Methodology 1821 Plant Materials

Leaves of the selected southern broadleaf tree species (Table 18.1, column 1) were collected from individual trees growing in Baton Rouge, Louisiana, USA, during two growing seasons from April to October in 2000 and in 2001. Leaf samples were collected each month from the sun portions of four unshaded individuals per species at the terminal 20 cm - 50 cm of a branch or stem, and were placed in humidified plastic bags in an insulated box for transporting to the laboratory. The experiment was a randomized complete block design with seven blocks arranged across time in a growing season. Each month was a block in which three trees per species were randomly selected for sampling. Species order was randomized. All species within a block were sampled in the shortest time possible during the first week of the month to minimize the environmental variation within the block. Samples were taken at approximately the same time each day between 8:00 a.m. -10:00 a.m. Analyses were finished within the six hours of the sample collection. A total of 980 samples (35 species x 4 samples/species/ month x 7 months) were collected in the field during the 2000 growing season to monitor the leaf optical properties, leaf UV-B absorbing compounds and chlorophyll concentration, and leaf thickness. The light penetration and spectral distribution within leaves and the anatomical research were conducted during the 2001 growing season.

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