Decreased energy synthesis is partially compensated by a switch to sucrose synthase pathway of sucrose degradation in restricted root of tomato plants

Tomato (Solanum lycopersium L.) plants were grown hydroponically to investigate the changes of energy metabolism and adaptive mechanism in response to root restriction. Root restriction resulted in a significant increase in root lipid peroxidation and reduction in leaf net CO2 assimilation rate, which was accompanied by increase of alcohol dehydrogenase (ADH; EC 1.1.1.1) and lactate dehydrogenase (LDH; EC 1.1.1.27) activities. Total, cytochrome pathway, and alternative pathway respirations were all decreased in the roots after 15 days of root restriction treatment. Accompanied with the decrease of ATP content, ratio of invertase/sucrose synthase activity was increased in the restricted roots together with a decrease in glucose content and an increase in fructose content. We concluded that the decreased energy synthesis under root restriction condition was partially compensated by the energy-conserving sucrose synthase pathway of sucrose metabolism.