Leaf photosynthesis and cold tolerance in Miscanthus genotypes

1. Leaf photosynthesis and cold tolerance in Miscanthusgenotypes Kirsten Kørup1, Xiurong Jiao1,5, Helle Baadsgaard1, Thomas Prade2, Stanisław Jeżowski3, Szymon Ornatowski3, Robert Borek4, Mathias N. Andersen1, Poul Erik Lærke1 and Uffe Jørgensen1 1 Aarhus University, Department of Agroecology, BlichersAllé 20, DK-8830 Tjele, Denmark; 2 Swedish University of Agricultural Sciences, Department of Agrosystems, SE-230 53 Alnarp, Sweden; 3 Institute of Plant Genetics of the Polish Academy of Sciences, Strzeszyńska 34, 60-479 Poznań, Poland; 4 Institute of Soil Science and Plant Cultivation - State Research Institute, Czartoryskich 8, 24-100 Puławy, Poland; 5Xiurong.Jiao@agrsci.dk • Results • All the genotypes measured showed a decline in CO2-assimilation rate at leaf level when the environmental temperature decreased from 25ºC (Fig. 3) to 14ºC (Fig. 4). • Asatmeasuredonclone no. KK55 showed the smallest decline (40%) after transfer from 25 to 14℃ for sevendays (Fig. 5). A large decline of 61 and 68% occurred in clone no. EMI3 and KK39, respectively. • Under both conditions, the M. tinctoriusspecies, clone no. KK24, showed the lowest level of photosynthesis (Fig. 3 and 4). • The M. sacchariflorusspecies or crossings, clone no. KK55, EMI4, M114 and EMI3, showed the highest photosynthetic capacity at the leaf level measured under cold conditions. Introduction Miscanthusspecies, which are C4 perennial grasses, are considered to be good candidates for a potential high production of biomass. They are of particular interest to meet the bioenergy goals using less land (Somerville et al., 2010). However, the productivity is challenged by inhibition of the photosynthetic capacity at temperatures below 15°C (Purdy et al., 2013). In unbredMiscanthus, biomass production of up to 20 Mg/ha dry matter has been recorded in Denmark (Jørgensen and Sander, 1997). Identification of genetic differences in cold tolerance may be useful to breed new genotypes with high photosynthetic capacity in a cool temperate climate, which might increase the yield further. Objective To identify Miscanthusgenotypes with high photosynthetic activity and productivity under cool growth conditions Materials and methods Figure 1 Miscanthus in the field (left) and greenhouse (right) Figure 3 Net photosynthetic rate versus photosyntheticactive radiation (PAR) of sixMiscanthusgenotypes grown under warmconditions (25℃). Figure 2 Leaf growthmeasurements in the field (left) and gas exchangemeasurements in the climatechamber (right) Plant material (Fig 1): A total of 15 genotypes ofM. sacchariflorus, M. sinensis, M. tinctorius, M.×giganteusorM.sinensis× M. sacchariflorus. Leaf growth measurements (Fig. 2, left) Shoot length was measured every second or third day. Daily growth was calculated for cold and warm periods. Gas exchange measurements, response of leaf photosynthesis to light measured by CIRAS-2 (PP Systems, Amesbury, MA, US) (Fig. 2, right) Climate chamber conditions : Day/night period: 14/10 hour; Temp. (d/n): 24/20ºC (warm), 14/10ºC (cold). Relative humidity (d/n): 85/85% (warm), 75/85% (cold); PAR: 670 µmol m-2 s-1; CO2-conc.: 400 ppm Cuvette conditions: Leaf temp.:24/14ºC (warm/cold); VPD:1.2/1.0 kPa(warm/cold); CO2-conc.: 400 ppm PAR: decreased from 2000 to 0 μmol m-2 s-1 in fourteen steps Figure 4 Net photosynthetic rate versus photosyntheticactive radiation (PAR) of sixMiscanthusgenotypes grown under coldconditions (14℃). • Results • Clone no. KK39 showed the highest rate in dailyleafgrowthduring the cool period, while EMI3 showed the highestgrowth rate during the warmperiod (Table 1). • Most M. sacchariflorus genotypes showed a highdailygrowth rate during the cool period. Figure 5Reduction in Asat from warm to coldconditions. Asatis the net photosynthetic rate at a PAR of 1500 µmolm-2 s-1 Table 1Dailyleafgrowth rates measured in fieldexperimentsduring a cold and a warmperiod in May 2012 • Conclusion • The genotypes showed large variation in the leaf photosynthesis level under both warm and cold growth conditions. • Some correlation between measurements of leaf growth and photosynthesis rate at the leaf level under both growth conditions was found. • The M. sacchariflorusgenotypes were found to have the highest level of photosynthesis at 14ºC, but none were superior to M. ×giganteus (clone no. EMI4). References Somerville C, Youngs H, Taylor C, Davis SC & Long SP (2010). Feedstocks for LignocellulosicBiofuels. Science. 329:790-792. PurdySJ, MaddisonAL & Jones LE et al. (2013) Characterization of chilling-shockresponses in four genotypes of Miscanthusreveals the superior tolerance of M.×giganteuscompared with M. sinensis and M. sacchariflorus. Annals of Botany. 111: 999-1013 Jørgensen U & Sander B (1997). Biomass requirement for power production: How to optimise the quality by agricultural management. Biomass and bioenergy. 12: 145-147 Acknowledgements Projects and financial support: BIORESOURCE www.bioresource.dk, The Danish Council for Strategic Research GrassMarginswww.grass,argin.com.The European Unions’sSeventh Framework Programme (FP7/2007-2013) under grant agreement no. 289461