Document Type : Original Article
Authors
1
Department of Agriculture, Bam.C., Islamic Azad University, Bam, Iran
2
Crop and Horticultural Science Research Department, Southern Kerman Agricultural and Natural Resources Research and Education Center, AREEO, Jiroft, Iran
10.22077/escs.2026.9310.2364
Abstract
Introduction
Medicinal and aromatic plants, especially cumin (Cuminum cyminum L.), face significant productivity challenges due to increasing drought stress in arid regions. Water scarcity, particularly during critical growth stages, disrupts photosynthesis and pigment synthesis, leading to substantial yield losses. While irrigation management is essential, integrating agro-technical strategies such as seed priming and foliar applications has emerged as a promising way to enhance stress tolerance. Seed priming with osmotic agents like polyethylene glycol (PEG) and the foliar application of micronutrients or plant growth regulators (e.g., putrescine) can mitigate drought impacts by maintaining metabolic functions and nutrient uptake. However, the combined effects of different irrigation regimes, seed priming methods, and foliar treatments on the physiological and yield components of cumin remain poorly understood. Therefore, this study aimed to evaluate the interaction between irrigation timing, seed priming, and foliar application of nano-chelated iron, zinc, and putrescine on the physiological traits and yield of cumin in Jiroft, southern Iran.
Materials and methods
A two-year study (2022–2023) in Jiroft, southern Iran, explored strategies to mitigate drought impacts on cumin by evaluating the effects of seed priming and foliar nutrient application. The experiment utilized a split factorial design within a randomized complete block framework, testing three irrigation regimes (full irrigation, irrigation termination after flowering, and irrigation termination after seed formation), three seed priming methods (control, distilled water, polyethylene glycol), and four foliar nutrient treatments (control, nano-chelated iron, nano-chelated zinc, putrescine).
Results and discussion
Increased rainfall in the second year improved key physiological and yield parameters, including a 5.5% rise in relative water content (RWC), a 27.7% increase in chlorophyll *a*, 17.8% more umbels per plant, and a 6.6% boost in seed yield compared to the first year. However, drought stress induced by early irrigation termination severely reduced performance. Terminating irrigation after flowering caused the most significant declines: a 44% drop in RWC, 20% and 28% reductions in chlorophyll *a* and *b*, respectively, and a 27.7% decrease in carotenoids. Yield-related traits were equally affected, with 18.4% fewer umbels per plant, 24% fewer seeds per umbel, 22.6% lower thousand-seed weight, and a 37% reduction in seed yield compared to fully irrigated plants. Irrigation cessation after seed formation also impaired yields but to a lesser extent, underscoring the critical sensitivity of the flowering stage to water scarcity. Seed priming and foliar nutrient applications emerged as effective countermeasures. Polyethylene glycol (PEG) priming outperformed distilled water, increasing chlorophyll *a* by 17%, umbels per plant by 23%, and seed yield by 2% compared to non-primed controls. Foliar sprays of nano-chelated iron, zinc, or putrescine further enhanced resilience, elevating chlorophyll *a* by 40%, RWC by 14.5%, and seed yield by 10%. Nano-chelated micronutrients demonstrated particular efficacy, likely due to improved nutrient absorption under stress. These interventions also boosted biological yield (10–20%) and stabilized plant water status, essential for maintaining metabolic functions during drought.
Conclusion
The findings emphasize the necessity of maintaining irrigation during flowering, the most drought-sensitive growth stage for cumin, as water scarcity at this phase disrupts photosynthesis, pigment synthesis, and seed development, leading to irreversible yield losses. Integrating agro-technical strategies such as PEG-based seed priming and foliar application of nano-micronutrients or putrescine can mitigate these effects. PEG priming enhances seed vigor and stress tolerance, while foliar nutrients compensate for reduced root uptake under drought, directly supporting chlorophyll synthesis and osmotic regulation. For farmers in arid regions like Jiroft, the study recommends prioritizing irrigation during flowering to safeguard yield potential, adopting seed priming (preferably with PEG) to improve drought resilience, and applying foliar sprays of nano-chelated iron/zinc or putrescine during critical growth stages to enhance physiological efficiency. These strategies not only address immediate drought challenges but also contribute to long-term agricultural resilience, aligning with global demands for sustainable production of medicinal plants. By combining moisture conservation, seed priming, and targeted nutrient management, cumin productivity can be stabilized even in water-limited environments, ensuring a reliable supply of this high-value crop.
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