Effect of Reciprocal Bud‐Graft Transfers Between Old Home and Bartlett Pears and Centrifugatiou on Trans‐location of Endogenous Growth Substances in Hardwood Cuttings

An investigation was made of the effect of bud‐graft exchanges between two pear varieties—the easily‐rooted Old Home and the hard‐to‐root Bartlett—on the root‐promoting activity of extracts obtained from basal segments of hardwood cuttings of each variety. The effect of a centrifugal force obtained from 2000 rpm for 30 minutes on the root‐promoting activity of diffusates and extracts from bases of centrifuged cuttings of these two varieties was also studied. Bud exchange treatments showed no appreciable influence on the root‐promoting or inhibiting activity of basal extracts unless the transbudded shoots (used for making cuttings) were girdled one month prior to the sampling date; in such cases an influence did appear. The centrifugation treatment increased the number of buds sprouting on cuttings. It also increased the root‐promoting activity of extracts from the basal parts of cuttings and of their growth‐active components (separated by paper chromalography) when bioassayed by the mung bean rooting test. Apparently some inhibitory materials from the buds were removed through the bases of the cuttings by centrifuging.