Abstract: Tomato (Lycopersicon esculentum Mill. ) seedlings were grown hydroponically to investigate the effect of root restriction on plant growth and some key physiological characteristics. Plant biomass, root respiration, root hydrolytic ATPase activities and ultrastructure of root tip cells were investigated during the experiment. The results showed that in the early phase, cytochrome pathway respiration was significantly stimulated while the alternative pathway respiration was inhibited by root restriction stress. In later stage, root restriction resulted in great decrease in plant biomass production especially in root, which was accompanied by significant decline in root total respiration and cytochrome pathway respiration. In addition, root restriction greatly depressed activities of root plasma membrane H⁺ -ATPase, vacuolar H⁺ -ATPase and H⁺-PPase, and resulted in degradation of root tip cell nucleolus.

Key words: Tomato, Root restriction, Root respiration, Plasma membrane H⁺ -ATPase, Vacuolar H⁺-ATPase, Vacuolar H⁺-PPase