Katinka Ojanperä

Grain protein accumulation in relation to grain yield of spring wheat (Triticum aestivum L.) grown in open-top chambers with different concentrations of ozone, carbon dioxide and water availability

The present investigation was undertaken in order to study the influence of ozone, carbon dioxide and water availability on the relationship between grain protein and grain yield in wheat (Triticum aestivum L.). Results were combined from spring wheat, field grown in 16 different open-top chamber experiments, from four different countries. Protein concentration of the grain was negatively (linear) associated with grain yield. This relationship was symmetrical for yield reductions and yield stimulations, despite the fact that the major cause for increases in yield (elevated carbon dioxide concentrations) was different from that causing crop loss (elevated ozone concentrations). The relationship between off-take (the amount of protein taken away from the farmland per unit area) of grain protein and grain yield was clear and highly consistent, but not linear. Yield loss in relation to the reference used (open-top chamber with non-filtered air) was associated with a larger negative change in protein off-take than the positive change in protein off-take corresponding to a yield increase of the same size. The water treatments used in some of the experiments influenced yield and protein content to a very limited extent. It is concluded from the present study that the change of the grain protein from factors such as ozone and carbon dioxide can be explained largely by a simple relationship between grain protein and grain yield at a certain level of nitrogen availability to the plants.

Effects of elevated carbon dioxide and ozone on potato tuber quality in the European multiple-site experiment 'CHIP-project'

Abstract Potato (Solanum tuberosum L cv. Bintje) was exposed to ambient and elevated carbon dioxide (CO2), to ambient and elevated ozone (O3) and to elevated levels of both gases during two growing seasons, 1998 and 1999. Experiments in open-top chambers (OTC) were carried out in Finland, Sweden, Ireland, United Kingdom, Germany and Belgium and a FACE (Free Air Carbon dioxide Enrichment) experiment was carried out in Italy. In OTCs the plants were grown under ambient CO2 concentrations or with 550 and 680 μl l−1 CO2 alone or in combination with ambient or elevated O3 concentrations (target seasonal mean of 60 nl l−1 8 h per day). In the FACE systems the plants were exposed to ambient or 550 μl l−1 CO2. In the OTC experiments the reducing sugar content of potato tubers decreased significantly with increased concentration of O3. The starch content of potato tubers decreased, with negative impact on tuber quality, but the ascorbic acid concentration increased as a function of the AOT40 (The sum of the differences between hourly ozone concentration and 40 nl l−1 for each hour when the concentration exceeds 40 nl l−1 during a relevant growing season). However, simultaneous exposure to elevated CO2 counteracted the ozone effect. With increase in the CO2 exposure, glycoalkaloid and nitrate concentrations decreased yielding improved quality, while the citric acid concentration decreased causing a higher risk for discoloration after cooking. The amount of dry matter and starch increased significantly in the FACE experiment.

