Journal of Agricultural Science and Sustainable Production (Jan 2015)
Study of Key Points of Salt Response Using Rapid Chlorophyll a Fluorescence, Defense Mechanisms and Membrane Stability Index in Wheat
Abstract
In attention to wheat importance in people nutrition and wide distribution of salt agricultural lands, bread wheat variety of karaj3 were aeroponicaly way grown to investigate weak and power points in response to salinity. After growing the seedlings as 4 -5 leaf stage, they were exposed to salt stress, 200 mM NaCl. Then, rapid chlorophyll a fluorescence, activities of enzymes involving plant defense mechanisms, indices related to oxidative stress and membrane stability index were measured. The obtained results displayed that total superoxide dismutase activity and its isozymes had no significant changes under stress conditions. In addition, activities of catalase, guaiacol peroxidase and ascorbate peroxidase were elevated under stress conditions. Hydrogen peroxide, a toxic metabolite, accumulated in leaf cells affecting by salt, though significant increasing of its scavenger enzymes. Also, significant alterations occurred for lipid peroxidation and membrane stability index by salt. Na and K values in variety of karaj3 showed that K/Na ratio was more than one, however, significant increasing of Na and high decreasing of K were found. Assessing of indices related to rapid chlorophyll a fluorescence revealed that Fv/Fm parameter has been just decreased under salt. Therefore, results showed that selection of salt tolerant varieties just by Fv/Fm index was not enough reliable and it is better to apply simultaneously other indices particularly yield index. Photosystem II was not susceptible to salinity in Karaj3 variety, too. It seems lack of increased activity of superoxide dismutase and its isozymes was the probable factor for accumulation of hydrogen peroxide and oxidative stress initiation, in spite of increased its scavenging enzymes activity.
