Changes in the phenology of flowering in soybeans caused by long-term growth at elevated CO<sub>2</sub> may be important to the responses of seed yield to elevated CO<sub>2</sub>. Here we utili...Changes in the phenology of flowering in soybeans caused by long-term growth at elevated CO<sub>2</sub> may be important to the responses of seed yield to elevated CO<sub>2</sub>. Here we utilized near-isogenic lines of soybeans differing in three genes influencing photoperiod sensitivity to determine whether these genes affected the response of flowering time to elevated CO<sub>2</sub>. Six isolines of Harosoy 63 were grown at ambient (380 μmol?mol<sup>-1</sup>) and elevated (560 μmol?mol<sup>-1</sup>) CO<sub>2</sub> concentrations in the field using free-air CO<sub>2</sub> enrichment systems, in air-conditioned glasshouses with natural summer photoperiods, and in indoor chambers with day lengths of 11, 13, 15, and 17 hours. The effect of CO<sub>2</sub> concentration on flowering time varied with genotype, and there was also an interaction between CO<sub>2</sub> and photoperiod in all genotypes, as indicated by ANOVA. Elevated CO<sub>2</sub> accelerated flowering in some cases, and delayed it in other cases. For all three of the isolines with single dominant genes, elevated CO<sub>2</sub> decreased the days to first open flower at the longest photoperiod. At the shortest photoperiod, elevated CO<sub>2</sub> delayed flowering in all but one isoline. The all-recessive isoline had slower flowering at elevated CO<sub>2</sub> at both the shortest and the longest photoperiods, and also in the field and in the glasshouse. Delayed flowering at elevated CO<sub>2</sub> in the field and glasshouse was associated with an increased final number of main stem nodes. It is concluded that the E1, E3, and E4 genes each influenced how the time to first flowering was affected by CO<sub>2</sub> concentration at long photoperiods.展开更多
Prior experiments in indoor chambers and in the field using free-air carbon dioxide enrichment (FACE) systems indicated variation among soybean cultivars in whether and how much elevated CO<sub>2</sub> pro...Prior experiments in indoor chambers and in the field using free-air carbon dioxide enrichment (FACE) systems indicated variation among soybean cultivars in whether and how much elevated CO<sub>2</sub> prolonged vegetative development. However, the cultivars tested differed in maturity group, and it is not known whether variation exists in CO<sub>2</sub> effects on the duration of vegetative growth within a maturity group. In these experiments, a total of five soybean cultivars of maturity group IV were grown at ambient and elevated CO<sub>2</sub> in the field in Maryland, USA using FACE systems, over three years. The time of first flowering, the time of the first open flowers at the apex of the main stem, the total number of main stem nodes at maturity, and seed yield were recorded. In each year of the study, there were cultivars in which elevated CO<sub>2</sub> did not affect the duration of vegetative growth or the main stem node number, and other cultivars in which elevated CO<sub>2</sub> prolonged vegetative growth and increased the number of main stem nodes and seed yield at maturity. The stimulation in yield by elevated CO<sub>2</sub> was highly correlated with the increase in the number of main stem nodes, indicating that CO<sub>2</sub> effects on the duration of vegetative growth may be important in adapting soybean to higher atmospheric CO<sub>2</sub>.展开更多
I tested whether elevated [CO2] affected which genotypes of Taraxacum officinale had highest fitness in two field experiments. In one experiment, T. officinale plants which persisted as weeds in alfalfa plots in open ...I tested whether elevated [CO2] affected which genotypes of Taraxacum officinale had highest fitness in two field experiments. In one experiment, T. officinale plants which persisted as weeds in alfalfa plots in open top chambers at ambient and elevated [CO2] were compared. In a second experiment, T. officinale seeds collected from local habitats were mixed and scattered in open top chambers at ambient and elevated [CO2], and plants producing seeds after one and two years in monocultures were compared. In both experiments seeds produced in each chamber were collected, and many plants from the seed lot from each chamber were grown in controlled environment chambers to test whether the [CO2] of the chamber of origin affected the mean value of various plant parameters. In both experiments, the results indicated that field exposure to elevated [CO2] altered the relative fitness of genotypes. Elevated [CO2] favored genotypes which produced biomass more rapidly at elevated [CO2] in both experiments, primarily because of faster rates of leaf initiation. The results suggest that genotypes of this species vary widely in fitness at elevated [CO2] whether grown in monocultures or in mixed communities, and that this species could adapt rapidly to rising atmospheric [CO2].展开更多
Corn, with C4 photosynthetic metabolism, often has no photosynthetic or yield response to elevated carbon dioxide concentrations. In C3 species, the yield stimulation at elevated carbon dioxide concentrations often de...Corn, with C4 photosynthetic metabolism, often has no photosynthetic or yield response to elevated carbon dioxide concentrations. In C3 species, the yield stimulation at elevated carbon dioxide concentrations often decreases with nitrogen limitation. I tested whether such a nitrogen interaction occurred in corn, by growing sweet corn in field plots in open top chambers at ambient and elevated (ambient + 180 mmol·mol-1) carbon dioxide concentrations for four seasons, with six nitrogen application rates, ranging from half to twice the locally recommended rate. At the recommended rate of nitrogen application, no carbon dioxide effect on production occurred. However, both ear and leaf plus stem biomass were lower for the elevated carbon dioxide treatment than for the ambient treatment at less than the recommended rate of nitrogen application, and higher at the highest rates of nitrogen application. There were no significant responses of mid-day leaf gas exchange rates to nitrogen application rate for either carbon dioxide treatment, and elevated carbon dioxide did not significantly increase leaf carbon dioxide assimilation rates at any nitrogen level. Leaf area index during vegetative growth increased more with nitrogen application rate at elevated than at ambient carbon dioxide. It is concluded that elevated carbon dioxide increased the responsiveness of corn growth to nitrogen application by increasing the response of leaf area to nitrogen application rate, and that elevated carbon dioxide increased the amount of nitrogen required to achieve maximum yields.展开更多
