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Photosynthesis can be challenging for instructors to teach and uninteresting for students to learn, but this shouldn't be the case. An activity developed by middle-school educators and university scientists lets students see how red light emitted from sunlit plants is captured by satellites to measure global photosynthesis. In plants, most of the absorbed light energy is channeled into photosynthesis, and the tiny amount that is emitted as red fluorescence is not visible by naked eye but is detectable by satellites. When chlorophyll is removed from plants into a solution – uncoupled from the photosynthetic apparatus – chlorophyll still is green and absorbs light, but the absorbed light energy has nowhere to go, and a large red glow is visible. In a readily accessible 1-hour middle-school classroom activity, students extract chlorophyll from spinach using rubbing alcohol (91% isopropyl alcohol) and then observe the abundant red fluorescence upon illumination with a flashlight. This simple observation of the red glow (fluorescence) from chlorophyll provides a terrific anchor for teaching photosynthesis in a biological, agricultural and global ecology context, thereby inspiring students to better appreciate the fascinating world of plants.
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Leaf-level chlorophyll fluorescence and reflectance spectra of high latitude plants
Abstract Little is known about the chlorophyll fluorescence spectra for high latitude plants. A FluoWat leaf clip was used to measure leaf-level reflectance and chlorophyll fluorescence spectra of leaves of common high latitude plants to examine general spectral characteristics of these species. Fluorescence yield (Fyield) was calculated as the ratio of the emitted fluorescence divided by the absorbed radiation for the wavelengths from 400 nm up to the wavelength of the cut-off for the FluoWat low pass filter (either 650 or 700 nm). The Fyield spectra grouped into distinctly different patterns among different plant functional types. Black spruce ( Picea mariana ) Fyield spectra had little red fluorescence, which was reabsorbed in the shoot, but displayed a distinct far-red peak. Quaking aspen ( Populus tremuloides ) had both high red and far-red Fyield peaks, as did sweet coltsfoot ( Petasites frigidus ). Cotton grass ( Eriophorum spp.) had both red and far-red Fyield peaks, but these peaks were much lower than for aspen or coltsfoot. Sphagnum moss ( Sphagnum spp.) had a distinct Fyield red peak but low far-red fluorescence. Reindeer moss lichen ( Cladonia rangiferina ) had very low fluorescence levels, although when damp displayed a small red Fyield peak. These high latitude vegetation samples showed wide variations in Fyield spectral shapes. The Fyield values for the individual red or far-red peaks were poorly correlated to chlorophyll content, however the ratio of far-red to red Fyield showed a strong correlation with chlorophyll content. The spectral variability of these plants may provide information for remote sensing of vegetation type but may also confound attempts to measure high latitude vegetation biophysical characteristics and function using solar induced fluorescence (SIF).
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- Award ID(s):
- 1836861
- PAR ID:
- 10326029
- Date Published:
- Journal Name:
- Environmental Research Communications
- Volume:
- 4
- Issue:
- 3
- ISSN:
- 2515-7620
- Page Range / eLocation ID:
- 035001
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1088/2515-7620/ac5365
