Vertical, horizontal and azimuthal variations in leaf photosynthetic characteristics within a Fagus crenata crown in relation to light acclimation
| Autor: | Atsuhiro Iio, Shuri Kato, Hisakazu Fukasawa, Yoshitaka Kakubari, Yachiho Nose |
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| Rok vydání: | 2005 |
| Předmět: |
biology
Physiology Nitrogen Fagus crenata Acclimatization Ribulose-Bisphosphate Carboxylase RuBisCO Crown (botany) chemistry.chemical_element Plant Science Carbon Dioxide biology.organism_classification Photosynthesis Photosynthetic capacity Carbon Plant Leaves chemistry Dry weight Botany biology.protein Fagus Sunlight |
| Zdroj: | Tree physiology. 25(5) |
| ISSN: | 0829-318X |
| Popis: | An understanding of spatial variations in gas exchange parameters in relation to the light environment is crucial for modeling canopy photosynthesis. We measured vertical, horizontal and azimuthal (north and south) variations in photosynthetic capacity (i.e., the maximum rate of carboxylation: V cmax ), nitrogen content (N), leaf mass per area (LMA) and chlorophyll content (Chl) in relation to relative photosynthetic photon flux (rPPF) within a Fagus crenata Blume crown. The horizontal gradient of rPPF was similar in magnitude to the vertical gradient of rPPF from the upper to the lower crown. The rPPF in the north quadrant of the crown was slightly lower than in the south quadrant. Nitrogen content per area (N area ), LMA and V cmax were strictly proportional to rPPF, irrespective of the vertical direction, horizontal direction and crown azimuth, whereas nitrogen content per dry mass, Chl per area and photosynthetic capacity per dry mass (V m ) were fairly constant.Statistical analyses separating vertical trends from horizontal and azimuthal trends indicated that, although horizontal and vertical light acclimation of leaf properties were similar, there were two significant azimuthal variations: (1) V cmax was lower in north-facing leaves than in south-facing leaves for a given N area , indicating low photosynthetic nitrogen-use efficiency (PNUE) of north-facing leaves; and (2) V cmax was lower in north-facing leaves than in south-facing leaves for a given LMA, indicating low V m of the north-facing leaves. With respect to the low PNUE of the north-facing leaves, there were no significant azimuthal variations in leaf CO 2 conductance from the stomata to the carboxylation site. Biochemical analysis indicated that azimuthal variations in nitrogen allocation to ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and in nitrogen allocation between carboxylation (Rubisco and other Calvin cycle enzymes) and light harvesting machinery (Chl pigment-protein complexes) were not the main contributor to the difference in PNUE between north- and south-facing leaves. Lower specific activity of Rubisco may be responsible for the low PNUE of the north-facing leaves. Anatomical analysis indicated that not only high leaf density, which is compatible with a greater fraction of non-photosynthetic tissue, but also thick photosynthetic tissue contributed to the low V m in the north-facing leaves. These azimuthal variations may need to be considered when modeling canopy photosynthesis based on the N area -V cmax or LMA-V cmax relationship. |
| Databáze: | OpenAIRE |
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