Abstract
The effects of CO2 elevation on sensitivity of photosynthetic electron transport system of wheat in relation to low temperature stress are unclear. The performance of photosynthetic electron transport system and antioxidant system in chloroplasts was investigated in a temperature sensitive wheat cultivar Lianmai6 grown under the combination of low temperature (2 days at 2/−1°C in the day/night) and CO2 elevation (800 μmol l−1). It was found that CO2 elevation increased the efficiency of photosynthetic electron transport in wheat exposed to low temperature stress, which was related to the enhanced maximum quantum yield for electron transport beyond QA and the increased quantum yield for reduction of end electron acceptors at the PSI acceptor side in plants under elevated CO2. Also, under low temperature, the activities of ATPases, ascorbate peroxidase, and catalase in chloroplasts were enhanced in wheat under elevated CO2. It suggested that the cold tolerance of photosynthetic electron transport system is enhanced by CO2 elevation.
Highlights
Low temperature stress is one of the most critical environmental stimuli affecting crop plant growth and grain yield
Significant changes in WOI were found between normal temperature treatments and low temperature treatments, which were due to the reductions between PSI and reduced NADP+
Photosynthesis is a highly sensitive process to temperature fluctuations, since it is important to keep the balance between light energy absorbed by photosystems and energy consumed by metabolic sinks (Krcek et al, 2008; Brestic et al, 2012; Zivcak et al, 2013)
Summary
Low temperature stress is one of the most critical environmental stimuli affecting crop plant growth and grain yield. Wheat is tolerant to some lower temperatures during the vegetative stage, but it is very sensitive to low temperature stress during the reproductive stage (Whaley et al, 2004). Studies have shown that the low temperature during vegetative stage could cause yield loss up to 10% (Frederiks et al, 2012). Low temperature stress rapidly affects the photosynthesis by direct and indirect effects (Thakur and Nayyar, 2013). Low temperature stress increases membrane viscosity and restricts the diffusion of plastoquinone, to inhibit the thylakoid electron transport (Thakur and Nayyar, 2013). Light energy trapping by the antenna of PSI and PSII and its contribution to drive charge-separation in the reaction centers (RCs) is disturbed by low temperature, due to the chlorophyll antenna complexes trap more energy than that can be processed biochemically (Ensminger et al, 2006)
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