Effects of Drought Stress on the Growth and Physiological Characteristics of Grafted Ziziphus jujuba var. inermis under RCP 6.0 Climate Change Scenarios

Climate change affects the frequency and intensity of extreme weather, such as drought and floods. This study aimed to investigate the effects of drought stress on the growth and physiological characteristics of Z. jujuba var. inermis based on the RCP 6.0 scenario. The experiment was performed in a soil-plant daylight system (SPDS) chamber under four conditions: Control-WW, Control-DS (Drought), RCP 6.0-WW (CO2 650 ppm, control + 3°C), and RCP 6.0-DS. Although the net photosynthetic rate (A) was higher under RCP 6.0 than the control condition, Vcmax and Jmax, which indicate the photosynthetic capacity, were lower by 19.6% and 27.8%, respectively. Furthermore, in the RCP 6.0 group, the carbon fertilization effect tended to stimulate growth; thus, the total dry weight in RCP 6.0-WW was approximately 35% higher than that in Control-WW. When the drought treatment was included, A decreased by 57% in Control-DS compared to Control-WW, and in RCP 6.0-DS, A decreased by 73% compared to RCP 6.0-WW. Moreover, RCP-DS showed the lowest values of Vcmax, Jmax, PIabs, DFabs, and SFIabs, meaning that the photosynthetic capacity and vitality of the photosynthetic apparatus were diminished under combined climate change and drought stress. Furthermore, stomatal limitations (Ls) regulated photosynthesis in Control-DS, whereas in RCP 6.0-DS, non-stomatal limitations, in this case Vcmax, Jmax, PIabs, DFabs, and SFIabs, were observed. Despite a decrease in mesophyll conductance (gm), gm/gs remained relatively high. Furthermore, even with stomatal closure, gm was maintained at a relatively high level by utilizing the intercellular CO2 concentration (Ci), demonstrating the plant's response to drought stress. Although there was an increase in the overall biomass, it was noted that water consumption increased under additional drought stress, showing that growth and physiological damage were aggravated. Therefore, it is essential to conduct experiments related to the growth and physiological characteristics of commercially valuable seedlings such as Jujube to identify the adverse effects of climate change alongside extreme weather. Further, active efforts with regard to plant management should be undertaken in addition to the implemented measures to reduce greenhouse gas emissions.