Movement of calcium (45Ca) from the peduncle to fruit of tomato during the days and night was investigated. Further, the effects of additional NaCl to the culture solution on the water potential in plants and 45Ca movement to fruit were also examined. The activity of 45Ca on a dry weight basis in the peduncle was higher during the day than at night, however, in calyx and fruit the 45Ca activity was similar both during the day and night. Import of 45Ca into the leaves from the peduncle was not different between the day and the night. Additional NaCl to the culture solution resulted in a greater water saturation deficit (WSD) of the immature leaves just below the 2nd and 3rd trusses, unlike with the mature leaves below the 1st truss where the WSD did not decrease with NaCl treatment. On the oher hand, the activity of 45Ca in the peduncle and calyx was not different between the NaCl treatment and the control. However, the activity in the distal part of the fruits was lower with, NaCl treament than in the control. These results suggested that the high WSD effectively decreased the import of calcium into fruits from the peduncle. It seems that the import of 45Ca into fruit not only dependent on the conductive tissues but also a possible driving force in xylem water flow, and that NaCl interferes with movement of calcium in the fruits.トマト果柄に木綿糸を通してカルシウム(45Ca)を処理し昼夜間別に果房各部位への45Caの移行、ならびに、培養液にNaClを添加した場合の樹体内の水分状態と果実への45Ca移行について調査した。昼夜間における単位乾物重当りの45Caの非活性は果柄で昼間に有意に高くなったが、がく・果実では昼夜間差は生じなかった。また、葉でも昼夜間差はなく昼夜同程度に45Caの移行が認められた。培養液にNaClを添加しても、第1果房直下葉(成熟葉)の水分欠差が生じなかったが、第2･3段果房直下葉(未成熟葉)ではNaCl添加のよって水分欠差は有意に増大し、果柄・がくの45Ca非活性も高くなる傾向を示した。しかし果実末端部の45Ca非活性は有意に低くなり、同時に、果実全体に占める果実末端部での45Ca非活性もNaCl添加によって減少した。本試験の結果から、木綿糸処理液の果柄内への流入は樹体の水分欠差に影響を受けると考えられた。果柄内に流入した45Caは、水の流れだけでなく他の要因によっても各部位に移行するものと思われた。また、培養液へのNaCl添加により、果実末端部へのカルシウム移行がより強く抑制されるのは、果実内でのカチオン移動に競合が生じるからではないかと推察された
