Studies On The Effect Of Excess Iron In The Pea Seedings

Iron toxicity is a widespread nutrient disorder caused by excess iron accumulation, especially in tropical and subtropical regions because of the lower redox potential in the acid soil. Iron toxicity can seriously suppress the growth of plants and affect the production. Exploring the tolerance mechanism of the plants to iron toxicity can not only provide us some guidance in theory and practice to the plants growth in iron toxicity-prone areas, but also be the key to improving plants production to a large extent. In this study, the method of manual simulation soil Fe2+ stress was used to study the toxic action caused by excess iron to the pea seedlings. The major findings are as follows:1. The excessive iron caused the unnormal growth of pea seedlings.The excessive Fe2+ suppressed the normal growth of pea seedling obviously. First, the old leaves displayed some white and chlorosis spot while the growth of main roots was supressed, which was mainly manifested in the drop of total length, cross-sectional area and surface area of pea roots. The last, the fresh and dry weight of roots, stems, leaves dropped remarkably.2. The excessive iron obviously caused oxidative damage to biologicamacro-molecule in pea seedling.With the increase of iron concentration, the content of DNA and the protein dropped gradually while the MDA increased. More serious damage were observed in roots rather than in leaves.3. The excessive iron decreased the leaf's photosynthesis capacity obviously.The excessive Fe2+ decreased the net photosynthetic rate (Pn),transpiration rate (Tr),stomatal conductance (Gs),intercellular CO2 concentration (Ci),water use efficiency (WUE) and carboxylation efficiency (CE) gradually. At the same time,the PSâ…¡potential photochemical efficiency (Fv/Fo),the Pâ…¡maximal photochemical efficiency (Fv/Fm),photosynthetic electron transport rate (ETR),maximum quantumyield (Yield),photochemical quenching coefficient (qP) dropped gradually while the initial fluorescence (Fo), the non-photochemical quenching coefficient (qN) rase. These results suggested that the iron stress not only caused stomatal inhibition but also destoryed the photosynthetic structure directly.4. The excessive iron induced the changees in the components of leaf chloroplast membrane and enhanced the membrane fluidity.Iron stress did not change the fatty acid composition of membrane but do influence the proportion obviously. In addtion, it also enhanced the membrane fluidity.5. The excessive iron caused the mineral nutrient out of balance in pea seedlings.Under the condition of excess iron stress, the content of N and P declined significantly in all parts of plants while the content of K increased gradually. Compared with controls, the content of Mn and Cu declined progressively in all parts, and the content of Zn declined significantly in aerial parts while increased in roots.6. The excessive iron induced more accumulation of osmotic materials in pea seedlingThe content of soluble organic osmoticum (soluble sugar, proline and betaine) increased under iron stress condition. Maybe the increase in osmotic materials was a protection mechanism against iron stress.