Remigius Manderscheid

Effects of elevated CO2 and drought on wheat: Testing crop simulation models for different experimental and climatic conditions

Effects of increasing carbon dioxide concentration [CO2] on wheat vary depending on water supply and climatic conditions, which are difficult to estimate. Crop simulation models are often used to predict the impact of global atmospheric changes on food production. However, models have rarely been tested for effects on crops of [CO2] and drought for different climatic conditions due to limited data available from field experiments. Simulations of the effects of elevated [CO2] and drought on spring wheat (Triticum aestivum L.) from three crop simulation models (LINTULCC2, AFRCWHEAT2, Sirius), which differ in structure and mechanistic detail, were compared with observations. These were from 2 years of free-air carbon dioxide enrichment (FACE) experiments in Maricopa, Arizona and 2 years of standardised (in crop management and soil conditions) open-top chamber (OTC) experiments in Braunschweig and Giessen, Germany. In a simulation exercise, models were used to assess the possible impact of increased [CO2] on wheat yields measured between 1987 and 1999 at one farm site in the drought prone region of Andalucia, south Spain. The models simulated well final biomass (BM), grain yield (GY), cumulative evapotranspiration (ET) and water use efficiency (WUE) of wheat grown in the FACE experiments but simulations were unsatisfactory for OTC experiments. Radiation use efficiency (RUE) and yield responses to [CO2] and drought were on average higher in OTC than in FACE experiments. However, there was large variation among OTC experiments. Plant growth in OTCs was probably modified by several factors related to plot size, the use (or not use) of border plants, airflow pattern, modification of radiation balance and/or restriction of rooting volume that were not included in the models. Variation in farm yields in south Spain was partly explained by the models, but sources of unexplained yield variation could not be identified and were most likely related to effects of pests and diseases that were not included in the models. Simulated GY in south Spain increased in the range between 30 and 65% due to doubling [CO2]. The simulated increase was larger when a [CO2]×drought interaction was assumed (LINTULCC2, AFRCWHEAT2) than when it was not (Sirius). It was concluded that crop simulation models are able to reproduce wheat growth and yield for different [CO2] and drought treatments in a field environment. However, there is still uncertainty about the combined effects of [CO2] and drought including the timing of drought stress and about relationships that determine yield variation at farm and larger scales that require further investigation including model testing.

Photosynthetic and growth responses of old and modern spring wheat cultivars to atmospheric CO2 enrichment

Abstract Cultivars of spring wheat (Triticum aestivum L.) introduced between 1890 and 1988 were cultivated in pots under optimal growth conditions and exposed during the whole growing season to normal (379 p.p.m.) and elevated CO2 concentrations (689 p.p.m.) in open-top chambers. CO2 effects were measured at anthesis on flag leaf composition (chlorophyll and protein) and photosynthetic parameters, and at maturity on plant growth and yield. CO2 enrichment did not affect light saturated rate of photosynthesis measured at 400 p.p.m. CO2 or protein, total chlorophyll and dry weight content per unit leaf area. However, single flag leaf area and fresh weight per leaf area were increased by CO2. This increase was possibly responsible for a significant decrease in the chlorophyll a/b ratio. Under normal atmospheric CO2 concentration, the total above-ground biomass, stem weight and height, and ear number were negatively correlated with the year of cultivar release. Despite no evidence of CO2 acclimation, i.e. changes in flag leaf composition, CO2 enrichment resulted in a greater growth stimulation of the older than the modern cultivars. This was due to a greater CO2 effect on those growth components that were altered during plant breeding of wheat in the past, i.e. stem weight and height, and ear number. The average CO2-related increase in biomass and grain yield amounted to ca 46% and 28% for the three old (1890–1943) and three modern cultivars (1965–1988), respectively. Differences in yield response to CO2 enrichment between old and modern cultivars could be mainly explained by changes in ear number.

Effects of season long CO2 enrichment on cereals. II. Nutrient concentrations and grain quality

Abstract Two cultivars each of spring wheat (Triticum aestivum L., cv. Star and cv. Turbo) and spring barley (Hordeum vulgare L., cv. Alexis and cv. Arena) were exposed season-long to ambient (384 p.p.m.) and above ambient CO2 concentrations (551, 718 p.p.m.) in open-top chambers. Plant samples were taken at the booting stage and at maturity. Concentrations (grams per gram dry weight) of macro (Ca, K, Mg, N, P, S) and micronutrients (Fe, Mn, Zn) were measured in stems, leaves, ears and grains, and the amino acid composition of the grain protein was determined. For most nutrients studied the sequence and size of the response of the four cereal plants to the CO2 enrichment was cv. Arena

Effects of season-long CO2 enrichment on cereals. I: Growth performance and yield

