Increasing CO2 threatens human nutrition.

Effects of elevated atmospheric carbon dioxide on insect–plant interactions

Terrestrial higher plants exchange large amounts of CO2with the atmosphere each year; c. 15% of the atmospheric pool of C is assimilated in terrestrial‐plant photosynthesis each year, with an about equal amount returned to the atmosphere as CO2in plant respiration and the decomposition of soil organic matter and plant litter. Any global change in plant C metabolism can potentially affect atmospheric CO2content during the course of years to decades. In particular, plant responses to the presently increasing atmospheric CO2concentration might influence the rate of atmospheric CO2increase through various biotic feedbacks. Climatic changes caused by increasing atmospheric CO2concentration may modulate plant and ecosystem responses to CO2concentration. Climatic changes and increases in pollution associated with increasing atmospheric CO2concentration may be as significant to plant and ecosystem C balance as CO2concentration itself. Moreover, human activities such as deforestation and livestock grazing can have impacts on the C balance and structure of individual terrestrial ecosystems that far outweigh effects of increasing CO2concentration and climatic change.In short‐term experiments, which in this case means on the order of 10 years or less, elevated atmospheric CO2concentration affects terrestrial higher plants in several ways. Elevated CO2can stimulate photosynthesis, but plants may acclimate and (or) adapt to a change in atmospheric CO2concentration. Acclimation and adaptation of photosynthesis to increasing CO2concentration is unlikely to be complete, however. Plant water use efficiency is positively related to CO2concentration, implying the potential for more plant growth per unit of precipitation or soil moisture with increasing atmospheric CO2concentration. Plant respiration may be inhibited by elevated CO2concentration, and although a naive C balance perspective would count this as a benefit to a plant, because respiration is essential for plant growth and health, an inhibition of respiration can be detrimental. The net effect on terrestrial plants of elevated atmospheric CO2concentration is generally an increase in growth and C accumulation in phytomass. Published estimations, and speculations about, the magnitude of global terrestrial‐plant growth responses to increasing atmospheric CO2concentration range from negligible to fantastic. Well‐reasoned analyses point to moderate global plant responses to CO2concentration. Transfer of C from plants to soils is likely to increase with elevated CO2concentrations because of greater plant growth, but quantitative effects of those increased inputs to soils on soil C pool sizes are unknown.Whether increases in leaf‐level photosynthesis and short‐term plant growth stimulations caused by elevated atmospheric CO2concentration will have, by themselves, significant long‐term (tens to hundreds of years) effects on ecosystem C storage and atmospheric CO2concentration is a matter for speculation, not firm conclusion. Long‐term field studies of plant responses to elevated atmospheric CO2are needed. These will be expensive, difficult, and by definition, results will not be forthcoming for at least decades. Analyses of plants and ecosystems surrounding natural geological CO2degassing vents may provide the best surrogates for long‐term controlled experiments, and therefore the most relevant information pertaining to long‐term terrestrial‐plant responses to elevated CO2concentration, but pollutants associated with the vents are a concern in some cases, and quantitative knowledge of the history of atmospheric CO2concentrations near vents is limited.On the whole, terrestrial higher‐plant responses to increasing atmospheric CO2concentration probably act as negative feedbacks on atmospheric CO2concentration increases, but they cannot by themselves stop the fossil‐fuel‐oxidation‐driven increase in atmospheric CO2concentration. And, in the very long‐term, atmospheric CO2concentration is controlled by atmosphere‐ocean C equilibrium rather than by terrestrial plant and ecosystem responses to atmospheric CO2concentration.

