Mineral Nutrition Test - 71

Khaira disease is a disease of rice which appear on the lower surface of the leaves, the grains are less and light in weight and on the lower leaves that are small brown colour spots. This disease is caused by the deficiency of zinc.

Nitrogen fixation is a process by which nitrogen in the Earth's atmosphere is converted into ammonia. After nitrogen has been fixed, other bacteria convert it into nitrate, in a process known as nitrification. In the first step of this process, Nitrosomonas convert ammonia into nitrite, and in the second step, nitrite is converted into nitrate, by Nitrobacter. This nitrate is then consumed by plants.

• A plant disorder known as lime-induced chlorosis occurs when it suffers from a deficiency of iron.
• Iron is required by plants to produce chlorophyll, therefore, deficiency of iron causes chlorosis.
  
• Even when the concentration of iron in the soil is high it cannot be absorbed if the pH of the soil is higher than 6.5.
• If the soil is excessively waterlogged or over fertilised it releases an excess of elements such as manganese in the soil which interfere with the iron uptake of the plants and causes iron deficiency.
• So, the correct answer is 'Fe'.
  

The ratio of auxin to cytokinin plays an important role in the effect of cytokinin on plant growth. Cytokinins are involved in many plant processes, including cell division and shoot and root morphogenesis. According to the "direct inhibition hypothesis," these effects result from the cytokinin to auxin ratio. Mature plant cells normally stop dividing. By adding cytokinin and auxin, differentiated cells can be induced to initiate cell division again. So, the correct option is 'IAA'.

PUFA or polyunsaturated fatty acids are not soluble in water. They have more than one double bond in their fatty acid chain. Polyunsaturated fatty acids (PUFA) contain multiple double bonds and are not stacked together that leads to the weaker intermolecular interaction; as a result,  PUFA has a lower melting point. PUFA improves blood cholesterol levels and thus lower the risk of cardiovascular diseases. 

Tea yellow disease is caused by sulphur deficiency in tea plants. It is characterised by a progressive degeneration of the bush, in which the leaves become chlorotic, small, uprolled and of stiff texture, and are finally shed.

• The electron transport system is the stepwise transfer of an electron from several across the inner mitochondrial membrane. Iron plays an important role in the transport of electron.
  
• During the process of chlorophyll synthesis, it was studied by Willstater that chlorophyll has two parts:

1. Head (Porphyrin)
2. Tail (Phytol)

iron helps in the formation of the porphyrin ring which is made up of two pyrrole rings.

Solution:

Correct answer is option D.

Explanation for correct option:

1. Hydroponics is a method of growing plants indoors without using any soil.
2. The word "hydroponics" means growing plants in water (from two Greek words meaning "water" and "toil")
3. This technique uses no soil but instead grows plants in a solution of water and nutrients.