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Greenhouse Gas Exchanges With Temperate Grassland Systems, S C. Jarvis, D J. Hatch, G J. Dollard Sep 2024

Greenhouse Gas Exchanges With Temperate Grassland Systems, S C. Jarvis, D J. Hatch, G J. Dollard

IGC Proceedings (1993-2023)

Preliminary studies are described which examine the fluxes of two important greenhouse gases from grassland systems, In the first, effects of different slurry application methods to a peat soil on the emission of N2O were examined. All methods resulted in a significant release of N20 at rates which varied with treatment, time and environmental conditions. The greatest rates of denitrification occurred with acidified slurry under wet conditions: this however, produced the lowest proportion of losses as N2O, In the second study, changes in CH4 concentration above a grazed sward were measured and indicated a definite positive flux from the system …

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Methane Production By New Zealand Ruminants, K Betteridge, M J. Ulyatt, J Knapp, R L. Baldwin Sep 2024

Methane Production By New Zealand Ruminants, K Betteridge, M J. Ulyatt, J Knapp, R L. Baldwin

IGC Proceedings (1993-2023)

Methane production by ruminants in New Zealand was estimated using a ma1hema1ical model of rumen digestion interfaced with census livestock numbers. New Zealand was divided into 4 climatic regions with each classified into improved, unimproved and tussock grasslands, and livestock were allocated to each class at appropriate stocking rates. Models of changing livestock numbers within n year were developed for each animal and land class. Food dry matter intake for each class of livestock was calculated from estimates of feed requirements and diet quality. Total methane production was estimated to be 1.50 Tg per year: 58.4% sheep, 20.7%, beef cattle, …

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Vertical And Diurnal Profiles Of Atmospheric Carbon Dioxide Concentrations In Manawatu, New Zealand, C C. Bell Sep 2024

Vertical And Diurnal Profiles Of Atmospheric Carbon Dioxide Concentrations In Manawatu, New Zealand, C C. Bell

IGC Proceedings (1993-2023)

Carbon dioxide concentrations were monitored at 2 heights above pasture, at Flock House, New Zealand using an infrared gas analyzer attached to a multiport sampler, Characteristic profiles for a calm day and a windy day are presented. At low wind speeds there was a marked diurnal cycle in CO2 concentration with a maximum difference of 336 ppm between day and night concentrations. An elevated CO2 concentration· was evident for some hours after sunrise. At higher wind speeds the CO2 cycle was less marked, with only a 20 ppm difference between day and night levels. At times, plants are exposed to …

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Nitrous Oxide Emissions From Grassland In Manawatu, New Zealand, R A. Carran, J P. Evans Sep 2024

Nitrous Oxide Emissions From Grassland In Manawatu, New Zealand, R A. Carran, J P. Evans

IGC Proceedings (1993-2023)

Nitrous oxide (Np) is a minor component of the atmosphere which acts as a potent greenhouse gas and also causes ozone depletion. Soil bacteria are the most important agents of N2O production, but both the New Zealand and the international data on N2O emission rates from soils are very poor at present. In order to help define the possible range of emission ranges from pasture soils· we selected sites with characteristics that would make then "high" or "low" emitters of N2O. The "high" emission site was a fine-textured, fertile but poorly drained flood plain soil. The "low" emission site was …

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Changing Stocking Rates And Burning Management To Reduce Greenhouse Gas Emissions From Southern Queensland Grasslands, S M. Howden, G M. Mckeon, J C. Scanlan, J O. Carter, D H. White Sep 2024

Changing Stocking Rates And Burning Management To Reduce Greenhouse Gas Emissions From Southern Queensland Grasslands, S M. Howden, G M. Mckeon, J C. Scanlan, J O. Carter, D H. White

IGC Proceedings (1993-2023)

