Rootstock Does Not Affect Net Photosynthesis, Dark Respiration, Specific Leaf Weight, and Transpiration of Apple Leaves1

There was no effect of rootstock on the net photosynthesis (Pn) of 1-year-old vegetative, containergrown ‘Delicious’ trees in 2 experiments. Rootstock effects on specific leaf weight (SLW) were slight in one experiment, and absent in another. There was no influence of rootstock on shoot growth, leaf number, transpiration rate (Tr) or dark respiration (Rd), each of which was determined in one experiment. These data fail to support reports of differences in Pn within a given cultivar on various rootstocks.