Comparative chlorophyll content and proline metabolism in wheat seedlings exposed to copper and iron stresses

In this study wheat seedlings cv Ningchun 4 is used to evaluate the changes of chlorophyll and osmotic regulator contents as well as the activities of proline metabolic enzymes in response to different CuCl2 and FeCl3 concentrations.The results show that chlorophyll a,chlorophyll b and total chlorophyll contents significantly increas in wheat treated with 100 μmol·L-1 copper,while these three parameters due to 300 μmol·L-1 and 500 μmol·L-1 Cu are obviously lower than those in untreated seedlings.By contrast,the 100 μmol·L-1 concentration of iron do not affect the amount of chlorophyll a,total chlorophyll,soluble sugar and soluble protein,but these parameters significantly elevate in the leaves of wheat under 300 μmol·L-1 and 500 μmol·L-1 Fe3+ treatments.In addition,Cu2+ and Fe3+ treatments induce an increase in proline content in wheat seedlings,but the enhanced degree under FeCl3 treatment is markedly higher than that in response to CuCl2.Further studies show that both copper and iron treatments result in the decrease of PDH activity,but a notable elevation in the activity of OAT is caused by 500 μmol·L-1 Cu2+ and different Fe3+ concentrations.In conclusion,these results suggest that 300 μmol·L-1 and 500 μmol·L-1 CuCl2 treatments lead to damage to chlorophyll in wheat seedlings,while 100 μmol·L-1 CuCl2,300 μmol·L-1 and 500 μmol·L-1 FeCl3 treatments have benefit to the synthesis of chlorophyll;both copper and iron induce the enhancements of soluble sugar,soluble protein and proline content,resulting in strong osmotic adjustment ability,which may improve wheat tolerance to Cu2+ and Fe3+ treatments.Additionally,proline accumulation may be associated with decreased PDH activity and elevated OAT activity in wheat seedlings under copper and iron stresses.