Effect of Salt Stress on Growth, Ionic Homeostasis and Ions Interaction in Sensitive and Tolerant Genotypes of Rapeseed (Brassica napus L.)

Salt stress inhibits plant growth and impair ionic homeostasis. Plant response to salinity stress is different at the cellular levels. In order to investigate the effect of salinity levels on growth, chlorophyll and ions content, an experiment was conducted in 2008, at the college of Agriculture, Shahid Chamran University of Ahvaz, Iran. The experiment was a split plot design on Completely Randomized Design. The treatments included three levels of salinity and cultivars. In this experiment, shoot and root ionic contents were studied in three genotypes of rape plants (Brassica napus L.) that grown hydroponically under three levels of salinity (0, 100, 150 mM NaCl) at growth chamber. Salinity treatments were imposed to seedlings at the 4 true-leaf stage by 8 true leaf stage. Results showed that salt tolerant genotypes had more ability to accumulate toxic ions (Na+ and Cl-) in their shoots. By increasing salt, shoots Cl- content increased and accumulation of NO3- reduced with increasing Cl- in shoots of all genotypes. Concentrations of shoot and root Ca2+ were increased by increasing salinity in all genotypes. In salt tolerant genotypes, more increasing root Ca2+, helped to improve salinity tolerance. Increase in shoots Na+ in salt sensitive genotype, resulted in a decline in chlorophyll a and b and quantum yield of PSII. Results indicated that high Na+ and Cl- accumulations in the shoots, were associated with salt tolerance in rapeseed.