Movement of Calcuium (45Ca) to Fruit from Peduncle of Tomato Plants

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.