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| Author(s): | McCree, K. J. |
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| Author Affiliation: | Dep. of Soil and Crop Sci., Texas A & M Univ., College Station, TX 77843, USA |
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| Title: | Daily photosynthesis totals calculated from solar radiation histograms |
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| Source: | Agricultural and Forest Meteorology. Vol. 33, No. 2/3, 1984, p. 239-248. |
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| Keywords: | TIC Keywords: Cynodon dactylon; Photosynthesis; Radiation
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| Geographic Terms: | Texas |
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| Abstract/Contents: | Histograms of the number of hours in the day in which the photosynthetic photon flux density (PPFD) of solar radiation was within 5 preset bands were constructed from readings made with a miniature battery-operated millivolt histogram recorder connected to a photon sensor. The number of histograms showing a bimodal distribution was much fewer than was expected from a review of the literature, even in a site shaded by trees, and this was attributed to smoothing of the data over a whole day, compared with published data which were mostly taken near noon. Bimodal distributions were found in a greenhouse under clear or partly cloudy conditions. The histograms were combined with published data for the instantaneous gross photosynthetic responses to PPFD of 2 Bermuda grass swards, one (a) of low LAI and highly non-linear response and other (b) of high LAI and more linear response. The daily photosynthesis totals of the swards were calculated by summing the products of the number of hours accumulated in each band by the photosynthetic rate in the centre of the band. Because of the non-linearity of response, the photosynthesis total in the greenhouse was 75-82% of that calculated for an open site on a clear day, while the daily photon total was only 70% of the open site value. Also, for the same daily photon total, the daily photosynthesis total of each sward on the open site was greater on a day of light clouds (moderate PPFD) than on a day of sunshine alternating with heavy clouds (bimodal histogram of PPFDs). The difference between the 2 days was greater for (a). These interactions between non-linearity of photosynthetic response and type of radiation histogram were in the expected direction. |
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| Language: | English |
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| References: | 20 |
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| ASA/CSSA/SSSA Citation (Crop Science-Like - may be incomplete):
McCree, K. J. 1984. Daily photosynthesis totals calculated from solar radiation histograms. Agric. Meteorol. 33(2/3):p. 239-248. |
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