GRASSMAN, an agricultural decision-support model, has been modified to include sources, sinks and storages of greenhouse gases. The modified model was used to investigate the effects of changes in stocking rate and burning management on greenhouse gas emissions of southern Queensland grasslands. These grasslands are significant net emitters of greenhouse gases in their natural state, resulting in large differences between net and anthropogenic (man-made) emissions and hence, to different conclusions regarding emission reduction strategies. At moderate stocking rates, anthropogenic emissions could be reduced by about 20% with little loss of productivity. However, similar reductions in net emissions require larger management …

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Development Of Plants Resistant To Insect Pests Using Gene Manipulation, D.W R. White, D R. Biggs, M T. Mcmanus, C R. Voisey, J T. Christeller, A H. Broadwell, E.P J. Burgess, C N. Chilcott, P J. Wigley, P G. Mcgregor Sep 2024

Development Of Plants Resistant To Insect Pests Using Gene Manipulation, D.W R. White, D R. Biggs, M T. Mcmanus, C R. Voisey, J T. Christeller, A H. Broadwell, E.P J. Burgess, C N. Chilcott, P J. Wigley, P G. Mcgregor

IGC Proceedings (1993-2023)

Damage to pasture plants caused by insect pests reduces the supply of feed for grassland animal production. In addition, the use of chemical insecticides for the control of pasture pests is undesirable for reasons of high cost and possible damage to the environment. One way to overcome these limitations is 10 utilize a recent development. in plant molecular biology which has seen the incorporation of cloned genes that confer insect _pest resistance into crop plants. To date, the most widely used genes for this purpose are those coding for insecticidal proteins from the bacterium Bacillus thuringiensis, and for inhibitors …

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Genetically Engineer Protection Against Viruses And Fungi, John Fitchen, Roger N. Beachy Sep 2024

Genetically Engineer Protection Against Viruses And Fungi, John Fitchen, Roger N. Beachy

IGC Proceedings (1993-2023)

The first examples of plant genetic engineering for disease resistance were for the control of virus diseases. Plants that were transformed with a gene to express the coat protein of tobacco mosaic virus (TMV) were shown to have increased resistance to infection by TMV. This approach, referred to as coat protein-mediated resistance (CP-MR), has been applied to give protection against at least 35 different viruses, belonging to 12 virus groups in at least 13 plant species. Field trials of some of these examples have demonstrated that CP-MR can effectively protect plants under field conditions. Other viral genes have also been …

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Bermudagrass Allelochemistry And Influence On Spodoptera Frugiperda Herbivory, S Quisenberry, M Mohamed Sep 2024

Bermudagrass Allelochemistry And Influence On Spodoptera Frugiperda Herbivory, S Quisenberry, M Mohamed

IGC Proceedings (1993-2023)

Cultivated area of bermudagrass (Cynodon dactylon L. Pers.), in the USA are under stress from a complex of insect and secondary fungal pests which has resulted in a loss in crop production. The fall armyworm (Spodoptera frugiperda (J.E. Smith)) is the major insect herbivore of bermudagrass in the south-eastern USA. Bermudagrass breeding programmes over the last decade have yielded germplasm with potential insect-resistant traits. Thus, a programme was initiated to define bermudagrass allelochemislry with respect to insect herbivory. Pall armyworm is variably responsive to bermudagrass cultivars, the basis being causally related to a differential concentration of the phagostimulant 6, …

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Purification And Characterization Of A Proteinase Inhibitor From Lolium Perenne L., Mohammed Tasneem, C A. Cornford, M T. Mcmanus, D W.R White Sep 2024

Purification And Characterization Of A Proteinase Inhibitor From Lolium Perenne L., Mohammed Tasneem, C A. Cornford, M T. Mcmanus, D W.R White

IGC Proceedings (1993-2023)

A proteinase inhibitor from dry seeds of Lolium perenne L. cv. Grasslands Ruanui has been partially purified and characterised. Standard protein separalion techniques have been used to enrich the presence of lhe inhibitor in seed extracts by 37-fold. Using synthetic substrates the inhibitor can retard the activity of bovine chymotrypsin, but not bovine trypsin. Gel filtration column chromatography indicates that the native protein has a molecular weight of c. 20 KDa.

