Abstract
Photosynthesis and root weight production in single leaf grafts were discussed from the point of view of sink-source balance. Cultivars used were Koganesengan (K), Siroyutaka (S), Beniaka (B) and Tsurunasigenji (T). Scion (leaf+petiole) and stock (petiole+roots) of the four cultivars were reciprocally grafted in 16 combinations. To elucidate the single and compound effects of sink and source on root weight (RX/Y), mathematical models were derived, from which scion effect (EX/*), stock effect (E*/Y) and their combination effects, general combining effect (GCEX/Y) and specific combining effect (SCEX/Y), were calculated. The relationships of these components were shown as the following equations. RX/*=EX/*+R*/*;R*/Y=E*/Y+R*/*GCEX/Y=(EX/*+E*/Y)/2;RX/Y=GCEX/Y+SCEX/Y+R*/*:where RX/* and R*/Y are the average root weights of the grafts with cv. (X) scion and cv. (Y) stock, respectively. RX/Y is the root weight of a graft with cv. (X) scion and cv. (Y) stock. R*/* is the average root weight of all the plants of 16 graft combinations. When K or B was used as scion, the root weight of grafted plants highly increased ; the scion effects of both cultivars were positive. Also the stock effect of K was positive. While both scion and stock effects of T were negative and the lowest. A positive linear relationship was detected between GCE and SCE, but T/S and T/B were excepted from the tendency. Photosynthetic rate increased in the plants grafted to K-scion or K-stock, while in T/S and T/T the rates significantly reduced. Root weight production was positively related to photosynthetic rate within a limited range. In T/S and the grafts with T-stock, peitole weights increased ; the petiole functioned as a sink when the tuber sink capacity was limited.
