| Abstract: | The first sign of initiation of growth in dormant gemmae ofL. cruciata is the formation of rhizoids. Gemmae in the cupcannot ‘germinate‘ until exposed to substrate conditionsallowing the outward diffusion of a growth inhibitor. Rhizoidproduction depends on temperature and light. With long lightperiods rhizoids are formed over a wide range of temperatures.Transference to darkness after 2 h white light causes about50 per cent of gemmae to produce rhizoids, and these are formedonly between 20 and 25 °C. Outside these temperature limitsthe percentage of gemmae with rhizoids soon drops to zero. Althoughrhizoid production is prevented in total darkness, gemmae remainalive for well over 6 months. Red light for as little as 5 spromoted, and far-red light inhibited, rhizoid formation inthe dark. Coumarin and indol-3yl-acetic acid can substitutefor light and partly reverse the effect of far-red irradiation. |
