Table 1.

Cells of maize root apices react to the presence of NO modulators in a cell type- and developmental stage-specific manner

Compound used	Root zone		Comments
	Transition	Elongation
250 μM SNAP	+++	+	Strong reorientation of actin cables in protoendodermal cells; formation of long actin cables in elongated cells, and cross-wall domains enriched with actin
1 mM NaNO2	+	+	Slight disorganization of actin in both zones with prevalence of longitudinal actin cables, but in the elongation zone not so long as in cells treated with SNAP or 8-Br-cGMP
200 μM cPTIO	−	+++	Complete reversal of SNAP action in transition zone; diffused organization of actin in elongated cells, and loss of actin labelling at the cross-walls
100 μM L-NMMA	+	++	Formation of very short actin bundles in transition zone cortex cells; long, undulated actin cables, accompanied by a distinct network of shorter microfilaments, in elongated cells; the latter transform into diffused actin after prolonged treatment
50 μM ODQ	+	+++	Actin reorganizes its orientation in protoendodermal cells, but actin-enriched domains at the cross-walls are still visible; induction of actin depolymerization in elongation zone (appearance of ‘clouds’ of depolymerized actin in the basal part of elongated cells)
100 μM 8-Br-cGMP	−	++	Normal actin organization in cells of transition zone; effects in elongation zone similar to those evoked by SNAP
250 μM SNAP+50 μM ODQ	−	+	Normal organization of actin in protoendodermal cells; slight enrichment in actin at cross-walls domains in elongated cells

Roots were incubated with respective compounds, and sampled for immunocytochemistry at various time points. Data on changes in the organization of the actin cytoskeleton in cells of two root zones are for samples collected after 2 h of treatment, when the maximal reaction to SNAP as the NO donor is normally observed. The observed effects varied from strong (+++) to weak (+). Cases where the organization of actin remains unaffected are indicated by (−). Exemplary images illustrating the observed changes are assembled in Figs 4 and 5.