The phytomelatonin clock in plants

Melatonin (N-acetyl-5-methoxytryptamine) is a natural compound that regulates the biological clock in humans, animals, and plants.

💤 In humans and animals, it is a sleep hormone produced in the pineal gland. In plants, it was discovered in 1995 and named “phytomelatonin.”

🔬 The biosynthesis of phytomelatonin is strongly dependent on the circadian rhythm and environmental signals, and its production begins with the amino acid tryptophan.

🧬 Unlike animals, which obtain tryptophan from their diet, plants synthesize it through the shikimic acid pathway using:

• tryptophan hydroxylase (TDC, T5H),

• serotonin N-acetyltransferase (SNAT),

• caffeic acid O-methyltransferase (COMT),

• and acetyl-O-methyltransferase (ASMT).

What do plants gain from producing phytomelatonin?

➡️ Its functions fall into two main groups: supporting plant development and improving stress tolerance.

🌱 In plant biology, it plays a role in:

• controlling seed development, dormancy, and germination,

• maintaining hormonal balance,

• regulating flowering, leaf senescence, and fruit ripening,

• and improving nutrient uptake.

🌡️ Under stressful conditions, it helps with:

• antioxidant protection by neutralizing reactive oxygen species (ROS),

• tolerance to abiotic stress,

• and protecting against pathogens.

🍃 Additionally, foliar application of melatonin helps plants protect themselves against diseases such as gray mold, black spot, and storage diseases.

🚜 Phytomelatonin is a natural regulator of plant life processes, supporting their healthy growth and sustainable agriculture.