Investigation of drought stress and post recovery performance of some ornamental shrubs used in landscaping

This study was carried out under greenhouse conditions with six different ornamental shrubs Berberis thunbergii DC. var. atropurpurea, Cotoneaster franchetti Bois, Euonymus japonicus 'Aurea', Euonymus japonicus Thunb. 'Bravo', Viburnum opulus 'Sterile', and Viburnum tinus L., which are important species in terms of aesthetic values. The plants were subjected to recurrent drought stress monitoring for two years to determine their response during the recovery period. For this purpose, 1 year before the year in which the treatments were to start, the plants were obtained in 1 year old and 2-3 liter pots. On May 4, 2023 and May 8, 2024, drought application was initiated. No irrigation was applied until the first wilt appeared on the plants. In the control group, irrigation was continued at field capacity. Recovery practices were terminated after irrigation of the drought-treated plants up to field capacity and observation of the plants at field capacity for 15 days. The results showed that among the morphological parameters, C. franchetti showed the best improvement in shoot length with P<0.01 significance level first year and P<0.05 significance level in the second year compared to the control, this species exhibited a good avoidance mechanism, this plant also displayed the best improvement in the recovery treatment. Leaf area of B. thunbergii var. atropurpurea exhibited good avoidance by decreasing in the first year treatment compared to the control at P<0.01 significance level, the best recovery was observed first year treatment of C. franchetti. Among the physiological parameters, B. thunbergii var. atropurpurea exhibited the best improvement in leaf relative water content in the first year treatment and all species except C. franchetti in the first year treatment reached the same levels with the control in the recovery treatment, B. thunbergii var. atropurpurea contained 66% more leaf water potential than the control in the first year recovery treatment. Stomatal conductance and photosynthesis exhibited a statistically significant decrease first year and second year treatments in which all species exhibited an avoidance mechanism, the first year treatment of B. thunbergii var. atropurpurea exhibited the best recovery and similar results were found in photosynthesis. In the second year drought treatment of C. franchetti, carbohydrate among biochemical parameters increased by 261% compared to the control and reached the highest value. The amount of proline, which is an important indicator of protection against drought stress, increased in other plants and treatments compared to the control group except for the first year treatment of V. opulus 'Sterile' and second year treatment of V. tinus. The amount of MDA increased only in E. japonicus 'Bravo' compared to the control at P<0.1 level of significance, which is an important parameter indicating that xiii our plants were not damaged by stress. Antioxidant enzyme activities of SOD, KAT, APX, GR and POD were increased in C. franchetti and V. tinus plants after stress compared to the control for all antioxidants in both years, but not in other species. Keywords: Ornamental Plants, Climate Change, Drought, Recovery, Antioxidant Enzyme Activity