Responses to Salt Stress

Salinity affects the growth and development of plants by impacting water and nutrient uptake as well as photosynthesis.

Plant cells have high solute concentrations that drive water from the soil into the plant. However, the presence of excess salt in the soil raises the soil solute concentration, impeding a plant’s ability to take up water even when there is sufficient water in the soil. 

Another issue with excessive salt levels in soil is that sodium and other ions in salts are toxic to plants at high concentrations. 

Many plants can respond to moderate levels of salt in the soil by producing solutes that they tolerate well at high concentrations; this raises the solute concentration in plant cells, enabling roots to absorb water from the soil without taking in toxic levels of sodium. 

Excessive sodium at the root surface also reduces potassium uptake, which inhibits plant growth.

Calcium can protect plants from sodium stress by regulating ion transporters, enzymes, and gene transcription. 

An excess of sodium and other salt-derived ions in the soil can also change the hormonal content in plants. For example, abscisic acid is produced in response to excessive salt levels, which closes stomata. 

Not all plants are sensitive to salt in their environment. Salt-tolerant plants—called halophytes—have adapted to high-salt environments. 

Halophytes have evolved features that confer resilience to salt stress, such as specialized epidermal glands—called salt glands—on their stems and leaves. The salt glands take up excess salt from neighboring tissues and excrete the salt onto the leaf surface, where it can be removed by rain or wind.