Investigation of some morphological, physiological andbiochemical parameters against salt stress in cotton (Gossypium hirsutum L.)

Salt stress, one of the most important abiotic stress factors, is accepted to limit yield in cotton production areas. In this study to obtain salt stress by applying different concentrations of NaCl on the calli obtained from the seeds of two different cotton cultivars, Carmen and NM-503 known as salt-resistant and salt-sensitive respectively, in vitro conditions and to analyze of the morphological, physiological and also biochemical effects investigation caused by the salt stress on the calli are the main points targeted. The seeds of Carmen and NM-503 varieties were cultured in semi-solid nutrient media (1/2 MS) for in vitro germination after surface sterilization provided by sulfuric acid and commercial sodium hypochlorite. The callus, formed from hypocotyl explants of sterile seedlings after 7 days of germination, mass-propagated by subculturing and transfered into the medium with determined salt concentration for 4 weeks. After 4 weeks, the morphological and biochemical parameters of the cultures are investigated and the state of salt tolerance of the callus are evaluated. Among the callus, which are analyzed by morphological and physiological properties such as wet weight, dry weight, callus color, callus structure and callus formation percentage, it is observed the growth of both cultivars stopped at 400 mM salt applied concentration. According to morphological and physiological observations, NM-503 species, known as salt-sensitive, are found to be more suitable for plant tissue cultures in vitro. It is observed that chlorophyll amounts did not change and carotenoid amounts decreased in increasing salt concentration of cultivars. In the presence of increased salt concentration, photosynthetic activities are not a distinctive feature for both cultivars of cotton plant and do not have a mechanism affected by salt stress. Increasing of the amount of proline in the cultivar Carmen, which is known to be resistant, and decreasing in the cultivar NM-503, which is known to be sensitive, in the presence of increased salt concentration, explains that cotton plant tolerates salt stress by osmotic regulation. DPPH analysis showed that % inhibition of antioxidative enzymes of both cultivars decreased with increasing salt concentration. While the proline content of Carmen cultivar was 2.65 and 3.10 µmol-1 g in 200 and 400 mM NaCl application, the same doses of NaCl in NM-503 were 0.22 and 0.21 µmol-1 g. It was observed that the amount of hydrogen peroxide in NM-503 variety was higher in the same NaCl concentration application. These results show that by increasing the activity of POX and APX enzymes in Carmen cultivar, hydrogen peroxide reduces harmful effects. Although NM-503 was morphologically and physiologically suitable for in vitro selection studies, Carmen was determined to tolerate salt with osmotic regulation and antioxidant enzyme activities up to 200 mM salt concentration.