Mechanisms Of Alleviating Effect Of Seed Soaking With Soybean Isoflavones On Glycine Max, Salt-born Glycine Soja And Their Hybrid Seedlings Under Salt Stress

The Glycine max N23674 cultivar (Lishui, Jiangsu province, the salt sensitive), the salt-born Glycine soja BB52 population (Kenli, Shandong province, the salt tolerant) and their 4 hybrid strains (F5):4013,4035,4076 and 4111 were used as the experimental materials in this study. The contents of isoflavones in soybean seeds were detected by HPLC. The relationship between the soybean isoflavone content and the salt tolerance was analyzed. Then N23674, BB52 and 4076 were used as the further experimental materials, the possible roles or mechanisms of soybean isoflavone in soybean salt tolerance were investigated by seed soaking with Daidzin or Genistin. The results showed as follows:The isoflavone content in seeds of N23674 was higher than that in BB52, and the hybrid 4076 strain was the highest, other hybrid strains were mostly between their parents; the isoflavone content in seeds and the salt tolerance of soybean seedlings was remarkably positive; Seed soaking with Daidzin or Genistin even at 0.01 mg/L could alleviate the NaCl-induced injury or growth inhibition in soybean seedlings; and Seed soaking with Daidzin and Genistin at 0.01 mg/L all elevated the isoflavone contents in soybean seedlings under salt stress.When the seedlings of the hybrid 4076 strain and its parents (N23674, BB52) pretreated by seed soaking with Daidzin or Genistin were stressed for 6 d with 130 mmol·L-1 NaCl, the K+content in leaves was increased, the Na+contents in stems and leaves were decreased, the Cl-content in stems was decreased and the Na+/K+ ratio in leaves was decreased significantly, when compared with the just NaCl treatment. The chlorophyll contents in 4076 seedlings, for which seeds were soaked with Genistin, were significantly increased in comparison with the just NaCl treatments, and as well as the carotenoid contents in N23674 for which seeds were soaked with Daidzin or Genistin. Under 130 mmol·L-1 NaCl for 6 d, the Pn of the three experimental materials were obviously decreased in comparison with the control, while it was alleviated in comparison with the materials pretreated by seed soaking with Daidzin or Genistin.Under NaCl stress, the TBARS content and the relative electrolytic leakage significantly increased in leaves of the three soybean seedlings, but the TBARS content in those of seed soaking with Daidzin and Genistin showed no obvious difference, and the relative electrolytic leakage remarkably decreased. The DPPH-radical scavenging activities in roots remarkably ascended when compared with the control, and were much higher when pretreated with the two isomers of isoflavone. The SOD and CAT activities in roots and leaves of salt-stressed seedlings were significantly increased, while the POD activities were decreased when compared with the control. But when the three soybean materials were pretreated by seed soaking with the two isomers of isoflavone, the SOD activities in the leaves of three materials and the CAT activities in 4076 leaves were all higher than the just NaCl stress, the POD activities were restored for some degrees, and that in N23674 were even recovered to the control level.