on their provenance, the development of these lateral root primordia is more or less
sensitive to calcium ions (Richter et al. 2009).
Neither local auxin cues nor their correlation with oscillating auxin maxima can
alone explain the patterning of lateral root primordia along the root axis. A recent set
Fig. 7.1 PIN expression and protein localization in gravistimulated roots of wild-type
(WT) Arabidopsis and pPIN1::PIN1-GFP, pDR5rev::3XVenus-N7 transgenic lines. (a) PIN1PIN2 immunolocalization. Epidermis (e), cortex (c), endodermis (en), pericycle (p), vascular bundle
(v), meristematic zone (MZ), elongation zone (EZ), arrows indicate inferred auxin fluxes. (b) PIN1GFP (green) and DR5-Venus (pink), DAPI labeled nuclei (blue), epidermis (e), cortex (c), endodermis (en), pericycle, (p) protoxylem (px), arrows indicate presumed direction of auxin flux,
asterisk (*) indicates PIN1 retrieval from basal side of one cell in protoxylem. (c) magnified view of
boxed area in (A) showing PIN1-PIN2 immunolocalization, epidermis (e), cortex (c), endodermis
(en), pericycle (p), vascular bundle (v), arrows indicate presumed direction of auxin flux, hash (#)
indicates PIN1 retrieval from lateral side in pericycle cell on the lower side of the root (Ditengou
et al. 2008)
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7 Gravitropism in Higher Plants: Molecular Aspects