Introduction

Potato (Solanum tuberosum L.) is a vital staple crop globally, ranking fourth after rice, wheat, and maize in terms of human caloric intake. Its popularity stems from its adaptability across climates, high productivity, nutritional content, and diverse uses in both fresh and processed forms1. Vegetative propagation through seed tubers remains the principal method of potato cultivation worldwide2. Currently, potatoes represent the third most consumed vegetable and the fourth most cultivated food crop globally. In Pakistan, potatoes are grown on approximately 0.19 million hectares, producing about 4.6 million tons annually, with an average national yield of 24.2 tons per hectare. The country holds the 19th position globally in potato production and ranks 12th in exports3.

Potato cultivation in Pakistan follows a multiseasonal calendar: the main crop is planted in autumn (September–January), contributing 80–85% of the total production, with additional harvests in spring (10–15%) and summer (1–2%)4. However, potato production is frequently challenged by both abiotic and biotic stressors. Abiotic constraints include temperature extremes, drought, salinity, nutrient imbalances, poor irrigation, and soil degradation, all of which directly affect tuber initiation and development. Biotic pressures such as late blight (Phytophthora infestans), early blight (Alternaria solani), Fusarium wilt, and viral infections (e.g., Potato virus Y and X) further exacerbate yield losses5.

An additional constraint arises from postharvest physiological processes, particularly the dormancy phase, which significantly affects the timing and uniformity of sprouting. Dormancy in potato tubers is a genetically and environmentally regulated phase characterized by a temporary suspension of sprout initiation, even under optimal growing conditions. This dormancy begins post-harvest and continues until the apical buds initiate visible sprouting (usually at 2 mm length)6. Although dormancy has adaptive significance—allowing tubers to withstand unfavorable storage or overwintering conditions—it presents practical challenges, especially in commercial seed tuber production, where controlled and timely sprouting is essential for uniform crop establishment7.

The dormancy period is influenced by several factors, including cultivar genetics, plant maturity at harvest, tuber size and physiological age, and storage conditions (temperature and relative humidity)8. Inappropriate dormancy duration can either delay planting or lead to pre-harvest sprouting, both of which reduce seed viability and crop performance. Premature sprouting is associated with increased respiration, carbohydrate depletion, tissue desiccation, and ultimately loss of commercial quality9.

To regulate dormancy, both chemical and environmental approaches have been explored. Among chemical treatments, gibberellic acid (GA₃), a naturally occurring plant growth regulator, has emerged as a promising agent for breaking dormancy and promoting sprouting in seed tubers. GA₃ influences physiological and biochemical pathways associated with sprout emergence by enhancing the activity of hydrolytic enzymes, stimulating hormonal signaling, and promoting cell elongation at the tuber eyes10.

The application of GA₃ initiates key molecular mechanisms, including the upregulation of GA-responsive genes and activation of enzymes such as terpene cyclases and cytochrome P450 monooxygenases, which are involved in endogenous gibberellin biosynthesis and action. These effects collectively contribute to enhanced meristematic activity and earlier sprout initiation. However, GA₃ uptake and efficacy depend significantly on the permeability of the periderm (tuber skin). Since intact skin can impede hormone absorption, higher efficacy is often observed when tubers are freshly harvested, slightly abraded, or have undergone curing11. Environmental factors such as storage temperature and humidity also modulate the tuber’s hormonal responsiveness12. Moreover, the effectiveness of GA₃ varies across cultivars, and the optimal concentration and immersion time remain inconsistent among studies. For example, while some studies report effective dormancy break at high concentrations (e.g., 1500 ppm GA₃ combined with thiourea), such treatments may not be economically viable or scalable for resource-limited farming systems13. Lower concentrations, when properly timed and combined with effective soaking durations, may offer a practical alternative for breaking dormancy without compromising tuber quality or causing hormonal overstimulation.

In Pakistan, the postharvest handling of potato seed tubers remains suboptimal due to limited access to cold storage, poor seed certification systems, and inadequate agronomic support. These issues, coupled with the natural dormancy of locally preferred cultivars such as ‘Ratta,’ often result in delayed or uneven sprouting during planting seasons.

