The effect of salicylic acid and potassium nitrate on germination characteristics, photosynthetic pigments and seedling proline seedlings of two safflower cultivars under salinity stress

Soil salinity causes major losses in crop production, especially in arid and semi-arid regions where 110 million out of 270 million ha of irrigated lands are located. Salinity is becoming more extensive as a result of land clearing and unsustainable irrigation and salinity management practices, as well as increasingly by bringing marginal lands into production. Priming is one of the effective methods to improve seed germination and seedling establishment in stressful environmental conditions such as salinity. Safflower (Carthamus tinctorius L.) is the most important oil seed crop from Asteraceae family. These plants are usually preferred in arid and semi-arid regions under rain-fed conditions, where low rainfall and high evapotranspiration during vegetation periods restricts the growth of crop plants. Under these conditions, drought and salinity are the major abiotic stresses that severely inhibit germination, seedling establishment and plant growth; consequently, seed yield decreases. The purpose of this experiment was to investigate the effect of salicylic acid and potassium nitrate pretreatments on germination components, growth characteristics, photosynthetic pigments and proline of two safflower cultivars under salinity stress.

In order to investigate the effect of salicylic acid and potassium nitrate on germination and photosynthetic indices of two safflower cultivars under salinity stress, a factorial experiment was conducted in a completely randomized design with three replications in the Seed Technology Laboratory of Shahed University of Agricultural Sciences in 2018. Experimental factors include safflower cultivars of Sofeh Isfahan and Goldasht cultivars, priming at three levels of control (distilled water), salicylic acid 0.5 mM and potassium nitrate 0.3% and salinity stress caused by Qom Lake salt at four levels of 0, 5, 10 and 15 dS/m, respectively.

The results showed that increasing the salinity of salt (sodium chloride) decreased the seed germination characteristics, relative water content and photosynthetic pigments and increased proline content. In Sefeh cultivar, the highest amount of germination components such as germination percentage (90%), germination rate (9.16 seeds per day), root length (25 mm), stem length (49.5 mm) Seedling fresh weight (1.25 g) and seedling dry weight (0.14 g) were obtained in the absence of salinity stress and application of salicylic acid. Also, under stress conditions of 15 dS/m and salicylic acid treatment, Sefeh cultivar had significant germination and growth. Salicylic acid pretreatment under salinity stress reduces the negative effects of salinity stress, thus increasing the germination percentage and seedling growth indices. Pretreatment of potassium nitrate increased photosynthetic pigments in Sefeh cultivar of Isfahan under salinity stress. Using cost-effective seed priming can improve seed germination components for growth in salinity conditions.

The results showed that salinity stress reduced the percentage and rate of germination, root and shoot length, fresh and dry weight of seedlings in both safflower cultivars. Negative effects of salinity stress on physiological parameters included reduction of photosynthetic pigments. Also, salinity stress affected the amount of proline in the contract and increased the amount of this trait. Sefeh cultivar under salinity stress with salicylic acid application had better tolerance than Goldasht cultivar. It is suggested that the quantitative and qualitative traits of safflower cultivars be evaluated under field conditions under salinity and priming to yield stages and yield components. To be able to more confidently recommend suitable cultivars in areas with saline soils.