Describe the feedback mechanism that occurs at the stomates of plants.
Describe the feedback mechanism that occurs at the stomates of plants.
http://regentsprep.org/Regents/biology/units/homeostasis/feedback.cfm
The feedback mechanism that occurs at the stomates of plants is known as stomatal regulation. Stomates are small openings present primarily on the surface of leaves, although they can also be found on other plant parts like stems and flowers. These stomates regulate the exchange of gases, including carbon dioxide and oxygen, as well as the loss of water vapor through a process called transpiration.
Stomatal regulation involves a complex interplay of factors that influence the opening and closing of stomates. The regulation is primarily controlled by two plant hormones: abscisic acid (ABA) and auxin. Here's a step-by-step breakdown of the feedback mechanism:
1. Water availability: The stomates respond to the water status within the plant. When water availability is high, the guard cells surrounding the stomate swell due to the entry of water, causing the stomate to open.
2. Hormonal control: Abscisic acid (ABA), a hormone released by various cells in response to water deficit, triggers stomatal closure. When the plant experiences water stress, ABA is produced and transported to the guard cells. This hormone causes the guard cells to shrink, closing the stomate.
3. Light intensity: Light is another critical factor that regulates stomatal opening. When light intensity is low, such as during the night, the stomates generally close to minimize water loss through transpiration.
4. CO2 concentration: Plants require carbon dioxide (CO2) for photosynthesis. When the CO2 concentration outside the leaf is low, the stomates open wider to allow more CO2 to enter. Conversely, when the CO2 levels are high, the stomates partially close to restrict CO2 intake.
5. Temperature: Temperature affects stomatal regulation. High temperature can increase water stress, leading to stomatal closure to conserve water. Additionally, some plants may have a specific temperature threshold at which stomates will close to reduce water loss.
6. Environmental cues: Other environmental factors, such as air humidity and air pollutants, can also trigger stomatal closure as a protective mechanism.
Understanding the feedback mechanism at the stomates involves studying the plant's response to various stimuli and the regulation of hormones. Experimental techniques like leaf-level gas exchange measurements, molecular analysis, and hormone profiling can provide insights into the complex mechanisms underlying stomatal regulation.