Rapid response of nonstructural carbohydrate allocation and photosynthesis to short photoperiod, low temperature, or elevated CO2 in Pinus strobus

Authors: Chang, Christine; UNDA, FARIDE - University Of British Columbia; MANSFIELD, SHAWN - University Of British Columbia; ENSMINGER, INGO - University Of Toronto

Submitted to: Physiologia Plantarum
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/16/2023
Publication Date: 11/28/2023
Citation: Chang, C.Y., Unda, F., Mansfield, S.D., Ensminger, I. 2023. Rapid response of nonstructural carbohydrate allocation and photosynthesis to short photoperiod, low temperature, or elevated CO2 in Pinus strobus. Physiologia Plantarum. 175(6). Article e14095. https://doi.org/10.1111/ppl.14095.
DOI: https://doi.org/10.1111/ppl.14095

Interpretive Summary: During the transition from long to short days, plants decrease daily carbon uptake, resulting in a temporary imbalance between carbon uptake and storage which is restored by adjusting carbohydrate metabolism and photosynthesis. We assessed how these adjustments are affected by low temperature, which inhibits both photosynthesis and carbohydrate metabolism, and elevated atmospheric CO2, which enhances photosynthesis and increases carbon supply. We found that P. strobus can rapidly adjust leaf carbohydrate levels to maintain carbon balance under warm temperature and short photoperiod at either ambient or elevated CO2. In contrast, the combination of low temperature and short photoperiod inhibits carbohydrate metabolism and photosynthesis and requires rapid induction of photoprotective mechanisms to dissipate excess energy.

Technical Abstract: During the transition from long to short photoperiod, plants decrease daily carbon uptake, resulting in a transient source-sink imbalance restored through adjusting carbohydrate metabolism and photosynthesis. We assessed how these adjustments are altered by low temperature, which inhibits both photosynthesis and carbohydrate metabolism, and elevated atmospheric CO2, which enhances photosynthesis and increases carbohydrate supply, by measuring leaf nonstructural carbohydrates and photosynthesis in Pinus strobus seedlings. Seedlings were initially acclimated to 14 h photoperiod, 22°C/15°C (day/night), and either 400ppm or 800ppm CO2. All seedlings were then shifted to short day (8 h photoperiod) combined with either low temperature with ambient CO2 (12°C/5°C, 400ppm), high temperature with ambient CO2 (22°C/15°C, 400ppm), or high temperature with elevated CO2 (22°C/15°C, 800ppm). After three days of exposure to short photoperiod, seedlings exhibited increased nighttime depletion of starch. Short photoperiod alone did not affect photosynthesis. Short photoperiod and low temperature induced accumulation of hexose and downregulation of photosynthetic gas exchange within 24 hours. Downregulation of light reactions and enhanced photoprotection developed after several days of low temperature exposure. Under elevated CO2, carbon uptake exceeded sink capacity under long photoperiod, but carbon demand was restored within 24 hours of shift to short photoperiod. Our findings suggest that P. strobus can rapidly adjust leaf carbohydrate pools to maintain carbon balance under warm temperature and short photoperiod at either ambient or elevated CO2. In contrast, the combination of low temperature and short photoperiod inhibits carbohydrate metabolism and photosynthesis and requires rapid induction of photoprotection to dissipate increased excess energy.