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Cell-wall-softening enzymes affect the plasticity of the tip wall of pollen tubes and modity tube elongation. Length of pear pollen tubes is increased by the addition of β-1,3-glucanase at the beginning of in-vitro germination. The longer tubes after 3 hours are primarily the result of earlier germination. Application of β-1,4-glucanase or pectinase to germinating pollen does not affect germination but enhances the growth rate of 1-hour-old pollen tubes. The stimulating effects of β-1,4-glucanase and pectinase are additive. Denatured enzymes had no effect. Proteinase, pectin esterase, acid phosphatase and α-amylase only inhibited growth and germination. Replacing the medium 1 hour after germination begins stops pollen-tube growth; growth can be restored by adding cellulase-pectinase mixtures to the replacement medium. These results provide evidence that cellulase and pectinase are important in pollen-wall extension, and that callose-hydrolyzing enzymes are involved in pollen germination but not wall extension.

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