All About Fungus Glomus Sp

Glomus is an important fungus found on nearly all terrestrial habitats, it belongs to the genus of arbuscular mycorrhizal fungi that form symbiotic associations between plant and soil. Glomus was previously classified based on its affinity to other fungi but now due to ribosomal subunit RNA sequences, it has its own group; there are close to 200 species currently identified in the group. Glomus is classified in the Kingdom Eumycota (walls are made of chitin and has no flagella), phylum Glomeromycota (symbiotic relationship with the plant roots), class Glomeromycetes (arbuscules in plant roots), order Glomerales (all biotrophic mutualists and produce large spores), family Glomeraceae (vesicle formation to create internal spores) and genus Glomus (Glomus Latin for ball; spores look like balls); different Glomus species are classified based on their distinguished spore structure (Alexopolous et al. 2004; Redecker and Raab. 2006).

Glomus specie symbiotic partner plays an important role in its life cycle, the host provides the fungus with all the nutrients needed but Glomus also needs the host to complete its life cycle without the host plant Glomus would not be able to reproduce. The fungus is not able to survive without its host so when Glomus is grown in vitro environment it's always grown with its host. With the help of the host plant, Glomus has been grown in vitro and scientist have done experiments to find the reproduction cycle of the fungus in vitro, this has allowed the discovery of only the asexual cycle of the fungi. There has been no sexual organs identified in Glomus specie so far which could mean that the fungi does not have a sexual life cycle, but since almost all the experiments are done in vitro no conclusion can be reached.

The fungi produces spores at its hypae tip which are produce within the host or outside the host. The spores are produce in large amount which helps increase the success rate for the fungus to regrow in a different location. The Fungi have a white, pale cream color when they are in their juvenile stage as they mature they turn to a yellowish brown color. When the metabolic and hydration requirement are met, DNA synthesis and nuclei replication begins, this starts the germination process of the fungus cycle; it gives rise to a thicked wall hypae or stunted hypae depending on the physiological status which is called the germination tube (Dalpe et al. 2005). During germination, synthesis of sterol, diaclyglycerol, phospholipids and free acid also occur; the energy for the process is obtained by consuming triacyl glycerides available inside the spore. If the environment is extremely dry, wet or acidic then these factor will inhibit the germination and no hypae will be produced (Dalpe and Monreal. 2004).The hypae continue to grow from the spore, they branch off at many ends to explore the media for plant roots. The branching off of the hypae helps them cover a larger area and form a hypae network, this network of hypae search for plant root but if the roots are not found than protoplasm shrinks from the hypae apex and hypae growth stops (Dalpe et al. 2005). The hypae that are successful in finding the host root, at contact orient themselves to form a swelled and organ known as the appressorium. The appressorium helps the hypae penetrate the cell wall at a single entry point by using ezyme and mechanical activities (Dalpe et al. 2005; Dalpe and Monreal. 2004).

Once inside the plant root, the fungus forms highly branched hypae around and inside cortical cells of plant roots called the arbuscules; they are really important for the symbiotic relation between Glomus specie and the host specie because it allows for the bidirectional nutrient exchange between the two organisms (Dalpe and Monreal. 2004). After the formation of arbuscules, the fungus forms special organs called the vessel in the roots of the plant which helps the fungus store nutrients that can be used later by the plant (Dalpe et al. 2005). The development of those organs established the symbiotic relationship which triggers vigorous development of hypae that branches all around the root and form a big hypae network in the soil while connecting to the roots of the plant (Dalpe et al. 2005). The hypae network cannot be function without the host root because it obtains all of it nutrients from there. Now the Glomus specie can form spores again which will repeat the life cycle of the fungi.

