Figure 5.

Formation of PIP₂, the lipid precursor of IP₃, increased in plasma membranes of lower halves of maize pulvini with the time of gravistimulation. Phosphorylation of endogenous PIP was measured in plasma membranes prepared from upper and lower halves of gravistimulated maize pulvini at the times indicated. The ratio of lower value/upper value for each time point was plotted. Basal PIP₂ formation in vertical plants was 680 ± 30 fmol per min per mg of protein. The data are from one representative experiment assayed in duplicate. Three experiments gave similar results.