Quantitative and Qualitative Differences in Plant Response to the Gibberellins

Abstract

Wittwer, S. H., and M. J. Bukovac. (Michigan State U., E. Lansing.) Quantitative and qualitative differences in plant response to the gibberellins. Amer. Jour. Bot. 49(5): 524–529. Illus. 1962.—The comparative biological activities of gibberellins A1 through A9 were evaluated, over a wide concentration range and in several test systems. All gibberellins were effective in promoting stem elongation of dwarf peas (Pisum sativum), and, with the exception of A8, epicotyl growth in Phaseolus vulgaris. Elongation of Cucumis sativus seedlings was strikingly greater with A4, A7, and A9 than with the other gibberellins. With mutant dwarfs of Zea mays, A5 and A9 were the most active gibberellins for d3 and d5, and relatively ineffective compared to A3 on d1. Gibberellins A2, A7, and A8 were less effective than A3 on all dwarfs. Qualitative and quantitative differences among the gibberellins were noted on seedstalk elongation and flowering of Lactuca sativa, with A3 the most active followed by A1, A7, A4, and A9. No flowering or seedstalk elongation occurred with A2, A6 or A8. Parthenocarpic fruit growth in Lycopersicon esculentum was a function of dosage with all gibberellins. At the lowest levels, A5 and A7 were the most active, while at the highest levels all gibberellins with the exception of A8 were equally effective. The results suggest a high degree of species and response specificity among the known fungal and higher plant gibberellins, and demonstrate the importance of utilizing a wide spectrum of plant responses and dosage levels in the biological assay of plant extracts for native gibberellins.