein through microbial fermentation. This process utilizes the carbon source in cellulose to produce protein-rich biomass.

NPK $:$ The elemental shorthand for the three major nutrients in fertilizers. “N” stands for Nitrogen, “P” stands for Phosphate (${ P } _{ 2 }{ O } _{ 2 }$) and “K” stands for Potash ($\\ { K } _{ 2 }O$). These are the chemical forms of nitrogen, phosphorus and potassium that are present in fertilizers.

Trace elements:-

The most essential elements required for the development of all plants are:-

 The most important elements that plants need, without which they won't thrive, are the three macronutrients: potassium, nitrogen, and phosphorus. Because they are basic building blocks of every plant are ATP, cell membranes and amino acids. Nitrogen is an element in every amino acid; ATP, which is the primary source of energy for all cells, contains phosphorus. Potassium is essential to a plant's ability to metabolize. This element also comprises up to two percent of a plant's weight.

• On the basis of the symptoms of chlorosis in the leaves, a student inferred that this was due to the deficiency of nitrogen. 
• This may be correct inference only if yellowing of leaves appeared first in young leaves then in old leaves. But Chlorosis is the main symptom of nitrogen deficiency. 
• Therefore, the leaves gradually become pale or yellow. These will first appear in old leaves and then in young leaves.
• The correct option is A.

Answer is option C i.e. "Critical concentration"
The concentration of the essential element below which plant growth is retarded is termed as critical concentration. Below this minimum level, plants start to show nutrient deficiency.
While, optimum concentration is the most desirable or satisfactory level of a nutrient. Maximum concentration is the highest concentration of nutrient and nutrient toxicity occurs when excess consumption of a nutrient does harm to an organism.

Iodine is a component of almost every living plant and animal. No standard measurements of iodine in food exist because iodine concentrations vary across the world. In general, foods from the sea contain the most iodine, followed by animal foods, then plant foods. Of all foods, seaweed (like kelp), is the most well known and reliable source of natural iodine. Egg and dairy products can also be good sources.