Time-course changes in the inorganic and organic components of germinating sunflower achenes under salt (NaCl) stress
2003
Ashraf, Muhammad | Zafar, Rafia | Ashraf, Muhammad Yasin
Achenes of sunflower (cv Hi-Corn) were subjected for seven days to salinized solution culture containing 0, 50, 100 or 150 mol NaCl m−3. Fresh weights of cotyledons and hypocotyl increased at all external salt regimes, although the increase was low at the highest salt level. Na+, Cl- and Ca2+ concentrations in hypocotyls increased with time in all salt treatments. The external salt concentration or the time of incubation had no significant effect on Na+, K+ and Ca2+ concentration of cotyledons, but in contrast, there was a significant time course increase in Cl- level upon addition of salt to the rooting medium; this was not the case with the hypocotyl Cl- accumulation. A gradual decrease of soluble proteins with time was noted in cotyledons, but addition of salt was without any effect. By contrast, the hypocotyl soluble proteins decreased consistently with increasing salt level. There was no significant effect of NaCl on free amino acids level of cotyledons up to the 5th day of germination, but thereafter, cotyledonary free amino acids decreased considerably with increased salt level. There was a time-course decrease in soluble sugars of cotyledons and hypocotyl in control and at 50 mol NaCl m-3, but at higher NaCl concentrations soluble sugars in the hypocotyl increased with time. Total lipids of cotyledons decreased significantly with time. The salt effect on germination of sunflower was found to be associated with a time-course dependend absorption of Na+ and Cl- by the hypocotyl. In addition, the deleterious effect of salt on seed germination could be ascribed to impairment in breakdown of seed lipids thereby diminishing the supply of soluble sugars to the growing embryonic tissues.
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