Taipei, Taiwan, Republic of China
Academia Sinica
Taipei, Taiwan, Republic of China
National Taiwan University
Buffalo, New York
State University of New York
Optical density of leaf --Lin, B-L, Cheng, P-c, Sun, C-K Recent development in laser technologies offers a number of wavelength choices in multi-photon fluorescence and harmonic generation microscopy. In order to assist in the selection of excitation wavelengths and suitable fluorescent probes, we measured the light attenuation of leaf in the spectral range of 250-2250nm. The spectrum covers UV, visible and extended IR range to include the emission wavelengths of Ti-sapphire (800nm), Nd-glass (1064nm), Cr-forsterite (1270nm), Cr-YAG (1500nm), Er-glass (1550nm) and other ultra-fast IR lasers, as well as the emission wavelengths of harmonic generations (second and third harmonic) and fluorescence probes. A Hitachi spectrometer equipped with a scattered light integrator was used in this study to measure the attenuation of maize leaf (field grown mature leaf). Therefore, the attenuation spectrum is mainly the result of absorption properties of leaf with minimum scattering contribution. In order to minimize the scattering contribution due to air spaces in the mesophyll, water logged leaf was used in the measurement.

The Figure shows the attenuation spectrum (Cheng et al., SPIE Proceedings, vol. 4262) of maize leaf. Note the high attenuation in UV as the result of proteins and other organic compounds. The attenuation in the blue and red spectral region is the result of chlorophylls and other photosynthetic pigments. The attenuation in the IR range (>1400nm) is mainly due to the presence of water in the leaf tissue. The translucent window of maize leaf suitable for light microscopy is within the spectral range of 350-1400nm.

Supported by the National Science Council, Republic of China under grant number: NSC-89-2311-B-001-032 (BLL), NSC-88-2811-B-001-0023 (PCC), NSC-89-2811-E-002-0058 (PCC), NSC-89-2215-E-002-064 (CKS).
 
 


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