Search

Abstract: The island-like populations of Fraser fir (Abies fraseri (Pursh) Poir.) have been isolated since the end of the late-Wisconsinien glaciation on the highest peaks of the Southern Appalachian Mountains [...]

The light microenvironment within leaves of Medreago sativa L. cv Armor was related to the anatomy of the epidermis Leaf epidermal cells had a Convex shape and appeared to act as lenses that focussed light within the upper region of the palisade. In leaves irradiated with collimated light, epidermal focussing was demonstrated by ray tracing, photomicrography and fiber optic probe measurements, where lens signatures were observed. No relationship was observed between the location of focal spots within the palisade and chloroplast positioning. Epidermal focussing could be largely eliminated by irradiating leaves with diffuse light or by coating their surface with a thin layer of mineral oil that closely matched the refractive index of the cell walls. Measurement of variable chlorophyll fluorescence after elimination of epidermal focussing on the adaxial leaf surface caused a 19 and 11% decrease in the initial fluorescence level (F0) and maximum fluorescence (Fmax), respectively, whereas similar measurements from the abaxial surface were twice as large. These results suggest that some of the chloroplasts within the leaf may be adapted to local highlight conditions created by the epidermis. [ABSTRACT FROM AUTHOR]