The function of the crystals may be variable depending on the amount, size, shape and position in the plant. Lemna crystal idioblasts function as calcium-inducible, specialized high-capacity but saturable sinks for bulk regulation of calcium, and crystal deposition is a highly controlled process requiring intravacuolar membrane systems and calcium-binding organic matrix materials.Ĭrystals of calcium oxalate (CaOx) are widely distributed throughout the families of higher plants ( Arnott & Pautard, 1970 Gallaher, 1975 Franceschi & Horner, 1980 Arnott, 1982 Horner & Wagner, 1995 Webb, 1999 Nakata, 2003), but their functions and the processes involved in formation of these remarkable crystals are still not well understood. A calcium-binding matrix protein was associated with idioblast vacuoles and crystal formation. The chambers, but not parallel membranes, had calcium associated with them. The CaOx crystals are formed in membranous ‘chambers’ and connected in rows by parallel membrane sheets, both forming de novo in the vacuole. Size and number of idioblasts had a distinct upper limit. Specialized crystal-forming cells (crystal idioblasts) increased in number and size CaOx, but not soluble oxalate, increased in response to increasing calcium in the growth medium. The function of calcium oxalate (CaOx) raphide crystal formation, and structural features related to regulation of crystal formation, were studied in Lemna minor fronds using physiological and microscopy techniques.
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