Cell wall modifications during auxin-induced cell extension in monocotyledonous and dicotyledonous plants

There are several differences between monocotyledonous and dicotyledonous plants. The sensitivity towards added galactose which inhibits auxin-induced coleoptile elongation but not stem elongation is one of the conspicuous differences between the two types of plants. InAvena coleoptile segments, galactose, probably as galactose-1-phosphate, inhibits the formation of UDP-glucose from glucose-l-phosphate. The inhibition of UDP-glucose formation due to galactose is not found inPisum epicotyl segments. InAvena UTP: α-D-glucose-1-phosphate uridyltransferase (EC 2.7.7.9) which catalyzes the reaction from glucose-1-phosphate to UDP-glucose seems to be inhibited by galactose-1-phosphate.