Tipburn is a great threat for the development of innovative cultivation techniques for leafy vegetables, since in hydroponic systems the production losses due to this disorder is estimated at 50%. Moreover, tipburn symptoms usually occur approximately a week or two before harvest, which corresponds with a significant waste of resources. Therefore, the researchers of the TIPRELET-project aim to elaborate a sustainable strategy to prevent tipburn in butterhead lettuce cultivated in soil or in hydroponic systems.

As a first step, the calcium content in the inner leaves was measured in different cultivars grown at several periods. The total calcium content was differentiated in a physiologically active and inactive fraction, which not always was the case in former tipburn studies. Solely physiologically active calcium can be built into new cell walls and determine the cell wall strength.

In general, concentrations of physiologically active calcium less than 2 g/kg dry weight were found in young developing leaves which had developed tipburn symptoms in contrast to healthy leaves with a calcium content of more than 4 g/kg dry weight. It is noteworthy to mention that in the outer mature leaves of healthy and affected plants, no differences in calcium content were found indicating the very local nature of the tipburn disorder. As such, the key of the influence of calcium on the occurrence of tipburn is that the calcium supply must keep pace with the calcium demand in the expanding marginal tissue of the inner developing leaves.

Therefore, this research will now focus on strategies, which enhance the calcium supply in the leaf tissues where it is mostly needed. The plants response to these different strategies will be continuously monitored to give insight in the behaviour of these lettuce plants.

The TIPRELET-project is an Agricultural Research project (IWT-080499) coordinated by inagro and in collaboration with Ghent University – Faculty of Bioscience Engineering, Research Station for Vegetable Production at Sint-Katelijne-Waver and the Research Centre Kruishoutem.