Determination of physiological and biochemical effects on drought tolerance under exogenous strigolactone application in pepper (Capsicum annuum L.)

In this thesis study, the physiological [germination rate (%), root length (cm), stem length (cm), stem diameter (mm) number of branches, leaf width (mm), plant height (cm), and fresh weight (g)] and biochemical [total protein amount, proline, lipid peroxidase (MDA), superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX)] effects of the 10 µM exogenous strigolactone application were determined under both drought stressed and unstressed conditions in two pepper cultivars (C. annuum L. cv. Oğuz and C. annuum cv. Çözüm) comparatively. It was determined that application of 10 µM exogenous GR24 which is a synthetic strigolactone analogue to alleviate detrimental effects of %10 PEG-6000 drought stress promoted germination rate (%), root and stem length (cm), plant height (cm), leaf width (cm) and stem diameter (mm) and support growth/development in both pepper cultivars. However, parameters studied on biochemical and antioxidant activity, it was revealed that total protein amount, proline, MDA, SOD, APX activities increased under drought stress conditions, and 10 µM exogenous strigolactone application had a healing effect in mitigating the negative effects of drought. On the other hand, CAT activity decreased in both cultivars under drought stress compared to the unstressed conditions for all parameters, while 10 µM exogenous strigolactone application in "Cozum" cultivar under drought stress conditions showed a more than 2-fold decrease in solution compared to strigolactone application under unstressed conditions. When all parameters are evaluated together, it has been revealed that Çözüm cultivar is more resistant to drought stress than Oguz cultivar, and that spreying application of appropriate concentration of exogenous stigolactone provides more successful results in mitigating the harmful effects of drought stress on pepper growth/development.