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Peer-reviewed lead-author papers (more papers can be found in my CV)
Loladze, I (2014) Hidden shift of the ionome of plants exposed to elevated CO2 depletes minerals at the base of human nutrition eLife 3:e02245 doi:10.7554/eLife.02245
Abstract:
Mineral malnutrition stemming from undiversified plant-based diets is a top global challenge. In C3 plants (e.g., rice, wheat), elevated concentrations of atmospheric carbon dioxide (eCO2) reduce protein and nitrogen concentrations, and can increase the total non-structural carbohydrates (TNC; mainly starch, sugars). However, contradictory findings have obscured the effect of eCO2 on the ionome—the mineral and trace-element composition—of plants. Consequently, CO2-induced shifts in plant quality have been ignored in the estimation of the impact of global change on humans. This study shows that eCO2 reduces the overall mineral concentrations (−8%, 95% confidence interval: −9.1 to −6.9, p<0.00001) and increases TNC:minerals > carbon:minerals in C3 plants. The meta-analysis of 7761 observations, including 2264 observations at state of the art FACE centers, covers 130 species/cultivars. The attained statistical power reveals that the shift is systemic and global. Its potential to exacerbate the prevalence of ‘hidden hunger’ and obesity is discussed.
eLife Digest:
The increase in CO2 in the atmosphere that has happened since the Industrial Revolution is thought to have increased the production of sugars and other carbohydrates in plants by up to 46%. CO2 levels are expected to rise even further in the coming decades; and higher levels of CO2 are known to lead to lower levels of proteins in plants. But less is known about the effects of CO2 levels on the concentrations of minerals and other nutrients in plants.
Loladze has investigated the effect of rising CO2 levels on the nutrient levels in food plants by analyzing data on 130 varieties of plants: his dataset includes the results of 7761 observations made over the last 30 years, by researchers around the world. Elevated CO2 levels were found to reduce the overall concentration of 25 important minerals—including calcium, potassium, zinc, and iron—in plants by 8% on average. Furthermore, Loladze found that an increased exposure to CO2 also increased the ratio of carbohydrates to minerals in these plants.
This reduction in the nutritional value of plants could have profound impacts on human health: a diet that is deficient in minerals and other nutrients can cause malnutrition, even if a person consumes enough calories. This type of malnutrition is common around the world because many people eat only a limited number of staple crops, and do not eat enough foods that are rich in minerals, such as fruits, vegetables, dairy and meats. Diets that are poor in minerals (in particular, zinc and iron) lead to reduced growth in childhood, to a reduced ability to fight off infections, and to higher rates of maternal and child deaths.
Loladze argues that these changes might contribute to the rise in obesity, as people eat increasingly starchy plant-based foods, and eat more to compensate for the lower mineral levels found in crops. Looking to the future, these findings highlight the importance of breeding food crops to be more nutritious as the world's CO2 levels continue to rise.
eLife Insight:
"unprecedentedly large dataset [of] the effects of elevated levels of CO2 on plant tissues, notably the effects on minerals and trace elements that are important for human health, such as calcium, zinc, and iron."
- Loladze, I. and Elser J.J. (2011) The origins of the Redfield nitrogen-to-phosphorus ratio are in a homeostatic protein:rRNA ratio, Ecology Letters, 14, 244-250
- #1 science journal in Ecology according to ISE Web of Science
- Science Editors' Choice
- March 4, 2011
- Biochemistry
- Minding Their Ps and Ns
- Nicholas S. Wigginton
- In the mid-20th century, Alfred Redfield posited that the bulk ratio of nitrogen to phosphorus atoms (N:P) in marine microorganisms should maintain a relatively constant value of ∼16. Work since then has shown that the ratio indeed remains relatively constant across many environments and time scales, including deep oceans and coastal waters, but questions remain about whether innate biochemical or environmental factors are responsible. Loladze and Elser compiled literature values of nutrient ratios in prokaryotic and eukaryotic microorganisms, which, combined with a theoretical model, suggest that the N:P ratio is determined by a balance of maximum macromolecule biosynthesis rates—specifically for nitrogen-rich proteins and phosphorus-rich ribosomal RNA. Although the analysis considered cases in which growth rates were optimal, an N:P ratio of ∼16 isn't necessarily always desirable for efficient growth; communities in environments where the paucity of nitrogen or phosphorus limits growth may have optimal N:P ratios that are shifted away from 16. Because one of these two nutrients is often the main limiting growth factor in aquatic and terrestrial systems, observable deviations in N:P ratios would therefore provide insight into the biogeochemical processes that shape microbial community structure.
- Abstract.