Glomus specie form symbiotic relationship with the plant which plays a really important role in the development of the plant and the fungi. The fungi get all of its nutrients needed for it survival from the plant while the plant benefit because the fungi helps it gather the nutrient more effectively and also provide many other benefits. Many scientist after examining the molecular evidence believe that Glomus species helped the plants colonized the land, without the help of the fungi plant would not have been to effectively gather resource on land and would not have survived (Heckman et al. 2001). The land is a totally different environment for the plants; the nutrients are not available in the water median, penetrating the soil for nutrient was really important. The fungi would have helped the plant in gather nutrient to support itself and grow into large bodies to gather better sunlight, therefore, adapting and colonizing land.

One of the main benefits that the fungi provide plant is by helping the plant increase its root density to absorb more nutrients. Nutrients are very important for a plant, it gather most of it nutrients from the soil that help the plant to develop, nourish and grow. The fungus plays a really important part in collecting nutrient for the plant because the hypae spreads much faster than the roots; it can increase the absorptive area of roots 10 to 1000 times. Using the bigger root density the plant can form bigger root and hypae network that can help absorb water and nutrient located at further distance; it helps plant outcompete its' competitors and be more healthy. Also, the plant also does not need to allocate a lot of energy to the root; it is more beneficial to the plant to give some energy to the fungi compare to using higher amount of energy to grow bigger roots.

Dell'Amico et al, did an experiment on tomato to test the influence of drought on plant; in the experiment a comparison was done between plant with Glomus specie and plant without the fungi. The plants were not provided with water for 72 hours and then provided with water for 120 hours, and the plant growth was measured afterwards. The plants that had Glomus fungus were able to survive drought much better than the plants without the fungi; the plant was able to use the fungi hypae to penetrate to places far and had a lot higher root density than the plant without Glomus fungi. The high density of the root helped the plant collect more water and nutrient allowing it to stay healthy in drought conditions while the other plant was not able to survive without water for long and suffered great effect of the drought (Dell'Amico et al. 2002). The result obtained from the experiment showed that the plant that formed a symbiotic relationship with the fungi was able to survive a lot better in drought conditions.

In another experiment done by Fidelibus et al, to test the effect of Glomus specie on its host plant was conducted by removing species from arid, semi-arid and mesic areas. Similar species were divided into two groups, one was treated with Glomus fungi and other were not; the experiment evaluated the effects on plant growth and water use under well water conditions, dry condition and moisture condition. The results obtained from the experiment showed that the plants that had Glomus fungi did better than the other plant under all condition, the biggest different in result were seem under drought conditions. Plant with Glomus fungi was had much longer and dense root, this allowed them to collect more nutrients from the soil and easily outcompete the plants without the fungi. With better water and nutrient the plant in this experiment stayed healthy as well regardless of the geographical range.

So from the both the experiment, we can see that Glomus plays a really important part in root density of the plant. The fungus helps the plant stay healthier and out competing other plants by covering a greater area and collecting more nutrients and water. Glomus fungi also help increase mobilization of nutrients for the plant; it helps the plant take up poorly mobile nutrient faster and help it grow better. There are many compounds in the soils that are hard to capture for the root but fungi can increase the nutrient mobilization by releasing chemicals to dissolve the nutrients.

The ability of the fungi to mobilize nutrient is very beneficial to the plant, not only it can cover more area to look for nutrient but absorb them faster to help it grow faster (Mathur and Vyas. 2000). Compounds like phosphate, copper, zinc and other amino acid can be hard to absorb for the plant; most of the time the compounds exist in solid state in the soil surface, some are also not easily soluble in water, these properties slow down the absorption rate for the root of the nutrients so the plant cannot grow as fast. The Glomus fungi releases enzymes in the environment, interacting with the nutrients on the molecular level helping them break off; the chemicals also dissolve the nutrient which helps with the absorptions rate (Mathur and Vyas. 2000).

In an experiment done by Khalil et al, to test the effect of Glomus specie on nutrient uptake was tested. Six Corn plants were used in the experiment, where half were provide with Glomus and other were not; the plants were evaluated for growth response and nutrient uptake (N, P, K, Ca, Mg, and Zn). The experiment was done in a green house and the result showed that the there was a 49 to 68% increase in nutrient uptake for corn that had form symbiotic relationship with the fungi from the Glomus genus (Khalil et al. 1994). So, it is very beneficial for plant to form symbiotic relation with the Glomus fungi since it can have a big difference in the nutrition mobilization rate for the plant.

