| MadSci Network: Botany |
This is an interesting observation. Below is one possible explanation. I'm not sure it is correct. It is quite likely that no botanist has ever published a study on the pigments in African violet leaves. The model research plant Arabidopsis and common food plants, such as corn, spinach, bean and tomato, are studied much more than ornamental plants. An article search in the Agricola Database for Saintpaulia gives 542 articles. A search for corn or arabidopsis each gives 10,000 articles. African violet (Saintpaulia ionantha) is an obligate shade plant, meaning that it is damaged or killed in full sunlight. The usual recommendation for African violets is to provide about 1,000 footcandles of light. Full sunlight is about 10,000 footcandles. Perhaps African violet has lower levels of carotenoid pigments than plants that can grow in full sunlight, such as grass. Carotenoids would be the yellow to orange bands. Carotenoids are a class of yellow, ornage or red pigments that includes carotene, lycopene, and xanthophylls, such as lutein and zeaxanthin. Cartenoids are accessory pigments that absorb wavelengths such as green that chlorophyll absorbs weakly. That light energy is then transferred to chorophyll and used in photosynthesis. Cartenoids also function as antioxidants so help protect chlorophyll from free radicals. "Photobleachin g (or photoinhibition or photooxidation) can occur when the light harvesting array captures more light energy than can be released by electron transport, so instead this energy is released during the formation of toxic radical compounds, like singlet oxygen, which can damage the proteins and lipids of the thylakoid." Shade plants are not exposed to high light levels so would not need as much protection. If you extracted the African violet leaf pigments with an organic solvent such as acetone or ethanol, you might find more bands in the chromatogram because the extraction could provide a higher pigment concentration. References African violet Carotenoid Functions Carotenoids Carotenoid Importance Absorption spectra of carotenoids Chlorophyll absorption spectra Chlorophyll chromatography Leaf Pigment Chromatography Re: How do you identify pigments as they show up on paper chromatography?
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