Abstract
AbstractMiscanthus, a perennial grass with C4 photosynthesis, is regarded as a promising energy crop due to its high biomass productivity. Compared with other C4 species, most miscanthus genotypes have high cold tolerances at 14 °C. However, in temperate climates, temperatures below 14 °C are common and our aim was to elucidate cold tolerances of different miscanthus genotypes and compare with a C3 perennial grass – festulolium. Eleven genotypes of M. sacchariflorus, M. sinensis, M. tinctorius, M. × giganteus as well as festulolium were grown under warm (24/20 °C, day/night) and three under cold (14/10 °C, 10/8 °C and 6/4 °C) conditions in a controlled environment. Measurements of photosynthetic light response curves, operating quantum yield of photosystem II (ΦPSII), net photosynthetic rate at a PAR of 1000 μmol m−2 s−1 (A1000) and dark‐adapted chlorophyll fluorescence (Fv/Fm) were made at each temperature. In addition, temperature response curves were measured after the plants had been grown at 6/4 °C. The results showed that two tetraploid M. sacchariflorus and the standard triploid M. × giganteus cv. Hornum retained a significantly higher photosynthetic capacity than other miscanthus genotypes at each temperature level and still maintained photosynthesis after growing for a longer period at 6/4 °C. Only two of five measured miscanthus genotypes increased photosynthesis immediately after the temperature was raised again. The photosynthetic capacity of festulolium was significantly higher at 10/8 °C and 6/4 °C than of miscanthus genotypes. This indicates that festulolium may be more productive than the currently investigated miscanthus genotypes in cool, maritime climates. Within miscanthus, only one M. sacchariflorus genotype exhibited the same photosynthetic capacity as Hornum at both cold conditions and when the temperature was raised again. Therefore, this genotype could be useful for breeding new varieties with an improved cold tolerance vis‐a‐vis Hornum, and be valuable in broadening the genetic diversity of miscanthus for more widespread cultivation in temperate climates.
Highlights
Bioenergy crops are a potential replacement source for fossil fuels
The aim of this work was to examine the cold tolerance of different C4 miscanthus genotypes through studies of net photosynthetic rate (An), PSII operating efficiency (ΦPSII), maximum quantum yield (Fv/Fm) and light response under various growth temperatures down to 6 °C
One C3 species, the grass festulolium, which is a hybrid of Lolium multiflorum and Festuca arundinacea (Cernoch et al, 2004; Zwierzykowski, 2004; Kopecky et al, 2008), and 11 genotypes of the C4 genus Miscanthus representing four different species (M. sinensis, M. sacchariflorus, M. tinctorius and M. 9 giganteus) were selected for climate chamber experiments (Table 1)
Summary
Bioenergy crops are a potential replacement source for fossil fuels. To make this option economically competitive and sustainable, major research issues include identifying crops that have a maximum biomass production and at the same time a minimum environmental impact when grown on marginal land under various abiotic stress conditions (Gabrielle et al, 2014). An important basic physiological trait influencing cold sensitivity and productivity in crops is the difference between C3 and C4 photosynthesis. Photosynthetic activity in C3 and C4 species differs under cold conditions. For C3 plants, the Rubisco capacity has been regarded as the predominant constraint to photosynthesis under a wide range of temperatures at CO2 levels below the current ambient concentration (Farquhar et al, 1980; Sage & Kubien, 2007). The C4 photosynthesis is usually advantageous at low CO2 concentrations and
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