Another benefit that the fungi provide to the plant is protection; the fungus protects the plant from various things that could be harmful to it. The type of protection the fungus provides to the plant could be divided into two categories; protection against pathogens and protection again parasites. Glomus fungus can be very useful in protecting plants from harmful pathogens that could infect the plant and cause damage to it; the fungus uses various methods to protect the plant from pathogens. Some of the fungus that has formed a symbiotic relationship with the plant protects the plant roots from being eaten by nematodes. Fungus also protect the plant other pathogens by producing anti-biotic substances that inhibit pathogen growth by killing most of the soil borne pathogen and protecting plant from soilborne plant diseases, namely Fusarium, Phytophthora, Pythium, Rhizoctonia, Thielaviopsis basicola, Macrophomina and Verticillium (Caron. 1989). The fungus also protects the plant from parasites by acting as a bio-control agent that consumes the nematode; the nematode eating fungi gain nitrogen while the plant benefit because the plant roots are protected from the fungi (Gianinazzi and Schüepp. 1994). The plant also benefit because the fungus can form natural defense walls around the roots of the plant so physically protect parasites from entering inside the plant (Fitter. 1991). The plant also chemically protected by the fungi because it produces compounds like chitinases and phytoalexins; chitinases can break glycosidic bonds in chitin causing many small pathogens to die, while phytoalexins compounds also defend the plant by acting as plant defense chemicals and having negative effect on the parasites.

In an experiment conducted by Abdel-Fattah and Shabana. (2002), the efficiency of protection provided by Glomus specie to the plant was tested. The Glomus specie was introduced to half of the cowpea plants in the study while the other half did not have any fungi; after sometimes both the plants were compared. The cowpea plants with the Glomus fungus had considerably less damaged caused by soil borne pathogen and parasites; the plants with the fungus were healthier than the other plants, they had grown more and had higher water content and dry weight in shoot and root. The result show that Glomus specie is really effective against protecting plants from different pathogens and parasite, the fungus protect the plant by producing chemicals and other mechanism, being very beneficial to the plant.

Glomus species have been recognized extensively for their role in helping the plant protect itself, gather nutrient faster and over a wider area, with the help of Glomus fungi plant can survive drought a lot better. During drought condition, Glomus fungi can help plant protect itself, locate water and nutrient that might be inaccessible to plants without the fungi. The plant needs to invest less energy in growing roots and protecting itself, this help the plant require less energy to grow in a drought environment and be more successful. The Glomus species can also help the plant survive better by reducing stress for the plant; when the plant is stressed it starts to abort its natural way of functioning and functions differently to cope with the stress, this has great physiological effects on the plant and will reduce its growth and affect the health. The fungus can help the plant reduce the stressful effect and perform normally under stress conditions; the fungus does that by using different ways. The fungus will reduce the starch and soluble sugar in roots so it can be used to carry out the normal functions by the plant, also it will increase protective fungus-specific sugar alcohol to protect the plant when it's under stress. These two ways can be very beneficial for the plant, they help the plant stay healthy and green and prevent it from shedding its leaves in many occasion, this way the plant can continue to function normally under stress. Also the fungus protect the plant when it might have low energy to allocate to its defense, many plants can get infected by pathogens or inflict lots of damage by parasites when the plant is stressed but the fungus provides higher protected to the plant from all the parasites and pathogens to help it cope better with stress and survive through a stressful period (Pugnaire and Valladares. 2007).

