Determining the optimum temperature, irradiation and CO₂ enrichment on the growth of lettuce and cabbage seedlings in plant factories

The development of fully enclosed plant factories enables more precise control of light (quantity, quality and duration), temperature and carbon dioxide levels.
Using light emitting diodes (LEDs) within the photosynthetically active range (PAR) it is possible to “eliminate” direct radiation heating from infra-red source.
In our studies we used predominantly red (80%) and blue (20%) radiation as the photosynthetic light source.
Seed of lettuce and cabbage was sown in foam after 3 days of imbibition at a constant temperature of 20°C, were placed in controlled climate facilities with the following conditions; temperatures: either 20, or 25 or 30°C. PAR level: 115, 240, 480 µmol m^-2 s^-1. The photoperiod was 23 h, in order to minimize the time required for each experiment, but still provide a “dark period”. Destructive plant samples were taken at intervals (a total of 5 harvest dates from each treatment), and regression lines fitted using plant growth analysis.
From these data we calculated the relative growth rates of the seedlings.
Thus it was possible to estimate the relationships between plant growth rate, PAR, temperature and CO₂ levels economically, efficiently and rapidly.
In our study the optimum temperature was 25°C, increasing CO₂ concentration significantly increased dry matter accumulation up to 1000 ppm.
Neither cabbage nor lettuce seedlings appeared to be light saturated up to 480 µmol m^-2 s^-1.

XXIX International Horticultural Congress on Horticulture: Sustaining Lives, Livelihoods and Landscapes (IHC2014): International Symposium on Innovation and New Technologies in Protected Cropping

D.I. Duggan-Jones, M.A. Nichols

led, foam, multi wave, PAR, CO2, temperature, plant-factory

https://doi.org/10.17660/ActaHortic.2015.1107.25