EFFECTS OF SCION AND STOCK ON ROOT-GROWTH OF GRAFTING PLANTS BETWEEN 2 POTATO VARIETIES WITH DIFFERENT ROOT MASS

The relationships of root growth with shoot and tuber growths have sti ll not been clear in potato plants. The aim of this report is to clari fy whether a varietal difference in root growth of potato plants is de termined by some inherent characteristics in the root organ per se, or affected by tile growth of other organs. Four combinations of graftin g plants between two late varieties, Norin 1 and Konafubuki, with diff erent root mass were produced and cultured in large pots (25 cm in dia meter, 50 cm in depth) with plentiful water supply. Dry weight (DW) of each organ and leaf area were measured at three stages, just after th e transplanting, approximately after the initial flowering and after t he last flowering, for three years. Analyses of variance for the chara cters were performed using the years as replications. The stock genoty pes significantly influenced root DW of the grafting plants at the thr ee stages examined. The effects of scion genotypes on root DW were not significant. The negative relationship was found between root DW and tuber DW in the grafting plants. Sheet DW and leaf area were not signi ficantly different among the grafting plants. We concluded that the di fference in root DW between the two varieties was mainly due to the in herent characteristic in the dry matter partition to roots and tubers just after the tuber initiation.