Endogenous Plant Growth Regulator Levels in Tomato Fruits During Development

SummaryTomato fruits exhibiting the characteristic sigmoid growth pattern were analysed for endogenous auxin, gibberellins, cytokinins and internal ethylene during ontogeny. The studies in this paper were concerned with changes occurring prior to the climacteric. With the exception of ethylene all the endogenous growth regulators studied showed a more or less bimodal distribution; however, the two peaks observed in each case did not occur at the same point in development. Levels of internal ethylene were high in the early stages of development but decreased subsequently. There was some evidence for sequential production of the hormones studied, in that increases in levels of gibberellins and neutral auxins preceded rises in the acidic auxin fraction. Nevertheless, in the final stages, levels of gibberellins and neutral auxins declined and only acidic auxins and cytokinins remained high.