The researchers studied how drought stress affects the photosynthesis of soybean seedlings to help find drought-resistant varieties. They compared three soybean types under light and severe drought conditions. They found that serious drought stress significantly reduced key photosynthesis parameters like net photosynthetic rates and actual photochemical quantum yields. The soybeans coped with drought stress by limiting stomatal function, but severe stress damaged the photosynthetic system in other ways. One variety, Qihuang 35, showed lower photosynthetic capacity under drought. The researchers also developed a new method to detect photosynthetic capacity in plants.