Iranian Journal of Seed Research

Introduction: Niger with the scientific name of Guizotia abyssinica (L.F.) Cass. belongs to the Asteraceae family. Niger seed contains 50-75 percentage of oil which is used in the treatment of rheumatism and burns, and as a substitute for olive oil. Its meal is also used for animal feeding. Environmental crises sustained by living systems are considered as stress. Drought stress is one of the non-biological stresses. Yield reduction due to this type of stress is reported to be higher than that related to other stresses. Since plant development starts from germination and for survival, the seeds should germinate to adapt themselves to the environmental conditions and establish themselves in the soil, the success of passing the germination stage will play an important role in other stages of plant establishment. Different studies have shown the positive effect of magnetic field on increasing germination characteristics. In this regard, applying a magnetic field before planting is a safe and inexpensive method for increasing germination and seedling growth. Seed priming is useful for a faster and more powerful response to drought stress and among different types of priming, physical priming is of particular importance for ecological reasons and for not having a negative impact on the environment.

Materials and Methods: In order to study the effect of seed physical pre-treatment and drought stress on seed germination characteristics of Niger, an experiment was conducted as factorial in a completely randomized design with three replications at the Research Laboratory of Seed Science and Technology at Shahrekord University. Different magnetic field intensities at five levels including (0, 50, 100, 150 and 200 mT (at 5 minutes period)) as the first factor and drought stress at five levels (0, -4, -5, -6 and -7 bar Polyethylene Glycol₆₀₀₀) as the second factor were considered.

Results: The results of variance analysis showed that the effect of drought stress, magnetic field intensity and their interaction were significant on all of the evaluated characteristics. The maximum germination percentage and rate and the minimum of T₁₀ and T₅₀ were observed in 50 mT field intensity under normal conditions. The minimum germination index under normal conditions and the maximum length and shoot dry weight under non-treatment conditions and the maximum root and shoot fresh weight in 200 mT field intensity under normal conditions were obtained. The maximum root length and dry weight were observed in 50 and 100 mT field intensity under normal conditions, respectively. 

Conclusions: Seeds which cross through a magnetic field, become swollen and probably as a result, the activity of auxin hormone in these seeds increases. In addition, the respiration level also increases in them and they have higher levels of energy and activity, which results in faster and more uniform germination and the creation of stress-resistant plants. In this study, although by increasing drought stress intensity, negative effects were observed on germination characteristics, the magnetic field under these conditions improved some germination characteristics. In general, for the purpose of improving germination and alleviating drought stress conditions, for 0, -5 and -7 bar potentials, the field intensity of 50 mT and for -4 and -6 bar potentials, the field intensity of 150 mT are recommended.

Introduction: Agriculture has been influenced by different abiotic stresses such as temperature, drought and salinity, which reduces roughly half of the yield of crops. In many forage plants, germination and early seedling growth are the most sensitive stages of their growth in the face of environmental stresses. Current research was conducted to study the effects of drought and salinity iso-osmosis stresses on germination indices and growth parameters of three clover species, including Trifolium resupinatum, T. alexandrinum and T. incarnatum.

Material and Methods: Two separate experiments (drought and salinity) were conducted as a factorial experiment based on a completely randomized design with three replications. The test factors included clover species with three levels, including T. resupinatum, T. alexandrinum and T. incarnatum and different levels of drought and salinity potentials (0, -2, -4, -6, -8, -10 and -12 bar) due to polyethylene glycol 6000 (PEG 6000) and sodium chloride (NaCl), respectively. Sterile disposable petri dishes with a diameter of 10 cm were used, in each of which, 27 seeds were placed on filter paper and then 5 ml of the desired treatment solution was added to each. Petri dishes were then placed in a germinator at 20°C and relative humidity of 75%. After the end of the desired time germination (About 14 days), from each petri, germination percentage and rate, number of secondary roots, time to get 50% germination (D50), root to shoot ratio and the number of abnormal seedlings were recorded.

Results: Inhibitory effects of salinity and drought stresses affected all germination indices. Germination percentage, rate of germination, root and shoot length all decreased with increasing stress levels, while time to get 50% germination (D50) increased with the increase in stress levels. Under both drought and salinity, all growth parameters of Trifolium resupinatum were higher than the other two species. Germination percentage of T. incarnatum was 0% at -12 bar of drought, but germination of T. resupinatum and T. alexandrinum was 70.33% and 7.33% at -12 bar of these stresses, respectively. Under salinity conditions, all the seeds of the three species germinated at -12 bar. Root to shoot ratio increased with increasing stress levels and at high stress levels, it decreased. The decreases were 41.39% and 0% in drought and salinity, respectively. The number of secondary roots increased with increasing stress levels and the maximum number was observed in Trifolium alexandrinum which was 5.42 and 1 in drought and salinity, respectively. The number of abnormal seedling increased with increasing salinity levels, while under drought conditions there was no abnormal seedling.

Conclusion: Comparison of the effects of sodium chloride and polyethylene glycol showed that sodium chloride reduced germination index due to toxic effects or osmotic effects more than polyethylene glycol solution. ­­­­­­­­­­­­­­­­­­­It seems that Trifolium resupinatum has the best yield in both drought and salinity stresses, and that in drought condition, Trifolium alexandrinum, and in salinity stress, Trifolium incarnatum have the best performance.