Inhibition of the formation of adventitious roots on cucumber hypocotyls by the fractions and methoxybenzylglutamine from xylem sap of squash foot

In studies of the functions of roots in the development of aboveground organs, the butanol fraction of xylem sap collected from squash root was found to have inhibitory activity against the formation of adventitious roots on the hypocotyls of cucumber in a culture of shoot cutting. The inhibitory activity was fractionated with reverse phase column chromatographies, and an inhibitory fraction was recovered with a single peak of absorbance at 280 nm, which contained a novel amino acid, N-5-(4-methoxyphenyl) methyl-L-glutamine (methoxybenzylglutamine) as a major component (Inouye et al. 1998). Chemically synthesized methoxybenzylglutamine (5 mM) inhibited the formation of adventitious roots and also inhibited the growth of first leaf and cotyledons in a culture of shoot cuttings. On the basis of the results obtained, discussed is possible regulation of the developmental events on the aboveground organs by the roots through xylem sap.