Abstract
Electrical impedance analysis was conducted from February to May in 2005 using current year shoots of four fruit species (grape, apple, kiwifruit and Satsuma mandarin) . When series resistance (Rs) and reactance (X) was plotted on the complex plane, three parameters (Rs measured at extremely low frequency (Z0) and high frequency (Z∞) and an angle of arch (2φ) ) were calculated. Z0 was decreased from the beginning of determination to April in grape and mandarin, and from March to April in kiwifruit, while in apple it was unchanged at the beginning of determination, and then was decreased after bud break. In grape and kiwifruit Z0 turned to be the minimum during bleed of xylem exudates, after that it slightly increased.Z∞ was decreased in apple and mandarin, while it fluctuating within small range in grape and kiwifruit. The value of 2φ was increased in all four species. Correlation coefficient between shoot water content and Z0 was significant in all four species, and of its absolute value was the highest in grape, followed by kiwifruit and mandarin, and the lowest in apple. These data showed that Z0 might be a suitable indicator for the status of sap flow.