Given this context, optimizing the concentration and exposure duration of GA₃ treatments offers a promising avenue to enhance seed tuber performance. While previous research has established the dormancy-breaking potential of GA₃, there remains a need for cultivar-specific, locally validated recommendations tailored to Pakistan’s agricultural conditions.

The present study was designed to evaluate the effect of different GA₃ concentrations (0, 50, 100, and 150 ppm) and dipping durations (6, 12, 18, and 24 hours) on dormancy break and sprouting behavior of ‘Ratta’ potato tubers. The study aimed to measure key physiological parameters such as sprouting percentage, days to first sprout emergence, number of sprouts per tuber, sprout length and diameter, sprout fresh and dry weights, weight loss during storage, and relative water content of sprouts. These metrics collectively provide a comprehensive understanding of GA₃-induced dormancy release and the quality of subsequent sprouting, offering practical recommendations for seed tuber management.

The outcomes of this research will contribute to developing effective and affordable dormancy-breaking protocols suitable for small- to medium-scale farmers, ultimately supporting improved crop establishment, higher productivity, and enhanced profitability in Pakistan’s potato sector.

Materials and methods

This experiment was carried out during the summer of 2023 in the experimental laboratory of the Department of Horticulture at the University of Haripur, Khyber Pakhtunkhwa, Pakistan. The study employed a Randomized Complete Block Design (RCBD) with a factorial arrangement comprising two factors: gibberellic acid (GA₃) concentration and dipping duration. The GA₃ concentrations tested were 0 ppm (control), 50 ppm, 100 ppm, and 150 ppm, while the dipping durations included 6, 12, 18, and 24 h. This combination resulted in twenty treatment groups; each replicated three times. To ensure statistical reliability and to address concerns regarding small sample size, each replicate contained 15 uniformly selected seed tubers, making a total of 900 tubers used in the entire study.

In order to reduce variability and ensure the genetic integrity of the seed tubers, all tubers were procured from the National Agricultural Research Centre (NARC) in Islamabad. The cultivar used was ‘Ratta’, a variety known for its moderate dormancy and suitability to local environmental conditions. Prior to treatment, tubers were stored under controlled conditions (4 °C and 90% relative humidity) for approximately eight weeks to maintain dormancy. The physiological age of the tubers was carefully verified to ensure they had not initiated sprouting. Furthermore, only medium-sized tubers weighing between 45 and 55 g were selected, as tuber size can significantly influence both dormancy duration and sprouting vigor. Any tubers showing signs of sprouting, disease, or physical damage were excluded from the experiment.

Preparation of gibberellic acid solution

Gibberellic acid was prepared by dissolving 50, 100, or 150 mg of GA₃ powder in one liter of distilled water to obtain the desired concentrations of 50, 100, and 150 ppm, respectively while 0 ppm treatment consisted of distilled water only and served as the control. Tubers were dipped in these solutions for their respective durations (6, 12, 18, or 24 h), with proper labeling and separation between treatments.

After treatment, all tubers were air-dried for 30 min at room temperature (approximately 25 °C), then placed in open plastic trays lined with absorbent paper. These trays were stored under uniform sprouting conditions in a dark room maintained at 20 ± 2 °C with a relative humidity of 85–90%, which simulated favorable storage conditions for sprout initiation and elongation. Equal spacing was maintained among the tubers to facilitate proper air circulation and to prevent cross-contamination between treatments.

Parameters of a research experiment

Throughout the 35-day observational period, various sprouting-related parameters were recorded at weekly intervals. These included sprouting percentage, days to first sprout emergence, number of sprouts per tuber, sprout length, sprout diameter, fresh and dry weight of sprouts per tuber, tuber weight loss, and relative water content (RWC) of the sprouts. Measurements were taken from five randomly selected tubers from each replicate to ensure that observed trends represented overall treatment effects.

