Antioxidant enzyme activity in salt tolerant selected clones of stylo 184 (Stylosanthes guianensis CIAT 184), an important forage legume
Faculty of Health, Engineering and Science
School of Natural Sciences/Centre for Ecosystem Management
In vitro shoots from five selected clones-one sensitive (T1) and four salt tolerant (T2, T3, T4 and T5)-of Stylosanthes guianensis CIAT 184 were multiplied in Murashige and Skoog medium with 0, 0.5 and 1% (weight per volume) NaCl for 1 wk followed by transfer to a recovery medium for a further week. Their relative fresh weight (RFW) and antioxidative enzymes-superoxide dismutase (SOD), catalase (CAT) and peroxidase (POX)-were measured after 7 d on the salt medium and again after another 7 d on a recovery medium (without additional NaCl). Exposure to NaCl reduced the growth of all clones at some stage. For the four clones selected as salt tolerant, the reduction in growth was evident after 7 d (up to 45%) on the NaCl media, however, for the clone selected as salt sensitive this reduction (50%) only occurred after 7 d on the recovery medium. Shoots of clones T2, T3 and T5, however, increased their growth on the recovery medium and this was associated with an increase in POX activity (from 0.5% NaCl medium for T2 and 1% NaCl medium for T3 and T5). The SOD activity of these clones was higher than the salt sensitive clone but decreased at 1% NaCl when shoots had been on the recovery medium for 7 d. In T4, the RFW increased to equal that of the control at 0.5% NaCl after recovery while the SOD activity was reduced and the POX activity was stable after both salt treatment and recovery. The NaCl treatments had no effect on the CAT activity for any of the clones. The lowest SOD activity was found in T1 while the tolerant clone, T5, showed the highest CAT and POX activity, providing the ability to distinguish between clones.