Читать книгу Physiology of Salt Stress in Plants - Группа авторов - Страница 14

Based on the origin and root cause, there are two different categories of salinity, namely, primary and secondary. Primary salinity is a natural phenomenon and mostly occurs due to the former presence of salt lakes, slat clads, tidal swamp, etc., at a particular location. It is majorly a kind of sodicity. At the same time, secondary salinity is imposed due to man‐made activities such as urbanization, saline irrigation, etc. (Shahid and Rahman 2011). Detailed reasons are delineated below.

Primary salinity:

1 Spreading from the saline artesian well.

2 Capillary rise from saline groundwater.

3 Seawater intrusion.

4 Canopy formation due to the movement of fine sea sand by the sea breeze.

5 Waterlogging.

Secondary salinity:

1 Irrigation with impeded drainage

2 Effluent discharge

3 Excess fertilizer dosing

4 Deforestation

5 Saline irrigation

Furthermore, based on the predominance of the type of anions present and the pH value, salt‐affected soils are categorized as saline soil and sodic soil. Sodic soil typically comprises sodium carbonate and or bicarbonate ions with a pH value beyond 8.5, but contrarily, saline soil majorly incorporates chloride and sulphate ions with pH value below 8.5. Certain plant species manage to compensate the imparted stress through its metabolism and survive in the severe salt conditions known as halophytes. Remaining plant species are termed as glycophytes with a higher mortality rate overexposure to 10% or more concentration of saline water (Gorham 1995; Parida and Das 2005; Mane et al. 2011; Gupta and Huang 2014).