Effects of different Solar spectrum lamps om photosynthesis and morphology of young tomato plant.

MSc-thesis abstract (submitted 22 January 2015):
Most artificial light sources, which are used in plant research and plant production systems, produce light with a spectral composition that is rather different from solar light and may therefore significantly influence plant photosynthesis and morphogenesis.

We investigated the effects on plants of different artificial solar light sources based on PLASMA and LED technology. Three continuous ‘solar’ spectra, which slightly differed from each other, were compared: a standard solar plasma lamp (PLASMA), a filtered solar plasma lamp, which was slightly enhanced in blue and reduced in far-red wavelengths (PLASMA+A), and a prototype solar LED source complemented with quartz halogen (LED+H). Tomato seedlings were grown for 15 days and plant morphological characteristics and leaf photosynthetic characteristics were evaluated. LED+H treatment resulted in a higher leaf area, stem length and shoot dry weight than the other two PLASMA treatments. Leaf photosynthetic characteristics were not different between treatments. We tested if the morphology of young tomato plants correlates with the calculated phytochrome photostationary state (PSS). Five light sources with a PSS-value close to solar light and a Red and Blue LED treatment with higher PSS-value were tested. Based on all the morphologies evaluated, we cannot relate the PSS with a prediction of the future morphology in tomato plants.