Publication Date:
2012-08-09
Description:
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 ( 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 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.
Print ISSN:
0829-318X
Electronic ISSN:
1758-4469
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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