Date of Award

5-24-2018

Document Type

Thesis

Degree Name

Bachelor of Science (B.S.) in Science and University Honors

Department

Science

First Advisor

Daniel J. Ballhorn

Subjects

Chlorophyll -- Effect of light exposure on, Photosynthesis -- Environmental factors, Ash (Plants), Shade-tolerant plants

DOI

10.15760/honors.583

Abstract

The purpose of this study is to determine the effect of light exposure on the total chlorophyll content, the chl a/b ratio, and the car/chl ratio and thus the shade tolerance of Fraxinus latifolia. Stems of Fraxinus latifolia seedlings were applied with aluminum foil for the 0% light exposure treatment, with shade cloth for the 50% light exposure treatment, and left uncovered for the 100% light exposure treatment. Chlorophyll from barks were extracted using 80% acetone and spectrophotometric analysis was carried out. The results revealed that in the 8-week samples, the 100% light exposure treatment showed the highest total chlorophyll content, inconsistent with the general trend that chlorophyll content increases under low light condition, but in the 4-week samples, the 50% light exposure treatment showed the highest total chlorophyll content. Consistent with shade characteristic, the chl a/b ratio of the 50% light exposure treatment was significantly lower than that of the 100% light exposure treatment in the 8-week samples. However, the reverse result was observed in the 4-week samples. Although the car/chl ratio of the 0% light exposure treatment was significantly lower than that of the 50% light exposure treatment in the 8-week samples, stems with 50% light exposure showed a significantly higher car/chl than those with 100% light exposure, inconsistent with shade characteristic. Remarkably, the results obtained challenge the general application of the shade tolerance criteria as the status of other environmental factors occurring over different time periods can influence shade tolerance.

Persistent Identifier

http://archives.pdx.edu/ds/psu/25381

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