Iranian Journal of Seed Research

Extended abstract
Introduction: Today, various technologies have been developed to improve seed quality with the aim of increasing the percentage, speed and uniformity of germination and improved seedling establishment under different environmental conditions. One of these technologies is seed pre-treatment or seed priming. In this regard, some studies confirmed that pre-treatment of seeds with hormones and plant growth regulators improve germination behavior and its related indices, including average germination time, seed vigor, radicle length, plumule length, germination rate and seedling establishment in primed seeds of sesame. Cognizant of the sensitivity of the germination process as the first plant developmental stage and the importance of improving germination indices and sesame seedling establishment, the aim of this study was to evaluate the seed priming efficiency, using salicylic acid, methyl jasmonate and humic acid in the germination performance, biochemical changes and early seedling growth of two sesame cultivars including Yellow white and local cultivar of Dezful.
Materials and Methods: This experiment was conducted as a factorial based on a completely randomized design with four replications in the seed technology Laboratory of Safi Abad Dezful Agricultural Research Center in the summer of 2015. The first factor was seed pre-treatment with distilled water (control), salicylic acid 0.1mM, methyl jasmonate 1µM, and humic acid 1.5% and the second factor was two varieties of sesame including Yellow white and the local cultivar of Dezful. Germination percentage, germination rate, seed vigor index, radicle length, plumule length, allometric coefficient, proline content, soluble proteins and catalase enzyme activity were determined to compare the treatments.
Results: The results of the experiment showed that seeds priming had a significant effect on germination percentage, germination rate, seed vigor index, radicle length, plumule length, allometric coefficient and seedling biochemical changes, and improved them. The effect of cultivar on all the traits studied, except mean daily germination and plumule length, was not significant. In this research, the Dezful cultivar had an average of 13.52 seeds per day with higher germination rates, compared with the other cultivar (Yellow white). In addition, the interaction of priming × cultivar was significant only in seed vigor index and allometric coefficient, where the comparison of the mean values indicated that the highest seed vigor was obtained by using humic acid 1.5% in the Dezful cultivar (10.09), while the highest allometric coefficient in seed pre-treatment with methyl jasmonate was found in the Yellow white cultivar (1.57).
Conclusions: In this study, the most effective seed priming treatments for improving germination, biochemical changes and seedling growth of sesame was humic acid 1.5%, recorded for the local cultivar of Dezful. Seed priming with humic acid 1.5% was significantly better than the control and Dezful cultivar’s germination performance was better than that of Yellow white cultivar; therefore it can be said that pre-treatment of seed with humic acid with significant effects on germination characteristics of sesame can be more effective in establishment of seedlings. It is advisable to use this organic acid for better root system development and sesame seedlings establishment, which is a major problem at the beginning of the growing season.
 
Highlights:

1. Humic acid was the most effective seed priming treatment on germination characteristics, biochemical changes and seedlings growth of sesame.
2. The effect of seed priming treatments on the germination characteristics of the Dezful cultivar was more pronounced than that of Yellow white.

Introduction: In order to take more advantage of the spring growing season, the mechanisms of germination of spring plants are of great importance at temperatures lower than the optimum temperature. Since one of the ways to reduce damage due to low temperature is enhancing the seedling antioxidant system, in this study the effects of salicylic acid and gibberellin on germination and antioxidant system of pumpkin (Cucurbita pepo) seeds were investigated under low temperatures.

Materials and Methods: A factorial experiment including four concentrations of gibberellin (0, 250, 350 and 450 mg/L), four concentrations of salicylic acid (0, 0.5, 1 and 1.5 mM) and three temperature levels (8, 11 and 14 °C) was performed with a completely randomized design within controlled conditions and six replications at Shahrekord University in 2017. The seeds were immersed in containers containing solutions of 0, 250, 350 and 450 mg/L of gibberellin and solutions with 0, 0.5, 1, and 1.5 mM salicylic acid, were placed in a growth chamber for 24 h under dark conditions at 15 °C. Then the seeds were washed at the desired temperatures, and the germination was recorded every 24 hours based on the 2 mm of radicle length. At the end of the eighth day, after the separation of normal and abnormal seedlings, 20 normal seedlings were selected from each petri dish. Following that, the germination rate, germination percentage, soluble protein, malondialdehyde, superoxide dismutase, guiacol peroxide enzyme, and catalase enzyme were measured. Comparison of means was conducted by the least significant difference test at the 0.05 probability level.

