Improvement of Salt Tolerance in Vicia faba (L.) Plants by Exogenous Application of Polyamines

SALINITY stress causes physiological drought and disturbances in plant physiology that lead to a reduction in plant growth. To search for an effective method to increase salt tolerance of Vicia faba (L.) plants, the effect of soaking the seeds in spermidine (Spd; 1.5 mM) or spermine (Spm; 1.5 mM) on growth, drought tolerance, contents of free proline, total soluble sugars, starch, endogenous Spm and Spd, and antioxidant system in plants grown under salt stress of a saline calcareous soil was studied. Spm or Spd alleviated the adverse effects of salt stress to convergent degrees. Soaking faba bean seeds in either Spd or Spm increased all plant growth characteristics and the activities of antioxidant enzymes compared to the control (seeds soaked in distilled water). In addition, soaking seeds in either polyamine significantly increased membrane stability index, relative water content, contents of ascorbic acid, glutathione, endogenous Spm and Spd. All these improved parameters reflected in enhanced yield and its components. In contrast, electrolyte leakage, concentrations of protein, starch, malondialdehyde and hydrogen peroxide were reduced compared to the control. Data of the present study also show that the variety Giza 429 exhibited better results than the variety Giza 40, concluding that Giza 429 was more salt-tolerant compared to Giza 40. These results are important as the potential of Spd or Spm to mitigate the deleterious effects of soil salinity stress offer an opportunity to increase the faba bean tolerance to growth under saline conditions.