Common Hormone Helps Marigolds Beat Salt Stress, Study Finds

Marigolds are among the world’s most forgiving ornamental plants, thriving in poor soils, blooming quickly and yielding essential oils prized by the flavor and fragrance industry. But even this hardy member of the Asteraceae family has limits, and one of them is salt. With roughly half of the world’s agricultural land now affected by salinity according to the United Nations Environment Program, researchers are racing to find simple, affordable ways to keep plants productive in soils that would once have been written off. A new study from the University of the Punjab in Lahore, Pakistan, offers a surprisingly accessible candidate: gibberellic acid, a naturally occurring plant hormone that can be sprayed directly onto leaves.

The research, published as an open-access paper in the journal Discover Plants, set out to test whether exogenous applications of gibberellic acid, commonly abbreviated GA3, could counteract the damage that sodium chloride inflicts on African marigold, Tagetes erecta. The team, led by Kinza Nazir with Muhammad Umair and Zahoor Ahmad Sajid, ran a pot experiment between December 2024 and March 2025 in the wire house of the university’s Botanical Garden, using two-week-old marigold seedlings raised in a mixture of garden soil and coco peat. The design was deliberately comprehensive: sixteen treatment combinations, each replicated three times, spanning four levels of salt stress and four levels of hormone application.

The salt treatments were applied fifteen days after transplanting, when seedlings were irrigated with sodium chloride solutions at concentrations of zero, 50, 100 and 150 millimolar. At the same time, plants received foliar sprays of gibberellic acid at 0, 150, 250 or 350 parts per million, applied early in the morning every seven days for a full sixty days. The hormone was first dissolved in a small amount of absolute ethanol and then diluted with distilled water, with Tween 80 added as a surfactant to improve absorption through the leaves. Because marigold leaves lack a thick cuticle, the researchers note that GA3 can enter readily through the stomata, making foliar delivery an efficient route.

The results paint a clear picture of what salt does to a marigold. As sodium chloride concentrations rose, nearly every measured parameter declined. The number of side branches fell from 12.0 in unstressed control plants to 8.5 under the harshest 150 millimolar treatment. Bud production dropped from 6.8 per plant to just 3.2. Shoot length shrank from 25.5 centimeters to 18.5, root length fell from 15.5 centimeters to under 10, and both fresh and dry weights of shoots, roots and flowers declined in parallel. Flowering was delayed too: control plants opened their first blooms after 70 days, while plants under 150 millimolar salt took 80 days, and the heaviest salt treatments produced the fewest and lightest flowers.

When gibberellic acid entered the picture, the trajectory changed. Plants receiving the hormone alongside salt grew taller, bushier and heavier than their salt-stressed counterparts. Under 50 millimolar salt, shoot length rose to as much as 29.0 centimeters with the 250 ppm spray, exceeding even the unstressed control. Branch numbers recovered substantially, with the highest count of 15.0 side branches recorded in plants given 150 ppm GA3 without salt. Root growth responded as well, with the longest roots, 18.6 centimeters, appearing in plants treated with 350 ppm GA3 alone. Fresh shoot biomass climbed dramatically in some combinations, reaching 44 grams in plants sprayed with 250 ppm GA3 under no salt, compared with values around 17 to 19 grams under salt stress without hormone.

The flowering data were equally striking. Salt-stressed plants that received GA3 bloomed earlier than salt-stressed plants without it, with flowering times under salinity dropping from as late as 80 days to as few as 69 or 70 days depending on the combination. Flower counts per plant, which fell to 4.0 under moderate salt stress without hormone, rose to as high as 9.0 flowers per plant under 150 millimolar salt combined with 350 ppm GA3. The single most productive treatment overall was 350 ppm GA3 without salt, which yielded 13.0 flowers per plant, along with the highest fresh flower weight of 18.0 grams. Flower dry weight followed the same pattern, peaking at 3.4 grams in hormone-treated plants.

To understand the mechanism behind these visible improvements, the team measured the activity of three key antioxidant enzymes: peroxidase, superoxide dismutase and catalase. These enzymes form the plant’s first line of defense against reactive oxygen species, the chemically aggressive molecules, including superoxide radicals, hydroxyl radicals and hydrogen peroxide, that accumulate when salt stress disrupts cellular metabolism. At low concentrations these molecules act as signaling agents, but in excess they trigger peroxidation of lipids, proteins and nucleic acids, damaging the very machinery the cell needs to survive. Salt stress alone produced a mild rise in enzyme activity at 50 and 100 millimolar NaCl, but activity fell back at the harshest 150 millimolar level, suggesting the plant’s native defenses were being overwhelmed.

Gibberellic acid pushed those defenses back up. Superoxide dismutase activity, measured in units per milligram of protein, increased by as much as 72 percent in plants under 150 millimolar salt sprayed with 150 ppm GA3, with gains of 49 percent at 100 millimolar and 30 percent at 50 millimolar also recorded. Peroxidase activity rose by between 2 and 12 percent across the salt levels, while catalase activity climbed sharply, reaching 4.96 units per milliliter in plants under 100 millimolar salt with 150 ppm GA3, compared with 2.97 in salt-stressed plants without the hormone. The authors interpret this as evidence that GA3 strengthens the antioxidant system, protecting cells from oxidative damage and thereby allowing growth and flowering to continue under conditions that would otherwise suppress them.

The findings align with a growing body of literature on hormone-mediated stress relief. Previous work has shown that GA3 can improve ion homeostasis, maintain membrane permeability, enhance the accumulation of compatible osmolytes and regulate the expression of stress-responsive genes. Studies on okra, castor bean, potato and goldenrod have all reported similar benefits under salinity, and the marigold results extend that pattern to a commercially important ornamental. The authors also point to GA3-induced invertase activity in elongating shoots, which promotes the accumulation of hexoses needed for cell wall biosynthesis, as a plausible route by which the hormone accelerates growth even when salt is present in the root zone.

The practical implications are considerable. Marigold is not merely decorative: the genus supplies roughly 15 tons of essential oil annually for the flavor and fragrance industry, its flowers are a source of flavonoids and phenolic compounds for pharmaceutical use, and the plant has documented potential for phytoremediation of heavy metals such as zinc, cadmium and nickel. In Pakistan, where agriculture contributes 22.7 percent of GDP and salinity is a persistent threat to the Indus Basin, a cheap foliar spray that partially restores productivity on saline land could matter far beyond the flower bed. The study’s conclusion identifies 350 ppm as the most effective concentration for alleviating salt stress, though the authors caution that the protection is partial rather than complete, and they call for field trials across different species and soil types. Still, the message is clear: one of horticulture’s oldest tools, a simple hormone spray, may help ornamental crops hold their ground as the world’s soils grow steadily saltier.

Subject of Research: Mitigation of salt stress in marigold (Tagetes erecta) using exogenous gibberellic acid

Article Title: Gibberellic acid assisted modulations in growth, morphology and antioxidant activity of marigold (Tagetes erecta L.) grown in saline soil

Article References: Nazir, K., Umair, M., & Sajid, Z. A. (2026). Gibberellic acid assisted modulations in growth, morphology and antioxidant activity of marigold (Tagetes erecta L.) grown in saline soil. Discover Plants, 3(1), Article 406. https://doi.org/10.1007/s44372-026-00879-4

Image Credits: AI Generated

DOI: 10.1007/s44372-026-00879-4

Keywords: gibberellic acid, salinity stress, Tagetes erecta, marigold, antioxidant enzymes, plant growth regulators, NaCl, floriculture, reactive oxygen species, foliar spray, phytohormones, plant physiology