Abstract
The experiment was designed to evaluate growth rates and concentrations of xylem exudate, root metabolic activity, leaf stomatal conductance and transpiration of tomato under the condition of root restriction. The Japanese cultivar ‘Reiyo’ and a Dutch cultivar ‘Levanzo’ were grown in 3 L pots. Root restriction treatment was carried out by limiting soil volume to 0.3 L. The growth of both cultivars were significantly reduced by root restriction treatment. Although the transpiration rate of leaf in cv. ‘Reiyo’ was not significantly reduced by root restriction treatment, that in cv. ‘Levanzo’ was significantly reduced by such treatment as compared with the control. The amount of water transport from root to leaf in cvs. ‘Reiyo’ and ‘Levanzo’ under the condition of root restriction were estimated to 1/3 and 1/8 of that in control plant, respectively. The root metabolic activity and rates of xylem exudate of both cultivars were low level in plants under the condition of root restriction. Minerals of xylem exudate in cv. ‘Levanzo’ were concentrated by root restriction treatment. These results suggest the differences of cause of growth reduction by root restriction treatment between Japanese and Dutch cultivars. The low levels in amount of nutrient transport to leaf by root restriction treatment promote the inhibition of plant growth in cv. ‘Reiyo’. Root restriction treatment induces unbalance of water absorption and transpiration in cv. ‘Levanzo’.