Statistical analysis

The data collected were subjected to statistical analysis using the software Statistix 8.1. Analysis of Variance (ANOVA) was performed to assess the main effects of GA₃ concentration and dipping duration, as well as their interaction effects. Mean separations were conducted using the Least Significant Difference (LSD) test at a 5% probability level (P ≤ 0.05).

Results

Sprouting percentage (%)

The data analysis revealed that GA₃ concentration, dipping duration, and their interaction significantly influenced the sprouting percentage of potato tubers (Fig. 1). The highest sprouting rate (98.33%) was recorded in tubers treated with 150 ppm GA₃ for 24 h. This was followed by sprouting percentages of 86.83% and 80.72% in tubers dipped in 150 ppm GA₃ for 18 and 12 h, respectively. In contrast, the lowest sprouting rate (57.41%) was observed in the control treatment, where tubers were not treated with GA₃. Overall, a nearly 50% increase in sprouting was achieved by dipping tubers in GA₃ for 24 h compared to the untreated control.

Fig. 1
Fig. 1
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Effect of GA3 concentration and dipping time on sprouting percentage of potato.

Time taken to sprouting (days)

The earliest sprouting (20.45 days) was observed in tubers treated with 150 ppm GA₃ for 24 h. This was followed by sprouting times of 21.48, 22.50, and 23.62 days in tubers dipped in the same concentration for 18, 12, and 6 h, respectively. In contrast, the longest time to sprouting (46.22 days) was recorded in the control treatment, where no GA₃ dipping was applied (Fig. 2).

Fig. 2
Fig. 2
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Effect of GA3 concentration and dipping time on the time taken to sprouting potato.

Number of sprouts per tuber

The highest number of sprouts per tuber (5.63 and 5.29) was observed in tubers treated with 150 ppm GA₃ for 24 and 18 h, respectively, followed by 4.76 sprouts per tuber in the 150 ppm GA₃ treatment with 12 h of dipping. In contrast, the lowest number of sprouts (2.22) was recorded in the control treatment, where no GA₃ was applied (Fig. 3).

Fig. 3
Fig. 3
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Effect of GA3 concentration and dipping time on number of sprouts per tuber of potato.

Fresh weight of sprouts (g)

The highest fresh weights (1.18 g and 1.14 g) were recorded in tubers treated with 150 ppm GA₃ and dipped for 24 h, followed by 1.10 g in the 150 ppm treatment with 18 h of dipping. In contrast, the lowest fresh weight (0.46 g) was observed in the control group (Fig. 4).

Fig. 4
Fig. 4
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Effect of GA3 concentration and dipping time on fresh weight of sprout (mg) of potato.

Dry weight of sprouts (g)

The highest dry weight (0.31 g) was observed in tubers treated with 150 ppm GA₃ for 24 h, followed by 0.27 g and 0.26 g in treatments with 100 ppm and 150 ppm GA₃ for 18 and 24 h, respectively. In contrast, the lowest dry weight (0.11 g) was recorded in the control group without GA₃ application (Fig. 5).

Fig. 5
Fig. 5
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Effect of GA3 concentration and dipping time on sprouting percentage of potato.

Percent weight loss (%)

The greatest weight loss of sprouts was observed in treatments with 150 ppm (77.66%) and 100 ppm (74.61%) GA₃, followed by the 50 ppm GA₃ treatment. In contrast, the control treatment without GA₃ resulted in the lowest weight loss (40.12%). With respect to dipping durations, the highest weight loss (73.42%) occurred with a 24-hour dipping period, followed by 67.86% in the 18-hour dipping treatment. The lowest weight loss (47.76%) was recorded in tubers that were not dipped (Fig. 6).

Fig. 6
Fig. 6
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Effect of GA3 concentration and dipping time on percentage weight loss (%) of potato.

Sprout length (cm)

The longest sprouts (10.23 cm) were recorded in the treatment with 150 ppm GA₃ concentration and a 24-hour dipping duration. Slightly shorter sprouts were observed in the treatments with 100 ppm GA₃ for 24 h (9.34 cm) and 150 ppm GA₃ for 18 h (9.44 cm). In contrast, the shortest sprout length (6.09 cm) was recorded in the control treatment without GA₃ application (Fig. 7).

