Seasonal response of photosynthetic electron transport and energy dissipation in the eighth year of exposure to elevated atmospheric CO2 (FACE) in Pinus taeda (loblolly pine)

Abstract

To determine the effect of growth under elevated CO(2) partial pressures (pCO(2)) on photosynthetic electron transport and photoprotective energy dissipation, we examined light-saturated net photosynthetic CO(2) assimilation (A(sat)), the capacity for photosynthetic O(2) evolution, chlorophyll fluorescence emission and the pigment composition of upper-canopy loblolly pine needles in the eighth year of exposure to elevated pCO(2) (20 Pa above ambient) at the free-air CO(2) enrichment facility in the Duke Forest. During the summer growing season, A(sat) was 50% higher in current-year needles and 24% higher in year-old needles in elevated pCO(2) in comparison with needles of the same age cohort in ambient pCO(2). Thus, photosynthetic down-regulation at elevated pCO(2) was observed in the summer in year-old needles. In the winter, A(sat) was not significantly affected by growth pCO(2). Reductions in A(sat), the capacity for photosynthetic O(2) evolution and photosystem II (PSII) efficiency in the light-acclimated and fully-oxidized states were observed in the winter when compared to summer. Growth at elevated pCO(2) had no significant effect on the capacity for photosynthetic O(2) evolution, PSII efficiencies in the light-acclimated and fully-oxidized states, chlorophyll content or the size and conversion state of the xanthophyll cycle, regardless of season or needle age cohort. Therefore, we observed no evidence that photosynthetic electron transport or photoprotective energy dissipation responded to compensate for the effects of elevated pCO(2) on Calvin cycle activity.

Maintenance of C sinks sustains enhanced C assimilation during long-term exposure to elevated [CO2] in Mojave Desert shrubs

“…Pigments are functional components of the photosynthetic machinery, providing information about biochemical investment and stress in the photosystems. The evergreen Larrea did not adjust pigment allocation in response to elevated [CO 2 ], as was documented for the evergreen tree loblolly pine after 8 years in FACE (Logan et al 2009). In the deciduous Ambrosia, plants growing under elevated [CO 2 ] reduced chlorophyll a and b throughout the growing season, suggesting that less light-absorbing and -processing capabilities may be part of the reason why A sat under elevated [CO 2 ] was not as high as expected for that species.…”

Rising temperature may negate the stimulatory effect of rising CO2 on growth and physiology of Wollemi pine (Wollemia nobilis)

“…We increased the measurement temperature in four steps, from 10 to 40 C, by circulating water, at the target temperature, around the electrode chamber. The air in the chamber was gently replaced with expired air before measurements to achieve CO 2 saturation, as in Li et al (2000), Wheelwright and Logan (2004) and Logan et al (2009).…”

Elevated CO2 affects photosynthetic responses in canopy pine and subcanopy deciduous trees over 10 years: a synthesis from Duke FACE

“…A number of relevant studies could not be included in the analysis (Myers et al, 1999;Singsaas et al, 2004), as raw data were inaccessible or not provided. Several other studies (Ellsworth, 1999;Springer et al, 2005;Springer & Thomas, 2007;Logan et al, 2009) that measured leaf photosynthesis at growth C a and/or light levels were not used, as additional physiological parameters could not be extracted, and therefore the data were outside the scope of this dataset.…”