What if the same hormone that helps ginseng conserve water during drought also boosts its valuable medicinal compounds? This study tests that connection—and finds ABA strengthens both drought resistance and ginsenoside biosynthesis. Drought stress adversely affects the production of the perennial medicinal herb Panax ginseng C.

A. Meyer, while abscisic acid, or ABA, regulates many processes in plant growth, development, and response to environments. The central question was whether drought resistance is regulated by ABA in Panax ginseng.

The study reports that exogenous ABA attenuated growth retardation and root shrinking under drought conditions. The abstract also reports protection of the photosynthesis system, enhanced root activity, improved antioxidant protection, and enhanced accumulation of ginsenosides, the pharmaceutically active components.

Plants face stresses including water deficit, salinity, extreme temperatures, and pathogen infections. Drought causes osmotic stress and water loss from plant tissues, adversely affecting plant growth and development. Plants respond through several mechanisms, including closing stomata, reducing photosynthesis, enhancing root activity, scavenging reactive oxygen species, and accumulating osmolytes.

ABA plays an important role in the plant response to drought stress and can promote stomatal closure to prevent water loss. Panax ginseng grows for four to six years, so it experiences environmental challenges over a long growth period. Its optimal relative soil water content is reported as sixty to eighty percent.

Drought can damage ginseng growth, making new strategies to mitigate drought stress essential for securing Panax ginseng production. The unresolved issue was whether ABA regulates drought resistance and ginsenosides biosynthesis in Panax ginseng. The study found both were significantly enhanced by ABA treatment.

The experiment used three-year-old Panax ginseng seedlings. Watering was stopped either without ABA, called drought treatment, or with fifteen micromolar ABA spraying, called drought plus ABA treatment. After thirty-five days, leaves in the drought group showed significant wilting, whereas leaves in the drought plus ABA group remained turgid.

The drought group also showed serious root epidermis shrinkage, while drought plus ABA did not cause a significant change in the root epidermis phenotype. Soil water content showed no obvious difference between the two treatments.

Figure one compares ginseng seedlings before and after thirty-five days without watering, with or without leaf-applied ABA. The leaves show marked wilting under drought, while the drought-plus-ABA plants remain visibly turgid; the root images provide the corresponding treatment comparison.

Panel C reports soil relative moisture content, with letters marking statistically significant differences at p less than zero point zero five, supporting ABA’s association with enhanced drought resistance. The study then examined stomatal movement after twenty-eight days of drought or drought plus ABA treatment, measuring stomatal apertures under a microscope.

Drought stress significantly induced stomatal closure, and stomatal apertures in the drought-plus-ABA group were smaller than those in the drought group. The stated result is that ABA improves stomatal closure under drought stress.

Figure two compares ginseng stomata under control conditions, drought, and drought plus ABA after twenty-eight days. The micrographs show progressively more closed pores, and the bar chart reports apertures of about one point six, one point zero, and zero point seven micrometers, respectively, with different letters indicating significant differences.

This matters because it supports the authors’ conclusion that drought induces stomatal closure and ABA treatment promotes that response, potentially limiting water loss. The study measured chlorophyll content to examine the effect of drought stress on photosynthesis.

Drought significantly reduced chlorophyll in leaves, but ABA spraying had no effect on chlorophyll content under the tested conditions. Root activity was another indicator of plant growth status under stress. Drought enhanced root activity, and root activity was stronger in the drought-plus-ABA group than in the drought group.

Figure three compares control, drought, and drought plus ABA treatments across six physiological indicators in ginseng after thirty-five days without water, with ABA sprayed every two days. Drought lowers chlorophyll, while ABA preserves it; the ABA treatment also shows increased root activity and antioxidant enzyme activities, alongside reduced MDA and soluble sugar relative to drought alone.

These measurements suggest that ABA helps ginseng maintain photosynthetic function and limit drought-related cellular damage. Plants use free-radical-scavenging enzymes to avoid reactive oxygen species damage to cells. The enzymes listed here include superoxide dismutase, catalase, and peroxidase.

Under drought, superoxide dismutase and catalase activities increased. Enzyme activity in the drought-plus-ABA group was higher than in the drought group. These results indicated that exogenous ABA improved the performance of the antioxidant protection system in Panax ginseng.

Ginsenoside is the most valuable active component in Panax ginseng. The study analyzed ginsenoside content in roots under drought or drought plus ABA using high-performance liquid chromatography, or HPLC. Both monomer and total ginsenoside increased greatly in roots under drought treatment and drought-plus-ABA treatment.

Ginsenoside content was higher with drought plus ABA than with drought without ABA, indicating that ABA enhanced ginsenoside accumulation under drought conditions. Figure four shows stacked HPLC measurements of ginsenoside content in Panax ginseng roots after thirty-five days of control, drought, or drought plus ABA treatment.

The bars separate other ginsenosides from Rg1, Re, Rb1, and Rd, while also showing their combined content. The authors use this profile to report that drought is associated with increased ginsenoside accumulation, with ABA treatment under drought conditions producing the highest total shown in the chart.

Three-hydroxy-three-methylglutaryl CoA reductase, or HMGR, is known as a rate-controlling enzyme of ginsenoside biosynthesis in Panax ginseng. To test potential regulation by ABA, the study treated Panax ginseng with ABA and examined PgHMGR expression using quantitative reverse-transcription polymerase chain reaction.

Expression of PgHMGR1 and PgHMGR2 was induced by ABA treatment, suggesting that their up-regulation might contribute to ABA-enhanced ginsenoside accumulation under drought conditions. Figure five compares relative PgHMGR1 and PgHMGR2 expression in control leaves with leaves treated with thirty micromolar ABA for three hours.

Both transcript levels show clear induction after ABA treatment, with PgHMGR1 reaching roughly fourteen-fold and PgHMGR2 roughly seven-fold on the plotted scale. Because HMGR is a rate-controlling enzyme in ginsenoside biosynthesis, the authors interpret this response as evidence that ABA-related upregulation of these genes may contribute to ginsenoside production.

The study's results showed that drought-related growth retardation and root shrinking in Panax ginseng were compromised by ABA treatment. Exogenous ABA application protected the photosynthesis system, enhanced root activity, improved the antioxidant protection system, and alleviated excessive soluble sugar accumulation under drought conditions.

Ginsenosides biosynthesis and PgHMGR expression were also enhanced by ABA treatment, supporting promotion of drought resistance and ginsenosides biosynthesis by ABA. The study connects its ginsenoside result with earlier findings that drought stress promoted ginsenoside accumulation and expression of ginsenoside biosynthesis genes, while ABA accumulation and signaling were also potentiated by drought stress.

PgHMGR1 and PgHMGR2 are described as key regulatory enzymes of ginsenoside biosynthesis and are predominantly expressed in roots. This study found that their expression was significantly enhanced by ABA treatment. The discussion therefore proposes that ABA might govern ginsenoside biosynthesis by directly regulating PgHMGR1 and PgHMGR2 expression, providing a new avenue for enhancing drought resistance and ginsenoside production in Panax ginseng.

In Panax ginseng, ABA treatment was associated with stronger drought resistance, improved physiological protection, higher ginsenoside accumulation, and increased PgHMGR1 and PgHMGR2 expression. That makes ABA a potential route toward protecting ginseng production while improving its medicinal output.