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Hypervariable Mini-Chromosomes Of Colletotrichum Gloeosporidoides Infecting The Pasture Legume Genus Stylosanthes, John M. Manners, Andrew Masel, John A.G Irwin Sep 2024

Hypervariable Mini-Chromosomes Of Colletotrichum Gloeosporidoides Infecting The Pasture Legume Genus Stylosanthes, John M. Manners, Andrew Masel, John A.G Irwin

IGC Proceedings (1993-2023)

Coiletotrichum gloeosporioides causes anthracnose disease of the tropical pasture legumes Stylosanthes, Two pathotypes and multiple physiological races are present in Australia. The mechanisms producing genetic variation in this pathogen are not understood. Electrophoretic karyotyping has revealed considerable variation in the size and number of a group of small chromosomes (0.2-1.2 Mb in size) both between and within types. Molecular analysis of a selected mini-chromosome using chromosome-specific DNA probes suggests that it has originated by horizontal transfer from a genetically distinct strain. This mini-chromosome is unique to race 3 within the Type B pathogen and may determine race specificity. A functional …

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Coat Protein-Mediated Protection Against White Clover Mosaic Virus And Potato Virus X In Tobacco, D L. Beck, C J. Van Dolleweerd, B Dudas, D R.W White, R.L S. Forster Sep 2024

Coat Protein-Mediated Protection Against White Clover Mosaic Virus And Potato Virus X In Tobacco, D L. Beck, C J. Van Dolleweerd, B Dudas, D R.W White, R.L S. Forster

IGC Proceedings (1993-2023)

The coat protein genes of the potexviruses white clover mosaic virus (WClMY) or potato virus X (PVX) were introduced into Nicotiana benthamiana plants by gene transfer. Transgenic plants expressing the coal protein gene of WCIMY or PYX were highly resistant to infection when challenge-inoculated with the virus from which the coat protein gene was obtained (homologous challenge). Similar resistance was obtained when homologous viral RNA was used as inoculum, The transgenic plants were also protected against infection with the heterologous virus, but only at low inoculum concentrations. The level of protection in PYX transgenic plants was directly correlated with the …

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Transformation Of White Clover With A Gene Encoding A Lepidopteran-Active- Endotoxin From Bacillus Thuringiensis Var. Berliner 1715, C R. Voisey, D.W R. White, P G. Mcgregor, B L. Barker Sep 2024

Transformation Of White Clover With A Gene Encoding A Lepidopteran-Active- Endotoxin From Bacillus Thuringiensis Var. Berliner 1715, C R. Voisey, D.W R. White, P G. Mcgregor, B L. Barker

IGC Proceedings (1993-2023)

During sporulation, Bacillus thuringiensis var. berliner 1715 produces insecticidal proteins (6-endotoxins) that are lethal specifically to Lepidopternn insects. Agrobacterium tumefaciens-mediated T-DNA transfer has been used to introduce a cry/A(b) li-endotoxin gene (the 812 gene) from this B. thuringiensis strain into a genotype of white clover (WR8). The aim is to protect white clover (Trifolium repens L.) from damage caused by Lepidopteran insects, including the pasture pests porina (Wiseana spp.) and sod-web worms (Crombidae), White clover plants were transformed with a binary vector (pGSH 163) containing the bidirectional mannopine synthase promoter which directs simultaneous expression of both …

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Prediction Of Grassland Plant Responses To Global Change, B D. Campbell, J P. Grime Sep 2024

Prediction Of Grassland Plant Responses To Global Change, B D. Campbell, J P. Grime

IGC Proceedings (1993-2023)

