Combined effect of elevated CO₂ concentration and drought on the photosynthetic apparatus and leaf morphology traits in seedlings of yellow poplar

To counter the threat of drought, which is expected to increase in the future, we analyzed the combined effects of elevated carbon dioxide (CO₂) concentration and drought on the photosynthetic apparatus and morphological traits in seedlings of yellow poplar (Liriodendron tulipifera). The plants were grown for four months in a phytotron under different CO₂ concentrations [ambient CO₂, 430 ppm, AC) and elevated CO₂, 640 ppm, EC] and water treatment [field capacity, FC and 50% of field capacity, FC50]. FC50 was sufficient for inducing a reduction in the photosynthetic rate of L. tulipifera. However, under FC50 combined with EC, we observed an increase in photosynthetic rate with increased photopigment content, photochemistry efficiency, and light harvesting ability. Further, decreased specific leaf area and increased wax coverage in EC suggested that EC contributed to protect chloroplasts and reduce water loss. In conclusion, functional improvements of the photosynthetic apparatus with changes in morphological traits were observed under FC50 combined with EC and EC ameliorated the adverse effect of FC50 on the seedlings of L. tulipifera.