Results: The results showed that none of the treatments used at 8 °C helped germination of the plant and, therefore, 8 °C treatment was removed from the experiment. At the temperature of 11 ° C, the use of salicylic acid 1 mM and at 14 °C, the use of gibberellin 350 mg/L showed the maximum germination rate and germination percentage, compared with the control. At 11 °C, the activity of antioxidant enzymes was more affected by gibberellin hormone so that the highest activity of superoxide dismutase enzyme was observed in 350 mg/L and the highest activity of catalase and guaiacol peroxidase enzymes and the lowest amount of soluble protein were observed in gibberellin 250 mg/L. The salicylic acid hormone was more successful at 14 ° C. The salicylic acid 1.5 mM increased the activity of superoxide dismutase enzyme; and salicylic acid 0.5 mM increased the activity of catalase and salicylic acid 1 mM improved the activity of guiacol peroxidase. This hormone also succeeded in reducing the amount of soluble protein.

Conclusion: In this experiment, seedling tolerance at low temperatures was confirmed by gibberellin and salicylic acid treatments. It is generally concluded that the use of gibberellin and salicylic acid increases the activity of antioxidant enzymes and, as a result, makes pumpkin (Cucurbita pepo) seedlings tolerant to low-temperature stress, and thus, can ameliorate the effect of possible chilling on growth of this crop at the beginning of the season.

Extended Abstract
Introduction: The use of seed priming technology to accelerate the germination and seedling emergence of multi-purpose plants such as halophytes (Alhagi) with the ability to produce medicine and forage under environmental stress conditions or use of saline water (such as seawater of Persian Gulf) has received much attention today. Therefore, the present study was conducted to investigate seed priming methods and different salinity levels on germination, seedling emergence, and some growth responses of Alhagi plant.
Material and Methods: Two separate split-factorial experiments were conducted based on a randomized complete block design with four replications as a petri dish culture (first experiment) and a pot experiment in the field was performed in the Department of Plant Production and Genetics, Faculty of Agriculture, Shahid Chamran University (Ahwaz, Iran) during 2020-21. In both experiments, different levels of salinity (municipal water source with EC=0.96 dS.m-1, 8 and 16 dS.m-1 using seawater of Persian Gulf) were assigned as the main plot, and different methods of seed priming (non-priming, hydro priming, hormonal priming with 50 ppm gibberellin and hydro priming+hormonal priming with 50 ppm gibberellin) and species (A. maurorum and A. graecorum) were assigned as sub-factors.
Results: The results showed the significance of salinity × species × priming interaction on all studied traits. According to the mean comparison results, the highest values of germination percentage, seed vigor index, seedling emergence, plant height, number of branches, total dry matter and stomatal conductance were obtained from a municipal water source with EC=0.96 dS.m-1 and hydro priming+hormonal priming with 50 ppm gibberellin for A. graecorum (29.1, 90.2, 24.0, 32.3, 52.5, 52.1 and 32.4% increase compared to non-priming and control salinity stress on this species, respectively). The output of the fitted logistic model to seedling emergence percentage showed that this model well explained the relationship between seedling emergence of two Alhagi species in responses to salinity and seed priming (R² adj≥0.98 and RMSE≤3.38). Therefore, in both studied species, the decline in seedling emergence started from the 8 dS/m salinity level. However, at the 16 dS/m salinity level, the slope of increase in seedling emergence percentage was slower per time unit.
Conclusion: To cultivate and exploit the saline coastal lands and also to restore the pastures in the country, A. graecorum species under the combined treatment of hydro priming + hormonal priming with 50 ppm gibberellin are recommended in comparison with other treatment levels.

Highlights:
1- Germination and growth responses of two Iranian Alhagi species and the possibility of production by irrigation of seawater of Persian Gulf were investigated.
2- Seed priming technique was used to accelerate seedling emergence and improve some traits in two Alhagi species.