A light conduction apparatus for photosynthetic reaction includes a rotatable light distributor which may be a transparent rod or disc. Converged light is guided by a solid or tubular light conducting member into the light distributor and routed along at least one optical path through the tight distributor as far as a radiation surface of the latter. The light output from the radiation surface is applied a moment to each of a number of light conducting rods, which lead to a confinement for photosynthesis, once for each full rotation of the light distributor. Thus, the confinement shares a single light source which can be small size for given dimensions of the confinement.