Reaching Natural Growth: The Significance of Light and Temperature Fluctuations in Plant Performance in Indoor Growth Facilities

Abstract

Recommendations for near-natural plant growth under indoor conditions have been described without considering environmental fluctuations, which might have important consequences for researchers and plant producers when comparing results from indoor facilities with natural ecosystems or production. Previous authors proposed that differences in temperature, light quantity, and the lack of their variation are sources of deviations between indoor and outdoor experiments. Here, we investigated the effect of fluctuating light, temperature, and humidity in an indoor environment on plant performance. Seven plant species from different functional plant types were grown outdoors during summer and spring. The same species were then grown in indoor growth chambers under different scenarios of climate complexity in terms of fluctuations of temperature, air humidity, and light: 1) fixed night and day conditions, 2) daily sinusoidal changes, and 3) variable conditions tracking the climate records from the field trials. In each scenario, the average of the environmental variables was the same as in the respective field trial. Productivity-, gas exchange-, and leaf pigment-traits were measured in all plants at the end of the experiments. The plant trait responses were highly dependent on species and treatment, but general trends were observed. The variable condition yielded lower biomass compared to the fixed and sinusoidal conditions, together with a higher specific leaf area and increased chlorophyll concentrations. A principal component analysis (PCA) across all plant traits in response to climatic conditions suggested that at least a sinusoidal fluctuation is recommended for a more natural-like plant performance in indoor growth facilities. However, prevailing significant differences for several traits between field- and indoor-grown plants even under variable climates indicate that additional factors other than those controllable in standard phytotrons (e.g., wind speed and direction, leaf and soil temperature) can still significantly bias plant performance in indoor facilities.

Opportunities and limits of controlled-environment plant phenotyping for climate response traits

“…Furthermore, several reports gave evidence for the potential of artificially fluctuating light to mimic naturally occurring photosynthetic acclimation processes (Suorsa et al 2012 ; Hirth et al 2013 ). Chiang et al ( 2020 ) examined the effect of different patterns of light, temperature and humidity (fixed day and night conditions, conditions following a sinusoidal curve, and mimicking of records of environmental conditions in field trials) in an indoor facility on different biomass, pigmentation and leaf gas exchange parameters in a range of plant species, comparing them to field grown plants. Depending on the species and examined parameter, plants exposed to the sinusoidal conditions or mimicked field conditions were more similar to the field-grown plants compared to the plants exposed to fixed day and night temperatures (Chiang et al 2020 ), showing the relevance of short-term fluctuations of environmental conditions, when a higher lab-to-field comparability is desired.…”

The effects of different daily irradiance profiles on Arabidopsis growth, with special attention to the role of PsbS

“…An increase in plant biomass produced per unit kWh of electricity used for lighting would provide an economic advantage. A hint that sinusoidal light does provide an advantage comes from the work of Chiang et al. (2020) , which shows that the leaf area of several species is larger for plants grown under sinusoidal light than for plants grown under square-wave light conditions with the same daily integral of irradiance.…”

“…Several studies have investigated the effects of fluctuating light on plant growth, e.g., through use of a square-wave irradiance profile ( Tikkanen et al., 2010 ), fluctuations that mimic a measured natural daytime light profile ( Vialet-Chabrand et al., 2017 ; Chiang et al., 2020 ), or a natural increasing and decreasing intensity profile with added random fluctuations ( Ferroni et al., 2020 ; von Bismarck et al., 2022 ). Here we have investigated the effects of different light regimes on the growth rate and biomass production of Arabidopsis plants.…”

Morpho-Physiological Responses of Arabidopsis thaliana L. to the LED-Sourced CoeLux® System

“…The great suitability of CoeLux ® technology for closed or underground environments raises the question of whether this lighting system could be appropriate to grow crop plants for human subsistence [ 8 ] or ornamental plants for human well-being [ 9 ]. In this context, it must be taken into account that both the quality [ 10 ] and quantity [ 11 ] of visible light received by plants are crucial for their growth and development. Terrestrial green plants absorb photons unevenly across the electromagnetic spectrum, and only photosynthetically active radiation (PAR) is used to carry out photosynthesis [ 12 ].…”