Chapter 5 - Plants and salt: Plant response and adaptations to salinity

Abstract

A substantial percentage of the world soils are salt affected. Salinity severely limits plant performance and crop yield and is a major abiotic constraint on agricultural food production worldwide. Accumulation of salts in the soil decreases the osmotic potential and water potential of the soil solution, diminishing the availability of water in the root zone for plant uptake. High concentrations of salts in the soil solution cause nutrient imbalances, which affect uptake of essential nutrients by the roots and their availability for the plant cells. The increased concentrations of Na and Cl in the plant induce specific toxicities as well as alterations in water relations. Other effects of salinity include alteration of metabolism, hormonal changes, oxidative damage, and impaired photosynthesis. The combined response is restriction of plant growth and development and reduced productivity. Plants evolved a variety of physiological mechanisms to enable survival under saline conditions. The main mechanisms involve osmotic adjustment, ion exclusion/inclusion and compartmentation, antioxidant defense response, and morphological and anatomical adaptations. The search of living systems in harsh environments on Earth, and studies into mechanisms of tolerance in identified extreme Halophiles that thrive under high salinities, have pointed at origins and evolution processes of life on Earth. Species that flourish under hypersaline conditions are good models for studying mechanisms for survival in extreme niches in the universe.