Melatonin acts as a circadian regulator, growth promoter, antioxidant, and free radical scavenger. Additionally, it promotes the development of flowers and fruits and provides defense against environmental stress conditions. The effectiveness of melatonin can vary among different plant species and under different environmental conditions. In an era where sustainability holds great importance, melatonin seamlessly aligns with the principles of organic farming. Its natural origins make it a valuable asset for those looking to adopt eco-friendly and sustainable agricultural practices.
Introduction
Melatonin, also known as N-acetyl-5-methoxytryptamine, is a hormone well-recognized in the pineal gland of mammals and identified by Lerner and colleagues in 1958. It is primarily associated with regulating sleep-wake cycles in animals. Beyond its role in the realm of sleep, melatonin has been gaining attention for its potential benefits in agriculture. The presence of melatonin in plants was initially identified independently by Dubbels et al. and Hattori et al. in 1995. The melatonin content varies across different plant organs and tissues, with higher concentrations observed in aromatic plants and leaves compared to seeds. Phytomelatonin plays a crucial role in regulating plant reproductive physiology and defending plant cells against apoptosis triggered by adverse environmental conditions.
Its various physiological functions include potential involvement in flowering, the maintenance of circadian rhythms and photoperiodicity, as well as acting as a growth regulator. This molecule is a potent antioxidant, preserving mitochondrial homeostasis and enhancing the expression of genes for antioxidant enzymes. It exhibits auxin-like activity, influencing the growth of roots, shoots, and explants. Melatonin also plays a role in activating seed germination and promoting the development of roots (both lateral and adventitious). Evidence also suggests the participation of melatonin in preserving chlorophyll, thereby enhancing photosynthesis. Additionally, it contributes to delaying induced leaf senescence. While research in this area is ongoing, the multifaceted advantages of using melatonin to enhance crop growth, stress tolerance, and overall agricultural productivity.
Biosynthesis of Melatonin in Plants:
While traditionally associated with animals, melatonin is also synthesized in plants. The entire biosynthetic pathways in plants and the enzymes responsible for phytomelatonin production have not been fully investigated yet. Studies utilizing radioisotope tracer techniques have shown that tryptophan serves as a shared precursor for serotonin, melatonin, and indole-3-acetic acid (IAA). Additionally, there is a possibility that plants can absorb plants can take it from the soil but also synthesize it through a series of enzymatic reactions, involving enzymes such as tryptophan decarboxylase and serotonin N-acetyltransferase. The presence of melatonin in various plant tissues, including roots, leaves, and seeds, suggests its widespread significance in the plant kingdom.
Benefits of melatonin in agriculture
- Biological Rhythms Regulation
- Stress Tolerance
- Delayed Senescence
- Enhanced Nutrient Uptake
- Improved Seed Germination
- Environmental Stress Mitigation
- Improved Disease Resistance
- Defense against herbivores
- Increased Crop Yield
- Potential for Organic Farming
1. Biological Rhythms Regulation:
Just as in animals, melatonin in plants is involved in the regulation of circadian rhythms. It helps synchronize various physiological processes within the plant to the day-night cycle, influencing aspects such as stomatal movement and photosynthesis. This circadian regulation by melatonin contributes to the overall fitness and adaptability of plants in their environment. Circadian fluctuations in melatonin levels have been reported not only in higher plants but also in algae and dinoflagellates. Understanding and manipulating these rhythms could help optimize various physiological processes, leading to improved crop performance.
2. Stress Tolerance:
One of the most significant contributions of melatonin to plant biology is its role in enhancing abiotic stress tolerance. Plants, like any living organisms, exposed to adverse environmental conditions, such as drought, salinity, or extreme temperatures, often experience increased levels of oxidative stress. Melatonin acts as a potent antioxidant, scavenging free radicals and mitigating oxidative damage. Additionally, melatonin helps regulate the expression of stress-related genes, promoting the plant's ability to withstand unfavorable conditions.
3. Delayed Senescence:
Senescence is the aging process in plants that leads to reduced growth and productivity. Melatonin may help delay senescence, allowing plants to maintain their vitality for a longer period and potentially increasing the overall yield.
4. Enhanced Nutrient Uptake:
Efficient nutrient uptake is crucial for plant health. Melatonin has been associated with increased nutrient uptake in some plant species. This could result in improved nutrient utilization efficiency and better overall plant health.
5. Improved Seed Germination:
The journey of a crop begins with a seed, seed germination is a critical phase in the plant life cycle. Melatonin facilitates an optimal start by positively impacting seed germination rates, ensuring a uniform and robust establishment of crops.This can be particularly beneficial for ensuring a more uniform and robust crop establishment.
6. Environmental Stress Mitigation:
In environments with high levels of environmental challenges, such as pollution or extreme weather conditions, melatonin may assist plants in coping with these challenges, leading to healthier and more resilient crops.
7. Improved Disease Resistance:
Beyond abiotic stress, melatonin also plays a role in plant defense against pathogens. Studies have demonstrated that melatonin can induce defense mechanisms, leading to increased resistance against various pathogens, including bacteria, fungi, and viruses. This highlights melatonin's potential as a natural alternative to chemical pesticides in crop protection.
8. Defense against herbivores
Melatonin, possessing a bitter and unpleasant taste, acts as an alkaloid and serves as a defense mechanism against herbivores16. Moreover, the consumption of plants with elevated melatonin levels, such as walnuts can disrupt the physiology of herbivores. Melatonin tends to accumulate in the bodies of animals.
9. Increased Crop Yield:
Studies suggest that melatonin application can lead to increased crop yields. This is attributed to its role in promoting plant growth, flowering, and fruit development.
10. Potential for Organic Farming:
As a naturally occurring substance, melatonin aligns seamlessly with the principles of organic farming. Its use offers a more sustainable and environmentally friendly approach to enhancing crop production.
Conclusion
As we conclude this exploration of the benefits of melatonin in agriculture, it's clear that this hormone holds immense potential for revolutionizing the way we approach crop cultivation. From stress tolerance to disease resistance by regulating various physiological processes and serving as a circadian regulator, growth promoter, antioxidant, and free radical scavenger. Melatonin emerges as a versatile ally for farmers seeking sustainable and high-yield agricultural practices.
