Abstract
The xylem sap in cucumbers (Cucumis sativus L.) which were or were not grafted onto figleaf gourd (Cucurbita ficifolia Bouché) was collected after decapitation from the cut end of the stems hourly. The exudation rate was highest in the first one hour collection regardless of grafting, and then decreased rapidly with time. However, there was a diurnal change in the exudation rate with the maxima occurring at 1:00 to 3:00 PM and the minima at 7:00 to 8:00 AM, irrespective of decapitation time. The grafted cucumbers were smaller in amplitude than the non-grafted ones.
The rate of xylem exudation and the concentrations of NO3-N, P, Ca and Mg in the first one hour exudate were higher in the grafted cucumbers than in the non-grafted ones. Only the K concentration was higher in the non-grafted cucumbers. The mineral concentration in the exudate changed remarkably with time after decapitation; the NO3-N, K and Ca concentrations decreased and the P concentration increased rapidly for the first several hours. The Mg concentration scarcely changed. Thereafter, the NO3-N and K concentrations of the exudate in the grafted cucumbers fell below the NO3-N and K concentrations in the nutrient solution, while in the non-grafted cucumbers the former was kept always above the latter.
From these results, the grafted cucumbers were considered to be superior to the non-grafted ones, in water uptake and nutrient absorption except for K and also to depend more intensely in NO3-N and K absorptions on some metabolities from the upper parts of the plants.
