Effects And Mechanisms Of Arbuscular Mycorrhizal Fungi On The Uptake Of Pahs By Plants

Polycyclic aromatic hydrocarbons (PAHs) polluted soil revised by arbuscular mycorrhizal (AM) fungi has become a research focus in the filed of agricultural environmente science. There will be a different influence on absorbing PAHs by plants, by reason of AM fungi being in soil, and this causes the researchers’attention. Full understanding of effects and mechanisms of AM fungi on how plants uptake and accumulate PAHs have considerable benefits for risk assessment of crop contamination and subsequent human exposure and the development phytoremediation. In this dissertation, the effect and mechanism of Glomus intraradices (G.i) as representative of AM fungi on PAHs uptake by alfalfa, maize and rice were investigated under different cultivation. Effect of AM fungi on plant biomass and root activity was discussed. How PAHs affected growth of AM fungi was studied. Besides, influence of AM fungi on how plants uptake and accumulate PAHs was also investigated. The main results obtained are shown as follows:(1) The influence of treatment G.i inoculation on uptake and translocation by plants was investigated. Results showed that treatment G.i inoculation had a significant influence on PAHs concentration, for instance, treatment G.i inoculation significantly enhanced phenanthrene and pyrene concentration in alfalfa, and there existed more phenanthrene in shoot of Maize inoculated by G.i and the variance reached a significant level (P<0.05) with time; treatment G.i inoculation had a influence on PAHs translocation in plants. Compared with the control treatment without G.i inoculation, the ratio of pyrene translocated from mycorrhiza-colonized root to shoot decreased by13.85%to37.47%, while, the plant translocation factors of G.i-inoculated maize affected by the concentration of phenanthrene, at lower concentration of phenanthrene, the G.i inoculation could improve the transloation of phenanthrene from root to shoot, and at higher concentration, the G.i inoculation had an inhibitory action on the translocation with the extension of the processing time. The plant translocation factors showed a tendency to decrease by added more phenanthrene, which was significantly negatively correlated with Per milliliter of spore quantity (r=-0.890, P<0.01).(2) The effect of PAHs on the activity of AM fungi was also investigated. Alfalfa, maize and rice all had a great mycorrhizal dependence on Gi, their roots were clealy colonized by G.i with pollutant, especially mycorrhizal colonization rate of rice reached to90%. The G.i dynaminc inoculation of maize root under time processing was investigated. It showed that growth trend of G.i spores assumed as S-shaped growth curve. Besides, phenanthrene could motivated the activity of G.i spores and shorten their growth circle. The biomass of Gi root external hyphae and spores were determinated to explore the Gi fungi’s activity under different concentration of phenanthrene polluted. Mycorrhiza-colonized root could produce large quantities of AM hyphae and spores to water environment, growth activity of which were motivated by phenanthrene under a certain degree. Density of fungi was the most at phenanthrene3.6mg/kg. Per milliliter of spore quantity increased with concentration of phenanthrene. However, as growth periodicity of AM fungi was unclear, the concentration of phenanthrene mostly beneficent for growth of fungi and spores were difficult to get.(3) The relationship between AM hyphae or spores and the ability of plant absorbing phenanthrene was explored. It was showed that adsorbed phenanthrene positively correlated with density of Gi hyphae, and hyphae played a critical role in phenanthrene adsorped by mycorrhiza-colonized roots. Hyphae in root became a new transmission channel from rhizoplane to interior root. Spores quantity per milliliter had a positive relation with absorbed phenanthrene, which indicated G.i spores played an important role in phenanthrene absorption by mycorrhiza-colonized roots. G.i spores strongly constraint phenanthrene leading to less absorbed phenanthrene translocation to shoots.