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Elevated CO2 increases photosynthesis in fluctuating irradiance regardless of photosynthetic induction state.

ABSTRACT: Leaves are often exposed to fluctuating irradiance, which limits assimilation. Elevated CO2 enhances dynamic photosynthesis (i.e. photosynthesis in fluctuating irradiance) beyond its effects on steady-state photosynthesis rates. Studying the role of CO2 in dynamic photosynthesis is important for understanding plant responses to changing atmospheric CO2 partial pressures. The rise of photosynthesis after a step-wise increase to 1000 ?mol m-2 s-1, the loss of photosynthetic induction after irradiance decreases, and rates of photosynthesis during sinusoidal changes in irradiance were studied in tomato (Solanum lycopersicum L.) leaves, using three CO2 partial pressures (200, 400, and 800 µbar). Initial irradiance was set to 0, 50, 100, and 200 ?mol m-2 s-1 to vary the initial induction state. Most responses at 200 µbar were not different from those at 400 µbar. In contrast, CO2 at 800 µbar increased the relative carbon gain by 12% after an increase in irradiance, decreased the loss of photosynthetic induction by 14%, and increased dynamic photosynthesis during sine waves by 17%, compared with 400 µbar. These effects were additional to steady-state effects of elevated CO2 on photosynthesis. The enhancement of dynamic photosynthesis rates by elevated CO2 may therefore additionally increase photosynthesis in a future, CO2-enriched climate.

SUBMITTER: Kaiser E

PROVIDER: S-EPMC5853276 | biostudies-literature | 2017 Nov

REPOSITORIES: biostudies-literature

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Elevated CO2 increases photosynthesis in fluctuating irradiance regardless of photosynthetic induction state.

Kaiser Elias E Zhou Dianfan D Heuvelink Ep E Harbinson Jeremy J Morales Alejandro A Marcelis Leo F M LFM

Journal of experimental botany 20171101 20

Leaves are often exposed to fluctuating irradiance, which limits assimilation. Elevated CO2 enhances dynamic photosynthesis (i.e. photosynthesis in fluctuating irradiance) beyond its effects on steady-state photosynthesis rates. Studying the role of CO2 in dynamic photosynthesis is important for understanding plant responses to changing atmospheric CO2 partial pressures. The rise of photosynthesis after a step-wise increase to 1000 μmol m-2 s-1, the loss of photosynthetic induction after irradia ...[more]

PMID: 29045757

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Project description:We were awarded a BBSRC grant about a year ago to undertake some affymetrix gene chip profiling of light and CO2 systemic signalling in Arabidopsis. The design of the proposed experiment is given below and the appropriate funding has been provided by the BBSRC. The aim of the project is to identify the temporal profile of those genes that respond to light and CO2 systemic signals in developing leaves. Moreover, as thes two signals have opposing effects on leaf development to ascertain whether they involve similar or parallel signalling pathways. The experiment is to examine the effect of exposing mature leaves to high CO2 or low light or both on the gene expression profile of developing leaves. We already have data for maize that changes in gene expression profile occur within 4h and that there are a variety of temporal responses that differ between individual gene transcripts. We have also demonstrated that Arabidopsis leaf development is altered by these systemmic signals and that lesions in the jasmonate and ethylene signalling pathways block these responses. Our experimental design is shown below: We have 4 treatments and 7 timepoints. (0, 2, 4, 12, 24, 48, 96 h) We would sample from 5 individual plants that would be pooled for each RNA preparation. This would require 28 chips and this would include extra replication of the 0 time-point control (deemed by many as nessary). Experimental details: All plants were germinated for 7 days under the following conditions: Humax multi-purpose compost, ambient carbon dioxide (370 ppm) and ambient light (250 µmol/m/s), constant temperature of 20°C and a 10 h photoperiod (8 am until 6 pm). After a week the the seedlings were potted up into 104-cell plug trays for a further 2 weeks and then potted up into 10 cm pots and the bottom part of the signalling cuvette system attached (see Lake et al., Nature 10th May 2001 Vol. 411, pp 154). Twenty four, 4 week old plants, then had the top part of the signalling system attached, trapping leaf insertions 5-13. Humidified, ambient air was passed through them at 500 mls/min via an oil-free air compressor. The three target leaves (19-21) were then marked with non-toxic, acrylic paint. After a 24 h period (the plants were sealed into the cuvettes from 10 am until 10am) of adjustment, the experiment was started by harvesting the target leaves from 4 plants and immediately freezing the tissue in liquid nitrogen to give the 0 h sample before RNA extraction. The remaining 20 plants were divided into 4 groups of five and given one of the following treatments: Ambient carbon dioxide/ambient light (Control) (A) Elevated carbon dioxide (750 ppm)/ambient light (E) Ambient carbon dioxide/low light (50 µmol/m/s) (AS) Elevated carbon dioxide/low light (ES) - For the Elevated CO2, elevated CO2 was pumped in using a CT room next door set to same temperature but with a CO2 cylinder inside and the same pump as used in the ambient room to supply the elevated CO2 laden, humidified air into the signalling room using rubber tubing. - Shade treatment consisted of neutral density filter (Cat. 210 0.6ND, Lee Filters) that had a hole cut in the middle to allow the middle developing leaves to grow through. A timecourse of 2, 4, 12, 24, 48 and 96 h were carried out each using a batch of 24 plants. This whole process was repeated with another batch of 24 plants at the same developmental stage to give a 2, 4, 12, 24, 48 and 96 hour sample from each of the four treatments. The whole timecourse was then repeated 4 times. For the mature leaves: We had 8 chips left over so we devised this little experiment to assess the gene changes that were occurring in the enclosed, treated, mature leaves that were signalling the environment to the young developing leaves. Experimenter name = Simon Coupe Experimenter phone = 0114 222 4115 Experimenter fax = 0114 222 0002 Experimenter institute = University of Sheffield Experimenter address = Animal and Plant Sciences Experimenter address = University of Sheffield Experimenter address = Western Bank Experimenter address = Sheffield Experimenter zip/postal_code = S10 2TN Experimenter country = UK Keywords: development_or_differentiation_design; growth_condition_design

Dataset Information

Elevated CO2 increases photosynthesis in fluctuating irradiance regardless of photosynthetic induction state.

Publications

Elevated CO2 increases photosynthesis in fluctuating irradiance regardless of photosynthetic induction state.

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