Light Piping to the Inner Plant Canopy Enhances Plant Growth and Increases O ₂ , CO ₂ , H ₂ O and Ethylene Gas Exchange Rates

In dense plant canopies, shaded leaves represent considerable unused photosynthetic capacity that can be exploited to improve production in closed environments. By coupling Fusion Systems Solar 1000 microwave powered lights to 100 mm diameter glass tubes lined with 3M Optical Lighting Film, energy equivalent to approximately 420 μmol m^-2 s^-1 PAR was delivered to the inner canopy of a developing soybean (Glycine max L. Merr. cv. Secord) crop. Inner canopy irradiation enhanced plant growth and altered biomass partitioning within the canopy. With inner canopy lighting, edible biomass, carbon dioxide removal and water and oxygen production were increased by 9, 30, 160, and 100 percent respectively. Ethylene production in the closed environment was also increased during several months of canopy development. Supplemental irradiation of the inner canopy has the potential to improve the capacity of higher plants to furnish food, oxygen, and potable water in bio-regenerative life support systems for human exploration missions.