Abstract: A water culture experiment was conducted with the seedlings of tomato (Lycoper sicon esculentum Mill.) cultivar Liaoyuanduoli to study the effects of salicyl ic acid (SA) on their sucrose metabolism under NaCl stress. The seedlings were t reated with different concentrations (100, 300, and 500 mg·L-1) of SA, and the contents of sucrose, glucose, and fructose as well as the related en zyme activities of sucrose metabolism, including acid invertase (AI), neutral in vertase (NI), sucrose phosphate synthase (SPS), and sucrose synthase (SS), in se edling leaves were determined. Under NaCl stress, SA could maintain or enhance t he leaf fructose and glucose contents and the leaf AI, NI, SPS and SS activities , with the highest increment of fructose and glucose contents being 300% and 311% and that of AI, NI, SPS and SS activities being 247%, 279%, 220 % and 245%, respectively, in comparing with no SA application, while had less effect on the leaf sucrose content, which suggested that SA could play a protec tive role in the NaCl-tolerance of tomato seedlings via enhancing the leaf inve rtase activity to increase leaf fructose and glucose contents. The best alleviat ing effect was observed at 500 mg·L-1 of SA.

Key words: Chinese onion, root exudates, cucumber, rhizosphere soil microorganism.