Glomus species have been proven by many experiments to play an important part in the symbiotic relationship between the fungus and plant; the relationship between the two organisms has many benefits to both. Glomus species are a natural remedy for helping crop plants grow better, nourish and be protected against disease and drought. After knowing the significance of the Glomus specie many companies are commercially selling Glomus for crops to help the farmers cut down the cost and try a natural way to grow their crops better. Glomus species are found in nature, but they are not found in gardens and other cultivated crops because of the over use of tending the soil, fertilizers and pesticide. Also, Many times there is not enough organic matter, optimal pH and fungus that require nematode can't satisfy their need for nitrogen because there are no nematodes in the soil; all these factor relate to the disappearances of Glomus fungi from our soils. Now due to the beneficial nature of the fungus to the plant, companies are trying to commercially sell the Glomus fungus so people can reintroduce the fungus back in their soil. Using a natural remedy to benefit the plant, companies are offering solutions to farmers and people to stop the use of pesticide, fertilizers and other chemicals that can cause harmful effect to the ecosystem with the water runoff.

The companies might have huge financial gain in selling Glomus fungi, but the symbiotic relationship between a fungus and plant is evident. Our agriculture practices have driven us away from natural ways which in turn have cause an arm race between pathogens, parasites and human development. New stronger chemical compounds are used to kill pest and pathogens to save our agriculture and get high yield but it's an ongoing battle with no end, the stronger substance we use, the stronger resistance is produced. So to end this battle natural remedies are the best way, and Glomus fungus are the perfect solution for the ongoing problems. They play the role of fertilizers, pesticide and other chemicals used to help grow the crops better, Glomus fungi species can help increase root density, uptake of nutrients, protect the plant from parasites and pathogens, also, save the plant from stress during drought; due to these characters Glomus fungus hold a great relevance to mankind and the ecosystem.

References:

Abdel-Fattah, G. M., and Shabana, Y.M. 2002. Efficacy of the arbuscular mycorrhizal fungus Glomus clarum in protection of cowpea plants against root rot pathogen Rhizoctonia solani. Z Pflanzenk Pflanzen. 109: 207-215.

Caron, M. Potential use of Mycorrhizae in control of soil-borne diseases. Can. J. Plant Path. 11: 177-179.

Dalpe, Y., and Monreal, M. 2004. The contribution of arbuscular mycorrhizal fungi in sustainable maintenance of plant health and soil fertility. Biol. Fert. Soils. 37: 1-16.

Dell'AMico, J., Torrecillas, A., Rodriguez, P., Morte, A., and Sanchez-Blanco, M. J. 2002. Responses of tomato plants associated with the arbuscular mycorrhizal fungus Glomus clarumduring drought and recovery. J. Agr. Sci. 138(4):387-393.

Elsen, A., Gervacio, D., Swennen, R., and Waele, D.D. 2008. AMF-induced biocontrol against plant parasitic nematodes in Musa sp.: a systemic effect. Mycorrhiza. 18: 251-256.

Fidelibus, M.W., Martin, C.A., and Stutz, J.C. 2001. Geographic isolates of Glomus increase root growth and whole-plant transpiration of Citrus seedlings grown with high phosphorus. Mycorrhiza. 10: 231-236.

Fitter, A. H. 1991. Costs and benefits of mycorrhizas: Implications for functioning under natural conditions. Expientia. 47.

Gianinazzi,S., and Schuepp,H. 1993. Impact of arbuscular Mycorrhizas on sustainable agriculture and natural Ecosystem. European Network Cost action., London. pp. 73-80.

Khalil, S., Loynachan, T.E., and Tabatabai, M. A. 1994. Mycorrhizal Dependency and Nutrient Uptake by Improved and Unimproved Corn and Soybean Cultivars. Agron. J. 86: 949-958.

Mathur, N., and Vyas, A. 2000. Influence of arbuscular mycorrhizae on biomass production, nutrient uptake and physiological changes in Ziziphus mauritiana Lam. under water stress. J. Arid. Environ. 45: 191-195.

Pugnaire, F.I., and Valladares, F. 2007. Functional Plant Ecology. Vol. 2. CRC Press., London. pp. 151-175.

Redecker, D., and Raab, P. 2006. Phylogeny of the Glomeromycota (arbuscular mycorrhizal fungi): recent developments and new gene markers. Mycologia. 98(6): 885-895.