The detection of 12CO2 emission from leaves in air containing 13CO2 allows simple and fast determination of the CO2 emitted by different sources, which are separated on the basis of their labelling velocity. This technique was exploited to investigate the controversial effect of CO2 concentration on mitochondrial respiration. The 12CO2 emission was measured in illuminated and darkened leaves of one C4 plant and three C3 plants maintained at low (30-50 ppm), atmospheric (350-400 ppm) and elevated (700-800 ppm) CO2 concentration. In C3 leaves, the 12CO2 emission in the light (Rd) was low at ambient CO2 and was further quenched in elevated CO2, when it was often only 20-30% of the 12CO2 emission in the dark, interpreted as the mitochondrial respiration in the dark (Rn). Rn was also reduced in elevated CO2. At low CO2, Rd was often 70-80% of Rn, and a burst of 12CO2 was observed on darkening leaves of Mentha sativa and Phragmites australis after exposure for 4 min to 13CO2 in the light. The burst was partially removed at low oxygen and was never observed in C4 leaves, suggesting that it may be caused by incomplete labelling of the photorespiratory pool at low CO2. This pool may be low in sclerophyllous leaves, as in Quercus ilex where no burst was observed. Rd was inversely associated with photosynthesis, suggesting that the Rd/Rn ratio reflects the refixation of respiratory CO2 by photosynthesizing leaves rather than the inhibition of mitochondrial respiration in the light, and that CO2 produced by mitochondrial respiration in the light is mostly emitted at low CO2, and mostly refixed at elevated CO2. In the leaves of the C4 species Zea mays, the 12CO2 emission in the light also remained low at low CO2, suggesting efficient CO2 refixation associated with sustained photosynthesis in non-photorespiratory conditions. However, Rn was inhibited in CO2-free air, and the velocity of 12CO2 emission after darkening was inversely associated with the CO2 concentration. The emission may be modulated by the presence of post-illumination CO2 uptake deriving from temporary imbalance between C3 and C4 metabolism. These experiments suggest that this uptake lasts longer at low CO2 and that the imbalance is persistent once it has been generated by exposure to low CO2.

Decomposition in Soil of C4 and C3 Plant Material Grown at Ambient and at Elevated Atmospheric CO2 Concentrations

The biodegradability of aerial material from a C4 plant, sorghum grown under ambient (345 µmol mol−1) and elevated (700 µmol mol−1) atmospheric CO2 concentrations were compared by measuring soil respiratory activity. Initial daily respiratory activity (measured over 10 h per day) increased four fold from 110 to 440 cm3 CO2 100g dry weight soil−1 in soils amended with sorghum grown under either elevated or ambient CO2. Although soil respiratory activity decreased over the following 30 days, respiration remained significantly higher (t-test;p>0.05) in soils amended with sorghum grown under elevated CO2 concentrations. Analysis of the plant material revealed no significant differences in C:N ratios between sorghum grown under elevated or ambient CO2. The reason for the differences in soil respiratory activity have yet to be elucidated. However if this trend is repeated in natural ecosystems, this may have important implications for C and N cycling.

We used open-top chambers (OTCs) to simulate the conditions of elevated atmospheric CO2 concentration at the Changwu State Key Agro-Ecological Experimental Station of the Loess Plateau. There were three treatments, CK (maize grown under field conditions with natural atmospheric CO2 concentration), OTC (maize grown in the open-top chamber under natural atmospheric CO2 concentration), and OTCe (maize grown in the open-top chamber under elevated atmospheric CO2 concentration of 700 μmol·mol-1).We explored the responses of non-structural carbohydrate (NSC) and grain quality (soluble sugar, starch and crude protein) of spring maize to elevated CO2 at different growth stages, aiming to provide scientific basis for revealing the adaptation mechanism of maize to elevated CO2. The results showed that the effects of elevated CO2 on NSC content and accumulation in maize varied across organs and growth periods. Elevated CO2 promoted the activation and redistribution of NSC in leaves, stems and roots during reproductive growth period, and significantly increased the amount of NSC conversion to the grains (ATMNSC), as well as the conversion rate to the grains (ARNSC) and the contribution to the grains (ACNSC) in leaves, stems and roots. Compared with CK, the warming effect of OTC inhibited the activation and redistribution of NSC in stems and roots, but promoted the activation and redistribution of NSC in leaves, significantly increased the ATMNSC, ARNSC, and ACNSC of maize leaves. Elevated CO2 did not affect the contents of soluble sugar, starch, and crude protein in maize grains.

