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C4 plants use fluctuating light less efficiently than do C3 plants: a study of growth, photosynthesis and carbon isotope discrimination

Kubásek, Jiří, Urban, Otmar, Šantrůček, Jiří
Physiologia plantarum 2013 v.149 no.4 pp. 528-539
C3 plants, C4 plants, Liliopsida, Magnoliopsida, assimilation (physiology), bundle sheath cells, canopy, carbon, carbon dioxide, gas exchange, isotopes, leaves, light intensity, meteorological parameters, photosynthesis, plant growth, shade, turbulent flow, understory
Plants in the field are commonly exposed to fluctuating light intensity, caused by variable cloud cover, self‐shading of leaves in the canopy and/or leaf movement due to turbulence. In contrast to C₃plant species, only little is known about the effects of dynamic light (DL) on photosynthesis and growth in C₄plants. Two C₄and two C₃monocot and eudicot species were grown under steady light or DL conditions with equal sum of daily incident photon flux. We measured leaf gas exchange, plant growth and dry matter carbon isotope discrimination to infer CO₂bundle sheath leakiness in C₄plants. The growth of all species was reduced by DL, despite only small changes in steady‐state gas exchange characteristics, and this effect was more pronounced in C₄than C₃species due to lower assimilation at light transitions. This was partially attributed to increased bundle sheath leakiness in C₄plants under the simulated lightfleck conditions. We hypothesize that DL leads to imbalances in the coordination of C₄and C₃cycles and increasing leakiness, thereby decreasing the quantum efficiency of photosynthesis. In addition to their other constraints, the inability of C₄plants to efficiently utilize fluctuating light likely contributes to their absence in such environments as forest understoreys.