The Control of Growth of Tomato Pollen

Tomato pollen grains germinate readily in a solution containingonly sugar and boric acid, although subsequent growth is ata rate much lower than that in the style. These experimentswere designed to test the hypothesis that the action of boronis to prevent the toxic effects of high auxin levels, and toinvestigate the role of auxin in germination and pollen-tubegrowth. No evidence could be found for an interaction between indol-3yl-aceticacid and boron of the kind required by the hypothesis. Severalinhibitors of growth and metabolism (maleic hydrazide, trans-cinnamicacid, iodoacetate and abscisic acid), and indol-3yl-acetic acidat high concentrations and ethylene inhibited germination tovarying extents, but promoted tube elongation. It is suggestedthat there are two distinct phases in the early growth of thepollen grain—germination and elongation—and thatthey differ in their sensitivity to chemical treatment. An activeendogenous inhibitory system appears to be established soonafter germination, which controls the rate of growth of thepollen tube. This inhibitory system can be inactivated by treatmentswhich cause the production of ethylene.