article · Journal of Plant Growth Regulation
Drought stress significantly restricts crop productivity and lowers agricultural yields, posing notable economic challenges. In geranium, an essential medicinal and aromatic crop, water deficit reduces overall biomass and depletes monoterpenoids such as citronellol, even while raising the proportion of essential oil and defensive secondary metabolites. Applying foliar treatments of riboflavin, also known as vitamin B2, counters these negative impacts. Across trials testing doses of 25, 50, and 100 milligrams per litre, a concentration of 50 milligrams per litre proved most effective. This treatment enhanced photosynthetic performance, stimulated pigment and phytohormone accumulation, boosted nutrient uptake, and supported antioxidant mechanisms. Crucially, it restored essential oil quality by preserving citronellol and generated peak essential oil yields of 41 litres per hectare in the initial harvest and 34 litres per hectare in the subsequent harvest under stress conditions.
Water scarcity increasingly threatens the cultivation of high-value aromatic and medicinal herbs. Identifying accessible treatments that sustain yields and protect oil composition during dry periods is critical for growers. Riboflavin acts as an effective, environmentally friendly biostimulant that protects plant physiology and retains the chemical quality of geranium oil without relying on synthetic chemical protectants.
This work demonstrates an applied, field-relevant approach for essential oil producers and agricultural input suppliers seeking eco-friendly biostimulants. The findings point to foliar riboflavin sprays at 50 milligrams per litre as an immediate agronomic intervention to secure crop yields and oil quality during water deficits. As the testing measured clear per-hectare yields, the intervention appears close to field-level validation and practical adoption by commercial herb growers.
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Abstract Drought is a major abiotic stress factor that reduces crop yields and causes substantial economic losses. This study focuses on understanding the mitigating effect of riboflavin on geranium, a valuable medicinal and aromatic herb, under drought stress to improve crop resilience and productivity. Riboflavin application at 25, 50, 100 mg/L significantly stimulated geranium growth, photosynthetic activity, pigment biosynthesis, phytohormone concentrations, and nutrient accumulation at the second cut stage. The most significant biostimulatory improvements were observed at 50 mg/L, resulting in the highest oil yield of 41 L/hectare for the first cut and 34 L/hectare for the second cut. Riboflavin acts as an elicitor, modifying the essential oil profile under both normal and drought conditions. Riboflavin’s impact on oil profiles varies by concentration. While low concentrations (25 mg/L) maintain control-like oil profiles, moderate levels (50 mg/L) preserve citronellol and restore oil quality under drought. High concentrations (100 mg/L) shift the oil profile towards oxygenated monoterpenoids. Drought typically reduces monoterpenoids, primarily citronellol (4.8–fold), while increasing sesquiterpenoids and oxidized derivatives, thereby stimulating defensive compounds such as parthenolide and rose oxide. Drought reduced yield but increased the oil percentage by 1.4–fold (first cut) and 2.7–fold (second cut) compared to non-stressed conditions. Additionally, drought increased levels of carotenoids, ABA, oxidative enzymes, antioxidant enzyme (catalase), osmoprotectants, and malondialdehyde, while reducing nutrient content. Riboflavin alleviated drought by enhancing antioxidant capacity and osmoprotection, optimizing catalase activity, growth-promoting phytohormone levels, and reducing malondialdehyde, oxidative enzymes, and sodium levels. This ultimately improved photosynthetic efficiency, growth, nutrients, and oil yield, offering a cost-effective, eco-friendly drought-mitigation strategy.
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DOI: 10.1007/s00344-026-12373-y
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