Long-Term Growth-Retardant Effects of (+)-Limonene Derivatives on Citrus1

Abstract

Abstract The growth-retardant effects of succinic acid-2,2-dimethylhydrazide (SADH), 1 n-alkyl and 2 benzyl quaternary ammonium derivatives of (+)-limonene were determined after application of 2 foliar sprays on young grapefruit (Citrus paradisi Macf.) seedlings which were subsequently pruned to remove all growth. Only the n-alkyl derivative, l-p-menthanol-2-dimethylamino heptyl bromide (Q-58), caused dwarfing and marked internode shortening of new growth on all treated plants 71 days after the second foliar spray. A similar experiment on a larger scale using Q-58 and 2 new n-alkyl derivatives of (+)-limonene produced retardation of new growth for 136 days after the second foliar spray. However, true dwarfing was only apparent in a few of the treated seedlings. These results indicate that n-alkyl quaternary ammonium derivatives of (+)-limonene are stored in the roots or lower stems of grapefruit seedlings and can continue to retard terminal shoot development for about 4 months after treatment.