Improvement of Seed Germination and Growth Indices of Satureja khuzistanica Jamzad Seedlings under the Influence of Different Light Spectrums

Satureja khuzistanica is a native plant of Iran, which is used as a vegetable, spice, decoction, painkiller and disinfectant in traditional medicine, food and pharmaceutical industries, and has antifungal, antimicrobial and antibacterial properties. It is pain-relieving, anti-diabetic, antioxidant, anti-inflammatory, reduces blood fat and triglycerides. One of the problems of mass production of plants through seeds and seed production industries is the low germination percentage of wild plant seeds due to the lack of ecological compatibility with domestic environment conditions. The quality of light is one of the most important environmental factors for the growth and development of plants, so the use of different light spectrums is one of the stimulating methods to increase the indicators of seed germination of different plants and their seedling growth.

In order to investigate the effects of light quality on the germination indices and biochemical characteristics of S. khuzistanica, an experiment was conducted in the form of a completely randomized design in three replications in 2022, in the Medicinal Plants and Drugs Research Institute of Shahid Beheshti University, Tehran. The experimental treatments included the combination of light at four levels (red light, 30% blue + 70% red, blue, fluorescent). S. khuzistanica seeds were obtained from the collection of medicinal plants of Shahid Beheshti University's Medicinal Plants and Drugs Research Institute and were washed for 30 seconds with a five percent sodium hypochlorite solution and then washed four times with sterile distilled water and 40 seeds were selected in each petri dish and in four Rows are arranged randomly. Germination indices (germination percentage and speed), growth indices (shoot and root length, shoot and root dry weight) and biochemical characteristics (chlorophyll a, chlorophyll b, carotenoid, total phenol, peroxidase, and super oxidase dismutase and catalase enzyme activity) were evaluated.

The highest percentage of germination (84.33%) and germination speed (45.87%) were achieved with the use of red light. Also, the highest length of radicle (3.53 cm), the highest dry weight of radicle (0.51 mg/seedling) and the dry weight of plumule (0.45 mg/seedling) in the treatment of 30% blue + 70% red and the highest length of plumule (1.68 cm) were obtained in the red treatment, respectively. The highest chlorophyll a (0.58 mg.g-1 FW) and chlorophyll b (0.49 mg.g-1 FW) were observed in red light treatment and the highest carotenoid content (0.48 mg.g-1 FW) was observed in blue light treatment. With the use of blue light, the activity of catalase and peroxidase enzymes increased and the activity of superoxide dismutase decreased.

The results of this research showed that the germination indices, growth and biochemical characteristics of S. khuzistanica seedlings were affected by different light spectrums. In general, the results indicated the possibility of improving the germination indices, growth and biochemical characteristics of S. khuzistanica seedlings using a combination of blue and red lights compared to fluorescent light.