Root mucilage

Root mucilage is made of plant specific polysaccharides or long chains of sugar molecules.[1][2] This polysaccharide secretion of root exudate forms a gelatinous substance that sticks to the caps of roots.[3] Root mucilage is known to play a role in forming relationships with soil dwelling life forms.[1][4] Just how this root mucilage is secreted is debated but there is growing evidence that mucilage derives from ruptured cells. As roots penetrate through the soil, many of the cells surrounding the caps of roots are continually shed, and replaced.[5] These ruptured or lysed cells release their component parts, which includes the polysaccharides that form root mucilage. These polysaccharides that come from the Golgi apparatus and plant cell wall, which are rich in plant specific polysaccharides.[6] Unlike animal cells, plant cells have a cell wall that acts as a barrier surrounding the cell providing strength, which supports plants just like a skeleton. This cell wall is used to produce every day products such as: timber, paper and natural fabrics including cotton.[7] Root mucilage is apart of a wider secrete from plant roots known as root exudate. Plant roots secrete a variety of organic molecules into the surrounding soil such as: proteins, enzymes, DNA, sugars and amino acids, which are the building blocks of life.[3][4] This collective secretion is known as root exudate. This root exudate prevents root infection from bacteria and fungi, helps the roots to penetrate through the soil, and can creates a micro-climate that is beneficial to the plant

Root mucilage composition

To determine the sugars within root mucilage, monosaccharide analysis and monosaccharide linkage analysis is undertaken. Monosaccharide linkage analysis involves methylating the root mucilage, which will contain polysaccharides. The root mucilage is hydrolysed using acid to break down the polysaccharides into their monosaccharide components.[8] The subsistent monosaccharides are then reduced to open their rings. The open ring monosaccharides are then acetylated, and separated by typically using gas chromatography, although liquid chromatography is used. The masses of the monosaccharides are then detected using mass spectrometry.[9] The gas chromatography retention times and the mass spectrometry chromatogram are used to identify how the monosaccharides are linked to form polysaccharides that make root mucilage. For monosaccharide analysis which reveals the sugars that make root mucilage, scientists hydrolyse the root mucilage using acid, and put the samples directly through gas chromatography linked to mass spectrometry.[8][9]

Several scientists have determined the composition of plant root mucilage using monosaccharide analysis and linkage analysis showing that Maize (Zea mays) root mucilage contained high levels of galactose, xylose, arabinose, rhamnose, glucose, and lower levels of uronic acid, mannose, fucose and glucuronic acid.[10] Wheat (Triticum aestivum) root mucilage also contained high levels of xylose, arabinose, galactose, glucose, and lower levels of rhamnose, glucuronic acid and mannose.[11] Cowpea (Vigna unguiculata) also contained high levels of arabinose, galactose, glucose, fucose, xylose, and lower levels of rhamnose, mannose and glucuronic acid.[11] Many other plants have had their root mucilage composition determined using monosaccharide analysis and monosaccharide linkage analysis. With the following monosaccharides determined as well as their linkages, scientists have determined the presence of pectin, arabinogalactan proteins, xyloglucan, arabinan, and xylan which are plant specific polysaccharides within the root mucilage of plants.

Importance and role of root mucilage

Plants secrete up to 60% of their energy as root mucilage, which they generate from photosynthesis that takes place in the leaves.[4] Root mucilage plays a role in developing a symbiotic relationship with the soil dwelling fungi. This relationship is known to affect 94% of land plants.[11] This important relationship benefits plants by increasing water and nutrient up take from the soil, particularly phosphorus. In return, the fungi receives food in the form of carbohydrate from the plant in the form of broken down root mucilage. Without this relationship many plants would struggle to gain sufficient water or nutrients.[12]

In many forests, mycorrhizae fungi forms relationships with most of the plants, and even form connections with other mycorrhizae fungi.[13] This interconnection links small plants to shrubs and to trees. This network of plant roots and fungi forms a web of hyphae or root-like branching filaments. This network is referred to as the Wood Wide Web.[13] This network of fungi hyphae can shuttle water and nutrients from one part of the forest to another as of when they are needed. As well as shuttling resources that the plants require, this network can shuttle carbohydrate throughout the network so that the network is not disrupted by a lack of carbohydrate input.[14] Root mucilage also helps soil to stick to roots.[15] The purpose of this sticking is to maintain the plant's contact with the soil so that the plant can regulate the levels of water it can absorb, decrease friction so that roots can penetrate through the soil, and to maintain a micro-climate.[16]

