Difference of Root Permeability of Dutch and Japanese Varieties of Single-Truss Tomato Plants

In order to investigate physiological difference between Dutch and Japanese beef tomato varieties, we examined permeability of roots to nutrient solutions and the water potentials of exudates. We grew non-grafted Dutch‘Dundee’ (D) and Japanese‘Reiyo’ (R) varieties of single-truss tomatoes in hydroponically. Also ‘Dundee’ grafted onto Dutch‘Maxifort’ (D/m) and‘Reiyo’ grafted onto Japanese‘Receive’ (R/r) were used in this study. We measured the root permeability of plants for a pressure chamber and the water potentials of exudates, which were able to infer the amount of total solutes of permeation solution, by using an isopiestic psychrometer. By comparison between Dutch and Japanese varieties, the root permeability of R was higher than that of D, but there was no difference significantly between D/m and R/r. The water potentials of exudates were similar between D and R, and D/m and R/r. By comparison between non-grafted and grafted plants, we found that there were no significant difference between D and D/m of the root permeability, and the water potential of exudates of D/m was lower than that of D. On this basis we found that the root of the Dutch variety was able to absorb more solutes by grafting. When R was grafted on‘Receive’, growth was inhibited, and the root permeability and the water potential of exudates became lower than R. This indicate that absorption of water and solute was decreased by grafting, resulting the vegetative growth inhibition.