- University of Toronto, Ecology and Evolutionary Biology, Graduate Studentadd
The C 4 plant sugarcane (Saccharum sp. Lin-naeus) is a chilling-sensitive crop grown at low latitudes for refined sugar and bioenergy. As a leading source of sugar and feedstock for bioethanol production, there is interest in cultivating... more
The C 4 plant sugarcane (Saccharum sp. Lin-naeus) is a chilling-sensitive crop grown at low latitudes for refined sugar and bioenergy. As a leading source of sugar and feedstock for bioethanol production, there is interest in cultivating it at higher latitudes and elevations where sub-optimal temperatures are common. To assess its potential for photosynthetic acclimation to temperature, we compared photosynthetic temperature responses of lowland and upland Hawaiian sugarcane cultivars grown at 32/26 and 21/18 °C day/night temperature. The temperature response of net CO 2 assimilation rate (A) of the cultivars was similar in both treatments, with the exception that short-term exposure to 45 °C greatly inhibited A in the 21/18 °C-grown plants of both varieties when subsequently measured below 21 °C. Plants grown at 32/26 °C exhibited a modest inhibition of A below 21 °C following a 45 °C exposure. Little variation between the cultivars was observed in their responses to intercellular CO 2 partial pressure and light at varying temperatures. We thus conclude sugarcane does not exhibit a strong thermal accli-mation response at moderately sub-optimal to supra-optimal temperatures, but will acclimate to warm growth conditions in a manner that increased tolerance of heat; however, the heat intolerance was manifested as reduced performance at cooler temperatures. This could be problematic in growing regions such as the southeastern USA and China where springtime conditions can include hot days followed by strong cold fronts that brings sub-optimal temperatures.
Research Interests:
There is much interest in cultivating C4 perennial plants in northern climates where there is an abundance of land and a potential large market for biofuels. C4 feedstocks can exhibit superior yields to C3 alternatives during the long... more
There is much interest in cultivating C4 perennial plants in northern climates where there is an abundance of land and a potential large market for biofuels. C4 feedstocks can exhibit superior yields to C3 alternatives during the long warm days of summer at high latitude, but their summer success depends on an ability to tolerate deep winter cold, spring frosts, and early growth-season chill. Here, we review cold tolerance limits in C4 perennial grasses. Dozens of C4 species are known from high latitudes to 63 °N and elevations up to 5200 m, demonstrating that C4 plants can adapt to cold climates. Of the three leading C4 grasses being considered for bioenergy production in cold climates-Miscanthus spp., switchgrass (Panicum virgatum), and prairie cordgrass (Spartina pectinata)-all are tolerant of cool temperatures (10-15 °C), but only cordgrass tolerates hard spring frosts. All three species overwinter as dormant rhizomes. In the productive Miscanthus×giganteus hybrids, exposure to ...
Research Interests:
This study investigates protocols to evaluate cold tolerance thresholds for overwintering rhizomes of perennial bioenergy grasses. Protocols examined include the temperature at which ice formation occurs, cooling rate, incubation time at... more
This study investigates protocols to evaluate cold tolerance thresholds for overwintering rhizomes of perennial bioenergy grasses. Protocols examined include the temperature at which ice formation occurs, cooling rate, incubation time at the treatment temperature, and the electrolyte leakage (EL) method to assess mortality thresholds. Using these protocols, we assessed low temperature injury in two genotypes of Miscanthus and two genotypes of lowland switchgrass (Panicum virgatum). Ice formed near À1 C in the rhizomes cooled at 1 C h À1 , but at variable temperatures at cooling rates of 3 and 5 C h À1. Rhizome temperature followed chamber temperature at a cooling rate of 1 C h À1 , whereas at faster cooling rates, there was a lag in rhizome temperature that affected treatment exposure time. A 1 C h À1 cooling rate is thus suitable. In rhizomes incubated for <4 h at the treatment temperature, EL values were variable, while there was no change in EL when samples were incubated 4–20 h. A continuous, steady rate of cooling at 1 C h À1 demonstrated the Miscanthus and lowland switchgrass varieties exhibited lethal levels of electrolyte leakage below À6 C. Continuous cooling does not allow for subzero acclimation and reflects thermal tolerances of sampled tissue in situ. To allow for maximum acclimation at subzero temperatures, a prolonged, staged-cooling procedure was adopted. This procedure showed diploid Miscanthus rhizomes could acclimate and adjust their tolerance limit to À12 C, while a triploid Illinois line showed little acclimation and was still killed below À6 C. Abbreviations EL = Electrolyte leakage RC = Relative conductivity LT 50 = Temperature at which the sample has a 50% mortality LEL 50 = Percentage of electrolyte leakage at which the sample has a 50% mortality
Research Interests:
The cold tolerance of winter-dormant rhizomes was evaluated in diploid, allotriploid, and allotetraploid hybrids of Miscanthus sinensis and Miscanthus sacchariflorus grown in a field setting. Two artificial freezing protocols were... more
The cold tolerance of winter-dormant rhizomes was evaluated in diploid, allotriploid, and allotetraploid hybrids of
Miscanthus sinensis and Miscanthus sacchariflorus grown in a field setting. Two artificial freezing protocols were
tested: one lowered the temperature continuously by 1°C h–1 to the treatment temperature and another lowered the
temperature in stages of 24 h each to the treatment temperature. Electrolyte leakage and rhizome sprouting assays after
the cold treatment assessed plant and tissue viability. Results from the continuous-cooling trial showed that Miscanthus
rhizomes from all genotypes tolerated temperatures as low as –6.5 °C; however, the slower, staged-cooling procedure
enabled rhizomes from two diploid lines to survive temperatures as low as –14 °C. Allopolyploid genotypes showed no
change in the lethal temperature threshold between the continuous and staged-cooling procedure, indicating that they
have little ability to acclimate to subzero temperatures. The results demonstrated that rhizomes from diploid Miscanthus
lines have superior cold tolerance that could be exploited to improve performance in more productive polyploid lines.
