The Effect Of Iron Stress On Iron Metabolism, Photosynthesis And Antioxidant System In Pisum Sativum Seedlings

The effect of iron at different concentrations (low iron: 0, 50μM; normal iron: 100μM; high iron: 200, 400μM, and 100μM Fe²⁺ group was as the control) on root morphology, iron metabolism, photosynthesis and antioxidation system of pisum Sativum seedlings was studied. The results are mainly concerned with following four aspects:1. Under low iron, plant height and primary root growth were inhibited, the number of lateral root increased and root fresh weight reduced. While under high iron, the plant height, number of lateral root and root fresh weight decreased except that the length of main root increased.2. Different Fe supplies affected the iron distribution in plant. With the iron concentration increased, the iron content increased in root and changed little in stem gradually. Iron accumulated in old leaves and little in new leaves under low iron. Ferric reductase activity was highest under low iron, lower under high iron and lowest under normal iron. The transcript levels of PsFOR, PsFER genes under low and high iron concentration treatments were investigated by Real-time PCR. Iron deficiency induced the transcript levels of PsFOR, while high iron concentration treatments induced the transcript levels of PsFER. These results demonstrated that the transcript levels of PsFOR, PsFER mRNA exhibited a close relationship with the iron supply.3. Low and high iron concentration treatments could lead to the decrease in the Net photosynthetic rate (Pn), transpiration rate (E) and stomatal conductance (Gs), and the increase in intercellular CO₂ concentration (Ci). In addition, these treatments caused gradual decrease in maximum quantum efficiency of PSII photochemistry (Fv / Fm), potential photochemistry efficiency (Fv/F₀), electron transfer rate (ETR), photochemistry quantum Yield (Yield) and photochemical quenching of fluorescence (qP); while both the initial fluorescence (F₀) and non-photochemical quenching fluorescence increased. These results indicate that Fe stress treatments not only cause stomatal inhibition of photosynthesis but also destroy the photosynthetic structure and make the PS II inactive, and induce decrease in original energy capture capacity and photosynthetic assimilation rate. Finally, all those cause decrease in photosynthesis capacity in pisum Sativum seedlings.4. Both the low concentration and high concentration of iron increased the content of MDA and reactive oxygen. With the concentration of iron increased, the activities of SOD, POD, CAT and APX increased. The activities of SOD and POD increased with treating time prolonging, while the activities of CAT and APX decreased. We believed that the increased activity in antioxidant enzymes is a resistance mechanism under iron stress.