ASGSB 1998 Annual Meeting Abstracts

[24]
IMAGING CYTOPLASMIC PH IN CAP CELLS OF ARABIDOPSIS PRIMARY ROOTS DURING GRAVISTIMULATION. A. Scott and N. Allen. Dept. of Botany, North Carolina State University, Raleigh.

Root gravitropism involves three phases: gravity perception, signal transduction, and the growth response. Although the growth response phase has been well characterized, very little is known about the perception and transduction phases. The root cap is proposed to be the site of perception and early transduction events in gravitropism, therefore, changes in putative signaling molecules are likely to occur in this region. In plant cells, changes in H⁺ concentrations have been suggested to be involved in the signaling cascades linking the perception of a stimulus to the physiological response. To determine whether pH changes occur in the cap during the early stages of root gravitropism, we used fluorescent pH indicators, ratio imaging and vertical stage fluorescence microscopy. To visualize cytoplasmic pH, we used BCECF linked to a 10kDa dextran. The dye was microinjected into the cytoplasm using iontophoretic methods and remained in the cytoplasm for the duration of the experiments. Preliminary measurements showed that there was a change in cytoplasmic pH in inner columella cells during gravistimulation and that the changes were different in the various tiers of columella. (Supported by NASA grant # NAGW-4984).

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