Phosphorus Metabolism Lab Report

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Phosphorus metabolism :
The endomycorrhizal symbiosis is beneficial for both fungi and plant. Fungi provide phosphorus to the plant while plant as a result give carbon to the fungi. But the phosphorus metabolism is the most important part of this association. Phosphorus is first absorbed by fungi from the soil and is stored in its cytoplasm while later fungi transport it to its vacuoles. Then these vacuolar components containing phosphoros are transported from outer mycelium of fungi to the plant. While in other words, the arbuscules of the endomycorrhizal fungi can be said as the respective site from where phosphorus is transferred to the apoplast and then to the plant. The detailed process of phosphorus metabolism and transport is discussed
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In case of fungi and soil solution the concentration difference usually never become more than the 10µM while in plant the concentration in cytosol lies around 10mM. While both the plants and fungi have developed the energy dependent system for the absorption of inorganic orthophosphate. Both high-affinity (low Km and Vmax) and low-affinity (high Km and Vmax) carrying systems have been recognized and include H+/Pi vital membrane proteins that are able to transfer compounds via plasma membrane, while required proton gradient is established by plasma membrane H+-ATPases (P-ATPases). The Km values of high-affinity systems in plants and fungi occur in series from 1 to 10 µM, while the values for the endomycorrhizae also fall in this range. While the the Km values are different in almost every endomycorrhizae i.e.: for germ tubes of Gigaspora margarita, the Km value of the high-affinity and low-affinity systems are 1.8-3.1 µM and 10.2-11.3 mM, respectively. However, a Km value of the high-affinity system of extraradical hyphae of AM fungi estimated from physiological-P uptake data in a soil culture system is about 0.17µM, a high-affinity Pi transporter expressed in the external mycelium of the AM fungus Glomus versiforme was much higher i.e. : 18 µM. The high value may be an indication of the yeast presence in the…show more content…
: Saccharomyces cerevisiae, or the filamentous fungus, Neurospora crassa. Both these mycobionts contain H+/Pi and Na+/Pi co-transport systems and the genes related to these co ordinations have also been identify recognized. In the case of yeast, both the H+/Pi and Na+/Pi delivery genes are managed in the PHO pathway which encourage gene transcription as a result to Pi shortage. The functioning task of these carrier’s can be deduced from their different pH optima: the H+/Pi system works optimally at neutral pH and the Na+/Pi system at alkaline pH, showing that these two mycobionts can absorb Pi in a well-organized resourceful way over an extensive pH range. While also many of the other AM fungi also contain a Na+/Pi and H+/Pi transportation system, making endomycorrhizae capable of absorbing phosphorus over different soil

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