XVI International Botanical Congess

Changes in the levels of cytoplasmic and apoplastic Ca2+ and pH have been linked to the signal/response systems involved in the touch and gravity responses of roots. We have used confocal microscopy and microinjection of fluorescent dyes to visualize changes in cytoplasmic Ca2+ and pH in Arabidopsis roots responding to these stimuli. To visualize apoplastic pH, the pH sensor Oregon green was conjugated to the cellulose binding domain of Clostridium cellulovarans cellulase, and infiltrated into the apoplastic space of the root. Touch or gravistimulation lead to stimulus specific patterns of changes in cytoplasmic Ca2+ and pH as well as alterations in apoplastic pH. Manipulating the levels of these ions with caged chelators indicates these stimulus-induced changes are required for the tropic responses of the plant root (Supported by NSF grant IBN 95-13991).