The modelled photosynthetic effects of different light colours on tomato crop growth and production

Photosynthesis characteristics of tomato plants grown under LED modules that produced blue, green, red, and white light were determined. Photosynthesis rates at low light intensity of plants grown and measured under the same colour related to each other as: white › red › green › blue. However, rates measured under red/blue light also related to each other as: blue › white › red = green. Photosynthesis rates at high light intensity measured under red/blue light related to each other as: blue › white › red › green. The INTKAM crop growth model was used to quantify the potential effects of light colours and levels on crop photosynthesis and seasonal growth and production. INTKAM was extended with 1) spectral composition of light, 2) light extinction profiles for different wavelengths, 3) colour effects on initial light use efficiency, and 4) on maximum carboxylation capacity. Various scenarios were examined, in which light colours provided with LEDs were or were not combined with solar radiation, and varied over the day. Daily PAR and initial light use efficiency were important causes of simulated differences in total dry matter production. The effects of differences in maximum carboxylation capacity proved small during the winter season with low light levels. A longer duration of lighting period also proved effective, even if the total light input was kept the same, due to the non-linearity of the photosynthesis-light response curve at lower light intensities.