Global change is challenging the predictive power of biology. Increasingly, biologists are being asked to draw together existing knowledge and new experimental data, in order to provide predictions of the effects of global change at regional, national and global scales. In this paper we examine how well global change effects on grassland plants can be predicted, and what avenues might be used in future to improve predictive capabilities. Broad predictions of the direction of change in grassland vegetation can be made quite simply and from a limited set of data. Predictions of the rate and magnitude of change are more …

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Climate Change And Grasslands: Ecosystem-Level Responses To Elevated Carbon Dioxide, Clenton E. Owensby Sep 2024

Climate Change And Grasslands: Ecosystem-Level Responses To Elevated Carbon Dioxide, Clenton E. Owensby

IGC Proceedings (1993-2023)

Elevated CO2 is the major greenhouse gas associated with global climate change. The impact of increasing atmospheric CO2 on grassland ecosystems has been studied little. Studies with single plants or populations in controlled environments have provided knowledge of the mechanisms involved in plant response to elevated CO21 but without ecosystem-level studies over an extended period, we will be unable to make any valid predictions. Primary production of grassland ecosystems under elevated CO2 will likely increase, with the greatest increase coming with C3-dominated plant communities, or plant communities that are .subjected to frequent drought stress. Increased nitrogen-use efficiency and reduced nitrogen …

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Variation In The Response Of Pasture Plants To Carbon Dioxide, B D. Campbell, W A. Laing, P.C D. Newton Sep 2024

Variation In The Response Of Pasture Plants To Carbon Dioxide, B D. Campbell, W A. Laing, P.C D. Newton

IGC Proceedings (1993-2023)

The percentage increases in growth resulting from a doubling of atmospheric CO2 concentration were measured for 37 common pasture plants under strictly controlled conditions of temperature, nutrient supply and irradiance. A wide range of variation in potential response lo CO2 was detected in the day/night temperature range 12n°c to 28/ 23°C. C4 species responded litlle to elevated CO2 The mean ± standard deviation of the distribution of c3 species responses ranged from l±21% at 1m•c to 90±40% at 28/23°C. These responses varied with the stage of plant development. The response by Lolium perenne cv. Grasslands Nui was of intermediate size …

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Will Subtropical Grasses Keep Spreading Through New Zealand?, B D. Campbell, R.J M. Hay Sep 2024

Will Subtropical Grasses Keep Spreading Through New Zealand?, B D. Campbell, R.J M. Hay

IGC Proceedings (1993-2023)

n this paper we briefly examine the effects that rising temperature and atmospheric CO2 concentrations may have on the spread of subtropical grasses in New Zealand. Data are presented from controlled-environment experiments measuring the growth and competitive suppression of white clover by a variety of local temperate and subtropical grasses at CO2 concentrations of 3S0 ppm and 700 ppm. These data support the prediction that some subtropical grasses may decline in aggressiveness relative to temperate species in New Zealand in the future as atmospheric CO2 levels rise. Some of the factors likely to modify the expression of temperature and CO2 …

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Effect Of Carbon Dioxide Concentration On The Competitive Ability Of Clover: Measurements Of Growth And Rubisco, W A. Laing, D H. Greer, B D. Campbell Sep 2024

Effect Of Carbon Dioxide Concentration On The Competitive Ability Of Clover: Measurements Of Growth And Rubisco, W A. Laing, D H. Greer, B D. Campbell

IGC Proceedings (1993-2023)

White clover (Trifolium repens cv. Grasslands Huia) was grown in competition with one of 10 established grass species or else grown alone. Plants were grown at either 350 or 700 ppm CO2, at 28/23°C and 700 µmol/m1/sec photon flux density. Plant growth and extractable ribulose bisphosphate carboxylase (rubisCO) were measured. Grass growth responded less to CO2 than clover. In the absence of grass competition, clover growth Increased 30% under 700 ppm CO2 compared with 350 ppm, but the response varied from 0% to 100% • when grass competition was present. Increased CO2 reduced extractable rubisCO activity (expressed on a …

