Growth Regulators (Phytohormones) MCQ MBBS CEE Entrance Nepal
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Growth Regulators (Phytohormones) in Plants
Introduction
Growth regulators, commonly known as phytohormones, are naturally occurring organic compounds that play a critical role in regulating various physiological processes in plants. They influence growth, development, and responses to environmental stimuli, ensuring plants can adapt and thrive.
Types of Phytohormones
There are several major classes of phytohormones, each with distinct functions:
1. Auxins
Auxins are primarily involved in cell elongation, apical dominance, and root formation. They promote phototropism (growth toward light) and gravitropism (growth in response to gravity).
2. Gibberellins
Gibberellins stimulate stem elongation, seed germination, and flowering. They play a vital role in breaking seed dormancy and promoting growth in response to environmental cues.
3. Cytokinins
Cytokinins promote cell division and differentiation, particularly in shoots and roots. They help delay leaf senescence and are involved in regulating nutrient mobilization and growth.
4. Abscisic Acid (ABA)
ABA is primarily associated with stress responses. It promotes stomatal closure during drought conditions, regulates seed dormancy, and helps plants cope with adverse environmental conditions.
5. Ethylene
Ethylene is a gaseous hormone that regulates fruit ripening, flower wilting, and leaf abscission. It plays a key role in responses to stress and developmental processes.
Functions of Phytohormones
Phytohormones regulate a wide range of processes in plants, including:
- Growth Regulation: Control the rate of cell division and elongation, influencing overall plant growth and architecture.
- Developmental Processes: Regulate processes such as flowering, fruit development, and seed germination.
- Responses to Environmental Stimuli: Enable plants to respond to changes in light, gravity, and water availability, ensuring survival in varying conditions.
- Stress Responses: Help plants adapt to abiotic stresses (e.g., drought, salinity) and biotic stresses (e.g., pathogens), contributing to resilience.
Interactions Among Phytohormones
The effectiveness of phytohormones often depends on their interactions with one another. For example:
- Auxins and cytokinins work together to regulate shoot and root development.
- Gibberellins can enhance the effects of auxins in promoting stem growth.
- ABA can inhibit the actions of gibberellins, affecting seed germination and growth during stress.
Conclusion
Understanding the role of growth regulators (phytohormones) in plants is essential for improving agricultural practices, enhancing crop yields, and developing sustainable management strategies. By manipulating phytohormone levels, we can optimize plant growth and resilience in changing environments.
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