The Role of Polar Movement of IAA in the Development of the Peg in Cucumis sativus L.

Abstract

The developmental anatomy of the "peg" in Cucumis seedlings, a radially growing structure composed largely of cortical cells, was studied. A physiological barrier to auxin transport in the transition zone of Cucumis seedlings and the lateral distribution of IAA as a function of gravity determine the position of radially enlarging cells. The lateral distribution of IAA-14C as a function of gravity explains how endogenous IAA can be limiting for radial extension on the upper side of horizontally growing seedlings. The role of IAA in radial growth is discussed.