With expected levels of soil insulation, low winter air temperatures should not harm rhizomes of tolerant diploid genotypes
of Miscanthus in temperate to sub-boreal climates (up to 60°N); however, the observed winter cold in sub-boreal
climates could harm rhizomes of existing polyploid varieties of Miscanthus and thus reduce stand performance.
Miscanthus sinensis and Miscanthus sacchariflorus grown in a field setting. Two artificial freezing protocols were
tested: one lowered the temperature continuously by 1°C h–1 to the treatment temperature and another lowered the
temperature in stages of 24 h each to the treatment temperature. Electrolyte leakage and rhizome sprouting assays after
the cold treatment assessed plant and tissue viability. Results from the continuous-cooling trial showed that Miscanthus
rhizomes from all genotypes tolerated temperatures as low as –6.5 °C; however, the slower, staged-cooling procedure
enabled rhizomes from two diploid lines to survive temperatures as low as –14 °C. Allopolyploid genotypes showed no
change in the lethal temperature threshold between the continuous and staged-cooling procedure, indicating that they
have little ability to acclimate to subzero temperatures. The results demonstrated that rhizomes from diploid Miscanthus
lines have superior cold tolerance that could be exploited to improve performance in more productive polyploid lines.
With expected levels of soil insulation, low winter air temperatures should not harm rhizomes of tolerant diploid genotypes
of Miscanthus in temperate to sub-boreal climates (up to 60°N); however, the observed winter cold in sub-boreal
climates could harm rhizomes of existing polyploid varieties of Miscanthus and thus reduce stand performance.
Research Interests: Biomass, Bioenergy, C4 Photosynthesis, Bioenergy (Biology), Biofuels, and 10 moreMiscanthus physiology, Miscanthus agronomy, Biofuel, Biofuel, bioenergy, biomass, Bioenergy and Biofuels, Cold Tolerance, Bioenergy from Biomass, Biomass, Bioenergy and Biofuels, Bioenergy Crops, and E.g. Switchgrass, Miscanthus
Miscanthus × giganteus grown in cool temperate regions of North America and Europe can exhibit severe mortality in the year after planting, and poor frost tolerance of leaves. Spartina pectinata (prairie cordgrass), a productive C4... more
Miscanthus × giganteus grown in cool temperate regions of North America and Europe can exhibit severe mortality
in the year after planting, and poor frost tolerance of leaves. Spartina pectinata (prairie cordgrass), a productive C4
perennial grass native to North America, has been suggested as an alternative biofuel feedstock for colder regions;
however, its cold tolerance relative to M. × giganteus is uncertain. Here, we compare the cold tolerance thresholds
for winter-dormant rhizomes and spring/summer leaves of M. × giganteus and three accessions of S. pectinata. All
genotypes were planted at a field site in Ontario, Canada. In November and February, the temperatures corresponding
to 50% rhizome mortality (LT50) were near −24°C for S. pectinata and −4°C for M. × giganteus. In late April, the
LT50 of rhizomes rose to −10°C for S. pectinata but remained near −4°C for M. × giganteus. Twenty percent of the
M. × giganteus rhizomes collected in late April were dead while S. pectinata rhizomes showed no signs of winter
injury. Photosynthesis and electrolyte leakage measurements in spring and summer demonstrate that S. pectinata
leaves have greater frost tolerance in the field. For example, S. pectinata leaves remained viable above −9°C while
the mortality threshold was near −5°C for M. × giganteus. These results indicate M. × giganteus will be unsuitable for
production in continental interiors of cool-temperate climate zones unless freezing and frost tolerance are improved.
By contrast, S. pectinata has the freezing and frost tolerance required for a higher-latitude bioenergy crop.
in the year after planting, and poor frost tolerance of leaves. Spartina pectinata (prairie cordgrass), a productive C4
perennial grass native to North America, has been suggested as an alternative biofuel feedstock for colder regions;
however, its cold tolerance relative to M. × giganteus is uncertain. Here, we compare the cold tolerance thresholds
for winter-dormant rhizomes and spring/summer leaves of M. × giganteus and three accessions of S. pectinata. All
genotypes were planted at a field site in Ontario, Canada. In November and February, the temperatures corresponding
to 50% rhizome mortality (LT50) were near −24°C for S. pectinata and −4°C for M. × giganteus. In late April, the
LT50 of rhizomes rose to −10°C for S. pectinata but remained near −4°C for M. × giganteus. Twenty percent of the
M. × giganteus rhizomes collected in late April were dead while S. pectinata rhizomes showed no signs of winter
injury. Photosynthesis and electrolyte leakage measurements in spring and summer demonstrate that S. pectinata
leaves have greater frost tolerance in the field. For example, S. pectinata leaves remained viable above −9°C while
the mortality threshold was near −5°C for M. × giganteus. These results indicate M. × giganteus will be unsuitable for
production in continental interiors of cool-temperate climate zones unless freezing and frost tolerance are improved.
By contrast, S. pectinata has the freezing and frost tolerance required for a higher-latitude bioenergy crop.