Mapping symplasmic fields at the shoot apical meristem using iontophoresis and membrane potential measurements

Abstract

Microinjections of fl uorescent dyes have revealed that the shoot apical meristem (SAM) is dynamically partitioned into symplasmic fi elds (SFs), implying that plasmodesmata (Pd) are held shut at specifi c locations in the proliferating cellular matrix. The SFs are integrated into a coherent morphogenetic unit by exchange of morphogens and transcription factors via gating Pd between adjacent SFs, and by ligand– receptor interactions that operate across the extracellular space. We describe a method for the real-time mapping of SF in the SAM by iontophoresis and membrane potential measurements.