The researchers studied how ryegrass plants respond to alkaline stress by exposing them to different levels of NaHCO3. They found that as the NaHCO3 concentration increased, the plants' chlorophyll and carotenoid levels decreased, affecting their ability to photosynthesize. The plants also showed decreased rates of photosynthesis and increased energy dissipation through heat. Overall, the study suggests that alkaline stress mainly affects the plants' photosynthetic processes and energy utilization.