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The process of integrating a Higher Plant Chamber (HPC) in the MELiSSA Pilot Plant demands reliable data on crop photosynthetic responses to varying light intensity. Such data allow for the development of dynamic photosynthetic models which, in turn, are used in the control of the HPC. A number of full canopy research trials have been conducted using sealed environment chambers with beet (Beta vulgaris cv. Detroit Medium Red) and lettuce (Lactuca sativa L. cv. Grand Rapids) as candidate crops. In this study, data were collected at the full canopy scale using a differential-compensating CO2 analysis system and at the leaf scale using a LI-6400 leaf gas exchange system in an attempt to derive parameter estimates for a leaf and canopy photosynthesis model. Results indicate that a rectangular hyperbola model was suitable in defining the leaf and the linear phase of full canopy Net Carbon Exchange Rate (NCER) response to light.

Mars is likely the best candidate for future planetary exploration however the Martian atmosphere is at a pressure of ~0.6 kPa. This extremely low pressure demands that plant growth structures be isolated from the ambient environment. While it is clear that it is desirable to predict the contributions that plants will make to bioregenerative life support systems at reduced atmospheric pressures, research has been limited. This study examines carbon exchange and evapotranspiration in order to establish a baseline that will aid in the development of an atmospheric composition that allows for reduced pressure plant growth without compromising the plant production yields required for human life support.

The concept for Tomatosphere originated in late 1999 and the project held its first formal meeting on February 7, 2000. The project was formally activated when 200,000 Heinz tomato seeds went into space on November 30, 2000, with Canadian astronaut, Dr. Marc Garneau. The seeds were part of an experiment designed to test the effects of short- term space travel on seed germination and interaction with new techniques designed to enhance germination rates. An equal number of seeds stayed behind on Earth and the two lots, space-flown and Earth-bound, were further sub-divided into two treatments using new Infra Red and Red light technology developed at the University of Guelph. The resulting four treatments were packaged and sent to almost 2700 classrooms across Canada, along with posters and a teacher's guide matched to the Pan-Canadian Protocol for Collaboration on School Curriculum, a framework of Science Learning Outcomes developed by the Council of Ministers of Education, Canada.

Due to its large proportion of edible biomass, beet (Beta vulgaris) has high potential as a candidate crop for bioregenerative life support systems. This paper summarizes data collected for beet under batch and staged stand culture in closed environment chambers. Full stand trials were conducted under the following conditions: 1000 μL L−1 atmospheric carbon dioxide concentration, light intensities ranging from 400–600 μmol m−2 s−1 PAR with a 14 hour photoperiod, 73% ± 5% relative humidity, a 26/20 °C day/night temperature regime and a fixed planting density of 17.6 plants m−2. For batch planted stands, total edible yield was determined to be 28.3 g dry weight basis (dwb) with a 95% Confidence Interval (CI) of [24.7, 31.8] g plant−1 with a harvest index of 94%. Under similar conditions, yield for staged beet stands was 31.4 g dwb with a 95% CI of [24.54, 38.31] g plant−1. Water use efficiency under these same conditions was found to be 0.003 mol C mol−1 H2O.

It is understood that plants and microorganisms will be an intrinsic part of future advanced life support (ALS) systems. The photosynthetic process is uniquely able to provide food and water from transpiration, remove carbon dioxide, and produce oxygen. However, atmospheric management with typical monoculture batch plant growth is made difficult due to fluctuating rates of CO2 assimilation and O2 production during different phases of plant growth and development. Experiments on the effect of continuous production of multiple crops with rotational planting on atmospheric stability within a sealed environment were performed in the Controlled Environment Systems Research Facility ambient pressure controlled environment chambers. Two of the ESA-MELiSSA candidate crops, beet and lettuce, were continuously grown with a ten day staggered planting interval, resulting in a plant canopy with all representative stages of physiological growth within a common atmosphere.

This study investigates the impacts of staged planting on the apparent quantum yield of beet stands. Experiments were conducted with both staged and batch planted beet in full canopy sealed environment chambers under fixed environmental (light, CO2, temperature) conditions. Empirical results indicated a higher average apparent quantum yield than that of the batch planted stand. Observed increases in quantum yield were used to simulate the joint effects of a range of additional daily labour requirements associated with staged scenarios and changes in crop production cost. The implications of these findings on bioregenerative system and physico-chemical system tradeoff are discussed.

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.