Simultaneous measurements of water stress with LVDT sensors and electrotensiometers: Application in pepper plants grown in two types of perlites

Continuous measurements of diameter variations and matrix potential using linear variable displacement transducers (LVDT) gauges, and tensiometers with pressure transducers, electro-tensiometers, were made on pepper plants grown in two types of perlites, A13 (coarse) and B6 (fine) in a control chamber. The plants were submitted to a cycle of drying and re-hydratation in comparison to a control. The same experiment was performed during the vegetative growth phase and during the setting and fruit formation phase; The objectives were to test these methodologies, to study the water behaviour of the soil and plant in these specific conditions, and to find a reliable indicator of water stress. The type of perlite has a clear influence on plant development and the setting and fruit formation phase is more sensitive to water stress. In the A13 perlite, daily shrinkage of stem diameter increased and growth was reduced. When water availability in the substrate strongly decreased, the daily shrinkage of stem diameter markedly increased and became more severe specially during the second growing phase. Automated recording of substrate water potential (Psi m) allowed characterisation and description of the root system water extraction and the substrate hydraulic characteristics. In both experiments Psi m of B6 perlite was lower. The micrometry measurements of shrinkage and swelling of stem diameter seems to be a sensitive indicator of the plant response to water conditions, and the simultaneous measurements of both parameters could be used as a reliable method of logging changes in substrate and plant water status and for irrigation control.