Photosynthesis in two wheat cultivars differing in salt susceptibility

Salinised (150 mM NaCl for 15 d) roots excised from salt sensitive wheat cu ltivar Giza 163 showed about 15-fold increase in the ratio of Na/K while sa lt tolerant Sakha 92 exhibited only 7.5-fold increase compared to their con trol ratios. Root ratio of saturated/unsaturated fatty acids was stimulated twice in the sensitive cultivar versus 1.7-fold increase in the tolerant o nes. Salinity enhanced greatly the accumulation of spermine (Spm) and sperm idine (Spd) contents associated with a decrease in putrescine (Put) content in both wheat cultivars. Higher ratios of Spm+Spd/Put associated with lowe r content of proline and low ethylene evolution were detected in shoots and roots of salt tolerant cultivar. Chlorophyll a/b ratio showed an increase from 1.3 in control of both cultivars to 1.6 and 1.4 in stressed Giza 163 a nd Sakha 92, respectively. A reduced Hill reaction activity (19 %) was obse rved in stressed chloroplasts isolated from leaves of the tolerant cultivar versus 40 % inhibition in the sensitive ones. Moreover, chloroplasts isola ted from stressed leaves of the sensitive cultivar showed about 25 % reduct ion in fluorescence emission at 685 nm as well as shifts in the peaks in th e visible region.