ROOT VOLUME AND SOLUTION NO₃-N CONCENTRATION EFFECTS ON TOMATO DRY MATTER PRODUCTION, FRUIT YIELD, NO₃ UPTAKE AND TRANSPIRATION

Restricting root volume by growing the plant in containers of limited volume often occurs in protected agriculture and may reduce tomato yield and fruit quality. The objectives of the present work were: a) to determine if high NO₃ concentration in the solution can compensate for limited root volume in relation to tomato (Lycopersicon esculentum Mill. cv. F 121) shoot growth and fruit yield and quality; b) to study the combined effect of root volume and solution nitrate concentration on N uptake and transpiration. Tomato plants were grown in an aero-hydroponic system in the greenhouse. The treatments were: intact roots, mild and severe pruned root (leaving two and one third of the root, respectively), factorially combined with 1.5 mM or 9 mM N-NO₃ complete cultural solution. Root pruning reduced dry matter production, fruit yield and the average fruit weight. Increasing the solution nitrate concentration did not compensate the pruned roots. Analysis of plant organs showed that root pruning did not effect N, P, and K content. Root pruning decreased the total N uptake per plant; yet, the uptake rate per unit root weight was higher in the pruned roots. Therefore, it seems 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. Yet, the transpiration rate per root unit increased after root pruning. The amount of water transpired per production of DM was higher in the pruned plants.