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Cross-section of Stem and Leaves

Cross-section of stem and seven small leaves from an Australian beefwood

The cross-section of a stem and seven small leaves (microphylls) from an Australian beefwood (Casuarina cunninghamiana). A special ultraviolet (UV) light was used to reveal the different colors under a microscope. Items under a UV-lamp fluoresce and do not look the same color as under daylight. The red fluorescence in the very small pentagon shaped leaves is from chlorophyll. The blue fluorescence is from secondary metabolites in the vascular (central) and epidermal (outer) tissue.

This beefwood appears to have needles when looking with the unaided eye, which are not found in this taxonomic group. Investigating with a UV microscope revealed that instead of a single needle, this is a stem with seven small leaves. Not everything is as it appears to the human eye.

Restrictions for Use of this Image: Arizona State University (ASU) has allowed the National Science Foundation (NSF) to include this image in the NSF Multimedia Gallery. ASU encourages the use of this image, as well as other material from the ASU "Ask a Biologist" website. Distribution of this image is permitted under the following rules:

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Credit: Image by Gregory Johnson; from Arizona State University's School of Life Sciences Ask a Biologist website.

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