GROWTH RATES OF YOUNG TOMATO PLANTS IN DIFFERENT INTENSITY RATIOS OF NATURAL AND ARTIFICIAL LIGHT

Young tomato plants were grown in a glasshouse during 25 days in January.
Artificial light, additional to natural light, was given daily from 12.00–24.00 with intensities ranging from 2–10 W/m2. Artificial light came from a high-pressure mercury lamp (HPI/T, 400 W) or a high-pressure sodium lamp (SON/T, 400 W). Harvesting was done every 5 days and fresh and dry weight of harvested plants were determined.
No differences in growth rate, due to differences in spectral composition of the lamps, were found.
Measured growth rates could fully be explained by assuming a hyperbolic relation between growth rate and light intensity in the wavelength region from 400–700 nm.
At an intensity of 20 W/m2 growth rate is half of the maximum growth rate at high intensity.
This hyperbolic model could be understood from a simple photosynthesis model.
The model may be used for the valuation of natural light for plant growth in difference seasons.
It also give the possibility to estimate duration and intensity of artificial light to be equivalent to natural light.

Symposium on More Profitable Use of Energy in Protected Cultivation

O. Elgersma, G. Meyer, J. van Gammeren

https://doi.org/10.17660/ActaHortic.1981.115.79