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THE PHOTOBIOLOGY OF Paphiopedilum STOMATA: OPENING UNDER BLUE BUT NOT RED LIGHT

1983; Wiley; Volume: 38; Issue: 5 Linguagem: Inglês

10.1111/j.1751-1097.1983.tb03394.x

1751-1097

Eduardo Zeiger, Sarah M. Assmann, H. Meioner,

Lichen and fungal ecology

Abstract— The responses of stomata from Paphiopedilum harrisianum , Orchidaceae, to light and CO 2 were studied in epidermal peels. Stomatal opening under red light was indistinguishable from that in darkness, whereas blue light promoted opening above dark levels. The ineffectiveness of red light in causing stomatal opening was confirmed in the presence of 100 μ M KCN; average apertures in both darkness and red light were 53% of those measured in the absence of the inhibitor, whereas under blue irradiation, the KCN inhibition was only 30%, with average apertures two‐fold of those measured under red light or darkness. Fluence rate response curves under blue light were typical of a single photoreceptor; removal of CO 2 increased aperture values without a significant light‐CO 2 interaction. The lack of a stomatal red light response contrasts with results obtained in species with chlorophyllous stomata in which red light consistently causes stomatal opening, and suggests that the previously reported red light responses in stomata from intact Paphiopedilum leaves resulted from indirect effects, such as depletion of intercellular CO 2 by mesophyll photosynthesis. In isolation, Paphiopedilum stomata appear to rely on a blue light photosystem for their responses to light and fail to open under red light because of their lack of guard cell chloroplasts.