Growth Promotion in Pea Stem Sections. I. Stimulation of Auxin and Gibberellin Action by Alkyl Lipids

Abstract

A section of pea stem after removal from the plant elongates markedly less than the same zone when it is left on the intact plant. No growth factor or conlbination of known factors restores more than half of this missing growth. This is particularly evident in studies with the gibberellins. The intact pea plants respond to gibberellin with large growth increments whereas sections cut from replicate plants are only slightly stimulated (6,11,22). Our previous paper (20) showed that several types of fatty acid esters can partly restore the missing growth of the excised sections. The increased growth was found to be due to a stimulation of auxin and gibberellin action by the fatty acid esters, since the latter substances were inactive by themselves. These unexpected findings indicate that lipid substances have a hitherto unappreciated action in plant growth. Their role in normal plant growth regulation may be exerted through a synergistic effect on hormones rather than as hormones in themselves. The present study has been directed at defining the chenmical structure required for this synergism.