Inducible calcium sinks and preferential calcium allocation in leaf primordia of Dracaena sanderiana Hort. Sander ex M.T. Mast. (Dracaenaceae)
2001
Pennisi, S.V. | McConnell, D.B.
The effect of 0, 3, and 7 mM Ca(2+) on the allocation and deposition of Ca(2+) into intracellular and sub-cuticular periplasmic calcium oxalate (CO) crystals was examined in leaf primordia of rooted cuttings of Dracaena sanderiana Hort. Sander ex M.T. Mast. Crystal development was monitored in two types of cuttings, those rooted in deionized water for 18 months and those rooted in Metro Mix 500 for 6 weeks. Response differed remarkably depending on the type of cutting. Cuttings rooted in deionized water deposited sub-cuticular crystals at the expense of intracellular crystals (raphides). The number of sub-cuticular crystals in leaf primordia of cuttings rooted in deionized water grown in solutions supplemented with either 0, 3, or 7 mM Ca(2+) was similar, but crystals were considerably smaller in plants grown in 0 mM Ca(2+). Sub-cuticular crystals appeared developmentally earlier in leaf primordia of all cuttings grown in either 3 mM or 7 mM Ca(2+) than in cuttings rooted in deionized water grown in 0 mM Ca(2+). This finding supports the premise that deposition of sub-cuticular crystals is modulated by Ca(2+) levels and could be induced at an earlier ontogenetical stage by raising rhizospheric Ca(2+) levels or delayed by lowering rhizospheric Ca(2+) levels. The total number of sub-cuticular crystals per epidermal cell did not differ significantly between treatments implying that crystal nucleation sites are predetermined and finite in number. In contrast, the formation of intracellular raphides was highly variable and depended on Ca(2+) concentrations. In terms of Ca(2+) prioritization, sub-cuticular CO crystals took precedence over intracellular CO raphides.
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