The contributions of cell division and cell elongation and the potential role of gibberellins in the far-red light stimulation of bean internode elongation were investigated. When bean plants, Phaseolus vulgaris cv. Kentucky Wonder, were grown in white light supplemented with far-red light a significant increase, up to threefold, in internode elongation was observed. Microscopic examination revealed that cell lengths were also increased but by a lower magnitude than internode length. Cell-labeling studies with [H-3]thymidine showed that nuclei labeling was increased in internodes receiving supplemental far-red light. Thus far-red light induced increased internode elongation is a result of both increased cell elongation and increased cell division. Gibberellins A(1), A(20), A(19), A(44), and A(4) and kaurenoic acid were identified in extracts of internode tissue by gas chromatography - mass spectroscopy using [H-2(2)]-labeled internal standards for quantification. It thus appears that the early C-13 hydroxylation pathway is operative in the elongating internode. Endogenous GA(1) and GA(20) were approximately twofold higher in the first internodes of plants receiving supplemental far-red light. A comparison of the metabolism of exogenously supplied [H-2(2)]GA(19) suggested that GA turnover was greater in tissues exposed to supplemental far-red light. These results indicate that both cell division and elongation contribute to the enhanced elongation response of bean internodes to far-red light and that these processes are correlated with an increase in CA levels and (or) metabolism.