The Effects of Several Rootstocks on Photosynthesis, Distribution of Photosynthetic Product, and Growth of Young Satsuma Mandarin Trees

The effects of 14 different rootstocks on leaf photosynthesis, distribution of photosynthetic product, and growth of one-year-old trees of satsuma mandarin (Citrus unshiu Marc.var.Sugiyama) were investigated.It was shown that leaves of satsuma mandarin grafted on trifoliate orange strains, such as `Rubidoux', `Pomeroy', and `USDA' showed higher photosynthetic rates than those on common trifoliate orange (Poncirus trifoliata Raf.) rootstock.However, `Oba' (Large leaf strain) , `Barnes', and `sour orange' rootstocks had lower rates.Stomatal density and ribulose-l,5-bisphosphate carboxylase (RuBPCase) activity in leaves seemed to be important factors for photosynthetic capacity.Also, the distribution of photosynthetic product differed among the rootstocks.The greatest value of top-root ratio was measured in `Rubidoux' trifoliate orange rootstock.Among the trifoliate oranges, tree size on `Rubidoux' rootstock was greatest and resulted in the highest dry matter production.This was mainly the result of total photosynthetic capacity of the trees.