Abstract Two cultivars each of spring wheat (Triticum aestivum L., cultivars ‘Star’ and ‘Turbo’) and spring barley (Hordeum vulgare L., cultivars ‘Alexis’ and ‘Arena’) were exposed throughout the growing season to ambient (384 p.p.m.) and above ambient CO2 concentrations (471, 551, 624, 718 p.p.m.) in open-top chambers. Plant samples were taken four times during plant development and biomass partitioning into stem, leaves and ear was measured. Total above-ground biomass increased mainly in the CO2 concentration range between 400–550 p.p.m. for wheat, and between 400–700 p.p.m. for barley. Stimulation of biomass was largely due to an increase in tillering rate. At the tiller level CO2 enrichment revealed a decrease in leaf dry weight at anthesis stage, which was due to a reduction in leaf size (barley) and in leaf number (wheat). Specific leaf weight of the mature flag leaf was unaffected by CO2. Stem biomass per tiller was temporarily (‘Star’, ‘Alexis’) or during the whole growth period (‘Turbo’, ‘Arena’) increased by CO2 exposure, while ear dry weight was increased (barley) or even decreased (‘Star’). Except for the barley cultivar ‘Arena’, which showed a 84% increase in the number of grains per ear, the number of ears was almost entirely responsible for the increased grain yield among the CO2 treatments. At the highest CO2 concentration yield increase amounted to 19% and 27% for the two wheat cultivars, and 52% and 89% for the two barley cultivars in comparison with the ambient CO2 level. Among all cultivars there was an inverse relationship between the total shoot biomass produced at ambient CO2 conditions and the plants response to the CO2 enrichment. This indicates that the genetic potential of wheat unlike barley is highly adapted to present atmospheric CO2 conditions and thus responsible for the small CO2 effect on wheat.

Seasonal Changes in Nitrogen Metabolism of Spruce Needles (Picea abies (L.) Karst.) as Affected by Water Stress and Ambient Air Pollutants

Summary Sixteen-year-old spruce trees ( Pice abies ) enclosed in their natural habitat in open-top chambers with charcoal-filtered and non-filtered air were studied from 1988 -1991 to evaluate the long-term impact of ambient air pollutants on needle nitrogen metabolism (contents of soluble protein and amino acids and activities of glutamine synthetase and glutamate dehydrogenase). Investigation of diurnal variations in soluble amino acid contents revealed a maximum of glutamate, serine and glycine and a minimum of aspartate at noon. The typical ontogenetic curves in nitrogen metabolism of young needles from flushing until October of the next year consisted of distinct phases: (1) within the first vegetation period a strong increase in needle protein and enzyme activities, (2) during winter a decrease in amino acid content, (3) in springtime a maximum in amino acid content, (4) in early summer a temporary decrease in protein content, and (5) in late summer an increase in arginine content in some trees. Beside seasonal changes, levels of the parameters were found to vary strongly between trees and over the four years of investigation. No relationship could be found between parameters of needle nitrogen metabolism and soil nitrate or ammonium concentrations. However, there was a relationship between the soil water potential and protein content (r = 0.8) and glutamine synthetase activity (r = 0.6) in the needles, indicating that both parameters increase under conditions of water stress. These physiological alterations are supposed to be based on stress-induced translocation of nitrogen from the old to the young foliage. Trees kept in chambers with non-filtered air showed higher levels of protein and glutamine synthetase activity than trees of the clean air treatment. However, the edaphic data indicate this hardly to be an effect of ambient ozone levels, but of differences in soil water status between the two variants.

Elevated CO2and drought stress effects on the chemical composition of maize plants, their ruminal fermentation and microbial diversityin vitro

Climate changes are supposed to influence productivity and chemical composition of plants. In the present experiments, it was hypothesised that the incubation of plants exposed to elevated atmospheric carbon dioxide concentrations ([CO2]) and drought stress will result in different ruminal fermentation pattern and microbial diversity compared to unaffected plants. Maize plants were grown, well-watered under ambient (380 ppm CO2, Variant A) and elevated [CO2] (550 ppm CO2, Variant B). Furthermore, each CO2 treatment was also exposed to drought stress (380 ppm and 550 ppm CO2,Variants C and D, respectively), which received only half as much water as the well-watered plants. Plant material from these treatments was incubated in a semi-continuous in vitro fermentation experiment using the rumen simulation technique. Single strand conformation polymorphism (SSCP) analysis was conducted for Bacteria and Archaea specific profiles. The analysis of crude nutrients showed higher contents of fibre fraction in drought stress Variants C and D. Crude protein content was increased by drought stress under ambient but not under elevated [CO2]. Fermentation of drought stress variants resulted in significantly increased pH values, decreased digestibilities of organic matter and increased ammonia–N (NH3–N) concentrations compared with well-watered variants. Additionally, the 550 ppm CO2 Variants B and D showed significantly lower NH3–N concentrations than Variants A and C. The Bacteria- and Archaea-specific SSCP profiles as well as the production rates of short-chain fatty acids and their molar percentages were not affected by treatments. During the first four days of equilibration period, a decrease of molar percentage of acetate and increased molar percentages of propionate were observed for all treatments. These alterations might have been induced by adaptation of the in vitro system to the new substrate. The rumen microflora appeared to be highly adaptive and could cope with altered contents of crude nutrients in plants as induced by elevated [CO2] and drought stress.

