The effects of different doses boron applications on morphological and biochemical properties of myrtle (Myrtus communis L.) in vitro conditions

In this study, shoot tips of the 'sweet myrtle' genotype which is a local variety with black fruit, were used as material. In this study, it was tried to determine the level of boron (B) that may cause toxicity problem from B concentrations added to the growing media and the changes in morphological and biochemical properties under possible boron stress were examined. For this purpose, 6 different boric acid (H3BO3) doses (12.4 mg L-1, 18.6 mg L-1, 24.8 mg L-1, 31 mg L-1, 37.2 mg L-1, 43.4 mg L-1) was added to the Murashige and Skoog (MS) medium and the development of the plants was followed with the control group. In the study, only standard B content (6.2 mg L-1) was added in MS medium to the plants in the control medium. As a result of examining the statistical evaluations; The number of shoots, the number of leaves per shoot, the wet weight of plantlest, the total chlorophyll content were found to be 1.9, 4.7, 0.09 g and 50.3 mg g-1, respectively, while the highest proline amount was obtained as 11.6 µg ml-1 in 43.4 mg L-1 application in the media which has highest H3BO3 concentration, the lowest proline amount was determined as 3.3 µg ml-1 in the control group. Ascorbat peroxidase (APX), superoxide dismutase (SOD), peroxidase (POD) enzyme activities increased as the application doses increased, and the lowest value was determined in the plants in the control group. As a result; As the amount of B added to the growing medium increased, a significant increase was observed in the enzymatic antioxidant activities that play a role in the stress mechanism, especially APX, catalase (CAT), SOD, POD, while a decrease was observed in parameters such as shoot number, leaf number per shoot, fresh weight of plantlets and total chlorophyll. There was no statistically significant difference value in regeneration rate and chlorophyll a. As a result of the study, it was determined that the tolerance limits of the myrtle plant against boron stress were high.