Investigating and comparing the methods of breaking seed dormancy in indicator range species of Zohreh watershed

There are many problems for the restoration and development of rangeland vegetation in the field of biological purpose, including the lack of proper germination of plant seeds. The seeds of many plant species cannot germinate despite suitable environmental conditions. Seed dormancy, hard and impenetrable shell and the presence of immature embryo are the main factors of seed not germinating. Seed dormancy is a temporary stagnation in seed life that enables it to complete its germination under favorable conditions and causes the distribution of germination in space and time. In general, research related to seed germination is one of the key and primary tools for biological projects. Because the results of this research can be used in the implementation of management programs for the preservation and development of vegetation. Researchers are trying to find suitable methods to break dormancy and increase the percentage and speed of germination of key plants by investigating the causes of dormancy in seeds. Among the native plants and indicators of winter rangeland in the south of the country, including the tropical areas of Kohgiluyeh Va Boyer Ahmad provinces, which are located in the Zohreh watershed, Zygophyllum eurypterum Boiss & Buhse. from Zygophyllaceae family, Sanguisorba minor L. from Rosaceae family and Salsola orientalis S. G. Gmelin (=Salsola rigida) belong to Chenopodiaceae family. Due to the destructive process of rangeland in the south of the country, resuscitation and development of the vegetation of these areas with indigenous and indicator species in line with biological operations is a priority. Therefore, the main purpose of the present study is to investigate and compare the germination stimulation methods of three indicator range species in order to introduce the best methods.

The present research was conducted to investigate the methods of dormancy of three index species of rangeland: Zygophyllum eurypterum, Sanguisorba minor, and Salsola orientalis in the rangeland of the Zahra watershed in the south of Kohgiluyeh and Boyer Ahmad provinces. For this purpose, after field investigations of the important habitats of the studied species, seeds were identified and sampled when they were fully ripened. The preliminary investigations revealed that all three species have sleep. Therefore, the germination test and determination of the best treatment for the mobility and improvement of germination of the studied species include the following treatments: Germination test using treatments including; Control, scraping, sulfuric acid 98% (for 20 and 40 minutes), potassium nitrate 0.2% and hot water. The experiment was conducted as a factorial in a completely randomized design with 4 replications. The measured traits included germination percentage, germination speed, length of root, shoot, seedling and seed germination index. Mean comparisons were done using Duncan's test.

The results showed that different dormancy treatments have a significant effect on the percentage of seed germination of the studied species (p<0.01). The highest percentage of S. minor germination was observed in potassium nitrate treatment (77.25%) and the lowest in sulfuric acid treatment for 40 minutes (27.5% ). The highest germination percentage of S. orientalis was observed in potassium nitrate treatment (67.50%) and the lowest in sulfuric acid treatment for 40 minutes (42.25%). The highest germination percentage of Z. eurypterum plant was observed in hot water treatment (70%) and the lowest germination percentage was observed in sulfuric acid treatment for 40 minutes (29.5%). Also, the results showed that different treatments have a significant effect on the germination rate of the studied species' seeds. The highest rate of germination of S. minor (3.05 seeds/day) and S. orientalis (1.85 seeds/day) in potassium nitrate treatment and the highest rate of germination of Z. eurypterum (2.3 seeds /day) was obtained in hot water treatment. The results of comparing the averages showed that the treatments used have different effects on the growth of the studied species. So that in S. minor plant, the highest effect on root length (5 cm) was the use of potassium nitrate treatments and scratching, and the highest length of shoot (5.62 cm) and seedling (10.6 cm) ) this plant was obtained in potassium nitrate treatment. In S. orientalis plant, the maximum length of root, shoot, and seedling was 1.8, 1.15, and 2.95 cm, respectively, in potassium nitrate treatment. Also, in Z. eurypterum plant, the maximum length of root, stem and seedling was 2.97, 2.85 and 5.82 cm respectively in hot water treatment. In all three species, the minimum length of root, shoot and seedling was observed in sulfuric acid treatment of 40 minutes. The results of the comparison of the averages show that there is a significant difference between the different sleep deprivation treatments on the seed germination index of the three species Z. eurypterum, S. orientalis and S. minor. The highest seed germination index of Z. eurypterum was obtained in hot water and potassium nitrate treatments, and the highest seed germination index of S. orientalis and S. minor species was obtained in potassium nitrate treatment.

In general, in this research, it was found that the highest percentage and speed of germination of S. minor and S. orientalis in the potassium nitrate treatment and Z. eurypterum in the hot water treatment were among the treatments of sleep failure. The lowest percentage and germination rate of all three species were observed in sulfuric acid treatment for 40 minutes. In S. minor and S. orientalis plants, the greatest effect on the length of root, shoot and seedling was obtained in potassium nitrate treatment. In Z. eurypterum plant, the maximum length of root, shoot and seedling was obtained in hot water treatment. In all three studied species, the lowest length of root, shoot and seedling and seed germination index were observed in sulfuric acid treatment of 40 minutes. Therefore, among the studied treatments for sleep failure, the best treatment for S. minor and S. orientalis species is potassium nitrate, and the best treatment for Z. eurypterum plant sleep failure is hot water treatment, Therefore, it is suggested to use the results of this research for related works in the direction of biological restoration of the studied area and pastures of other areas with similar ecological conditions.