Ca2+ as developmental signal in the formation of Ca-oxalate crystal spacing patterns during leaf development inCarya ovata |
| |
Authors: | Rolf Borchert |
| |
Institution: | (1) Department of Physiology and Cell Biology, University of Kansas, 66045-2106 Lawrence, KS, USA |
| |
Abstract: | Changes in the spacing patterns of Ca-oxalate crystals during enlargement ofCarya ovata Mill. leaves were quantified by computerized image-analysis. Single Ca-oxalate crystals form in the vacuoles of young mesophyll
cells transformed into crystal cells Crystals are very small in newly induced crystal cells and increase in size throughout
leaf development. Crystal patterns thus reflect both induction and relative age of crystal cells. Shortly after the emergence
of young leaves from the bud, very small crystals are formed in the mesophyll at high density. As leaves expand, these crystals
grow larger and become separated by increasing distances. New small crystals appear in the gaps between the older, larger
crystals. Later crystal patterns consist of widely spaced, larger crystals only. Finally, clusters of small crystals are formed
again in the gaps between large crystals. No crystals were observed in young leaves expanding in a moist chamber, but large
numbers of crystal cells were induced experimentally in sections of immature leaves floating on 4 mM Ca-acetate. The observations
support the following mechanism of crystal-pattern formation: Ca2+ carried into leaves with the transpiration stream acts as the developmental signal inducing transdifferentiation of a few
mesophyll cells into crystal cells when apoplastic Ca2+] rises. Crystal cells precipitate absorbed Ca2+ as oxalate and, acting as Ca2+ sinks, inhibit crystal-cell induction in their vicinity by depleting apoplastic Ca2+. This prevents close spacing of crystal cells. New crystal cells form in the gaps between the depletion zones of older crystal
cells when these move apart during leaf expansion. Later changes in crystal patterns result from increasing sink strength
of crystal cells, lowered inducibility of mesophyll cells, and increased Ca2+ influx into leaves during intensive transpiration. Throughout leaf development, spacing of crystal cells permits rapid secretion
of apoplastic Ca2+ as Ca-oxalate.
Dedicated to Professor Erwin Bünning, University of Tübingen, Germany, who pioneered the analysis of spacing patterns |
| |
Keywords: | Calcium-oxalate crystals Carya Leaf development Spacing patterns |
本文献已被 SpringerLink 等数据库收录! |
|