Iranian Journal of Seed Research

Extended Abstract
Introduction: Germination and seedling establishment are the primary stages of crop growth that are highly sensitive to salinity and drought stresses. On the other hand, seed hardness affects the quality of plant germination. Therefore, the aim of this study was to analyze the effect of seed pre-treatment on germination characteristics of Medicago scutellata var Rabinson.
Material and methods: In the present study, the effects of pre-treatment methods of scarification (sand paper, knife and sand), stratification (0, -5, -10, and -15 ^°C), ultrasonic waves (3, 6, 9, 12, and 15 min), and magnetic field (two intensities of 125 and 250 mT in 4 times exposure by 6, 12, 18, and 24 h) on seed germination of annual medic germination affected by salinity and drought stresses (0, -3, -6, -9, and -12 bar) were investigated with three replications. Twenty seeds per Petri dish were used for each treatment. Seedlings were incubated in the dark at 20/18±0.3^°C in a growth chamber. After ten days, the dry weight of the seedling was obtained after oven drying at 70^°C. Root length, shoot length, seed germination percentage, seedling growth rate (SLGR), the weight of mobilized seed reserve (WMSR), seed reserve depletion (SRDP), and seed reserve utilization efficiency (SRUE) were measured.
Results: Based on the preliminary results using Taguchi method, the -15 °C stratification treatments under salinity and drought, 6 and 9 min of exposure to ultrasonic waves under salinity and drought, and magnetic field intensity of 250 mT for 6 and 9 h were chosen for the experiment of salinity and drought, respectively. In salinity experiment, the maximum root length (23.47 mm), shoot length (15.76 mm), weight of mobilized seed reserve (0.119 mg per seed), and seed reserve depletion percentage (58.9 %) was in scarification treatment; the maximum seed germination (47.2 %) was observed in control treatment; the maximum seedling dry weight (0.195 mg) was identified in magnetic field treatment; and the maximum seed reserves utilization efficiency (0.665 mg.mg.seed^-1) was obtained in ultrasonic waves treatments. In drought experiment, the maximum root length (22.84 mm), shoot length (8.09 mm), seed germination (49.93 %), the weight of mobilized seed reserve (0.096 mg per seed), and seed reserve depletion percentage (43.1 %) was measured in ultrasonic treatment; the maximum seedling dry weight (0.09 mg) was found in magnetic field treatment; and the maximum SRUE (0.516 mg.mg.seed^-1) was observed in control treatment.
Conclusions: According to the results, there is a direct relationship between the decline in seedling dry weight and the decline in the weight of mobilized seed reserve. However, the scarification and ultrasonic waves' treatments had significant effects on seedlings resistance to salinity and drought, respectively. Furthermore, the use of ultrasonic waves and scarification produced higher germination percentage and more vigorous seedlings under drought and saline conditions. In terms of germination and seedling growth, the differences among the treatments increased by the increase in stress intensity. This advantage led to greater seed reserve utilization. Moreover, pre-treatment methods resulted in longer cotyledon length and improvement in vigorous seedlings. Future studies should focus on the study of enzymes activity and/or hormones affecting seed reserve utilization rate in response to drought and salinity stress.

 
Highlights:
1- The most sensitive growth stage of annual medic (seedling production stage) to salinity and drought stress was evaluated.
2- Various pre-treatments to improve the germination of annual medic to enter crop rotation in arid and semi-arid regions due to self-seeding and short growing period were investigated.

Objective: This study investigated the effectiveness of electromagnetic priming in improving drought tolerance of Hashemi rice (Oryza sativa L.) during germination and early seedling growth.
Method: A factorial experiment based on a completely randomized design with three replications was conducted in 2024 at the Islamic Azad University, Astara Branch. Rice seeds were exposed to magnetic fields (0, 50, 100, and 150 mT) for 20 or 40 minutes and then subjected to four PEG-induced drought levels (0, -2, -5, and -10 bar). Germination indecies and physiological traits including proline, MDA, and chlorophyll were measured after 25 days.
Results: The mean comparison of interaction effects showed that in the absence of an electromagnetic field (0 mT), increasing drought stress from 0 to −10 bar significantly decreased germination percentage from 97% to 66.53%, germination rate from 0.43 to 0.19 seeds day⁻¹, radicle length from 65.80 to 28.66, and plumule length from 45.33 to 17.33 mm. However, application of a 100 mT magnetic field considerably limited these reductions to approximately 24% and 49% for germination percentage and seedling length, respectively, indicating an improvement of more than 20% in maintaining germination capacity. With increasing drought stress, proline content significantly rose from 1.01 to 8.34 µmol g⁻¹ FW, and MDA increased from 4.40 to 8.00 mmol g⁻¹ FW, while chlorophyll a decreased from 0.64 to 0.17 and chlorophyll b from 0.75 to 0.32 mg g⁻¹ FW. In the control (0 mT), chlorophyll a exhibited a 72% reduction, whereas at 100 mT this reduction was limited to 56.8%, reflecting approximately 15% improvement. Regression analysis revealed that the effect of magnetic field intensity on the measured traits depended strongly on the drought stress level and did not follow a consistent pattern; under severe stress (−10 bar), no significant linear relationship was detected.
Conclusions: The application of magneto-priming within the optimal range may serve as a simple, eco-friendly, and practical approach to enhance drought tolerance in rice seeds and improve early seedling establishment under unfavorable environmental conditions. In the present study, the treatment with 100 mT for 40 minutes resulted in improved seedling vigor indices for both length and weight. These findings offer new perspectives for the application of physical technologies in agricultural stress management and provide a basis for further field-based studies.

Highlights

• Germination responses to magnetic fields are nonlinear and depend on field intensity and drought stress level.
• Electromagnetic priming at 100 mT for 40 minutes mitigates drought stress effects by up to 20% in germination traits.
• Magneto-priming offers a simple, eco-friendly strategy for improving rice seedling establishment under drought conditions.