Spatial variation in root system activity of tomato (Solanum lycopersicum L.) in response to short and long-term waterlogging as determined by 15N uptake

Root system activity is affected by abiotic stresses, which often creates spatial differences in root conditions. This is expected to influence plants ability to cope with suboptimal conditions. Changes in root system activity were determined as N-15 root uptake in top and bottom layers of potted tomato plants (Solanum lycopersicum L.), after waterlogging the bottom layer for 24 h or 5 d. The plants were grown in peat-based media; non-compacted or highly-compacted, resulting in differences in gas diffusion, air permeability and oxygen availability. The roots were affected by short-term waterlogging (24 h) by decreasing uptake in the bottom layer and increasing uptake in the pot top layer. Long-term waterlogging (5 d) decreased the N-15 root uptake more in both layers. Root uptake recovered fast (within 6 h) after short-term waterlogging, whereas recovery of long-term waterlogged roots took more than 24 h, suggesting production of new root biomass. Despite affecting physical properties, medium compaction did not affect root uptake. Aboveground biomass was affected by waterlogging by increasing the dry matter percentage, decreasing nitrogen (N) percentage and increasing starch content. The results confirmed that root uptake in different layers of small pots could be distinguished by the N-15 technique, which was applicable under potentially denitrifying conditions. The results demonstrated that during short-term stress in part of the root system plants increased uptake from the non-affected parts of the root system, probably as compensation for suboptimal conditions.