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Response Of Natural Turves Of Pasture To Elevated Carbon Dioxide In A Controlled Environment, P.C D. Newton, H Clark, C C. Bell, E M. Glasgow Sep 2024

Response Of Natural Turves Of Pasture To Elevated Carbon Dioxide In A Controlled Environment, P.C D. Newton, H Clark, C C. Bell, E M. Glasgow

IGC Proceedings (1993-2023)

Large natural turves from a ryegrass-white clover (Lolium pernne, trifolium repens) pasture were exposed to increasing day/nighl temperatures at 350 and 700 µVI CO2 over a 7•month period. Growth rate al the highest temperature (22/16°C day/night) was IS% higher at the elevated CO2 level; at lower temperatures the response to CO2 was reduced or even negative (-6% at 10/4°C). The growth rate of ryegrass was much lower at elevated CO2 while that of white clover and other grasses was increased. These results are compared with previous studies using synthetic communities, and the limited response to CO2 is noted …

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Implications Of A Doubling In Ambient Carbon Dioxide Levels Of Herbage Quality In Perennial Ryegrass And White Clover, H Clark, C C. Bell, P.C D. Newton, B D. Campbell Sep 2024

Implications Of A Doubling In Ambient Carbon Dioxide Levels Of Herbage Quality In Perennial Ryegrass And White Clover, H Clark, C C. Bell, P.C D. Newton, B D. Campbell

IGC Proceedings (1993-2023)

Digestibility (DMD) and crude protein (CP) percentage in leaf and stem of 4 cultivars each of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) grown at 3 day/night temperatures (12f7, 18/ 13, 28/23°C) and 2 CO2 concentrations (35 0 or 700 ppm) was estimated using near infrared reflectance spectroscopy (N[RS). Differences between cultivars in DMD and CP were small and non-significant. Higher temperatures reduced DMD andCP in both species. DMD was unaffected by CO2 concentration in either species. The higher concentration of CO2 reduced leaf and stem CP by 14.6 and 10% respectively in white clover …

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Long-Term Exposure To Global Changes In Grassland Ecosystems: Whole-Season And Temporal Trends In Changing Productivity In Response To Increased Carbon Dioxide Level And Air Temperature, I Nijs, H Teughels, I Impens, T Behaeghe Sep 2024

Long-Term Exposure To Global Changes In Grassland Ecosystems: Whole-Season And Temporal Trends In Changing Productivity In Response To Increased Carbon Dioxide Level And Air Temperature, I Nijs, H Teughels, I Impens, T Behaeghe

IGC Proceedings (1993-2023)

Six commercial grass cultivars were exposed to elevated CO2 level (±700 ppm), increased air temperature (+4°C) or a combination of both during an entire growing season, using a "field tracking system" for continuous simulation of outside field temperatures (or ambient 44C), inside sunlit greenhouse units. On a whole-season basis, elevated CO2 positively affected above-ground productivity, with a range of 11-30%, depending on species, although early-season stimulation was smaller than late spring CO2 gain. Effects of increased temperature were positive in spring, but decreased towards summer and became negative for almost all species, yielding a "no effect" seasonal balance. Almost no …

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Effect Of Elevated Carbon Dioxide On The Performance Of Nine Coexisting Grassland Species, J Watson, J D. Graves Sep 2024

Effect Of Elevated Carbon Dioxide On The Performance Of Nine Coexisting Grassland Species, J Watson, J D. Graves

IGC Proceedings (1993-2023)

Microcosms were constructed to represent a neutral grassland community under traditional agricultural management. During a season of fumigation at ambient and 600 µmot/mot CO2, plant performance was recorded. An increase of biomass for the whole community resulted at elevated CO2, but the response of individual species differed, There are indications that competitive interactions may change within a community due to the effects of CO2 enrichment; this may eventually result in a change in species composition.

