Photosynthetic traits around budbreak in pre-existing needles of Sakhalin spruce (Picea glehnii) seedlings grown under elevated CO2 concentration assessed by chlorophyll fluorescence measurements.
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.
Hokkaido Research Center, Forestry and Forest Products Research Institute, Sapporo 062-8516, Japan. kitao@ffpri.affrc.go.jp
Mitsutoshi
M
Kitao
Hiroyuki
H
Tobita
Hajime
H
Utsugi
Masabumi
M
Komatsu
Satoshi
S
Kitaoka
Yutaka
Y
Maruyama
Takayoshi
T
Koike
D002245:Carbon Dioxide / Q000378:metabolism / Q000494:pharmacology*; D002734:Chlorophyll / Q000502:physiology; D015536:Down-Regulation; D005453:Fluorescence; D008027:Light; D018519:Meristem / Q000187:drug effects* / Q000254:growth & development; D010788:Photosynthesis / Q000187:drug effects* / Q000502:physiology; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D028222:Picea / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology; D018515:Plant Leaves / Q000187:drug effects* / Q000378:metabolism; D012621:Seasons; D036226:Seedlings / Q000254:growth & development / Q000502:physiology; D013213:Starch / Q000378:metabolism*; D014197:Trees / Q000187:drug effects / Q000254:growth & development / Q000502:physiology
D045332:Photosystem II Protein Complex; D002734:Chlorophyll; D002245:Carbon Dioxide; D013213:Starch