Elucidating some physiological mechanisms of salt tolerance in Brassica napus L. seedlings induced by seed priming with plant growth regulators

摘要

Present study was undertaken to elucidate some physiological mechanisms of induced salt tolerance by different plant growth regulators (PGRs) in rapeseed ( Brassica napus L.) seedlings. Three salt stress levels were given; tapwater (0.7 dS m -1 ), 6 dS m -1 and 12 dS m -1 , which made by NaCl and CaCl 2 as 2:1 molar ratio. The eight seed priming agents were included: dry seeds (no-priming), hydropriming and six PGRs primings. The used PGRs were; abscisic acid (ABA), auxin (AUX), salicylic acid (SA), chlorocholine chloride (CCC), ascorbic acid (AS) and brassinosteroid (Brs). The results revealed that salinity, depending on level, reduced seedling emergence, shoot and root growth, potassium (K ) concentration and enhanced sodium (Na ) concentration and antioxidant enzymes. These reductions could be attributed to oxidative stress and/or ion balance disturbance due to salinity stress. It is documented by reduced K and increased Na in both root and shoot as well as enhanced antioxidant enzyme activity and H 2 O 2 in salt stressed rapeseed seedlings. Higher storage factor (SF) refers to a higher ions content kept in roots rather than transporting these to the shoot as salinity level increased. PGRs priming modulates some negative effects of salt stress on emergence, growth and physiological functions of plants. In triggering the ameliorating role of PGRs, it appeared that the ratio of Na to K is more important than their individual concentrations. Moreover, H 2 O 2 concentration was found to be a better key for estimation of the oxidative damage rather than antioxidative enzymes. Among the PGRs, SA and Brs showed better performance, and it seems that the main mechanism of action for SA was creating ion balance and changing ion partitioning in favor of roots. For Brs it appeared to be reactive oxygen species (ROS) scavenging by inducing higher activity of antioxidant enzymes, particularly catalase.