The Influence of Biochar Application on Seed Germination Indices and Growth Parameters of Satureja khuzistanica Jamzad Seedlings

Satureja khuzistanica is native to Iran, which is used as a vegetable, spice, decoction, and painkiller and disinfectant in traditional medicine, food and pharmaceutical industries, and has antifungal, antimicrobial, and antibacterial properties. This plant has pain-relieving, anti-diabetic, antioxidant and anti-inflammatory characteristics, and reduces blood fat and triglycerides. Biochar, called black gold in agriculture, is a carbon-rich organic substance, which is obtained by pyrolyzing biomass or plant residues in the presence or absence of oxygen at 300-1000 ˚C. The material can affect soil physico-chemical characteristics, leading to a change in its biological characteristics and better fertility, and consequently, more plant yield. In addition, biochar results in absorbing and retaining nutrients, raising water holding capacity, increasing cation exchange capacity, improving soil structure, and subsequently providing mineral nutrients (P, Mg2+, Ca2+ and K+) for plants.           

To investigate the impact of pomegranate biochar on the germination, biochemical and growth indices of khuzistanica, an experiment was conducted in the Ecophysiology Laboratory of Medicinal Plants, Medicinal Plants and Drugs Research Institute of Shahid Beheshti University of Tehran during 2022. To prepare biochar, the required amount of pomegranate wood (Punica granatum) was collected from the pomegranate orchards located in Saveh region, and then dried, packed in aluminum sheets, and placed in a furnace at 450 ˚C for four h to perform the pyrolysis process. The experiment was conducted based on completely randomized design with three replications. In this study, the effects of biochar treatment at four different levels including 0 (control), 1, 2 and 3 % (w/w) on germination indices, growth indices, leaf relative water content, chlorophyll content and activity of superoxide dismutase and catalase enzymes were investigated.

Results showed that the effect of pomegranate biochar on germination percentage, germination speed, mean germination time, seed vigour index, shoot and root length, fresh and dry weight of shoot and root, leaf relative water content and chlorophyll a and b content was significant at 1 % probability level, but the effect on activity of superoxide dismutase and catalase enzymes was not significant. Based on results, a significant improvement was observed in germination percentage, germination speed, and mean germination time and growth indices with the application of biochar 2 %. The mean comparing results showed that the levels of 1, 2, and 3 % of pomegranate biochar increased the germination percentage. In this study, the lowest (61 %) and highest (88 %) germination percentages were observed in control and biochar 2 %, respectively. Also, the highest germination speed was recorded under application of biochar 2 % (with an average rate of 11.66 seed d-1). The lowest germination speed was observed in control (with an average rate of 6.66 seed d-1). Increasing the level of pomegranate biochar to 2 % decreased the duration of germination, so that the longest germination duration (5.86 d) was for the control and the shortest duration (4.33 d) was for biochar 2 %. The highest germination index (2024.67) was observed in seeds sown in culture trays filled with soil mixed with 2 % pomegranate biochar, and the lowest value (777.13) was observed in the control. The highest length (23 cm), fresh weight (1.05 g) and dry weight (0.124 g) of the shoots were observed in the treatment of 2 % pomegranate biochar, and the lowest values were recorded in control. In the present study, increasing the level of pomegranate biochar up to 2 % increased the root length, but increasing the level of pomegranate biochar up to 3 % decreased root length. The maximum amount of length (7.6 cm), fresh weight (0.31 g) and dry weight (0.034 g) of the root was obtained under the application of 2 % pomegranate biochar, which had a significant increase compared to the control. By increasing the use of pomegranate biochar, the leaf relative water content increased, so that the highest relative water content (80.33 %) was observed with the use of biochar 3 %. The highest levels of chlorophyll a (2.91 mg g-1 FW) and b (0.95 mg g-1 FW) were obtained with the application of biochar 2 %, and the lowest values were for the control.

In conclusion, the use of biochar as an organic fertilizer in the production of khuzistanica medicinal plant, in addition to having a positive effect on the seed germination indices, can lead to improving growth rate and producing stronger seedlings.