Druse (botany)

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 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]

Druses in onion scales (100x magnification)

For other uses, see Druse.

Formation

A number of biochemical pathways for calcium oxalate biomineralization in plants have been proposed. Among these is 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. Still, it has been suggested that a number of factors influence crystal shapes 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

• Idioblast
• Raphide
• Phytolith
• Plant defense against herbivory

References

1. Franceschi VR, Nakata PA (2005). "Calcium oxalate in plants: formation and function". Annu Rev Plant Biol. 56: 41–71. 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. Libert B, Franceschi VR (1987). "Oxalate in crop plants". J Agric Food Chem. 35 (6): 926–938. 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. JSTOR 2436337.
5. Prychid CJ, Jabaily RS, Rudall PJ (2008). "Cellular ultrastructure and crystal development in Amorphophallus (Araceae)". Ann. Bot. 101 (7): 983–995. doi:10.1093/aob/mcn022. PMC 2710233. PMID 18285357.
6. Lersten NR, Horner HT (2006). "Crystal macropattern development in Prunus serotina (Rosaceae, Prunoideae) leaves". Ann. Bot. 97 (5): 723–729. doi:10.1093/aob/mcl036. PMC 2803424. PMID 16513655.
7. Jáuregui-Zúñiga D, Reyes-Grajeda JP, Sepúlveda-Sánchez JD, Whitaker JR, Moreno A (2003). "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. Bibcode:2003JPPhy.160..239J. doi:10.1078/0176-1617-00947. PMID 12749080.
8. Katayama H, Fujibayashi Y, Nagaoka S, Sugimura Y (2007). "Cell wall sheath surrounding calcium oxalate crystals in mulberry idioblasts". Protoplasma. 231 (3–4): 245–248. doi:10.1007/s00709-007-0263-x. PMID 17922267. S2CID 29944485.
9. Hodgkinson A (1977). "Oxalic acid metabolism in higher plants". In A Hodgkinson (ed.). Oxalic Acid Biology and Medicine. Vol. 101. New York: Academic Press. pp. 131–158. doi:10.1016/0014-5793(79)81066-2. ISBN 9780123517500. {{cite book}}: |journal= ignored (help)
10. Yang J, Loewus FA (1975). "Metabolic conversion of L-ascorbic acid in oxalate-accumulating plants". Plant Physiol. 56 (2): 283–285. doi:10.1104/pp.56.2.283. PMC 541805. PMID 16659288.
11. Nuss RF, Loewus FA (1978). "Further studies on oxalic acid biosynthesis in oxalate-accumulating plants". Plant Physiol. 61 (4): 590–592. doi:10.1104/pp.61.4.590. PMC 1091923. PMID 16660342.
12. Li XX, Franceschi VR (1990). "Distribution of peroxisomes and glycolate metabolism in relation to calcium oxalate formation in Lemna minor L.". Eur J Cell Biol. 51 (1): 9–16. PMID 2184039.
13. Keates SA, Tarlyn N, Loewus FA, Franceschi VR (2000). "L-Ascorbic acid and L-galactose are sources of oxalic acid and calcium oxalate in Pistia stratiotes". Phytochemistry. 53 (4): 433–440. Bibcode:2000PChem..53..433K. doi:10.1016/S0031-9422(99)00448-3. PMID 10731019.
14. Horner HT, Wagner BL (1980). "The association of druse crystals with the developing stomium of Capsicum annuum (Solanaceae) anthers". Am J Bot. 67 (9): 1347–1360. doi:10.2307/2442137. JSTOR 2442137.
15. Arnott HJ, Webb MA (1983). "Twin crystals of calcium oxalate in the seed coat of the kidney bean". Protoplasma. 114 (1): 23–34. doi:10.1007/BF01279865. S2CID 180834.
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. PMC 144206. PMID 10213791.