About the Cover
Structural and functional deformations resulting from damage inflicted during experimental manipulation have hampered efforts to elucidate the ultrastructure and mode of action of sieve tubes. On pages 35-50 of this issue, Knoblauch and van Bel present a confocal laser scanning microscopy-based method that provides definitive images of undamaged and functional sieve elements in whole plants. They use this technique to reveal the nature of the damage caused by impaling sieve elements with microelectrodes and by irradiating tissue with high intensity laser light. Mechanical injury, for example, seems to trigger the explosion of P plastids, the contents of which may coagulate with P proteins to form sieve plate plugs. The cover shows the fluorochrome 5,6-carboxyfluoresceindiacetate (CFDA) moving through sieve elements and accumulating in the vacuoles of companion cells in intact Vicia faba phloem tissue. In this false-color image, increasing concentrations of CFDA are represented in a gradient from blue, through green and red, to white.
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Copyright © 2007 by the American Society of Plant Biologists
