EFFECTS OF ROOT PRUNING AND N-NO3 SOLUTION CONCENTRATION ON NUTRIENT-UPTAKE AND TRANSPIRATION OF TOMATO PLANTS

Root pruning of tomato plants (Lycopersicon esculentum cultivar F 121) grown in an aerohydroponic system in a greenhouse resulted in reduced dry matter production. Increasing the solution nitrate concentration failed to compensate for the pruned roots. The objective of the present manuscript was to study the combined effect of root volume and nitrate solution concentration on nitrogen (N) uptake and transpiration. Root pruning decreased the total N uptake per plant, but the rate of uptake per unit root weight was higher in the pruned roots. Analysis of plant organs showed that root pruning did not affect N content per unit dry matter. Increasing the solution nitrate concentration from 1.5 to 9.0 mM increased significantly the nitrate uptake of plants with pruned and intact roots. It seems, therefore, that the reduced dry matter production of plants with pruned roots was not caused by N deficiency. Weekly transpiration was also reduced by root pruning, but the transpiration rate per unit root volume increased after root pruning. The water-use efficiency of the plants was also reduced by root pruning. It was concluded that the reduction in dry matter production following root pruning was not caused by restriction of transpiration.