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- Broberg, Malin, 1989
(författare)
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Effects of carbon dioxide and ozone on wheat crop yield and grain quality
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Atmospheric concentrations of carbon dioxide (CO2) and ozone (O3) have steadily increased since the industrial revolution. CO2 and O3 directly affect plant physiology, CO2 being an essential substrate for photosynthesis, while O3 is an oxidative agent causing damage to plant tissues. Due to strong concerns for future food security, effects on crop production are of particular interest. Wheat is a major food crop globally, being the second most important energy source. Accordingly, the overall aim of this thesis was to explore the general effects of elevated CO2 and O3 on wheat crops. CO2 and O3 impacts on wheat crops were systematically reviewed, using meta-analysis to estimate average effects, and deriving response functions to assess the effect size in relation to the concentration of either CO2 or O3. The underlying effects of O3 on grain nutrients was further explored in three experimental studies. Wheat yield increased by 25% on average under elevated CO2, but there was no further yield stimulation above 600 ppm. Elevated CO2 decreased grain protein concentration by 8% on average, but the effect was overestimated in pot grown plants. There was also a CO2-induced reduction in concentration of other grain nutrients, where CO2 effects on Fe and S were strongly correlated to the effects on protein but showed no relationship with grain yield stimulation. O3-induced reductions in wheat grain yield was shown to be mainly due to a decrease in grain mass, while grain number was only reduced to a small extent. Grain starch concentration was significantly reduced under O3 exposure, making starch yield the wheat yield variable most strongly affected by O3. O3 enhanced concentrations but strongly reduced the yield of important wheat grain nutrients such as protein, P, Mg, K, Ca, Zn and Mg. Both concentration and yield of Cd were reduced by O3. A comparison among our most important staple crops showed that O3 promoted a larger protein yield loss in soybean compared to rice and wheat. O3 reduced harvest index (HI) for most nutrient elements, but also for Cd, while the total element pool in aboveground biomass was unaffected (except for P). Consequently, the O3-induced reduction in grain element yield can be explained by lower remobilization rates rather than reduced uptake. There was a strong correlation of element HI when comparing sites and cultivars, indicating that it is primarily element specific and not strongly dependent on growing environment and genotypic differences. An experiment testing the interaction between O3, heat and drought stress showed that O3 effects on light saturated photosynthesis, grain mass and several grain nutrient concentrations were reduced under drought. Grain concentrations of protein, Ca and Zn were closely linked to grain yield regardless of O3, heat and drought stress. The significant impacts on wheat yield and grain quality suggest that there is a need to incorporate the influence of both CO2 and O3 in assessments of current and future global food security, but also account for the modifying effect of soil moisture.
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| 2. |
- Broberg, Malin, 1989, et al.
(författare)
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Harvest index and remobilization of 13 elements during wheat grain filling: Experiences from ozone experiments in China and Sweden
- 2021
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Ingår i: Field Crops Research. - : Elsevier BV. - 0378-4290. ; 271:15 September 2021
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Tidskriftsartikel (refereegranskat)abstract
- Wheat efficiently remobilize and allocate a large fraction of aboveground biomass and nutrients into their grains during maturation. This senescence process has been streamlined through crop breeding, which lead to increasing harvest index (HI) for biomass. With field data from two ozone exposure experiments, we derived HI for 13 elements, both nutrients and non-essential, to determine how efficiently they are allocated into the wheat grain in two different agro-ecological environments (Sweden and China) and under different ozone exposure regimes. Element HI ranged from 10 to 90 %, with highest rates for P, N and Zn (90 %, 80 % and 70 %, respectively), while HI was low for the non-mobile elements Ba, Sr and Ca (<10 %). HI for biomass was about 50 %, and the non-essential and toxic element Cd was in the same range (∼40 %). Overall element HI was very similar in Chinese and Swedish wheat cultivars. This was also the case when comparing the two Chinese genotypes. We conclude that element HI for wheat crops are highly element specific and not strongly dependent on site or cultivar. Ozone exposure significantly reduced HI for both macronutrients (Ca, K, Mg, N, P) and micronutrients (Cu, Mn, Mo, Zn), but also for Cd, while there was no ozone effect on the total aboveground pool for any element except P and Ba. Consequently, the reduction in grain element yield induced by elevated ozone, observed in previous studies, can be explained by lower remobilization rates rather than reduced total uptake. Our results provide new insights of nutrient use efficiency in wheat crops in general and under ozone exposure, which can be implemented in crop modelling and also useful for breeding strategies aiming to improve the nutritional value of food crops.
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| 4. |
- Pleijel, Håkan, 1958, et al.
(författare)
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Mercury accumulation in leaves of different plant types – the significance of tissue age and specific leaf area
- 2021
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 18, s. 6313-6328
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Tidskriftsartikel (refereegranskat)abstract
- Mercury, Hg, is one of the most problematic metals from an environmental perspective. To assess the problems caused by Hg in the environment, it is crucial to understand the processes of Hg biogeochemistry, but the exchange of Hg between the atmosphere and vegetation is not sufficiently well characterized.We explored the mercury concentration, [Hg], in foliage from a diverse set of plant types, locations and sampling periods to study whether there is a continuous accumulation of Hg in leaves and needles over time. Measurements of [Hg] were made for deciduous and conifer trees in Gothenburg, Sweden (botanical garden and city area), as well as for evergreen trees in Rwanda. In addition, data for wheat from an ozone experiment conducted at Östad, Sweden, were included. Conifer data were quantitatively compared with literature data. In every case where older foliage was directly compared with younger, [Hg] was higher in older tissue. Covering the range from the current year up to 4-year-old needles in the literature data, there was no sign of Hg saturation in conifer needles with age. Thus, over timescales of approximately 1 month to several years, the Hg uptake in foliage from the atmosphere always dominated over Hg evasion. Rwandan broadleaved trees had generally older leaves due to lack of seasonal abscission and higher [Hg] than Swedish broadleaved trees. The significance of atmospheric Hg uptake in plants was shown in a wheat experiment where charcoal-filtrated air led to significantly lower leaf [Hg]. To search for general patterns, the accumulation rates of Hg in the diverse set of tree species in the Gothenburg area were related to the specific leaf area (SLA). Leaf-area-based [Hg] was negatively and non-linearly correlated with SLA, while mass-based [Hg] had a somewhat weaker positive relationship with SLA. An elaborated understanding of the relationship behind [Hg] and SLA may have the potential to support large-scale modelling of Hg uptake by vegetation and Hg circulation.
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