Journal Article

Photosynthetic traits around budbreak in pre-existing needles of Sakhalin spruce (<i>Picea glehnii</i>) seedlings grown under elevated CO<sub>2</sub> concentration assessed by chlorophyll fluorescence measurements

Mitsutoshi Kitao, Hiroyuki Tobita, Hajime Utsugi, Masabumi Komatsu, Satoshi Kitaoka, Yutaka Maruyama and Takayoshi Koike

Edited by David Tissue

in Tree Physiology

Volume 32, issue 8, pages 998-1007
Published in print August 2012 | ISSN: 0829-318X
Published online June 2012 | e-ISSN: 1758-4469 | DOI: http://dx.doi.org/10.1093/treephys/tps048
Photosynthetic traits around budbreak in pre-existing needles of Sakhalin spruce (Picea glehnii) seedlings grown under elevated CO2 concentration assessed by chlorophyll fluorescence measurements

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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 pre-existing 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.

Keywords: CO2 enrichment; leaf starch accumulation; photoinhibition; photosynthetic down-regulation

Journal Article.  5971 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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