Scion, rootstock and their interaction affect the photosynthesis of citrus

Abstract

Photosynthesis is an essential biological process of the plant. The performance of photosynthesis could remarkably affect the final yield and quality of the fruit. However, the effect of the scion, rootstock and their interaction in the scion-rootstock combinations on photosynthesis of the tree was not clear. In this research, the performance of photosynthesis was analyzed with 21 citrus scion-rootstock combinations derived from three navel oranges (Citrus sinensis cv. ‘Banfield’, ‘Chislett’ and ‘Powell’) grafted on seven rootstocks (Swingle citrumelo (C. paradisi × Poncirus trifoliata), Carrizo citrange (C. sinensis × P. trifoliata), X639 (C. reticulata × P. trifoliata), MXT (C. sinensis × P. trifoliata), Hongju (C. reticulata), Ziyang xiangcheng (C. junos) and Trifoliate orange (P. trifoliata), respectively. Results indicated that photosynthesis was significantly affected by either scion, rootstock or the interaction of scion-rootstock, and rootstock had more effect in the scion-rootstock combinations, but the effects among the rootstocks were variable. The combinations of Swingle demonstrated higher values of photosynthesis indexes. Two of three scions grafted on Swingle had significantly higher net CO₂ assimilation rate (A_CO2). All three scions grafted on Swingle showed the highest electron transport rate (ETR) and quantum yield of PSII (Yield II). Photosynthetic pigments (Chla, Chlb, Car and Chlt) of the three scions were highest on Ziyang xiangcheng. Banfield/Trifoliate, Powell/Trifoliate and Chislett/Ziyang had the highest Rubisco activities. The scion-rootstock interaction made the light quanta enter into other reactions during the processes of photosynthesis. Electron transport rate (ETR) is probably the predominant factor determining the photosynthesis of plant.