Fig. 4.

Growth stimulation and sufficient incorporation of applied nucleotide sugars into pectins. A, phenotypes of wild-type ovules collected at 1 dpa and cultured in the presence of 5 μm UDP-Rha, UDP-GlcA, UDP-GalA, UDP-Glc, or UDP-Xyl or in the same concentration of free Rha, GlcA, or GalA for 6 days. The measurements (mean ± S.E. in mm) are shown below each representative ovule. * and ***, significant at p < 0.05 and p < 0.001 levels, respectively. None, no extra chemical added. B, wild-type cotton ovules with growing fibers took up significantly more ¹⁴C-labeled nucleotide sugars than fl ovules. Chemical uptake was calculated by subtracting the radioactivity remaining in the medium and in the wash from the amount of radiolabels applied initially in each culture. Error bars indicate standard deviations. C, most of the radiolabel from the exogenous nucleotide sugar feeding experiments was recovered in cotton fiber cell walls. D, the majority of the exogenous UDP-Rha and UDP-GlcA was incorporated into pectic polymers. E, UDP-Xyl was incorporated mainly into hemicelluloses.