Variable accumulation of cadmium in flax (Linum usitatissimum L.)
Keywords:Hyperaccumulators, Metal accumulation, Metal stress, PR proteins
Given the potential use of flax in metal-contaminated soil remediation programs, the uptake and accumulation of cadmium was studied in five varieties of flax (Linum usitatissimum L.) including var. Belinka, Escalina, Jitka, Marina and Krasnoder. Early stage plants in hydroponics were exposed to Cd to assess their tolerance by means of growth parameters and content of photosynthetic pigments. All varieties exerted tolerance indexes in the range of 63 – 89 %, while oxidative stress was not detected in either variety. Chitinase enzymes were analyzed in leaf protein extracts since activities of these enzymes have previously been correlated with plant tolerance to Cd. However, total enzyme activities remained unchanged in presence of Cd in all flax varieties. A more detailed analysis of these enzymes identified up to 3 chitinase isoforms upon separation of leaf protein extracts in polyacrylamide gels, and their quantification confirmed responsiveness to Cd for each of them. The obtained data were interpreted in light of metal uptake rate, which we measured using gammaspectrometry in growth media spiked with 109Cd and in the plant tissue. The variety Jitka showed the most sensitive to Cd and accumulating fast and the highest amounts of metal. In contrast, the variety Belinka appeared most tolerant, accumulating the least Cd in a slow rate. Activation of chitinase isoforms correlated with more sensitive varieties and suggests activation of general defense mechanisms. The obtained data suggest the variety Jitka as most promising for phytoremediation programs and the var. Belinka as the most suitable when avoidance of potential health risk is of interest.