Fig. 7
Fig. 7
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Effect of GA3 concentration and dipping time on sprout length (cm) of potato.

Sprout diameter (mm)

The thickest sprouts, measuring 5.7, 5.6, and 5.5 mm, were observed in treatments with 150 ppm GA₃ and dipping durations of 24, 18, and 12 h, respectively. Additionally, a sprout diameter of 5.6 mm was recorded with 100 ppm GA₃ and a 24-hour dipping time. In contrast, slightly thinner sprouts were observed with 100 ppm GA₃ and dipping durations of 12 and 6 h, measuring 5.05 and 4.92 mm, respectively. The control treatment, which did not involve any GA₃ dipping, exhibited the smallest sprout diameter of 4.45 mm (Fig. 8).

Fig. 8
Fig. 8
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Effect of GA3 concentration and dipping time on sprout diameter (mm) of potato.

Relative water contents (%)

The highest relative water content of sprouts was recorded in treatments with 150 ppm (83.31%) and 100 ppm (82.61%) GA₃ applications, followed by 50 ppm GA₃ (77.61%). In contrast, the lowest relative water content (73.9%) was observed in the control treatment. Regarding dipping durations, the highest relative water contents were noted with 24-hour (81.12%) and 18-hour (80.82%) dipping periods, followed by 12 h (78.97%), while the lowest value (77.22%) was recorded in tubers that were not dipped in GA₃ (Fig. 9).

Fig. 9
Fig. 9
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Effect of GA3 concentration and dipping time on relative water contents (%) of potato.

Discussion

The results of this study demonstrate that exogenous application of GA₃ significantly enhances sprouting behavior in potato tubers, including sprout emergence, growth rate, and physiological quality. These findings are consistent with earlier reports that GA₃ promotes dormancy break by triggering a cascade of physiological, biochemical, and molecular changes, including enhanced enzyme activity, activation of DNA/RNA synthesis, and increased mobilization of stored carbohydrates14,15,16,17.

The observed increase in sprouting percentage and reduction in days to first sprout emergence with increasing GA₃ concentration and immersion duration reflect GA₃ role in reprogramming dormancy-related hormonal balances. Specifically, GA₃ application is known to reduce the levels or inhibitory effects of ABA—a primary hormone involved in enforcing dormancy—and promote cytokinin activity at the tuber eyes, which enhances cell division and meristem activation18,19. The earlier emergence of sprouts in the 150 ppm GA₃ + 24 h treatment (20.45 days) compared to the control (46.22 days) suggests that GA₃ effectively shifted the tubers from a quiescent to a metabolically active state. This is likely achieved by upregulating GA-responsive genes and enhancing transcription of hydrolytic enzymes, including α-amylase, which breaks down starch into sugars used for respiration and sprout development.

The increase in the number of sprouts per tuber (up to 5.63 sprouts in the highest GA₃ treatment) can be explained by GA₃’s ability to activate multiple dormant eyes, which would otherwise remain suppressed due to apical dominance. GA₃ reduces auxin-mediated suppression of lateral bud growth, thereby allowing more eyes to break dormancy and initiate sprouting. This phenomenon is well-supported by hormonal cross-talk models where GA₃ counteracts the inhibitory effects of both auxin and ABA on lateral bud outgrowth, leading to more uniform and profuse sprouting.

In terms of sprout length, the promotion of cell elongation by GA₃ is a well-documented effect. GA₃ stimulates the synthesis of expansins and other cell wall-loosening enzymes, allowing for rapid elongation of sprouting tissue20,21. The longest sprouts (10.23 cm) in the 150 ppm GA₃ + 24 h treatment indicate that prolonged exposure enhances hormone uptake and signaling, resulting in extended cell elongation phases. Moreover, the increased availability of soluble sugars from starch hydrolysis likely supports higher osmotic potential at the elongating tips, drawing water into cells and expanding sprout tissues more rapidly.

