Swiss chard and spinach belong to the family Amaranthaceae. Swiss chard is rich in the pigment betacyanin, which has antioxidant properties. This study compared the salt tolerance of spinach and Swiss chard in terms of the suppression of Na penetration into the plants and the reduction of oxidative stress. The Na content of spinach increased in the roots and shoots with the increase in Na concentration of the treatment. The ability to inhibit Na penetration into the roots—examined on the basis of plasmalemma ATPase activity and glycine betaine content—was lower in spinach than in Swiss chard. However, Na treatment increased the plasmalemma ATPase activity and glycine betaine content in the shoots of both plants. In swiss chard, the pattern of Na content increase by Na treatment was markedly different from that in spinach. Within Na treatment concentrations that maintained plant growth, the Na content in the shoots increased with the increase in Na treatment concentration. However, no increase occurred at higher treatment concentrations. Meanwhile, the Na content in the roots did not change with the Na treatment concentration that maintained plant growth, but it increased rapidly above that concentration. Hydrogen peroxide content and superoxide dismutase （SOD） activity of both spinach and Swiss chard increased with Na treatment and increased markedly at growth-maintenance and growth-inhibitory Na concentrations, respectively. The catalase activity of spinach was substantially increased with Na treatment at all tested concentrations, while that of Swiss chard increased only at growth-inhibitory Na concentrations. Betacyanin content did not change regardless of Na treatment and treatment concentration, and a constant amount was maintained in the shoots.
Thus, salt tolerance was higher in betacyanin-containing Swiss chard than in spinach. The amount and mode of elimination and distribution of excess Na penetrating into the plants differed between both species. The findings suggested that betacyanin contributes to reducing oxidative stress at least at Na concentrations lower than the growth-inhibitory concentration, resulting in increased salt tolerance of Swiss chard. Because the betacyanin content did not change with Na treatment, the antioxidant levels might not be affected in Swiss chard grown under high-salt conditions.
In this study, we investigated the influence of student’s expertise, learning situations and the teacher’s consciousness on opinion fluctuation regarding the pros and cons of restarting nuclear power plants. Results were obtained from observations of discussions of controversial issues involving the concept of “citizenship” from the perspective of the formation of political literacy. In terms of the degree of change in the ratio of pros to cons, the standard deviation （S） differed depending on academic department, which of departments focus on science tended to be smaller than departments of letters. And, in departments that were higher average score of placement test “English”, that is departments in which students had a wealth of learning experience, the standard deviation tended to be small and these results were negative correlation （S=7.3～24.1, r=–0.438）. In addition, in a class where a teacher had an explicit dissenting opinion about restarting nuclear power plants, the degree of change in the ratio of pros to cons was small （S=5.3）; the high ratio of dissenting opinion was maintained. In terms of lecture style, in a class where a teacher lectured emphatically （as opposed to in a calm or detached demeanor）, there tended to be a larger degree of change in the ratio of pros to cons （S=16.6）. In this way, the data demonstrated the possibility of influencing a student’s expertise, learning situations and teacher’s consciousness on opinion fluctuation regarding the pros or cons of restarting nuclear power plants. These results suggest the importance of further investigation into teaching methods that might be influential in citizenship education dealing with controversial issues.