Response of Dry Matter Partitioning, Growth, and Carbon and Nitrogen Levels in the Tomato Plant to Changes in Root Temperature: Experiment and Theory

Growth, dry matter partitioning, and the levels of various substancesin tomato plants grown in liquid nutrient culture at four roottemperatures (15, 20, 25, and 30°C) in controlled environmentcabinets were measured. In order to understand the role of roottemperature in growth and development, the partitioning modelof Thornley (1972) was used to try and describe the observedbehaviour. The steady-state behaviour could be simulated reasonablyby the model, although certain aspects of the time-course datapresent problems. It was observed that relative growth rateis proportional to the product of the carbon and nitrogen levels(one of the two principal assumptions of the model). The modelalso made realistic predictions about the influence of roottemperature on the fraction of the plant dry matter in the root,and on the carbon and nitrogen levels. The effect of root temperaturewas incorporated into the model by assuming that certain valuesof specific root activity correspond to the different temperatures.In addition the model predicted an experimentally reasonablerelation between net assimilation rate and relative growth rate.