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

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Abstract
Growth, dry matter partitioning, and the levels of various substances in tomato plants grown in liquid nutrient culture at four root temperatures (15, 20, 25, and 30°C) in controlled environment cabinets were measured. In order to understand the role of root temperature in growth and development, the partitioning model of Thornley (1972) was used to try and describe the observed behaviour. The steady-state behaviour could be simulated reasonably by the model, although certain aspects of the time-course data present problems. It was observed that relative growth rate is proportional to the product of the carbon and nitrogen levels (one of the two principal assumptions of the model). The model also made realistic predictions about the influence of root temperature on the fraction of the plant dry matter in the root, and on the carbon and nitrogen levels. The effect of root temperature was incorporated into the model by assuming that certain values of specific root activity correspond to the different temperatures. In addition the model predicted an experimentally reasonable relation between net assimilation rate and relative growth rate.

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