Tomato Stem and Fruit Dynamics Predicted with a Whole-Plant Water and Carbon Flow Model

Tomato fruit production is economically very important in horticulture. In order to improve competition on the world market, growers' main focus is shifting to fruit quality (e.g., organoleptic and nutritional). Although these quality traits are very complex, they are to a large extent influenced by water and carbon translocation towards the fruits. A mechanistic model is presented which integrates fruit fresh and dry weight production with overall plant water and carbon status. Experimental data of stem and fruit diameter variations and stem sap flow rates, collected on tomato plants (Solanum lycopersicum L.), were used to construct a fruit growth simulation model. The presented model offers insights into the fruit dry and fresh weight production in relation to the water relations at the whole-plant level. The model was calibrated for a period of three days based on stem and fruit diameter data and using sap flow data as input for the model. The integrated approach enables to map out the different opposite and cooperating xylem and phloem flows within the plant and towards the fruit. This way, sound relationships between the entire plant and the diurnal fruit diameter dynamics were revealed. Implementation of the obtained insights in greenhouse management systems can lead to optimized environmental conditions for fruit production and fruit quality.