Abscisinsäure

Abscisinsäure, often abbreviated as ABA, is a plant hormone that plays a crucial role in various developmental and stress responses. It is a sesquiterpenoid molecule found in virtually all plant tissues, including roots, stems, leaves, flowers, and seeds. ABA is synthesized primarily in the leaves, roots, and developing seeds, and its production is significantly influenced by environmental factors such as drought, salinity, extreme temperatures, and mechanical stress.

The primary functions of abscisinsäure revolve around its role as a stress hormone. During drought conditions, ABA levels rise, leading to the closure of stomata, small pores on the leaf surface responsible for gas exchange. This stomatal closure reduces water loss through transpiration, helping the plant conserve water. ABA also plays a role in seed dormancy, preventing premature germination and ensuring that seeds germinate only when environmental conditions are favorable. Furthermore, it is involved in abscission, the shedding of plant parts like leaves, flowers, and fruits, although its role in this process is complex and often interacts with other hormones. ABA also contributes to the acclimatization of plants to cold temperatures and influences root growth. Its signaling pathways are intricate, involving a complex network of receptors and downstream effectors that mediate its diverse physiological effects.