Neurobiological View of Plants and Their Body Plan - Communication in Plants: Neuronal Aspects of Plant Life - page 26

Fig. 2.3. Sensory zones in the root apex. There are two clearly defined sensory zones in the
root apex: the root cap covering the meristem and the transition zone interpolated between
the meristem and elongation region. Both these sensory zones receive diverse signals and
the output is differential switch-like onset of rapid cell elongation, resulting in either straight
growth (when all postmitotic cells start their rapid cell elongation simultaneously) or rapid
turnings of the root apex. The transition zone is flooded with sucrose, which allows energy-
demanding 'brain-like' information processing in its cells
RNA translation (van Bel 2003). Mature xylem elements represent non-
living and water-filled tubes surrounded by metabolically active cells of
xylem parenchyma (de Boer and Volkov 2003; Gilliham and Tester 2005).
Xylem tubes are specialized for transmission of hydraulic signals, which
are self-transmitting waves induced and driven by changes in hydrostatic
pressure (Mancuso 1999).