Yields Of Salad Crops Grown Under Potential Lunar Or Mars Habitat Environments: Effect Of Temperature And Lighting Intensities

Growth Temperatures And Lighting Intensity Are Key Factors That Directly Impact The Design, Engineering, And Horticultural Practices Of Sustainable Life-Support Systems For Future Long-Term Space Missions. The Effects Of Exposure Of Lettuce (Cv. Flandria), Radish (Cv. Cherry Bomb Ii). And Green Onion (Cv. Kinka) Plants To Controlled Environment Temperatures (Constant Day/Night Temperature Of 22, 25, Or 28 °C) And Lighting Intensities (8.6, 17.2, Or 25.8 Mol M⁻² D⁻¹ Photosynthetic Photon Flux [Ppf]) At Elevated Co₂ (1200 µMol Mol⁻¹) Was Investigated To Ascertain Overall Yield Responses. Following 35 Days Growth, The Yields Of Lettuce Indicated That Increasing The Growing Temperature From 22 To 28°C Slightly Increased The Edible Fresh Mass Of Individual Plants. However, Even Though Lettuce Plants Grown Under High Ppf Had The Highest Fresh Mass, The Resultant Increase In The Incidence And Severity Of Tipburn Reduced The Overall Quality Of The Lettuce Head. As A Result Of The Tipburn, The Quantum Efficiency (G Fm Mol⁻¹ Ppf) Of Lettuce Plants Grown At The Highest Ppf Was Also Significantly Reduced. In Contrast, Radish Was More Sensitive To Higher Growth Temperatures, With Reductions In Fresh Mass Of The Storage Root As Growth Temperature Increased, Especially At Higher Daily Ppfs. As A Result, High Ppf And High Growing Temperatures Translated Into Lower Storage-Root Quality, As Surface Cracking And Hollow Heart Of Storage Roots Was Severe For Radish. Quantum Efficiencies Were Also Lowest At The Higher Growth Temperature. Yields Of Onion Were Significantly Enhanced By Increasing Growth Temperature And, More Importantly, Light Intensity. Unlike Lettuce And Radish, There Were No Indications Of Any Physical Deformities Of Onion At Any Ppf/Temperature Treatment.