Abstract: In order to explore the effects of combined application of sulfur and iron on the growth and physiological characteristics of broccoli seedlings under stress, two kinds of combined application solutions of sulfur and iron（7 mmol/L Na₂SO₄+0.5 mg/L FeCl₂ and 7 mmol/L Na₂SO₄+20 mg/L EDTA-Fe）were sprayed on the leaves of broccoli seedlings, and 150 mmol/L NaCl solution and 15% PEG6000 solution were used to simulate salt and drought stress. Xanthomonas campestris was inoculated on the leaves of broccoli seedlings by acupuncture method to simulate the stress of black rot fungus. The antioxidant enzyme activities, malondialdehyde, osmotic adjustment substances and glucosinolate contents of broccoli seedlings in each group were determined. The results showed that: under salt and drought stress, the broccoli seedlings of salt control（CKs）and drought control（CKd）both appeared the phenomenon of yellow leaves and wilting, and the broccoli seedlings treated with sulfur and iron fertilizer had a better growth state, without obvious wilting or leaf abscission. Under salt stress, the activities of SOD, POD and soluble protein content of T1s and T2s treatment groups were significantly higher than those of CKs; The content of glucosinolate in T1s treatment group was significantly higher than that in CKs, and the content of malondialdehyde in T2s treatment group was significantly lower than that in CKs. Under drought stress, POD activity in T1d treatment group was significantly higher than that in CKd; The proline content in T2d group was significantly higher than that in CKd; The content of MDA in T1d and T2d treatment groups was significantly lower than that in CKd. Under the stress of black rot fungus, the control（CKb）treatment of black rot fungus showed obvious yellowing, black spots and leaf rot; The growth status of broccoli seedlings in T1b and T2b treatment groups was better, only the local phenomenon of leaf etiolation occurred and the black spot was smaller. The activities of SOD, POD and CAT in T1b treatment group were not significantly different from those in CKb, but they all increased in varying degrees; The activities of SOD and POD in T2b group were significantly higher than those in CKb group; The contents of soluble protein and proline in T1b and T2b treatment groups were significantly higher than those in CKb, and the content of malondialdehyde was significantly lower than that in CKb. The membership function analysis showed that the combined application of 7 mmol/L Na₂SO₄+0.5 mg/L FeCl₂ could alleviate the stress damage of broccoli seedlings and effectively improve their comprehensive stress resistance.

Key words: broccoli, combined application of sulfur and iron, physiological characteristics, stress resistance