Evaluation of seed germination indices of Grammosciadium platycarpum Boiss. & Hausskn. under the influence of stratification and gibberellic acid treatments

The genus Grammosciadium of the Apiaceae family has nine species, of which three species pterocarpum, G. platycarpum and G. scarbridu grow in Iran, which grow in most temperate or cold temperate regions and in mountain pastures. G. platycarpum species is a perennial plant with a height of 40 to 100 cm, which is known as mountain parsley or mountain dill and is distributed in Iran, Turkey, Iraq and Armenia. It is used as an infusion to reduce fat and blood sugar and as Vegetables are consumed raw and cooked in some regions of Iran. It has a pleasant taste and smell and is used as a vegetable and food additive in different regions in spring. Since wild and medicinal plants usually have weak and uneven germination, therefore, the use of methods to improve germination can have a positive effect on improving the production of these plants. Therefore, the purpose of this research is to investigate the effect of stratification and gibberellic acid pretreatments on seed germination characteristics and to determine the best method of seed treatment to improve the germination of mountain G. platycarpum seeds.

To investigate the impact of stratification and gibberellic acid pretreatments on the germination and growth indices of platycarpum, an experiment was conducted in the Ecophysiology Laboratory of Medicinal Plants, Medicinal Plants and Drugs Research Institute of Shahid Beheshti University of Tehran during 2023. The seeds used in this experiment were collected in August 1402 from its habitats in the northwest of the country from the city of Mahabad (longitude: 45°40', latitude: 36°41', altitude: 1426) located in West Azarbaijan province. In order to improve the germination indices of mountain dill seeds, an experiment in a factorial format based on a completely randomized design with two factors of wet chilling at 4 times (0, 2, 4 and 8 weeks) and gibberellic acid at four concentrations (0, 300, 500 and 700 ppm) was implemented with three iterations in 2023. Before conducting the experiment, in order to disinfect the seeds collected from nature, they were disinfected with a 1% sodium hypochlorite solution and then with a 70% ethanol solution for 5 minutes in each step, and then they were disinfected with distilled water in several steps and then They were washed with distilled water in several stages. In order to apply gibberellic acid treatment, concentrations of 300, 500 and 700 ppm were prepared and the seeds were soaked in it for 48 hours. In each petri dish, 40 seeds were placed on a filter paper and placed in the refrigerator at 4°C for wet chilling treatment, and according to the treatments, after 0, 2, 4 and 8 weeks and adding 10 ml of water to the germinator at 25°C, 60% relative humidity and 12 hours of light and 12 hours of darkness were transferred. Germinated seeds were counted daily 24 hours after the start of the experiment. The seeds whose roots were visible (that is, about 2 mm long) were counted as germinated seeds and the results were recorded. Germination percentage, germination rate, mean germination time, seedling vigor, fresh and dry weight of seedlings were measured.

The results showed that with increasing the duration of stratification and increasing the concentration of gibberellic acid, the germination percentage, germination rate germination, rate index, seedling vigor, fresh and dry weight of the seedling improved and had a significant difference compared to the control. The highest germination percentage (94.66 percent), germination rate (90.66 seeds per day), germination index (5.2), seedling vigor (2325), fresh weight (1.51 g) and dry weight (0.41g) seedlings were observed in the combined treatment of 700 ppm gibberellic acid and stratification for 8 weeks. Also, the lowest mean germination time (1.6 days) was obtained in the treatment of 700 ppm gibberellic acid and 8 weeks of stratification, and the longest (6.93 days) was in the control.

Familiarity with the seeds of medicinal plants and knowledge of their germination characteristics can be a big step in domestication, development of their cultivation methods and prevention of their extinction in natural habitats. In general, the results of this research showed that the combined use of 700 ppm gibberellic acid with 8 weeks of stratification was the best treatment in breaking dormancy and seed germination of platycarpum. Based on the results of G. platycarpum dormancy breaking treatments and the use of gibberellic acid was able to replace part of the cold requirement, it can be concluded that G. platycarpum has different degrees of physiological dormancy.