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Proceedings Paper

Penetration of UV-A, UV-B, blue, and red light into leaf tissues of pecan measured by a fiber optic microprobe system
Author(s): Yadong Qi; Shuju Bai; Thomas C Vogelmann; Gordon M. Heisler
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Paper Abstract

The depth of light penetration from the adaxial surfaces of the mature leaves of pecan (Carya illinoensis) was measured using a fiber optic microprobe system at four wavelengths: UV-B (310nm), UV-A (360 nm), blue light (430nm), and red light (680nm). The average thickness of the leaf adaxial epidermal layer was 15um and the total leaf thickness was 219um. The patterns of the light attenuation by the leaf tissues exhibited strong wavelength dependence. The leaf adaxial epidermal layer was chiefly responsible for absorbing the UV-A UV-B radiation. About 98% of 310 nm light was steeply attenuated within the first 5 um of the adaxial epidermis; thus, very little UV-B radiation was transmitted to the mesophyll tissues where contain photosynthetically sensitive sites. The adaxial epidermis also attenuated 96% of the UV-A radiation. In contrast, the blue and red light penetrated much deeper and was gradually attenutated by the leaves. The mesophyll tissues attenuated 17% of the blue light and 42% of the red light, which were available for photosynthesis use. Since the epidermal layer absorbed nearly all UV-B light, it acted as an effective filter screening out the harmful radiation and protecting photosynthetically sensitive tissues from the UV-B damage. Therefore, the epidermal function of the UV-B screening effectiveness can be regarded as one of the UV-B protection mechanisms in pecan.

Paper Details

Date Published: 4 November 2003
PDF: 10 pages
Proc. SPIE 5156, Ultraviolet Ground- and Space-based Measurements, Models, and Effects III, (4 November 2003); doi: 10.1117/12.506629
Show Author Affiliations
Yadong Qi, Southern Univ. and A&M College (United States)
Shuju Bai, Southern Univ. and A&M College (United States)
Thomas C Vogelmann, Univ. of Vermont (United States)
Gordon M. Heisler, U.S. Dept. of Agriculture Forest Service (United States)

Published in SPIE Proceedings Vol. 5156:
Ultraviolet Ground- and Space-based Measurements, Models, and Effects III
James R. Slusser; Jay R. Herman; Wei Gao, Editor(s)

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