Photosynthesis in reciprocal grafts of drought-tolerant and drought-sensitive cultivars of soybean under water stress

Maintaining greater photosynthetic performance is important to improve drought resistance in soybean. However, photosynthetic response mechanisms to drought via the interaction between root and shoot remain to be clarified. Here, we investigated the roles of roots and shoots in photosynthetic responses to water stress. Grafted plants of drought-tolerant cultivar L14 and drought-sensitive cultivar L21 were grown in the pot-culture experiments. Some photosynthetic and physiological traits were measured after water-stress treatments during a podding stage. The L14 as rootstock showed a stronger growth vigor under water stress, leading to increases in some photosynthetic traits. Although the photosynthesis of L21 scion was improved by grafting onto L14 rootstock, it was still lower than that of L14 scion. This indicated that not only the greater water absorption capacity via roots but also the physiological property of leaves conferred a higher photosynthetic capacity and drought resistance in soybean.