اثر پرایمینگ بذر بر ویژگی‌های ظهور و رشد گیاهچه چغندر قند در گلخانه در شرایط نرمال و تنش شوری

Extended Abstract
Introduction
Soil salinity is a major adverse environmental problem that reduces crop yields globally and threatens more than 833 million hectares of arable land. Salinity-affected soil has been reported in over 100 countries worldwide, with most salinity cases resulting from irrigation. Seed germination is a stage in which the plant is susceptible to abiotic stress such as salinity. Salinity stress affects plant growth and yield through ionic toxicity, reduced seed germination percentage, and increased germination time. Since germination is facilitated by energy stored in the seed, the inhibition of seed germination caused by salinity stress may primarily be due to energy changes in metabolic activities caused by osmotic and ionic pressure. Sugar beet (Beta vulgaris L.) is a valuable source of sugar and bioethanol production in temperate regions of the world. Priming treatments have beneficial effects such as increased germination, synchronized emergence, early seedling growth, and minimization of the harmful effects of abiotic and biotic stress. In this study, the effect of different priming levels on the germination and morphological traits of sugar beet cultivars called Pars
and a Rizofort were investigated under normal and salinity stress conditions.
Materials and Methods
In order to investigate the effect of chemical priming with different substances on the germination and growth of seedlings under greenhouse conditions, experiments were carried out under normal and salt stress conditions in the crop season of 2018-19. Experimental treatments included two cultivars (Rizofort and Pars) and ten levels of priming [without seed priming (control), polyethylene glycol, potassium nitrate, calcium chloride, zinc sulfate, salicylic acid, hydrochloric acid, mannitol, potassium dihydrogen phosphate, and distilled water]. At harvest, five samples were selected from each treatment in all replications. The length and width of the leaves as well as the length of the petiole were measured. The mean length and width of the leaves and the length of the petiole from these five plants were then utilized for statistical calculations. After harvesting the roots of the selected plants from each experimental treatment, the distance from the cutting point of the collar to the end of the root was measured, and the average was recorded as the root length. The length and diameter of the hypocotyl of the selected plants was measured. . The weight of the aerial parts of the selected plants and the roots that were separated from the collar after weighing were measured using a digital scale. The aerial parts and roots of the seedlings were placed in paper bags for drying in an oven at 85 ͦC for 24h and then weighed again. The analysis of variance of the data was performed using SAS 9.1, and mean comparison was done by the Duncan method at five percent significant level
Results and Discussion
Analysis of variance of the studied traits showed that the effect of cultivar treatment was significant on seedling germination percentage and rate, shoot dry weight, root dry weight, root length, petiole length, hypocotyl diameter, hypocotyl length, and leaf length, which indicated the existence of genetic diversity between cultivars. Different levels of priming also affected the above traits at 5% probability level. The interaction effect of cultivar on priming was significant for all traits except seedling emergence rate and leaf length. Under salinity stress, the effect of cultivar and the interaction effect of cultivar on priming was significant (P < 0.01) on seedling emergence percentage and rate, shoot weight, shoot dry weight, root weight, root dry weight, root length, petiole length, hypocotyl diameter, hypocotyl length and leaf length, which indicated the existence of genetic diversity between the studied cultivars. Different levels of priming also had significant effect on the above-mentioned traits (P < 0.05). Results showed that the highest percentage of seedling emergence, shoot and root dry weight, root and leaf tail length, hypocotyl diameter and length related to the Rizofort variety and the application of zinc sulfate pretreatment with 50 mM concentration in both conditions. Calcium chloride priming with 50 mM concentration also improved and increased the studied traits in the Rizofort cultivar under normal condition. Zinc sulfate priming in both conditions (normal and salinity stress) increased the characteristics of seedling emergence and seedling growth of two sugar beet cultivars compared with no priming and was able to moderate the adverse effects of salinity stress. The application of micronutrients, especially zinc, has emerged as a promising strategy to mitigate the adverse effects of salinity stress on plants. This essential micronutrient plays a vital role in plant growth and development. Previous studies report that the application of micronutrients plays an important role in various physiological and biochemical processes in plants, including ion uptake and transport. Reduced yield and growth due to salinity stress have been attributed to high concentrations of sodium ions, which hinder the uptake of other nutrients essential for growth.
Conclusion
Since ZnSO4 can mitigate the negative effect of NaCl by limiting the absorption of sodium and chlorine or its translocation in the plant, under normal conditions, the highest fresh and dry weight of the aerial parts and roots, root length, leaf petiole length, hypocotyl length and diameter, leaf length, percentage and seedling emergence rate under normal and salinity stress conditions resulted from zinc sulfate priming. The results of the interaction effect of priming on the cultivar under normal and salinity stress conditions also followed this pattern. Given the higher genetic potential of the Rizofort cultivar compared with Pars cultivar under normal and salinity stress conditions, the highest traits resulted from priming with zinc sulfate. In summary, the use of zinc sulfate priming as an effective method to improve seedling emergence and seedling growth of sugar beet under salinity stress conditions can help growers to improve their crop yields.
Keywords
 Calcium chloride, Potassium nitrate, Priming,Salicylic acid, Zinc sulfate
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