文摘Changes in the phenology of flowering in soybeans caused by long-term growth at elevated CO<sub>2</sub> may be important to the responses of seed yield to elevated CO<sub>2</sub>. Here we utilized near-isogenic lines of soybeans differing in three genes influencing photoperiod sensitivity to determine whether these genes affected the response of flowering time to elevated CO<sub>2</sub>. Six isolines of Harosoy 63 were grown at ambient (380 μmol?mol<sup>-1</sup>) and elevated (560 μmol?mol<sup>-1</sup>) CO<sub>2</sub> concentrations in the field using free-air CO<sub>2</sub> enrichment systems, in air-conditioned glasshouses with natural summer photoperiods, and in indoor chambers with day lengths of 11, 13, 15, and 17 hours. The effect of CO<sub>2</sub> concentration on flowering time varied with genotype, and there was also an interaction between CO<sub>2</sub> and photoperiod in all genotypes, as indicated by ANOVA. Elevated CO<sub>2</sub> accelerated flowering in some cases, and delayed it in other cases. For all three of the isolines with single dominant genes, elevated CO<sub>2</sub> decreased the days to first open flower at the longest photoperiod. At the shortest photoperiod, elevated CO<sub>2</sub> delayed flowering in all but one isoline. The all-recessive isoline had slower flowering at elevated CO<sub>2</sub> at both the shortest and the longest photoperiods, and also in the field and in the glasshouse. Delayed flowering at elevated CO<sub>2</sub> in the field and glasshouse was associated with an increased final number of main stem nodes. It is concluded that the E1, E3, and E4 genes each influenced how the time to first flowering was affected by CO<sub>2</sub> concentration at long photoperiods.
文摘Prior experiments in indoor chambers and in the field using free-air carbon dioxide enrichment (FACE) systems indicated variation among soybean cultivars in whether and how much elevated CO<sub>2</sub> prolonged vegetative development. However, the cultivars tested differed in maturity group, and it is not known whether variation exists in CO<sub>2</sub> effects on the duration of vegetative growth within a maturity group. In these experiments, a total of five soybean cultivars of maturity group IV were grown at ambient and elevated CO<sub>2</sub> in the field in Maryland, USA using FACE systems, over three years. The time of first flowering, the time of the first open flowers at the apex of the main stem, the total number of main stem nodes at maturity, and seed yield were recorded. In each year of the study, there were cultivars in which elevated CO<sub>2</sub> did not affect the duration of vegetative growth or the main stem node number, and other cultivars in which elevated CO<sub>2</sub> prolonged vegetative growth and increased the number of main stem nodes and seed yield at maturity. The stimulation in yield by elevated CO<sub>2</sub> was highly correlated with the increase in the number of main stem nodes, indicating that CO<sub>2</sub> effects on the duration of vegetative growth may be important in adapting soybean to higher atmospheric CO<sub>2</sub>.
文摘I tested whether elevated [CO2] affected which genotypes of Taraxacum officinale had highest fitness in two field experiments. In one experiment, T. officinale plants which persisted as weeds in alfalfa plots in open top chambers at ambient and elevated [CO2] were compared. In a second experiment, T. officinale seeds collected from local habitats were mixed and scattered in open top chambers at ambient and elevated [CO2], and plants producing seeds after one and two years in monocultures were compared. In both experiments seeds produced in each chamber were collected, and many plants from the seed lot from each chamber were grown in controlled environment chambers to test whether the [CO2] of the chamber of origin affected the mean value of various plant parameters. In both experiments, the results indicated that field exposure to elevated [CO2] altered the relative fitness of genotypes. Elevated [CO2] favored genotypes which produced biomass more rapidly at elevated [CO2] in both experiments, primarily because of faster rates of leaf initiation. The results suggest that genotypes of this species vary widely in fitness at elevated [CO2] whether grown in monocultures or in mixed communities, and that this species could adapt rapidly to rising atmospheric [CO2].
文摘Corn, with C4 photosynthetic metabolism, often has no photosynthetic or yield response to elevated carbon dioxide concentrations. In C3 species, the yield stimulation at elevated carbon dioxide concentrations often decreases with nitrogen limitation. I tested whether such a nitrogen interaction occurred in corn, by growing sweet corn in field plots in open top chambers at ambient and elevated (ambient + 180 mmol·mol-1) carbon dioxide concentrations for four seasons, with six nitrogen application rates, ranging from half to twice the locally recommended rate. At the recommended rate of nitrogen application, no carbon dioxide effect on production occurred. However, both ear and leaf plus stem biomass were lower for the elevated carbon dioxide treatment than for the ambient treatment at less than the recommended rate of nitrogen application, and higher at the highest rates of nitrogen application. There were no significant responses of mid-day leaf gas exchange rates to nitrogen application rate for either carbon dioxide treatment, and elevated carbon dioxide did not significantly increase leaf carbon dioxide assimilation rates at any nitrogen level. Leaf area index during vegetative growth increased more with nitrogen application rate at elevated than at ambient carbon dioxide. It is concluded that elevated carbon dioxide increased the responsiveness of corn growth to nitrogen application by increasing the response of leaf area to nitrogen application rate, and that elevated carbon dioxide increased the amount of nitrogen required to achieve maximum yields.
