Studies On The Effect Of Excessive Fe²⁺ For The Ginseng

Iron is one of essential elements for plant growth; the iron toxicity is widespread nutrient disordercaused by excessive Fe²⁺, especially in a long period of flooding or poor condition breathable of thealbic bed soil. In this study, the method of manual ginseng simulation growing environment inecological conditions under soil culture used to discuss the toxic action caused by excessive Fe²⁺stressand the physiological response mechanism of ginseng to3years ginseng seedlings by installing6Fe²⁺concentrations. This research has achieved the main results are as follows:1. The excessive Fe²⁺stress decreased the content of chlorophyll a, chlorophyll b andcarotenoids in different growth period of ginseng.The chlorophyll a, chlorophyll b and carotenoids content of controlled are higher than the contentof iron processing concentration, but the chlorophyll a, chlorophyll b and carotenoids content of ironprocessing concentration showed a trend of increased at first and then decreased; the chloroplastpigment reached a high level when the Fe²⁺concentration was in0.2mol/L-0.4mol/L.2. The excessive Fe²⁺stress increased the activities of antioxidant enzymes of ginseng leaves.The activities of SOD, POD, CAT increased gradually with the increasing of Fe²⁺concentration,but the antioxidant enzymes activities of ginseng increased also have a definite limition. All theactivities of antioxidant enzymes showed the trend of decline when the Fe²⁺concentration was0.4mol/Lor even higher. At this time the antioxidant enzymes of ginseng leaves have not been sufficient ability toremove oxidation free radicals. In general, the antioxidant enzymes variation of ginseng leaves betweendistinct growth periods of ginseng is the trend of increased at first and then decreased in dynamicchanges in the process.3. The excessive Fe²⁺stress increased the content of osmotic regulation substances of ginsengleaves.The Fe²⁺concentration is proportional to the MDA content in ginseng leaves, the MDA contentkeeps the same level of5growth period of ginseng, yet the MDA content of the flowering period, greenfruit and red fruit period are higher than other growth period of ginseng leaves. The trend of the solublesugar content is not constant for different growth period of ginseng leaves, the soluble sugar content isthe highest in leaf-expansion period and red fruit period when the Fe²⁺concentration is0.6mol/L, are8.25mg/g and7.94mg/g respectively, it shows increasing trend gradually in other growth period. Thechange tendency of the proline content and MDA content are basically identical in every growth periodof ginseng leaves, the proline content reached the highest when the Fe²⁺concentration is0.8mol/L, butproline content and controlled are significantly different（P<0.05）.4. The excessive Fe²⁺stress resulted in the disorders of mineral metabolism of ginsengThe treatments of altered iron concentration seriously affected the absorption and transportion ofiron and11other trace mineral elements in ginseng. In leaf-expansion period, the excessive Fe²⁺stressincreased the content of Al, Cr, Mg and Ti and decreased of Fe, Cu, Pb, Mn and Zn of ginseng in aboveground portion, and increased the content of Al and Ti and decreased Fe, Cu, Pb, Mg, Mn and Znof ginseng in underground portion. In florescence and green-fruit period, the excessive Fe²⁺stressincreased the content of Fe, Pb, Mg and Ti and decreased Al, Cu, Mn and Zn of ginseng in abovegroundportion, and increased the content of Fe, Cr, Pb, Mg and Ti and decreased Al, Cu, Mn and Zn of ginsengin underground portion. In ripe fruit period, the excessive Fe²⁺stress increased the content of Fe, Al, Cr,Pb, Mg and Ti and decreased Fe, Cu, Mn and Zn of ginseng in aboveground and underground portion.In wilting time, the excessive Fe²⁺stress promoted the absorption and accumulation of Cr and Cu andinhibited the absorption and transporter of Fe, Al, Pb, Mn, Zn, Mg and Ti of ginseng in abovegroundportion, and specially increased the content of Fe, Mg, Mn and Zn and decreased Fe, Al, Cr, Cu, Pb, Mg,Mn, Zn and Ti of ginseng in aboveground portion.5. The excessive Fe²⁺stress is caused by ginseng abnormal growth.The excessive Fe²⁺stress significantly damaged the growth of ginseng, and it mainly presented thatthe area that ginseng leaves lost green increased with Fe²⁺concentration increasing. The area of ginsengred coating root and decay is positively related to Fe²⁺concentration. The microstructure of ginseng rootshows that xylem vessels markedly tightened the number of vessels specially increased. Protoxylemdeveloped incompletely and catheter cavity considerably lessened. Ginseng root epidermis of theexcessive Fe²⁺stress destroyed more seriously and is more prone to shed than control ginseng root.The excessive Fe²⁺stress interference the normal growth of ginseng, the physiological responsemechanism can be clearly by integrateding antioxidant enzymes system, osmotic regulation system andmineral elements metabolism in the excessive Fe²⁺stress.