Effect of different salinity levels on physiological characteristics, phenylalanine ammonia lyase activity and some flavonoid compounds in hydroponic cultivation of saffron (Crocus sativus L.)

The use of salt tolerant plants in arid and semi-arid regions of the world, including Iran, is one of the ways to achieve high yields. The aim of this study was to investigate the effect of different salinity treatments in hydroponic culture on physiological characteristics, phenylalanine-ammonialyase (PAL) activity and also the small amount of flavonoid compounds kaepmferol and quercetin in field saffron (Crocus sativus L.). For this purpose, saffron corms were planted in pots containing perlite and irrigated in controlled laboratory conditions with ½ Hoagland nutrient solutions containing concentrations of 0, 30, 60, 90, 120 and 150 mM sodium chloride. Based on the obtained results, the effect of salinity stress was not significant on chlorophyll a and b levels at 5% level. Carotenoids and glucose levels in the 60 mM treatment had a significant increase of 27% and 56%, respectively, compared to the control treatment. The effect of salinity on leaf amino acid proline was not significant..The relative water content (RWC) in 150 mM with a decrease of 20%, had the highest decrease compared to the control treatment. The activity of PAL enzyme in only 150 mM had a significant increase of 50%. The amount of kaempferol in all concentrations except 150 mM and the amount of quercetin in only 150 mM showed a significant increase (100%) compared to the control treatment. It seems that according to the test results, the tolerance threshold of saffron plant to salt is in the range of 60 to 90 mM and the defense mechanisms mentioned in this range and above help the plant to tolerate salt.