Photosynthetic traits around budbreak in pre-existing needles of Sakhalin spruce (Picea glehnii) seedlings grown under elevated CO2 concentration assessed by chlorophyll fluorescence measurements

• Published in: Tree Physiology
• Main Authors: Kitao, Mitsutoshi, Tobita, Hiroyuki, Utsugi, Hajime, Komatsu, Masabumi, Kitaoka, Satoshi, Maruyama, Yutaka, Koike, Takayoshi
• Format: Text
• Language: English
• Published: Oxford University Press 2012
• Subjects: Research Paper; Sakhalin
• Online Access: http://treephys.oxfordjournals.org/cgi/content/short/tps048v1; https://doi.org/10.1093/treephys/tps048

To assess the effects of elevated CO 2 concentration ([CO 2 ]) 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 [CO 2 ] levels (ambient: 360 μmol mol−1 and elevated: 720 μmol mol−1). Budbreak was accelerated by elevated [CO 2 ] accompanied with earlier temporal declines in the quantum yield of PSII electron transport (Φ PSII ) and photochemical quenching ( q L ). Plants grown under elevated [CO 2 ] showed pre-budbreak leaf starch content twice as high with no significant difference in Φ PSII from ambient-CO 2 -grown plants when compared at the same measurement [CO 2 ], 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 [CO 2 ]. Conversely, lower excitation pressure adjusted for the efficiency of PSII photochemistry ((1 − q P ) F v ′/ F m ′) was observed in plants grown under elevated [CO 2 ] around budbreak when compared at their growth [CO 2 ] (i.e., comparing (1 − q P ) F v ′/ F m ′ measured at 720 μmol mol−1 in elevated-CO 2 -grown plants with that at 360 μmol mol−1 in ambient-CO 2 -grown plants), which suggests lower rate of photoinactivation of PSII in the elevated-CO 2 -grown plants around spring budbreak. The degree of photoinhibition, as indicated by the overnight-dark-adapted F v / F m , however, showed no difference between CO 2 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.