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- Title
Photosynthetic traits around budbreak in pre-existing needles of Sakhalin spruce (Picea glehnii) seedlings grown under elevated CO<sub>2</sub> concentration assessed by chlorophyll fluorescence measurements.
- Authors
Mitsutoshi Kitao; Hiroyuki Tobita; Hajime Utsugi; Masabumi Komatsu; Satoshi Kitaoka; Yutaka Maruyama; Takayoshi Koike
- Abstract
To assess the effects of elevated CO2 concentration ([CO2]) on the photosynthetic properties around spring budbreak, we monitored the total leaf sugar and starch content, and chlorophyll fluorescence in 1-year-old needles of Sakhalin spruce (Picea glehnii Masters) seedlings in relation to the timing of budbreak, grown in a phytotron under natural daylight at two [CO2] levels (ambient: 360 µmol mol-1 and elevated: 720 μmol mol-1). Budbreak was accelerated by elevated [CO2] accompanied with earlier temporal declines in the quantum yield of PSII electron transport (ΦPSII) and photochemical quenching (qL). Plants grown under elevated [CO2] showed pre-budbreak leaf starch content twice as high with no significant difference in ΦPSII from ambient-CO2-grown plants when compared at the same measurement [CO2], i.e., 360 or 720 μmol mol-1, suggesting that the enhanced pre-budbreak leaf starch accumulation might not cause down-regulation of photosynthesis in preexisting needles under elevated [CO2]. Conversely, lower excitation pressure adjusted for the efficiency of PSII photochemistry ((1 - qP) Fv'/Fm') was observed in plants grown under elevated [CO2] around budbreak when compared at their growth [CO2] (i.e., comparing (1 - qP) Fv'/Fm' measured at 720 μmol mol-1 in elevated-CO2-grown plants with that at 360 μmol mol-1 in ambient-CO2-grown plants), which suggests lower rate of photoinactivation of PSII in the elevated-CO2-grown plants around spring budbreak. The degree of photoinhibition, as indicated by the overnight-dark-adapted Fv/Fm, however, showed no difference between CO2 treatments, thereby suggesting that photoprotection during the daytime or the repair of PSII at night was sufficient to alleviate differences in the rate of photoinactivation.
- Subjects
PHOTOSYNTHESIS; NEEDLES (Botany); SPRUCE; CARBON dioxide; CHLOROPHYLL spectra; COMPOSITION of leaves; PHYTOTRON; ELECTRON transport; PLANTS
- Publication
Tree Physiology, 2012, Vol 32, Issue 8, p998
- ISSN
0829-318X
- Publication type
Article
- DOI
10.1093/treephys/tps048