Polyols: The Key to Enhancing Plant Stress Tolerance
Polyols are organic compounds derived from sugars, with a hydroxyl group attached to each carbon atom. Because they contain multiple hydroxyl groups, they are classified as polyols. Examples of sugar alcohols include mannitol, sorbitol, and xylitol.
Unlike regular sugars such as glucose, sugar alcohols have a linear structure rather than a cyclic one. This structural difference allows them to easily enter plants through stomata. Additionally, since plants naturally produce these compounds, they readily recognize and absorb them. This property makes polyols an efficient carrier for delivering essential nutrients to plants. Moreover, they have a high storage energy capacity, unlike conventional sugars.
The Role of Mannitol in Plants
Mannitol plays a crucial role in enhancing a plant’s ability to withstand salt stress. Beyond that, it also boosts the plant’s defense response against pathogens such as fungi. This makes mannitol metabolism a vital factor in improving both biotic (caused by living organisms) and abiotic (environmental) stress tolerance in plants.
Mannitol falls under a category called compatible solutes—small organic molecules with a neutral charge that exhibit low toxicity, even at high concentrations. These molecules help plants recover from stress conditions, whether caused by salinity or fungal attacks, without disrupting cellular metabolic processes.
How Does Mannitol Function?
Mannitol primarily accumulates in the cytosol of plant cells, where it mitigates stress-induced damage and supports metabolic processes, ensuring the plant continues to function normally despite environmental stressors.
Why Are Sugar Alcohols Effective Carriers?
Sugar alcohols contain hydroxyl groups similar to those found in water, allowing them to mimic water molecules. This property helps maintain a hydrated protective layer around macromolecules, facilitating their absorption by plants more efficiently than EDTA or amino acids.
Additional Benefits of Mannitol
Beyond stress alleviation, mannitol acts as a scavenger for reactive oxygen species (ROS), which are harmful free radicals responsible for lipid oxidation and cell damage. These free radicals are generated under stress conditions such as high salinity, fungal infections, and pesticide use.
Where Is Mannitol Stored in Plants?
Approximately 80% of mannitol is stored in the vacuole, while the remaining 20% is found in the cytosol, where it performs its protective functions.
Research & Development Team – Smart Land Company
