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Pigments extracted from guard cell protoplasts (GCP) and mesophyll tissue from Vicia faba L., were separated by high performance liquid chromatography and identified by absorbance spectroscopy. Water soluble, UV‐absorbing pigments, presumably flavonoids, were present in the GCP in large amounts. Chlorophyll and carotenoid content in GCP and mesophyll tissue was qualitatively similar, with both cell types having chlorophylls, xanthophylls and carotenes. Some quantitative differences were found. Beta‐carotene was less abundant in the GCP, while some of the xanthophylls, notably violaxanthin and lutein‐antheraxanthin, were more abundant. Lutein and neoxanthin occurred in similar amounts. The similarity between the action spectrum for the stimulation of stomatal conductances by blue light and the absorbance spectrum of guard cell carotenoids points to carotenoids as putative photoreceptors in the stomatal response to blue light.
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Karlsson et al. (1992) studied this question.
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