Low growth temperatures modify the efficiency of light use by photosystem II for CO2 assimilation in leaves of two chilling-tolerant C4 species, Cyperus longus L. and Miscanthus x giganteus.

Two C4 plants, Miscanthus x giganteus and Cyperus longus L., were grown at suboptimal growth temperatures and the relationships between the quantum efficiencies of photosynthetic electron transport through photosystem II (PSII) (PSII operating efficiency; Fq'/Fm') and CO2 assimilation (phiCO2) in leaves were examined. When M. x giganteus was grown at 10 degrees C, the ratio of the PSII operating efficiency to phiCO2 increased relative to that found in leaves grown at 14 and 25 degrees C. Similar increases in the Fq'/Fm': phiCO2 occurred in the leaves of two C. longus ecotypes when the plants were grown at 17 degrees C, compared to 25 degrees C. These elevations of Fq'/Fm': phiCO2 at low growth temperatures were not attributable to the development of anthocyanins, as has been suggested for maize, and were indicative of the operation of an alternative sink to CO2 assimilation for photosynthetic reducing equivalents, possibly oxygen reduction via a Mehler reaction, which would act as a mechanism for protection of PSII from photoinactivation and damage. Furthermore, in M. x giganteus grown at 10 degrees C, further protection of PSII was effected by a 20-fold increase in zeaxanthin content in dark-adapted leaves, which was associated with much higher levels of non-photochemical quenching of excitation energy, compared to that observed in leaves grown at 14 and 25 degrees C. These differences may explain the long growing season and remarkable productivity of this C4 plant in cool climates, even in comparison to other C4 species such as C. longus, which occur naturally in such climates.

[1]  MICHAEL B. Jones,et al.  C4 photosynthesis in Cyperus longus L., a species occurring in temperate climates , 1981 .

[2]  P. Jolliffe,et al.  Ecological evidence concerning the adaptive significance of the C4 dicarboxylic acid pathway of photosynthesis , 2004, Oecologia.

[3]  N. Baker,et al.  Characterization of chilling effects on photosynthetic performance of maize crops during early season growth using chlorophyll fluorescence , 1995 .

[4]  R. Furbank,et al.  C4 Photosynthesis at Low Temperature. A Study Using Transgenic Plants with Reduced Amounts of Rubisco1 , 2003, Plant Physiology.

[5]  D. Idle,et al.  An integrating sphere leaf chamber , 1983 .

[6]  P. Haldimann,et al.  Photosynthetic performance and resistance to photoinhibition of Zea mays L. leaves grown at sub‐optimal temperature , 1996 .

[7]  Stephen P. Long,et al.  Cold Tolerance of C4 photosynthesis in Miscanthus × giganteus: Adaptation in Amounts and Sequence of C4 Photosynthetic Enzymes1 , 2003, Plant Physiology.

[8]  Fabrizio Pietrini,et al.  Leaf anthocyanin content changes in Zea mays L. grown at low temperature: Significance for the relationship between the quantum yield of PS II and the apparent quantum yield of CO2 assimilation , 1998, Photosynthesis Research.

[9]  R. Sage,et al.  Low‐temperature photosynthetic performance of a C4 grass and a co‐occurring C3 grass native to high latitudes , 2004 .

[10]  Stephen P. Long,et al.  Can perennial C4 grasses attain high efficiencies of radiant energy conversion in cool climates , 1995 .

[11]  Stephen P. Long,et al.  Leaf photosynthesis in the C4-grass Miscanthus x giganteus, growing in the cool temperate climate of southern England , 1996 .

[12]  F. Loreto,et al.  The effect of growth at low temperature on photosynthetic characteristics and mechanisms of photoprotection of maize leaves , 1995 .

[13]  L. Tieszen,et al.  The distribution of C3 and C4 grasses and carbon isotope discrimination along an altitudinal and moisture gradient in Kenya , 2004, Oecologia.

[14]  K. Asada,et al.  THE WATER-WATER CYCLE IN CHLOROPLASTS: Scavenging of Active Oxygens and Dissipation of Excess Photons. , 1999, Annual review of plant physiology and plant molecular biology.

[15]  G. Nie,et al.  Modifications to Thylakoid Composition during Development of Maize Leaves at Low Growth Temperatures. , 1991, Plant physiology.

[16]  Thomas B. Voigt,et al.  A quantitative review comparing the yields of two candidate C4 perennial biomass crops in relation to nitrogen, temperature and water , 2004 .

[17]  Baker,et al.  Relationship between CO2 Assimilation, Photosynthetic Electron Transport, and Active O2 Metabolism in Leaves of Maize in the Field during Periods of Low Temperature , 1998, Plant physiology.

[18]  D. Ort,et al.  Factors Associated with Depression of Photosynthetic Quantum Efficiency in Maize at Low Growth Temperature , 1995, Plant physiology.

[19]  R. Sage.  1 – Why C4 Photosynthesis? , 1999 .

[20]  D. R. Hoagland,et al.  Crop production in artificial culture solutions and in soils with special reference to factors influencing yields and absorption of inorganic nutrients. , 1940 .

[21]  J. Briantais,et al.  The relationship between the quantum yield of photosynthetic electron transport and quenching of chlorophyll fluorescence , 1989 .

[22]  N. Baker,et al.  Response of the photosynthetic apparatus in maize leaves grown at low temperature on transfer to normal growth temperature , 1995 .

[23]  C. Foyer,et al.  Effect of Chilling on Carbon Assimilation, Enzyme Activation, and Photosynthetic Electron Transport in the Absence of Photoinhibition in Maize Leaves , 1997, Plant physiology.

[24]  R. Hamilton,et al.  Antioxidant enzyme responses to chilling stress in differentially sensitive inbred maize lines , 1997 .

[25]  Eva Rosenqvist,et al.  Applications of chlorophyll fluorescence can improve crop production strategies: an examination of future possibilities. , 2004, Journal of experimental botany.

[26]  Stephen P. Long,et al.  Potential mechanisms of low-temperature tolerance of C4 photosynthesis in Miscanthus × giganteus: an in vivo analysis , 2004, Planta.

[27]  Stephen P. Long,et al.  Measurement of leaf and canopy photosynthetic CO2 exchange in the field , 1996 .

[28]  D. Ort,et al.  A photoprotective role for O(2) as an alternative electron sink in photosynthesis? , 2002, Current opinion in plant biology.

[29]  D. Ort,et al.  The involvement of the photoinhibition of photosystem II and impaired membrane energization in the reduced quantum yield of carbon assimilation in chilled maize , 1990, Planta.

[30]  The Seasonal Pattern of Growth and Production of a Temperate C4 Species, Cyperus longus , 1986 .

[31]  S. Long,et al.  The effects of development at sub‐optimal growth temperatures on photosynthetic capacity and susceptibility to chilling‐dependent photoinhibition in Zea mays , 1992 .

[32]  T Lawson,et al.  High resolution imaging of photosynthetic activities of tissues, cells and chloroplasts in leaves. , 2001, Journal of experimental botany.

[33]  P. Rundel.  The ecological distribution of C4 and C3 grasses in the Hawaiian Islands , 2004, Oecologia.

[34]  S. Long.  7 – Environmental Responses , 1999 .

[35]  S. Long,et al.  Chilling stress and oxygen metabolizing enzymes in Zea mays and Zea diploperennis , 1991 .

[36]  J. A. Teeri,et al.  The distribution of C4 species of the Cyperaceae in North America in relation to climate , 1980, Oecologia.