Question

A soil is said to be physiologically dry when
(a)Soil is waterlogged
(b)Soil has a high salt concentration
(c)Soil has a low temperature
(d)All the above cases prevail

Answer 1

Hint An estimated 70 percent of the earth’s surface is roofed with water, while the remaining 30 percent constitutes land. Scientifically, the soil is a mixture that comprises minerals, organic matter, and living organisms. But broadly, soil can ask for any loose sediment.

Complete answer:
Physiologically dry soil means that water is present within the soil but is not accessible to the plants either because of higher salt concentration, or lack of water in a liquid state, or poor aeration. These conditions appropriately take place in saline marshes, cold deserts, and waterlogged soil. Physiologically dry soil possesses much high concentration of salts. It is generally dead soil from lack of oxygen and higher salt content. The halophytes are plants of physically moisten but physiologically dried habitats. Such plants are basically present near sea-shores where mesophytes and freshwater hydrophytes cannot thrive well. Although these plants grow within the areas which are well saturated with water yet they can't avail of the water due to the high concentration of salts within the soils.

Additional information:
Physiologically dry soil means water is present in the soil but because of high levels of salt, it's not available to plants as plants cannot easily absorb the water present in the soil. Such plants are called halophiles, for example, are mangrove plants such as Sonnertia, Rhizophora, Avicennia, etc. Such plants show several unique features like the presence of pneumatophores and vivipary. Sunken stomata are not shown through mangroves but are exhibited through xerophytes which develop in physically dry soil.

So, the correct answer is ‘Soil has high salt concentration’.

Note: Halophytes grow in physiologically dry soil. The soil has water but the soil solution features a high concentration of salts. Therefore, the water is not easily present to plants, as water flows from an area of high water potential to an area of low water potential. Excess salt in soil solution means the water potential of soil solution is extremely less. To counter the reduction in water potential within the soil solution, the halophytes maintain a highly concentrated cell sap.