Photosynthesis, growth, and yield of Paeonia ostii in tree-based agroforestry systems

Paeonia ostii T. Hong & J.X. Zhang, an emerging oil crop, was intercropped with 3-year-old plantations of pawpaw [Chaenomeles sinensis (Thouin.) Koehne], Chinese toon (Toona sinensis Roem.), and walnut (Juglans regia L.). In order to achieve a better production system, we studied the effects of intercropping on the photosynthesis, growth, and yield of P. ostii. The results showed that different pattern of agroforestry systems changed microclimatic and growing site conditions in comparison to the control treatment. The correlation analysis demonstrated that both similarities and differences were found in relationship between net photosynthetic rate (PN) and main ecophysiological factors at different treatments. Agroforestry systems significantly reduced transpiration rate and increased water-use efficiency (WUE), maximal quantum yield of PSII photochemistry, chlorophyll (Chl) a and total Chl contents, whereas there were no differences between PN, intercellular CO2 concentration, photochemical efficiency of PSII in the light, and plant height in these systems. The obviously exponential relationship between PN and PAR during a day were observed in Chinese toon and walnut treatments. The highest effective quantum yield of PSII photochemistry, electron transport rate, and photochemical quenching coefficient were observed in walnut treatment. The higher WUE and SPAD value, the thinnest stem, the biggest crown, the lowest stomatal conductance, and Chl a/b ratio as well as the fewest pods and harvest seed yield were observed in pawpaw treatment. In addition, there was a significant correlation between SPAD value and Chl (a+b) of P. ostii in agroforestry system. This study could be an important contribution for the science of land management in oil peony and other understory crops.