Growth Promotion in Pea Stem Sections. III. By Alkyl Nitriles, Alkyl Acetylenes and Insect Juvenile Hormones.
C(14), C(15), and C(16) alkyl nitriles, and C(16) and C(18) alkyl acetylenes at 10 to 105 micromolar concentrations promote the growth of stem sections from red-light-exposed seedlings of dwarf peas (Pisum sativum L. cv. Progress No. 9). Similar results were obtained with substances active as insect juvenile hormones, namely farnesol, the racemic ethyl ester of 1 of the natural hormones, and a "synthetic juvenile hormone" mixture, the latter 2 having as high an activity in the pea assay as any lipid reported previously. A sterically nearly identical compound, methyl-RS-10,11-epoxyfarnesoate, is a weak insect hormone and did not promote plant growth. Thus activity in peas and in insects is in some cases parallel. Other similarities and some differences are discussed. Peas appear to require molecules longer than 20A, while insect activity is maximal at that length. All active molecules are ineffective in promoting pea stem elongation by themselves, indole acetic acid must also be present. The lipid effect in plants and the juvenile hormone response in insects have much in common and the evidence suggests they could have a similar locus of action in a membrane controlling respiratory function.