The effect of Pretreatment of Salicylic Acid on Seed Germination, Total Phenol and Antioxidant Activity of Nepeta nuda L. Seedling Under Salt Stress

Seed pretreatment with salicylic acid plays an important role in improving germination and increasing resistance of plants to environmental stresses. Delay in germination, decrease in the rate and percentage of germination are from the effects of salinity stress in germination stage. In order to find out the effects of salinity stress along with salicylic priming on seed germination of Hairless Catmint (Nepeta nuda L.), a factorial experiment based on completely randomized design was conducted using salt stress at four levels (0, 50, 100 and 150 mM), three levels of alleviators (0, 0.2 and 0.5 mM) and three times (6, 12 and 24 hours) with 3 replication at physiology laboratory of Department of Horticulture, Faculty of Agriculture, Ferdowsi University of Mashhad in 2016. Indicators of germination with radicle exit at size 2 mm were evaluated for 21 days. After 21 days and completion of recording of germination indices, the plumules were separated for phytochemical evaluation; and determination of total phenol content and antioxidant activity by spectrophotometric methods were carried out by using methanol extract (extracted in a porcelain mortar), Folin-Ciocalteu method and DPPH free radical scavenging, respectively. According to experiment results, the positive effect of salicylic acid on improving germination of this plant in concentration 0.5 mM was more evident than concentration of 0.2 mM. With increasing salinity, the measured traits were strongly reduced. So that the lowest germination percent and germination rate were 0.81 and 0.02 in 150 mM salt stress, respectively. Salicylic acid is also used as an alleviator to improve germination in different levels of salinity. So that the highest germination percent (25.11) and germination rate (0.62) were obtained from pretreatment with salicylic acid for 24 hours. The highest amount of antioxidant activity (68.92%) and total phenol (1.2 mg.g-1 FW) was related to level of 50 mM stress and the use of salicylic acid at different salinity levels reduced the amount of these traits. In general, although salinity stress markedly reduced germination in Nepeta nuda, but using pretreatment with salicylic acid can significantly improve germination indices in these conditions.