Tomato sap flow, stem and fruit growth in relation to water availability in rockwool growing medium

摘要

Background and aims Irrigation strategies for glasshouse tomato are often based on solar radiation sums. However, due to new energy-saving climate control, current strategies might result in inappropriate irrigation. Because of the limited water buffering capacity of soilless growing media like rockwool, this could have adverse effects on fruit production and quality. We present an overview of tomato plant ecophysiological responses to substrate water availability to allow the evaluation of mechanistic hypotheses about internal plant water storage and depletion and reversible stem-fruit water transport. Methods The hydraulic properties of the growing medium were determined and plant water uptake, stem and fruit diameter variations were studied. Results A low substrate matric suction (-2 to -3 kPa) had a significant effect on stem and fruit growth dynamics. The substrate water retention curve indicated a sharp decrease in hydraulic conductivity, limiting the water availability for plant roots significantly. Conclusions The hydraulic properties of the growing medium are of utmost importance for plant water uptake, and should therefore be incorporated in plant models describing water flow. Internally stored water responds instantaneously to varying water availability and rates of water backflow from tomato fruits can be quite substantial.