Friesen Patrick C, Peixoto Murilo M, Busch Florian A, Johnson Daniel C, Sage Rowan F
Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada, M5S 3B2
Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada, M5S 3B2.
J Exp Bot. 2014 Jul;65(13):3749-58. doi: 10.1093/jxb/eru105. Epub 2014 Mar 18.
Miscanthus hybrids are leading candidates for bioenergy feedstocks in mid to high latitudes of North America and Eurasia, due to high productivity associated with the C4 photosynthetic pathway and their tolerance of cooler conditions. However, as C4 plants, they may lack tolerance of chilling conditions (0-10 °C) and frost, particularly when compared with candidate C3 crops at high latitudes. In higher latitudes, cold tolerance is particularly important if the feedstock is to utilize fully the long, early-season days of May and June. Here, leaf gas exchange and fluorescence are used to assess chilling tolerance of photosynthesis in five Miscanthus hybrids bred for cold tolerance, a complex Saccharum hybrid (energycane), and an upland sugarcane variety with some chilling tolerance. The chilling treatment consisted of transferring warm-grown plants (25/20 °C day/night growth temperatures) to chilling (12/5 °C) conditions for 1 week, followed by assessing recovery after return to warm temperatures. Chilling tolerance was also evaluated in outdoor, spring-grown Miscanthus genotypes before and after a cold front that was punctuated by a frost event. Miscanthus×giganteus was found to be the most chilling-tolerant genotype based on its ability to maintain a high net CO2 assimilation rate (A) during chilling, and recover A to a greater degree following a return to warm conditions. This was associated with increasing its capacity for short-term dark-reversible photoprotective processes (ΦREG) and the proportion of open photosystem II reaction centres (qL) while minimizing photoinactivation (ΦNF). Similarly, in the field, M.×giganteus exhibited a significantly greater A and pre-dawn F v/F m after the cold front compared with the other chilling-sensitive Miscanthus hybrids.
芒草杂交种是北美和欧亚大陆中高纬度地区生物能源原料的主要候选品种，这是因为它们具有与C4光合途径相关的高生产力以及对较凉爽条件的耐受性。然而，作为C4植物，它们可能缺乏对低温条件（0-10°C）和霜冻的耐受性，特别是与高纬度地区的候选C3作物相比。在较高纬度地区，如果原料要充分利用五月和六月漫长的早季白昼，耐寒性就尤为重要。在此，利用叶片气体交换和荧光来评估五个耐寒性芒草杂交种、一个复杂的甘蔗杂交种（能源甘蔗）以及一个具有一定耐寒性的旱地甘蔗品种光合作用的耐寒性。低温处理包括将在温暖环境中生长的植株（日/夜生长温度为25/20°C）转移到低温（12/5°C）条件下1周，然后评估回到温暖温度后的恢复情况。还在室外春季生长的芒草基因型中，在一次伴有霜冻事件的冷锋前后评估了耐寒性。基于芒草×巨穗芒在低温期间保持高净二氧化碳同化率（A）的能力以及回到温暖条件后A恢复到更大程度的能力，发现它是最耐寒的基因型。这与增加其短期暗可逆光保护过程（ΦREG）的能力以及开放的光系统II反应中心比例（qL）相关，同时将光失活（ΦNF）降至最低。同样，在田间，与其他对低温敏感的芒草杂交种相比，芒草×巨穗芒在冷锋过后表现出显著更高的A和黎明前F v/F m。
