Comparative effects of NaCl and Na2SO4 on germination and early seedling stages of the halophyte Carthamus tinctorius L.

Salinity is one of the primary environmental problems limiting the agricultural productivity and affecting soil physicochemical properties, especially on arid and semi-arid areas. Hence, early screening of salt-tolerant species is a promising strategy for the recovery of salt affected lands. Safflower (Carthamus tinctorius L.), is a medicinal plant used as a laxative, pain relieving, antipyretic and an antitoxin against poisoning. It provides an interesting perspective in becoming a salt-tolerant and high-value crop at saline conditions. In this regard, the aim of the present investigation was to evaluate the effect of salt stress on the germination and early seedling stages of safflower. A laboratory experiment was carried out in a phytotron at a temperature of 25 degrees C and in the dark for 7 days. The seeds were germinated in Petri dishes treated with various concentrations 0 (control) to 600 mM of NaCl and Na2SO4, with 4 repetitions. The presented results indicate that increasing salinity delayed the beginning of germination and gradually reduced germination percentages. At salt levels beyond 400 mM Na2SO4 and 500 mM NaCl germination was completely inhibited. The germination stress tolerance index displayed that seed germination of safflower was restricted more with Na2SO4 compared to NaCl. Ungerminated seeds in high salt treatments (>= 300 mM Na2SO4 and >= 400 mM NaCl) when transferred to distilled water recovered and kept their ability to germinate. Although, total germination percentages progressively decreased with increasing salinity levels, suggesting that the adverse impact of these treatments were osmotic effect and specific ion toxicity. In addition, increasing salinity concentrations led to a significant decrease in the seedling vigor index by means of reduced radicle and hypocotyl growth irrespective of the salt agents applied. These findings suggest that safflower may be considered as a promising species for saline soil rehabilitation and by consequence for ecological balance improvement.