Biology:Druse (botany)

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Druses in onion scales (100x magnification)

A druse is a group of crystals of calcium oxalate,[1] silicates, or carbonates present in plants, and are thought to be a defense against herbivory due to their toxicity. Calcium oxalate (Ca(COO)2, CaOx) crystals are found in algae, angiosperms and gymnosperms in a total of more than 215 families. These plants accumulate oxalate in the range of 3–80% (w/w) of their dry weight[2][3] through a biomineralization process in a variety of shapes.[4] Araceae have numerous druses, multi-crystal druses and needle-shaped raphide crystals of CaOx present in the tissue.[5] Druses are also found in leaves and bud scales of Prunus, Rosa,[6] Allium, Vitis, Morus and Phaseolus.[7][8]

Formation

A number of biochemical pathways for calcium oxalate biomineralization in plants have been proposed. Among these are the cleavage of isocitrate, the hydrolysis of oxaloacetate, glycolate/glyoxylate oxidation, and/or oxidative cleavage of L-ascorbic acid.[9] The cleavage of ascorbic acid appears to be the most studied pathway.[10][11][12][13] The specific mechanism controlling this process is unclear but it has been suggested that a number of factors influence crystal shape and growth, such as proteins, polysaccharides, and lipids or macromolecular membrane structures.[14][15][16] Druses may also have some purpose in calcium regulation.

See also

References

  1. ↑ "Calcium oxalate in plants: formation and function". Annu Rev Plant Biol 56: 41–71. 2005. doi:10.1146/annurev.arplant.56.032604.144106. PMID 15862089. 
  2. ↑ Zindler-Frank E. (1976). "Oxalate biosynthesis in relation to photosynthetic pathways and plant productivity: a survey". Z. Pflanzenphysiol. 80 (1): 1–13. doi:10.1016/S0044-328X(76)80044-X. 
  3. ↑ "Oxalate in crop plants". J Agric Food Chem 35 (6): 926–938. 1987. doi:10.1021/jf00078a019. 
  4. ↑ McNair JB (1932). "The interrelation between substances in plants: essential oils and resins, cyanogen and oxalate". Am J Bot 19 (3): 255–271. doi:10.2307/2436337. 
  5. ↑ "Cellular ultrastructure and crystal development in Amorphophallus (Araceae)". Ann. Bot. 101 (7): 983–995. 2008. doi:10.1093/aob/mcn022. PMID 18285357. 
  6. ↑ "Crystal macropattern development in Prunus serotina (Rosaceae, Prunoideae) leaves". Ann. Bot. 97 (5): 723–729. 2006. doi:10.1093/aob/mcl036. PMID 16513655. 
  7. ↑ "Crystallochemical characterization of calcium oxalate crystals isolated from seed coats of Phaseolus vulgaris and leaves of Vitis vinifera". J Plant Physiol 160 (3): 239–245. 2003. doi:10.1078/0176-1617-00947. PMID 12749080. 
  8. ↑ "Cell wall sheath surrounding calcium oxalate crystals in mulberry idioblasts". Protoplasma 231 (3–4): 245–248. 2007. doi:10.1007/s00709-007-0263-x. PMID 17922267. 
  9. ↑ Hodgkinson A (1977). "Oxalic acid metabolism in higher plants". in A Hodgkinson. Oxalic Acid Biology and Medicine. 101. New York: Academic Press. 131–158. doi:10.1016/0014-5793(79)81066-2. ISBN 9780123517500. 
  10. ↑ "Metabolic conversion of L-ascorbic acid in oxalate-accumulating plants". Plant Physiol 56 (2): 283–285. 1975. doi:10.1104/pp.56.2.283. PMID 16659288. 
  11. ↑ "Further studies on oxalic acid biosynthesis in oxalate-accumulating plants". Plant Physiol 61 (4): 590–592. 1978. doi:10.1104/pp.61.4.590. PMID 16660342. 
  12. ↑ "Distribution of peroxisomes and glycolate metabolism in relation to calcium oxalate formation in Lemna minor L.". Eur J Cell Biol 51 (1): 9–16. 1990. PMID 2184039. 
  13. ↑ "L-Ascorbic acid and L-galactose are sources of oxalic acid and calcium oxalate in Pistia stratiotes". Phytochemistry 53 (4): 433–440. 2000. doi:10.1016/S0031-9422(99)00448-3. PMID 10731019. Bibcode: 2000PChem..53..433K. 
  14. ↑ "The association of druse crystals with the developing stomium of Capsicum annuum (Solanaceae) anthers". Am J Bot 67 (9): 1347–1360. 1980. doi:10.2307/2442137. 
  15. ↑ "Twin crystals of calcium oxalate in the seed coat of the kidney bean". Protoplasma 114 (1): 23–34. 1983. doi:10.1007/BF01279865. 
  16. ↑ Webb MA (1999). "Cell-mediated crystallization of calcium oxalate in plants". Plant Cell 11 (4): 751–761. doi:10.1105/tpc.11.4.751. PMID 10213791. 



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