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Eduncle posted an MCQ
December 30, 2019 • 16:50 pm 0 points
  • CSIR NET
  • Life Sciences

Stomata from detached epidermis of common dayflower (Commelina communis) were treated with saturating photon fluxes of red light. In a parallel treatment, stomata treated with red light were also illuminated with blue light (indicated by arrow). From the graphs shown below, select the correct pattern of stomata opening (solid lines and dotted lines represent stomatal aperture under red and blue lights, respectively).

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    Eduncle Best Answer

    Both red and blue light stimulate stomatal opening. Because chlorophyll also absorbs these wavelengths, sensitivity to red and blue light is consistent with a role of guard cells in opening stomata under conditions conducive for photosynthesis. Indeed, in most species guard cells are the only epidermal cells that contain chloroplasts, and guard cell chlorophyll is implicated as a photoreceptor in the light responses of stomata. However, the greater quantum efficiency of blue light over red light in stimulating stomatal opening suggests that guard cells also possess a specific blue-light photoreceptor. So most appropriate response is seen in graph 1.

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