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Effects Of Different Grass Species On Nitrogen Fixation By White Clover Under Conditions Of Elevated Carbon Dioxide And Temperature, J R. Crush, B D. Campbell Sep 2024

Effects Of Different Grass Species On Nitrogen Fixation By White Clover Under Conditions Of Elevated Carbon Dioxide And Temperature, J R. Crush, B D. Campbell

IGC Proceedings (1993-2023)

Growing clover in binary mixtures reduced clover shoot dry matter (DM) and nitrogenase activity compared with clover in monoculture. Nitrogenase activity/g clover shoot OM increased in the mixtures to a similar extent with 5 different companion grass species. Elevated atmospheric 002 increased nitrogenase activity/g clover OM in the mixtures but specific nitrogenase activity was not changed with increased temperature. Using nitrogenase activity/unit grass OM as a competitive index showed that elevated CO2 reduced competitive stress on white clover. Two tropical grasses (Pennisetum clandestinum and Paspalum dilatatum) were less competitive to white clover at 18/13°C than 3 temperate species …

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Effect Of Elevated Atmospheric Carbon Dioxide Levels On Nodule Relative Efficiency In White Clover, J R. Crush, B D. Campbell, J.P M. Evans Sep 2024

Effect Of Elevated Atmospheric Carbon Dioxide Levels On Nodule Relative Efficiency In White Clover, J R. Crush, B D. Campbell, J.P M. Evans

IGC Proceedings (1993-2023)

Plant growth, total nitrogenase activity and hydrogen evolution rates were determined for 39-, 47- and 54-day-old white clover (Trifo/ium repe11s L.) plants growing at 350 or 700 ppm CO2 with day/night temperatures of 18/13°C or 28/23°C. The three plant parameters increased with plant age, temperature and CO2 concentration. Nitrogenase activity/g plant dry matter (DM) and hydrogen evolved/ g DM decreased as plants developed, presumably as nitrogen was cycled internally and plants became less reliant on recently fixed nitrogen. Nodule relative efficiency - an expression of the energy flux to nitrogenase relative to hydrogen production - was significantly lower initially in …

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Climate, Land Use And Plant Life Form Distribution In A Semi-Arid Savanna, Christina Skarpe Sep 2024

Climate, Land Use And Plant Life Form Distribution In A Semi-Arid Savanna, Christina Skarpe

IGC Proceedings (1993-2023)

Number of plant species, total vegetation cover and the abundance of different life forms are compared over a rainfall gradient between savanna woodland and semi-desert. The effects of different land use intensities are superimposed on the differences in rainfall regimes. The outcome is discussed in the light of present global change scenarios,

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Vegetation Response To Climate: A 35 Year Study At Bibury, Gloucestershire, A J. Willis, R Hunt, J P. Grime, S R. Band, N Dunnett Sep 2024

Vegetation Response To Climate: A 35 Year Study At Bibury, Gloucestershire, A J. Willis, R Hunt, J P. Grime, S R. Band, N Dunnett

IGC Proceedings (1993-2023)

Important information on the climate-responsiveness of plant species has been gleaned from an unlikely source. The annually recorded control {unsprayed) plots from a 35-year field e, experiment assessing the effects of spraying herbicide and a plant growth regulator onto the vegetation of roadside verges near Bibury, Gloucestershire, have provided an opportunity to examine the detailed effects of year-to year variations in climate on the yields of different ·species and functional types within the vegetation. The results confirm the usefulness of plant functional types and genome size as predictors of plant community response to climatic change.

