Growth relations of rootstock and scion in apples

SummaryFive virus-free apple rootstock clones, worked as scion and rootstock in their 25 combinations, were grown unpruned but annually deblossomed for five seasons after the maiden year at wide orchard spacings and then lifted. Dry weights of rootstock, scion and whole tree show marked differences between the influences of clones, both individually and in their respective roles as rootstock or as scion. The relative growth rate of the compound tree in particular reflects the closely additive relationship between the influences of rootstock and scion. Nevertheless significant interaction of very limited extent was demonstrated; its origins in deviations of the means of individual combinations from the additive relation are illustrated and classified.