The observed increase in sprout diameter in GA₃-treated tubers (up to 5.7 mm) is a direct result of enhanced vascular development and assimilate flow toward the sprout apex. Thicker sprouts suggest that not only is there more rapid elongation but also better structural development, possibly involving increased lignin and cellulose deposition for mechanical support22,23,24. Sprout thickness is positively correlated with seedling vigor; thicker sprouts are generally more robust and less prone to mechanical injury during planting or transplanting.

Relative water content was significantly higher in GA₃-treated tubers, reaching 83.31% in the best treatment combination. This indicates a higher level of cellular hydration, which is essential for active metabolism and rapid cell division. GA₃ likely enhances membrane permeability and aquaporin expression, facilitating more efficient water uptake and retention11,25. The strong correlation between increased sprout length and elevated RWC supports the idea that GA₃ not only stimulates biochemical growth mechanisms but also improves water relations, allowing better turgor maintenance and tissue expansion.

The enhancement of fresh and dry sprout biomass further supports GA₃’s role in stimulating reserve mobilization. The increased dry matter indicates successful translocation and conversion of stored carbohydrates into structural biomass, while higher fresh weight reflects improved water uptake and tissue hydration. This aligns with findings that GA₃ enhances sink strength of growing tissues, enabling preferential allocation of nutrients and photo assimilates26,27.

Interestingly, GA₃ treatment also led to a noticeable increase in tuber weight loss, particularly in the 150 ppm GA₃ + 24 h treatment, which reached 77.66%, nearly double that of the control. This can be attributed to increased metabolic activity, especially respiration, during the transition from dormancy to active growth. Mobilization of starch reserves to support sprouting is associated with CO₂ loss and moisture depletion, resulting in reduced tuber mass28,29,30,31. Although this weight loss may appear disadvantageous, it represents a necessary physiological cost of breaking dormancy. Efficient sprouting and higher energy turnover are typically accompanied by greater mass loss, which is acceptable in the context of seed tuber performance.

The cumulative impact of GA₃ on sprout number, length, diameter, RWC, biomass, and emergence timing indicates a coordinated physiological enhancement driven by hormonal regulation. The interaction between GA₃ concentration and immersion time is particularly noteworthy, as the best outcomes were observed at the highest levels of both variables. This suggests a threshold effect, beyond which hormonal signaling and tissue responsiveness are maximized. From a practical standpoint, the findings indicate that 150 ppm GA₃ applied for 24 hours is an effective protocol for promoting dormancy break in the ‘Ratta’ cultivar, potentially improving planting uniformity and early vigor.

Future research should investigate the molecular expression patterns of GA₃-responsive genes and explore the potential synergy between GA₃ and other hormones or treatments such as cold conditioning, ethylene inhibitors, or thiourea. Additionally, field validation under variable environmental conditions will help confirm the long-term agronomic benefits of this approach.

GA₃ application represents a viable strategy to break dormancy and enhance sprouting in potato seed tubers. Its efficacy depends not only on the concentration used but also on the duration of exposure, with longer soaking periods allowing for more effective hormone penetration and signal transduction. These findings provide actionable insights for improving seed tuber management, particularly in regions like Pakistan where storage conditions and planting windows are often constrained.

Conclusion

This study emphasizes the pivotal role of gibberellic acid (GA₃) in breaking tuber dormancy and enhancing sprout growth. The results clearly demonstrate that both higher concentrations of GA₃ and longer dipping durations significantly improved sprout number, length, diameter, and relative water content, while also promoting robust root development. These improvements are likely attributed to GA₃’s influence on carbohydrate mobilization and enhanced metabolic activity, which collectively foster sprout growth. Although GA₃ treatment accelerated tuber weight loss, this was linked to the increased metabolic rate and growth of sprouts, highlighting its potential to optimize seed tuber quality. This research offers valuable insights into the application of GA₃ for improving seed potato production and can serve as a foundation for future studies aiming to enhance crop management and seed multiplication strategies.