TOMATO STEM AND FRUIT DIAMETER DYNAMICS IN RESPONSE TO CHANGING WATER AVAILABILITY

Tomato plant water relations are crucial for fruit production and fruit quality. 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. The aim of this study was to investigate the effect of decreasing water availability in the rockwool growing medium on stem and fruit diameter variations. This study indicated that a small difference in plant positioning inside the greenhouse could lead to an important difference in plant water uptake, by which some risk might occur for under-watering border plants. The combination of continuous measurements of sap flow and stem diameter allowed a powerful interpretation of the plant water status. Finally, this study has shown that tomato plants are able to extract water from their fruits into the stem under conditions of high leaf transpiration and low water availability in the growing medium.