Introduction: Natural plant growth regulators, also known as plant hormones, are chemical substances produced by plants that regulate various physiological processes including growth, development, and responses to environmental stimuli. They play crucial roles in plant adaptation and productivity.

Key Types of Natural Plant Growth Regulators:

1. Auxins:
   • Description: Auxins are involved in the regulation of plant growth, especially in elongation and differentiation. They promote cell elongation in stems and inhibit it in roots, influencing plant tropisms.
   • Function: Auxins are critical in processes like phototropism (growth towards light) and gravitropism (growth in response to gravity). They also play a role in fruit development and root initiation.
   • Recent Example: The use of IAA (Indole-3-acetic acid), a natural auxin, in agriculture has shown to enhance root development in cuttings and improve crop yields. Researchers are exploring its application in precision agriculture to optimize plant growth.
2. Gibberellins:
   • Description: Gibberellins are involved in promoting cell division and elongation, seed germination, and flowering. They also influence the transition from juvenile to adult stages in plants.
   • Function: Gibberellins are essential for seed germination, stem elongation, and flowering. They counteract the effects of plant growth inhibitors and can help in overcoming dormancy.
   • Recent Example: Gibberellic acid (GA3) is used in agriculture to increase the size of fruits like grapes and strawberries, leading to improved marketability and yield.
3. Cytokinins:
   • Description: Cytokinins promote cell division and differentiation and are involved in the development of shoots and roots. They also influence nutrient mobilization and delay leaf senescence.
   • Function: Cytokinins play a role in lateral bud development, leaf expansion, and delaying aging of plants. They interact with auxins to balance growth between shoots and roots.
   • Recent Example: Zeatin, a natural cytokinin, is used in tissue culture to induce shoot formation and improve plant regeneration rates. It is also utilized in horticulture to enhance plant health and productivity.
4. Abscisic Acid (ABA):
   • Description: ABA is primarily involved in stress responses and regulating plant water balance. It plays a crucial role in seed dormancy and stomatal closure during water stress.
   • Function: ABA helps plants cope with drought conditions, cold stress, and salt stress. It inhibits growth during unfavorable conditions and promotes seed desiccation.
   • Recent Example: The application of ABA in agriculture is being explored to enhance drought resistance in crops like wheat and maize, improving yield stability under water-scarce conditions.
5. Ethylene:
   • Description: Ethylene is a gaseous hormone that regulates fruit ripening, flowering, and leaf abscission. It also influences the response to stress and senescence.
   • Function: Ethylene accelerates fruit ripening, promotes flowering, and induces leaf drop. It is crucial in the plant’s response to biotic and abiotic stresses.
   • Recent Example: The use of ethylene inhibitors in the fruit industry helps in prolonging shelf life and controlling ripening of fruits like bananas and tomatoes, thereby reducing post-harvest losses.

Applications and Benefits:

• Agriculture: Natural plant growth regulators are widely used to enhance crop yields, improve fruit quality, and optimize plant growth. For example, gibberellins and cytokinins are applied to boost crop productivity and manage plant growth.
• Horticulture: These regulators are employed in plant tissue culture for cloning and regeneration, and in floriculture to manage flowering and plant size.
• Stress Management: ABA and ethylene are used to develop stress-resistant crops and manage post-harvest processes, improving food security and sustainability.

Conclusion: Natural plant growth regulators, including auxins, gibberellins, cytokinins, abscisic acid, and ethylene, are essential for regulating plant growth and development. Their applications in agriculture and horticulture enhance productivity, manage stress, and improve crop quality. Recent advancements in understanding and utilizing these regulators continue to contribute to sustainable agricultural practices and innovative plant management strategies.