| Abstract: | Horizontal growth of seedling roots of Lepidium sativum L. cv.Curled is sensitive to white light with a photon flux densityas low as 7.5 µEinsteins m–2 S–1. Inhibitionof growth is positively correlated with light intensity. Rootsgrowing in the vertical plane are much less sensitive to light.The light inhibition of horizontal root growth can be overcomeby the application of an axial force. The effects of light andaxial force are reversible. Although geotropic responsivenessis not dependent on exposure to light, there is evidence thatlight induces a heightened geosensitivity. The results are discussedin relation to the counter-current theory of the regulationof root growth. |