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Response Of White Clover To Soil Phosphate Levels At Different Temperatures And Carbon Dioxide Concentrations, R A. Carran Sep 2024

Response Of White Clover To Soil Phosphate Levels At Different Temperatures And Carbon Dioxide Concentrations, R A. Carran

IGC Proceedings (1993-2023)

Nutrient availability is generally managed to remove limitations when the effects of elevated temperature or CO2 concentrations on plants are investigated. Relating the resulls of such experiments to field situations where nutrients are frequently in short supply is difficult. Phosphorous response curves were obtained for white clover (Trifolium repens L,) seedlings grown at temperatures of 18-13 or 28-23°C, nod 350 or 700 ppm CO2. At low P, response to other variables was non-significant and at 18-13° there was no response to increased CO2, Increasing temperature to 28-23° resulted in increased gcowth, apparently due to increased P availability, and at …

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The Integrated Screening Programme: Patterns Of Ecological Specialization In British Species, K Thompson, J P. Grime, R Colasanti Sep 2024

The Integrated Screening Programme: Patterns Of Ecological Specialization In British Species, K Thompson, J P. Grime, R Colasanti

IGC Proceedings (1993-2023)

The Integrated Screening Programme (ISP), a major part of the UCPB research programme during the period 1987-1994, applies standardised procedures for the ecological, physiological and biochemical characterisation of plant species, populations or cultivars. The objectives are: (1) to establish the range of variation in selected plant attributes; (2) to recognise recurring patterns of ecological and evolutionary specialisation; (3) to devise a functional classification of plants relevant to the analysis of communities and ecosystems and the management of vegetation .. To date, the programme has been confined largely to the herbaceous species from central northern Britain. Later, and in particular as …

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Interaction Of Climate Management As Controls On Species Composition, S H. Hillier, F Sutton, J P. Grime, R Colasanti Sep 2024

Interaction Of Climate Management As Controls On Species Composition, S H. Hillier, F Sutton, J P. Grime, R Colasanti

IGC Proceedings (1993-2023)

A new technique for the manipulation of temperature near the soil surface without the aid of cloches or screens has been developed at UCPE. This system is being used to manipulate the length of the growing season in an experiment in which the critical interaction between growth and the timing of two important meadow management activities - cutting and grazing - is being investigated. The technique has also been used to expose synthesised meadow communities to an artificially induced mild winter. Temperature manipulations of this kind offer a new approach to understanding the role which climate plays as a mechanism …

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Comparison Of Photosynthetic Responses To Carbon Dioxide In Pasture Species, D H. Greer, W A. Laing, B D. Campbell Sep 2024

Comparison Of Photosynthetic Responses To Carbon Dioxide In Pasture Species, D H. Greer, W A. Laing, B D. Campbell

IGC Proceedings (1993-2023)

Thirteen major pasture species were grown in controlled environments at 3 temperatures (12n, 18/13 and 28/23°C) and at 350 nnd 700 ppm CO2 for 4-8 weeks and net photosynthesis measured under these conditions. In C1 cultivars, short-term (within minutes) exposure to elevated CO2 had the greatest effect on photosynthesis, with an average of 55% higher rates than that at ambient CO2. There was also a response to long-term growth at high CO2, with a,1 average of 40% higher rates of photosynthesis than at ambient CO2 (both measured al their growth CO2) and a marked alteration in the temperature dependence Qf …

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Photosynthesis And Water Relations Of A C4 And A C3 Grass Under Doubled Carbon Dioxide, D Nie, M B. Kirkham, E T. Kanemasu Sep 2024

Photosynthesis And Water Relations Of A C4 And A C3 Grass Under Doubled Carbon Dioxide, D Nie, M B. Kirkham, E T. Kanemasu

IGC Proceedings (1993-2023)

The objective of this project was to determine during an entire season the photosynthetic rate and water potential of a C3 grass (Kentucky bluegrass, Poa pratensis L.) and a C4 grass (big bluestem, Andropogon gerardii Vitman) grown with 2 levels of CO2 (ambient or twice ambient) and 2 water levels (field capacity or no water added). Elevated CO2 increased the photosynthetic rate of Kentucky bluegrass by an average of 76%. During mid-season (11 June-16 July), photosynthetic rate of high-water big bluestem with ambient CO2 was about the same as that of low-water big bluestem with doubled CO2• Under both water …

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