Low doses of ozone affect nitrogen metabolism in bean (Phaseolus vulgaris L.) leaves

Summary Bush bean ( Phaseolus vulgaris L. cv. Rintintin) plants were exposed 34 days for 8 h day -1 to three levels of ozone (7, 62 and 111 ppb) in open-top chambers. During anthesis concentrations of amino acids, polyamines and soluble protein as well as the activity of the enzyme glutamine synthetase were measured in leaves in order to investigate the effect of chronic ozone stress on characteristics of nitrogen metabolism. Protein content and enzyme activity of glutamine synthetase were both shown to decrease with increasing ozone concentrations. Spermidine was elevated at the highest ozone level. Analysis of amino acids yielded similar results showing a significant increase of total amino acids at the highest treatment level. This was associated with an increase of the concentrations of the individual amino acids glutamate, glutamine, alanine, threonine and, especially, asparagine. At the intermediate ozone level only the concentration of glutamate was found to be higher.

Interacting effects of photosynthetic photon flux density and temperature on canopy CO2 exchange rate of spring wheat under different CO2-concentrations.

Summary The objective of the present study was to quantify the interaction between photosynthetic photon flux density (PPFD) and temperature on canopy CO2 exchange race (CCER) of wheat at ambient and elevated CO2-concentrations. Spring wheat (Triticum aestivum L. cv. Minaret) was grown from emergence to maturity in open-top chambers under ambient (360 ppm) and elevated CO2-concentrations (680 ppm). CCER was measured using a specifically designed open system consisting of two canopy chambers (ca. 1.26 m3 each) and a monitoring unit. Air temperature and light intensity were measured directly above the canopy. CCER was measured from the first node stage until anthesis when leaf area index ranged between 2–3. PPFD ranged from 0 — ca. 1,100 μmolm−2s−1 and temperature from 7.5°–39°C. CCER increased with increasing temperature and PPFD and was light-satured at 800 μmol m−2s−1 under ambient CO2-concentration. CO2-enrichment stimulated CCER by up to 50% bui there was no complete light saturation. Under high PPFD conditions (> 600 μmolm−2s−1) and at low temperatures ( 30 °C) and low PPFD conditions (

The effect of free air carbon dioxide enrichment and nitrogen fertilisation on the chemical composition and nutritional value of wheat and barley grain

A rising atmospheric CO2 concentration might influence the nutrient composition of feedstuffs and consequently the nutritional value for livestock. The present study investigates the effects of atmospheric CO2 enrichment on the chemical composition and nutritional value of winter wheat cv. “Batis” and winter barley cv. “Theresa”. Both cereals were grown at two different atmospheric CO2 concentrations (ambient CO2 [AMBI]: 380 ppm and enriched CO2 [free air carbon dioxide enrichment, FACE]: 550 ppm) for two growing seasons. The influence of two different nitrogen (N) fertilisation levels (adequate N supply [N100] and nearly 50% of adequate N supply [N50]) were studied as well. A significant effect was observed for the crude protein content, which declined at FACE condition in a range of 8–16 g kg−1 in wheat and of 10–20 g kg−1 in barley. A reduced N fertilisation level resulted in a strong reduction of crude protein concentration in both cereal species. In wheat, a decrease in N supply significantly enhanced the concentration of starch and crude fibre. In barley, only the concentration of fructose increased under FACE condition and reduced N fertilisation. The FACE did not have major effects on the concentrations of minerals, while the influence of N fertilisation was different for both cereals. Whereas no effects could be observed for barley, a reduced N supply caused a significant reduction in concentrations of zinc, manganese and iron in wheat. Furthermore, an undirected effect of atmospheric CO2 and N fertilisation levels were found for the amino acid concentrations. Based on these results, future scenarios of climate change would have an impact on the nutritional value of cereal grains.

Effect of rising atmospheric carbon dioxide concentration on the protein composition of cereal grain.

The present study investigates effects of rising atmospheric CO2 concentration on protein composition of maize, wheat, and barley grain, especially on the fractions prolamins and glutelins. Cereals were grown at different atmospheric CO2 concentrations to simulate future climate conditions. Influences of two nitrogen fertilization levels were studied for wheat and barley. Enriched CO2 caused an increase of globulin and B-hordein of barley. In maize, the content of globulin, α-zein, and LMW polymers decreased, whereas total glutelin, zein, δ-zein, and HMW polymers rose. Different N supplies resulted in variations of barley subfractions and wheat globulin. Other environmental influences showed effects on the content of nearly all fractions and subfractions. Variations in starch-protein bodies caused by different CO2 treatments could be visualized by scanning electron microscopy. In conclusion, climate change would have impacts on structural composition of proteins and, consequently, on the nutritional value of cereals.