Growth and marketable-yield responses of potato to increased CO2 and ozone

Central to the CHanging climate and potential Impacts on Potato yield and quality project (CHIP) was the consideration of the potential impacts of ozone and CO2 on growth and yield of future European Potato crops. Potato crops, cv. Bintje, were exposed to ambient or elevated ozone; targeted daily average, 60 nl l−1 for 8 h, and ambient or elevated CO2; targeted 680 μl l−1 averaged over the full growing season, in open top chambers (OTCs) at six European sites in 1998 and 1999, or to elevated CO2 (550 μl l−1) in Free Air Carbon dioxide Enrichment facilities (FACE) at two sites in both years. Some OTC experiments included 550 μl l−1. Above and below ground biomass were measured at two destructive harvests; at maximum leaf area (MLA) and at final-harvest. Final-harvest fresh weight yields of marketable-size tubers, >35 mm diameter, from ambient conditions ranged from 1 to 12 kg m−2. There was no consistent (P>0.1) CO2×O3 interaction for growth or yield variables at either harvest. No consistent effects of ozone were detected at the maximum-leaf-area harvest. However, at final harvest, ozone had reduced both above-ground biomass and tuber dry weight (P 50 mm) size class. These yield losses showed linear relationships both with accumulated ozone exposure; AOT40 expressed as nl l−1 h over 40 nl l−1, and with yields from chambered ambient-ozone treatments (P<0.05) but, because of partial confounding between the treatment AOT40s and the ambient-ozone yields in the data, the two relationships were not completely independent. Yields from ambient-ozone treatments, however, explained a significant (P<0.01) amount of the residual variation in ozone effects unexplained by AOT40. When averaged over all experiments, mean dry weights and tuber numbers from both harvests were increased by elevated CO2. Only green leaf number at the MLA harvest was reduced. The CO2 responses varied between sites and years. For marketable-size tubers, this variation was unrelated to variation in ambient-CO2 treatment yields. Yield increases resulting from the 680 μl l−1 and 550 μl l−1 treatments were similar. Thus elevating [CO2] from 550 to 680 μl l−1 was less effective than elevating [CO2] from ambient to 550 μl l−1. On average, CO2 elevation to 680 μl l−1 increased the dry weight of marketable-size tubers by about 17%, which far exceeded the average ozone-induced yield loss of about 5%. The net effect of raising CO2 and O3 concentrations on the European potato crop would be an increase marketable yield.

Chlorophyll concentration of potatoes grown under elevated carbon dioxide and/or ozone concentrations

Abstract Potato cv. Bintje was grown in open-top-chambers and free-air-CO2-enrichment systems at 7 sites across Europe for 2 years (1998–99). The effect of different treatments (CO2 enrichment and O3 fumigation) on the chlorophyll content of fully expanded upper and lower canopy leaves was investigated collecting Minolta SPAD-502 meter readings. In both CO2 treated and O3 fumigated plants, leaves had lower chlorophyll content than those in ambient air controls; season-long chlorophyll averages were 9.3% lower in the ‘CO2’ treatments, 9.1% lower in ‘O3’ treatments and 12.3% lower in ‘CO2+O3’ treatments. The analysis of chlorophyll content in three different growth phases (Emergence–Tuber Initiation; Tuber Initiation–Maximum Leaf Area; Maximum Leaf Area–Harvest) showed that in the early growth period, i.e. before tuber initiation there was a slight indication for an higher chlorophyll content at elevated CO2 (+3.8%) or O3 (+1.7%). However, from tuber initiation onwards the leaves of plants grown under elevated CO2 or O3 showed a progressively lower chlorophyll content (−4.8% for CO2 treatments and −2.6% for O3 treatments) indicating a faster senescence of leaves that increased during the late growth period (−12.8% for CO2 treatments and −12.7% for O3 treatments) and that was enhanced by CO2–O3 interaction (−17.8%).

CO2 and ozone effects on canopy development of potato crops across Europe

This paper describes the effects of elevated CO2 (550 and 680 μl l−1) and O3 (60 nl l−1 O3 as an 8 h mean), alone or in combination, on canopy development and senescence in potato (Solanum tuberosum L. cv Bintje) across a range of European agro-climatic conditions. The assessments were made within the European CHIP project (CHanging climate and potential Impacts on Potato yield and quality) that was conducted for two growing seasons (1998 and 1999) in free air CO2 enrichment systems (FACE) and open-top chamber facilities (OTCs) at seven European sites. A comparison of chambered and unchambered experimental plots was included to examine the effects of chamber enclosure. Phenological growth stages, plant height, leaf area index (LAI) and the number of green and yellow leaves were recorded non-destructively throughout the growing season and by a destructive intermediate harvest at maximum leaf area (MLA). In the dynamic growth analysis CO2 and O3 effects were studied over three developmental stages: canopy expansion, full canopy and canopy senescence. Chamber enclosures promoted potato crop development (taller plants, more leaves) during the initial growth stages and led to a faster decline of LAI and a higher number of yellow leaves. The growth in ambient plots varied between sites and seasons, as did the scale of the treatment responses. Despite the large background variation, some overall treatment effects could be detected across all sites. Both levels of increased CO2 reduced final plant height in comparison to ambient concentrations, which indicates a premature ending of the active plant growth. At the stage of full canopy and crop senescence the average number of green leaves was significantly (P<0.05) decreased by 680 μl l−1 CO2 (OTC experiments) and LAI showed the same tendency (P=0.07). As there was however no indication of a decreased leaf formation during initial growth and at full canopy, this must have been due to an earlier leaf fall. In the FACE experiments LAI had already began to decline at the stage of full canopy at 550 μl l−1 CO2 but not in ambient CO2 (DAE×CO2, P<0.05). These observations strongly indicated that elevated CO2 induced a premature senescence during full canopy. O3 did not have an overall detrimental effect on crop development during initial growth nor at full canopy, but did induce a faster reduction of LAI during crop senescence (DAE×O3, P<0.05). Final plant height was not affected by O3. There were few CO2×O3 interactions detected. There was a suggestion (P=0.06) that O3 counteracted the CO2-induced decrease of green leaves at full canopy, but on the other hand during crop senescence the decline of LAI due to elevated O3 was faster at ambient compared to elevated CO2 (P<0.05). These responses of canopy development to elevated CO2 and O3 help to explain the treatment responses of potato yield within the CHIP project at sites across Europe.

