The relationship between carbon dioxide fixation and chlorophyll a fluorescence during induction of photosynthesis in maize leaves at different temperatures and carbon dioxide concentrations
✍ Scribed by C. R. Ireland; S. P. Long; N. R. Baker
- Publisher
- Springer-Verlag
- Year
- 1984
- Tongue
- English
- Weight
- 917 KB
- Volume
- 160
- Category
- Article
- ISSN
- 0032-0935
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✦ Synopsis
The rate of CO 2 fixation (Fr and 680 nm chlorophyll fluorescence emission (F680) were measured simultaneously during induction of photosynthesis in Zea rnays L. leaves under varying experimental conditions in order to assess the validity of fluorescence as an indicator of in vivo photosynthetic carbon assimilation. Z. mays leaves showed typical 'Kautsky' fluorescence induction curves consisting of a fast rise in emission (O to P) followed by a slow quenching via a major transient (S-M) to a steady-state (T). After an initial lag, net CO 2 assimilation commenced at a point corresponding to the onset of the S-M transient on the F680 induction curve. Subsequently, Fr and F680 always arrived at a steady-state simultaneously. Decreasing the dark-adaption period increased the rate of induction of both parameters. Alteration of leaf temperature produced anti-parallel changes in induction characteristics of F~ and F680. Reducing the CO 2 level to below that required for saturation of photosynthesis also produced anti-parallel changes during induction, however, at CO 2 concentrations tenfold greater than the atmospheric level the rate of F680 quenching from P to T was appreciably reduced without a similar change in the induction of F~. Removal of CO 2 at steady-state produced only a small increase in F680 and a correspondingly small decrease in F680 occurred when CO 2 was re-introduced. The complex relationship between chlorophyll fluorescence and carbon assimilation in vivo is discussed and the applicability of fluorescence as an indicator of carbon assimilation is considered.