A team of agronomists from RUDN University, in collaboration with colleagues from China and Iran, has made a significant breakthrough in mitigating the toxic effects of aluminum on tomatoes in acidic soils. Their research, published in the South African Journal of Botany, unveils the protective role of melatonin, a hormone that aids in nitric oxide production, preventing the destructive impact of aluminum on plant cells.
Approximately 40% of the world’s agricultural soils are acidic, posing a challenge for optimal crop growth. In highly acidic soils, aluminum transforms into soluble forms, inhibiting the growth of high-quality crops. The toxic nature of aluminum disrupts cell membranes and signaling pathways, prompting plants to employ various strategies for aluminum tolerance. Nitric oxide emerges as a crucial gas in aiding plants to combat stress, including exposure to heavy metals like aluminum.
Dr. Meisam Zargar, a doctor of agricultural sciences and associate professor of the Agrobiotechnological Department at RUDN, highlighted the significance of nitric oxide in plant resistance. “One of the most important gases in plants—nitric oxide—increases resistance to stress, including heavy metals,” explained Dr. Zargar.
To enhance nitric oxide production in plants and counteract aluminum toxicity, agronomists turned to melatonin. Known for regulating circadian rhythms and the antioxidant system in animals and plants, melatonin also has a known association with nitric oxide production. However, it was uncertain whether additional melatonin could aid plants in coping with the toxic effects of aluminum.
In their experiment, the agronomists planted tomato seeds in an acidic environment and treated them with various combinations and concentrations of aluminum, melatonin, and potassium salt, a nitric oxide absorber. After 42 days, the researchers observed and compared various plant indicators.
The addition of aluminum led to an increase in oxidative stress markers and aggressive oxidants, slowing plant growth and reducing photosynthetic pigment content. However, the introduction of melatonin alongside aluminum activated antioxidant activity, protecting cell walls and preserving photosynthetic pigments. Notably, the content of nitric oxide in both leaves and roots increased, indicating melatonin’s role in blocking aluminum at the root and preventing its progression into stems and leaves.
The researchers also discovered that potassium salt, a nitric oxide absorber, neutralized the protective effect of melatonin, affirming the crucial role of nitric oxide in plant defense mechanisms.
Dr. Zargar concluded, “Melatonin increased the activity of antioxidant enzymes in roots and leaves, minimizing oxidative stress and protecting the cell membrane. The results indicate the participation of nitric oxide in protective reactions. We have shown that melatonin contributes to the adaptation of tomato seeds to the toxic effects of aluminum through the regulation of nitric oxide.” This research opens up new avenues for harnessing melatonin to enhance crop resilience in acidic soil conditions, marking a significant stride in sustainable agronomy practices.