Abscisic acid
Abscisic acid (ABA) is an important plant hormone. In the 1940s, Hemberg provided the first experimental evidence of growth inhibitors in potato tubers. It was later named abscisic acid because of its role in causing leaf abscission and bud dormancy. ABA plays an important role in inducing stomatal closure in the epidermis and increasing plant tolerance to various types of stress, earning it the nickname “stress hormone”.
Biomass
Abscisic acid can be found in various plant parts including roots, stems, buds, leaves, fruits and seeds, as well as in xylem sap, phloem sap and honey. It is produced primarily in root caps and terminal buds, with minor amounts produced in chloroplasts. After production, it spreads to other parts of the plant.
Metabolic activity of Abscisic acid
Stomatal closure
Abscisic acid regulates stomatal movements, especially under water deficit conditions. As water availability decreases, the permeability of the chloroplast membrane to ABA increases, allowing the release of stored ABA. ABA then diffuses through the middle cell layer of the leaf and reaches the guard cells of the stomata.
ABA receptors bind to ABA and stimulate the production of IP3, which allows calcium ions to enter guard cells. This generates ROS (reactive oxygen species), which further facilitates calcium ion entry into immune cells. The influx of calcium ions inhibits the import of potassium ions and promotes the export of chloride ions, leading to an osmotic imbalance in the guard cells and subsequent water loss. This causes guard cells to shrink, leading to stomatal closure. When the supply of ABA is stopped, the stomata return to their normal state.
Effect on plant growth of Abscisic acid
Abscisic acid plays a role in stimulating the growth and development of the root system so that the roots exhibit positive geomorphology. However, it inhibits shoot growth and induces dormancy in some tubers such as dahlia and potato. Under unfavorable weather conditions, ABA inhibits shoot growth, while under favorable conditions, ABA levels decrease in the plant, allowing growth to resume.
During winter, ABA arrests mitosis in the vascular cambium.
Seed dormancy
In developing seeds, the embryos produce abscisic acid, which prevents the activation of enzymes necessary for germination by inhibiting water absorption until the seed matures.
These revisions and clarifications will help provide a more accurate and understandable description of abscisic acid and its role in plants.
Environmental response
Abscisic acid plays an important role in plant responses to environmental factors, including:
Drought stress: ABA acts as a signaling molecule that triggers various physiological responses to water deficit. It promotes the closing of stomata to reduce water loss through transpiration. Additionally, ABA regulates the expression of stress-responsive genes that help the plant adapt to drought conditions.
Salinity Stress: High salt concentration in soil can lead to salt stress in plants. ABA helps plants cope with salt stress by regulating ion transport and osmotic balance. It also affects the synthesis of compatible solutes that aid in salt tolerance.
Cold stress: In response to low temperatures, ABA can trigger defense mechanisms in plants. This helps regulate the expression of genes involved in cold acclimation, improving the plant’s ability to withstand freezing temperatures.
Pathogen Defense: ABA is involved in plant defense against pathogens. While it promotes susceptibility to certain diseases, it activates defense mechanisms in response to certain pathogens, contributing to the plant’s immunity.
Commercial applications of Abscisic acid
An understanding of the role of ABA in plant physiology has led to practical applications in agriculture and horticulture. Some business applications include:
Crop yield improvement: ABA research has provided insights into improving crop yields, particularly in drought-prone areas. Scientists are exploring ways to manipulate ABA signaling pathways to create more drought-tolerant crop varieties.
Fruit Ripening: ABA is involved in the regulation of fruit ripening. It is used to control the ripening process, extend the shelf life of fruits, and reduce post-harvest losses.
Stress mitigation: ABA-based treatments or foliar applications can be used to mitigate the negative effects of environmental stresses on plants, such as drought, salinity, and extreme temperatures.
In conclusion, abscisic acid (ABA) is a versatile plant hormone that has significant effects on plant growth, development, and responses to environmental challenges. Its role in stomatal regulation, stress tolerance and various aspects of plant physiology has been the subject of extensive research with potential applications in agriculture and horticulture. Understanding the functions of ABA continues to contribute to the development of strategies to improve crop resilience and productivity in a changing climate.
