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  • Lighting is essential element for plant growth. The most common used spectrum include red (R), white (W) and blue (B) lights are highly active for photosynthesis. The effect of R, W and B spectral components on plant physiology and biochemistry and resource use efficiency were studied during a  experiment in a deep cycle hydroponic tray system. 

  • The initial experiments were simply to identify the growth characteristics of different species of plants when exposed to the appropriate wavelength for photosynthesis. The study aimed to identify which light format best suited which variety of plant to produce the highest yield. Essentially this was about identifying a ‘Goldilocks’ zone for optimal plant performance.

  • In four experiments in relatively controlled conditions (PPFD = 215 μmol m−2 s−1, daylength 18hrs). LED lighting increased yield (1.8 folds) and energy use efficiency (2.8 folds) as compared with fluorescent lamps. 

  • Adoption of MTRWB (RB = 3) maximised yield (by 2 folds as compared with TTWR 1.5 folds), also increasing leaf chlorophyll and flavonoids concentrations and the uptake of nitrogen, phosphorus, potassium and magnesium. As the red portion of the spectrum increased, photosystem II quantum efficiency decreased but transpiration decreased more rapidly, resulting in increased water use efficiency up to RWB (75 g fW L−1 H2O). The transpiration decrease was accompanied by lower stomatal conductance, which was associated to lower stomatal density, despite an increased stomatal size. Both energy and land surface use efficiency were highest at RWB. We hereby suggest a RWB ratio of R =70%, B=25% with nominal use of W=5% (to view the plant colour and density) for most effective plant cultivation, however further experimentation is required to find the optimal balance and ratio of this LED configuration with respect to density of the overall wavelength.

  • By measuring the LED wavelength in different sections of the tray over the most productive plant growth showing the highest stomatal density, leaf growth and overall weight it was possible to identify the optimal light balance.  

  • The LED strip configuration resulted in different plant growth over individual plant species allowing us to record specific growth in that region of the tray. 

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