Effects of tropospheric ozone on the yield and grain protein content of spring wheat (Triticum aestivum L.) in the Nordic countries

Eight Nordic open‐top chamber experiments with field‐grown spring wheat were combined to obtain relationships between ozone exposure and yield loss. Two exposure indices, AOT30 and AOT40 (AOT = accumulated exposure over threshold), were tested. Strongly significant linear regressions between relative yield and exposure were obtained with both indices. The coefficient of determination (r2) was higher and the model assumptions of linear regression were satisfied to a larger extent with AOT30 than with AOT40. The exclusion of charcoal‐filtered treatments from the analysis made little difference to the regressions. The AOT30 regression model predicted larger yield loss than the AOT40 regression model, especially for the range of exposures, which is likely to occur in the Nordic countries. The protein content of the grain increased with increasing ozone exposure in all eight experiments, but to a varying degree.

Yield and quality of spring barley, Hordeum vulgare L., exposed to different concentrations of ozone in open-top chambers

Abstract Spring barley ( Hordeum vulgare L., cv. ‘Lina’) was exposed to different concentrations of ozone in open-top chambers (OTCs) for 6 weeks following anthesis at a site located in south-west Sweden during the summer of 1989. The chambers were placed in a field of commercially grown barley. The treatments were charcoal-filtered air (CF), non-filtered air (NF) and non-filtered air plus extra ozone (NF +). Presence of the OTCs reduced grain yield, number of ears per unit area, and 1000-grain weight, probably due to increased drought during the warm and dry weather in the summer of 1989. The chamber also increased the crude protein content of grain. These effects were, however, not statistically significant. Grain yield was not affected by 7 h day −1 seasonal mean ozone concentrations up to 45 nl l −1 (24 h seasonal mean = 22 nl l −1 ) compared to charcoal-filtered air. It is concluded that barley is likely to be less sensitive to ozone than wheat. The possible role of differences in the process of grain filling between the two species for the differences in ozone sensitivity is discussed.

Potato tuber sugars, starch and organic acids in relation to ozone exposure

SummaryData from two Swedish and one Finnish open-top chamber experiments were combined to investigate effects of ozone exposure on potato (Solanum tuberosum L.) tuber content of starch, sucrose, fructose, glucose, malic, citric and ascorbic acids. The glucose, fructose and malic acid concentrations showed strong negative correlations with ozone exposure, while citric acid, consistently increased with ozone exposure. No ozone effects could be demonstrated on starch, sucrose or ascorbic acid concentrations. It is discussed to what extent the changes found in potato tuber composition can be explained in terms of ozone effects on tuber maturity. Ozone exposure was expressed as the accumulated exposure over a cut-off concentration of 40 nmol mol−1 (AOT40) and as the accumulated uptake of ozone over an ozone uptake rate threshold of 7 nmol m−2 s−1 (CUO 7). The difference in ability of the exposure indices to explain observed effects was small.