Photon delivery in space horticulture

Two aspects of photon delivery in microgravity are considered. The first is the effect of microgravity on the source of photons, which essentially a direct effect on convective flow of gases in the lamp. The second is the effect of microgravity on the plant due to the complex interaction of light and gravity in plant functions. The output of the light source, which is strongly influenced by heat transfer, has been shown to be altered significantly in both spectral quality and radiant flux. Plant structural form and orientation, as well as general direction of growth, are influenced by combined forces of gravity, light direction, light quantity and spectral quality. The engineering of effective systems for plant culture will thus require a careful sorting out and balancing of the microgravity physics of both the light source and the plant system. Available evidence suggests that much of the key information must be acquired through flight experimentation.<>