The researchers studied how wheat plants infected with stripe rust disease affect their photosynthesis and water use. They found that leaves with low disease severity behaved similarly to healthy leaves, with only slight decreases in water use efficiency. However, leaves with medium to high disease severity showed significant decreases in photosynthesis and water use efficiency, with increased water loss through transpiration. These severely affected leaves lost the ability to control water loss and had lower chlorophyll content, impacting their photosynthetic activity.