Dipyridyl-induced Cell Elongation and Inhibition of Cell Wall Hydroxyproline Biosynthesis

Incubation of soybean hypocotyl sections with 0.1 millimolar 2,2'-dipyridyl in the absence of auxin results in increases in growth rate and in cell wall extensibility lasting for about 3 hours. This is accompanied by greatly decreased biosynthesis of hydroxyproline, which ultimately appears in the wall, and in slightly reduced oxygen uptake, both of which continue for at least 9 hours. Continuous synthesis of hydroxyproline which appears in the cell wall is thus not necessary for short term growth. The decrease in growth and cell wall extensibility that occurs between the 3rd and 9th hours of dipyridyl inhibition cannot be attributed to cross-linking of newly synthesized hydroxyproline, since its synthesis is still inhibited.