See also

External links

References

  1. 1 2 Walker, Travis S.; Bais, Harsh Pal; Grotewold, Erich; Vivanco, Jorge M. (2003-05-01). "Root Exudation and Rhizosphere Biology". Plant Physiology 132 (1): 44–51. doi:10.1104/pp.102.019661. ISSN 1532-2548. PMC 1540314. PMID 12746510.
  2. ↑ Baetz, Ulrike; Martinoia, Enrico (2014-02-01). "Root exudates: the hidden part of plant defense". Trends in Plant Science 19 (2): 90–98. doi:10.1016/j.tplants.2013.11.006.
  3. 1 2 Jackson, Mike (2003-06-01). "Ridge, I. (ed) Plants". Annals of Botany 91 (7): 940–941. doi:10.1093/aob/mcg100. ISSN 0305-7364. PMC 4242402.
  4. 1 2 3 "The Rhizosphere - Roots, Soil and Everything In Between | Learn Science at Scitable". www.nature.com. Retrieved 2015-09-01.
  5. ↑ McCully, Margaret E. (1999-01-01). "ROOTS IN SOIL: Unearthing the Complexities of Roots and Their Rhizospheres". Annual Review of Plant Physiology and Plant Molecular Biology 50 (1): 695–718. doi:10.1146/annurev.arplant.50.1.695. PMID 15012224.
  6. ↑ Read, D. B.; Gregory, P. J. (1997-12-01). "Surface tension and viscosity of axenic maize and lupin root mucilages". New Phytologist 137 (4): 623–628. doi:10.1046/j.1469-8137.1997.00859.x. ISSN 1469-8137.
  7. ↑ Albersheim, Peter; Darvill, Alan; Roberts, Keith; Sederoff, Ron; Staehelin, Andrew (2010-04-23). Plant Cell Walls. Garland Science. ISBN 9781136843587.
  8. 1 2 Pettolino, Filomena A.; Walsh, Cherie; Fincher, Geoffrey B.; Bacic, Antony (2012-09-01). "Determining the polysaccharide composition of plant cell walls". Nature Protocols 7 (9): 1590–1607. doi:10.1038/nprot.2012.081. ISSN 1754-2189.
  9. 1 2 Lindberg, Bengt (1972-01-01). Enzymology, BT - Methods in, ed. [12] Methylation analysis of polysaccharides. Complex Carbohydrates Part B 28. Academic Press. pp. 178–195.
  10. ↑ Bacic, Antony; Moody, Susan F.; Clarke, Adrienne E. (1986-03-01). "Structural Analysis of Secreted Root Slime from Maize (Zea mays L.)". Plant Physiology 80 (3): 771–777. doi:10.1104/pp.80.3.771. ISSN 1532-2548. PMID 16664700.
  11. 1 2 3 Moody, Susan F.; Clarke, Adrienne E.; Bacic, Antony (1988-01-01). "Structural analysis of secreted slime from wheat and cowpea roots". Phytochemistry 27 (9): 2857–2861. doi:10.1016/0031-9422(88)80676-9.
  12. ↑ Gianinazzi-Pearson, V (1996-10-01). "Plant Cell Responses to Arbuscular Mycorrhizal Fungi: Getting to the Roots of the Symbiosis.". The Plant Cell 8 (10): 1871–1883. doi:10.1105/tpc.8.10.1871. ISSN 1040-4651. JSTOR 3870236. PMC 161321. PMID 12239368.
  13. 1 2 Helgason, T.; Daniell, T. J.; Husband, R.; Fitter, A. H.; Young, J. P. W. (1998-07-30). "Ploughing up the wood-wide web?". Nature 394 (6692): 431–431. doi:10.1038/28764. ISSN 0028-0836.
  14. ↑ Beiler, Kevin J.; Durall, Daniel M.; Simard, Suzanne W.; Maxwell, Sheri A.; Kretzer, Annette M. (2010-01-01). "Architecture of the wood-wide web: Rhizopogon spp. genets link multiple Douglas-fir cohorts". New Phytologist 185 (2): 543–553. doi:10.1111/j.1469-8137.2009.03069.x. ISSN 1469-8137.
  15. ↑ Jones, D. L.; Nguyen, C.; Finlay, R. D. (2009-02-25). "Carbon flow in the rhizosphere: carbon trading at the soil–root interface". Plant and Soil 321 (1-2): 5–33. doi:10.1007/s11104-009-9925-0. ISSN 0032-079X.
  16. ↑ Morel, Jean Louis; Habib, Leila; Plantureux, Sylvain; Guckert, Armand (1991-09-01). "Influence of maize root mucilage on soil aggregate stability". Plant and Soil 136 (1): 111–119. doi:10.1007/BF02465226. ISSN 0032-079X.
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