- One of the most intriguing patterns in the biosphere is the similarity of the atomic nitrogen-to-phosphorus ratio (N:P) = 16 found in waters throughout the deep ocean and in the plankton in the upper ocean. Although A.C. Redfield proposed in 1934 that the intracellular properties of plankton were central to this pattern, no theoretical significance for N:P = 16 in cells had been found. Here, we use theoretical modelling and a compilation of literature data for prokaryotic and eukaryotic microbes to show that the balance between two fundamental processes, protein and rRNA synthesis, results in a stable biochemical attractor that homoeostatically produces a given protein:rRNA ratio. Furthermore, when biochemical constants and reasonable kinetic parameters for protein synthesis and ribosome production under nutrient-replete conditions are applied in the model, it predicts a stable protein:rRNA ratio of 3 ± 0.7, which corresponds to N:P = 16 ± 3. The model also predicts that N-limitation, by constraining protein synthesis rates, will result in N:P ratios below the Redfield value while P-limitation, by constraining RNA production rates, will produce ratios above the Redfield value. Hence, one of most biogeochemically significant patterns on Earth is inherently rooted in the fundamental structure of life.
- Abstract. The competitive exclusion principle (CEP) states that no equilibrium is possible if n species exploit fewer than n resources. This principle does not appear to hold in nature, where high biodiversity is commonly observed, even in seemingly homogenous habitats. Although various mechanisms, such as spatial heterogeneity or chaotic fluctuations, have been proposed to explain this coexistence, none of them invalidates this principle. Here we evaluate whether principles of ecological stoichiometry can contribute to the stable maintenance of biodiverse communities. Stoichiometric analysis recognizes that each organism is a mixture of multiple chemical elements such as carbon (C), nitrogen (N), and phosphorus (P) that are present in various proportions in organisms. We incorporate these principles into a standard predator–prey model to analyze competition between two predators on one autotrophic prey. The model tracks two essential elements, C and P, in each species. We show that a stable equilibrium is possible with two predators on this single prey. At this equilibrium both predators can be limited by the P content of the prey. The analysis suggests that chemical heterogeneity within and among species provides new mechanisms that can support species coexistence and that may be important in maintaining biodiversity.
- Loladze, I. (2002) Rising CO2 and human nutrition: toward globally imbalanced plant stoichiometry? Trends in Ecology and Evolution, 17, 457-461
- Loladze, I. (2002) Rising CO2 and human nutrition: toward globally imbalanced plant stoichiometry? Trends in Ecology and Evolution, 17, 457-461Abstract. Terrestrial vascular plants obtain their major constituent – carbon (C) – from atmospheric carbon dioxide (CO2), but draw all other chemical elements largely from the soil. Concentrations of these elements, however, do not change in unison with steadily increasing concentrations of CO2. Thus, relative to pre-industrial times, modern plants are experiencing a global elemental imbalance. Could this imbalance affect the elemental composition of plants, the most important food source on Earth? Apart from an overall decline in nitrogen concentration, very little is known about the effects of high CO2 on other chemical elements, such as iron, iodine and zinc, which are already deficient in the diets of the half of human population. Here, I apply stoichiometric theory to argue that high CO2, as a rule, should alter the elemental composition of plants, thus affecting the quality of human nutrition. The first compilation, to my knowledge, of published data supports the claim and shows an overall decline of the (essential elements):C ratio. Therefore, high CO2 could intensify the already acute problem of micronutrient malnutrition.
- In Media:
- All organisms are composed of multiple chemical elements such as carbon, nitrogen and phosphorus. While energy flow and element cycling are two fundamental and unifying principles in ecosystem theory, population models usually ignore the latter. Such models implicitly assume chemical homogeneity of all trophic levels by concentrating on a single constituent, generally an equivalent of energy. In this paper, we examine ramifications of an explicit assumption that both producer and grazer are composed of two essential elements: carbon and phosphorous. Using stoichiometric principles, we construct a two-dimensional Lotka-Volterra type model that incorporates chemical heterogeneity of the first two trophic levels of a food chain. The analysis shows that indirect competition between two populations for phosphorus can shift predator-prey interactions from a (+, -) type to an unusual (-, -) class. This leads to complex dynamics with multiple positive equilibria, where bistability and deterministic extinction of the grazer are possible. We derive simple graphical tests for the local stability of all equilibria and show that system dynamics are confined to a bounded region. Numerical simulations supported by qualitative analysis reveal that Rosenzweig's paradox of enrichment holds only in the part of the phase plane where the grazer is energy limited; a new phenomenon, the paradox of energy enrichment, arises in the other part, where the grazer is phosphorus limited. A bifurcation diagram shows that energy enrichment of producer-grazer systems differs radically from nutrient enrichment. Hence, expressing producer-grazer interactions in stoichiometrically realistic terms reveals qualitatively new dynamical behavior.
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