## 5 Results  
### Effects of Warming and Drought Stress on Stomatal Morphology of Winter Wheat Leaves  
Figure 1 shows the stomatal structure of winter wheat leaves under different treatments. Under the same field of view, R-g has 15.6% more stomata than R-d, while N-g has 21.6% more stomata than the N-d treatment. The stomatal densities of R-g, R-d, N-g, and N-d are 72.6, 62.8, 69.9, and 57.5/mm\({}^{2}\), respectively. The results show that the stomatal numbers and densities decreased under warming and drought stress.  
Effects of Warming and Drought Stress on Stomatal Conductance, Photosynthetic Rate, and Transpiration Rate of Winter Wheat  
Figure 2 shows the differences in stomatal conductance among the four treatments of winter wheat at the jointing, grain-filling, and mature stages. Under the same temperature conditions, R-g is 29.2%, 3.4%, and 7.7% higher than R-d, while N-g is 54.9%, 11.9%, and 42.5% higher than N-d at the jointing, grain-filling, and mature stages, respectively. Under the same water conditions, R-g is 16.1%, 27.6%, and 4.9% lower than N-g.  
Figure 3 shows the differences in photosynthetic and transpiration rates among the four treatments of winter wheat at the jointing, grain-filling, and maturity stages. For the net photosynthetic rate (Figure 3a), under the same temperature conditions, R-g is 25.6%, 27.3%, and 21.4% higher than R-d, while N-g is 20.2%, 31.0%, and 29.3% higher than  
Figure 1: Stomatal morphology of winter wheat leaves at the anthesis stage. Subgraphs (**a–d**) show stomatal morphology of R-g, R-d, N-g, and N-d, respectively, treated under a microscope at 200 times magnification.  
Figure 2: Effects of warming and drought stress on stomatal conductance of winter wheat. Each data point indicates the average value of three replicates. The lowercase letters indicate significant differences (\(p<0.05\)).  
N-d at the jointing, grain-filling, and maturity stages, respectively. Under the same water conditions, R-g is 20.4%, 14.8%, and 23.9% lower than N-g, and R-d is 29.1%, 9.0%, and 11.5% lower than N-d. For the transpiration rate (Figure 3b), at the same temperature, R-g is 20.2%, 17.8%, and 13.7% higher than R-d, and N-g is 54.9%, 11.9%, and 42.5% higher than N-d at the jointing, grain-filling, and maturity stages, respectively. Under the same water conditions, R-g is 13.9%, 15.3%, and 89.5% lower than N-g, and R-d is 0, 18.8%, and 79.8% lower than N-d at the jointing, grain-filling, and maturity stages, respectively.  
Effects of Warming and Drought Stress on Photosynthetic Rate Were Simulated Based on the Ball-Berry Model  
Based on the Ball-Berry model, basic indicators were used to calculate the value of the photosynthetic rate, and the relevant data for the winter wheat season were substituted into Equation (5) to obtain a simulated value of the photosynthetic rate. Li-COR 6400 XT photosynthetic apparatus was used to record the measured values. Then, the measured and simulated values were fitted. Figure 4 shows a comparison between the simulated and measured values. This is represented by the R\({}^{2}\) value, which shows that the performance was good. In the R-g, R-d, N-g, and N-d treatments, the RMSE values of the R-g, R-d, N-g, and N-d treatments were 4.404, 4.336, 4.188, and 4.891, and the R\({}^{2}\) values were 0.962, 0.958, 0.964, and 0.943, respectively (Figure 4). Under the conditions of no warming and water deficit, the fitting effect between the simulated and measured photosynthetic rates was the worst (N-d: R\({}^{2}\) = 0.943, RMSE = 4.891).