Crop productivity in plant factories

Plant factories, where the grower has absolute control over the environment, is a totally different situation from greenhouse production, and will require a complete re-think of many well established protected growing concepts. For example the use of monochromatic LEDs removes variation in leaf temperature with canopy position. Information on the interaction of temperature, light intensity and carbon dioxide levels on crop productivity are critical to developing efficient production systems. Results from our factorial studies, in which the growth of lettuce, and cabbage seedlings was measured at 3 levels of LED light, 3 temperatures and 3 CO₂ concentrations will be presented in support of this thesis. We are not aware of any other similar studies for plant factories, and using greenhouse information or even the photosynthesis principles developed by Gaastra in the 1960s are probably not appropriate for plant factories. The potential to provide photosynthetic radiation for up to 24 h day^‑1 at any (reasonable) intensity, without the normal diurnal fluctuations provides the opportunity to modify intensive crop production well beyond present systems. Over the past 60 years we have seen greenhouse yields increase by a factor of 4×. It is impossible to imagine what the next 60 years will bring forth in plant factories!!