Aims The influence of elevated atmospheric CO2 concentration and nitrogen(N) addition on soil carbon pool is one of the foci among international ecological research communities. The changes of soil carbon pool induced by atmospheric CO2 concentration and/or N deposition will lead to changes in atmospheric carbon pool and thus the global climate change. However, few studies have been carried out in the subtropical China. Our objective was to understand the effect of elevated CO2 concentration and N addition on soil carbon stability in south subtropical experimental forests. Methods Experimental forest ecosystems were constructed in open top chambers. Six native tree species in southern China were planted in these experimental forest ecosystems. The species were exposed to elevated CO2 and N addition in the open top chambers beginning in May 2005. The four treatments were: elevated CO2 and high N addition(CN), elevated CO2 and ambient N deposition(CC), high N addition and ambient CO2(NN), and ambient CO2 and ambient N deposition(CK). The elevated CO2 was(700 ± 20) μmol·mol–1. The total amount of added NH4NO3-N was 100 kg N·hm–2·a–1. In January 2010, soil samples were collected from the open top chambers and then relevant variables were measured. Important findings Elevated CO2 concentration and N addition(CN) effectively increased the soil total organic carbon in different soil layers, among which the increases in the lower soil layers(5–60 cm) were statistically significant. Different components of the active organic carbon pool differed in the responses to treatments. The differences in microbial biomass carbon were significant in the 0–5 cm, 5–10 cm and 10–20 cm soil layers amongthe treatments, and the readily oxidized carbon showed significant responses to the elevated CO2 concentration and N addition treatments in the 10–20 cm and 20–40 cm soil layers, while there was no significant difference in the dissolved organic carbon among different treatments in all the soil layers. The responses of carbon in different aggregate fractions differed among the treatments. The carbon in the 250–2 000 μm aggregates was significantly different among treatments in the 20–40 cm and 40–60 cm soil layers. The carbon in the 53–250 μm aggregates was susceptible to treatments in the 40–60 cm soil layer as both the CC and NN treatments facilitated the chronic carbon accumulation in deeper soil layers, especially under the CN treatment. Carbon in the 53 μm fraction showed significant differences among treatments in deeper soil layers(10–20 cm, 20–40 cm and 40–60 cm). In conclusion, elevated CO2 concentration and N addition increased soil organic carbon in the experimental forest ecosystems, and facilitated the accumulation of carbon in micro-aggregates and silt-clay fraction in deep soil layers, thus strengthened the stability of soil organic carbon pool.

PDF HTML阅读 XML下载 导出引用 引用提醒 大豆主要株型和产量指标对大气CO2和温度升高的响应 DOI: 10.5846/stxb201411122240 作者: 作者单位: 南京农业大学,南京农业大学,南京农业大学,南京农业大学,南京农业大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目(31272051,31101491,31470454) Morphological traits and yield of soybean under elevated atmospheric CO2 concentration and temperature Author: Affiliation: Nanjing Agricultural University,Nanjing Agricultural University,Nanjing Agricultural University,Nanjing Agricultural University,Nanjing Agricultural University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:针对当前气候变暖和大气CO2浓度升高同步发生现实,以高光效大豆品种黑农41(HN41)和3个常规对照品种周豆16号(ZD16)、中豆35号(ZD35)和桂黄豆2号(GHD2)为研究对象,通过开顶式气室模拟高CO2浓度(650μL/L)和温度升高(±0.5-0.6℃)研究了大气CO2和温度升高对大豆的生长发育与产量影响。结果表明,CO2浓度升高对株高、茎粗、单株干重和单株籽粒重影响极显著;温度、CO2与品种互作极显著地影响单株籽粒重。CO2浓度升高有增加大豆株高、茎粗、干重和单株籽粒重的趋势,且高温下CO2浓度升高对株高和茎粗的促进作用更大,而正常温度水平下高CO2浓度升高更有利于干物质积累。与对照CO2浓度比,高CO2浓度显著促进了高温下HN41、ZD16和GHD2的株高,并显著提高了正常温度下HN41、ZD16、ZD35和GHD2的单株干重。与正常温度相比,高温仅显著提高了高CO2处理下HN41的茎粗,并显著提高了对照CO2处理下HN41的单株籽粒重。此外,同一CO2浓度和温度处理下,高光效大豆HN41的茎粗、根冠比和单株籽粒重等都显著高于ZD16、ZD35和GHD2;而仅在正常温度与高CO2浓度处理下HN41的单株干重显著高于ZD16和GHD2。CO2浓度和温度升高显著影响了高光效大豆的生长,其中,高温下CO2浓度升高有利于其生长势,正常温度下CO2浓度升高有利于其光合产物积累。 Abstract:Increasing levels of atmospheric CO2 and temperature are the two most important factors of global climate change. As two key environmental factors for plant growth, the changes in atmospheric CO2 concentration and temperature can affect photosynthetic productivity of crop plants. Moreover, used as a raw material in plant photosynthesis, increasing atmospheric CO2 concentration will have a direct positive impact on photosynthesis and a series of physiological and biochemical process in plants and finally on crop yield. The atmospheric CO2 level is increasing sharply with the expanding scope of human economic activities, which raises Earth surface temperature, eventually leading to global warming. In general, the photosynthetic rate is not saturated in most crop species under ambient CO2 level (about 375 μL/L); hence, the increasing atmospheric CO2 level can enhance the photosynthetic rate in most crop plants. Howerver, the effect of climate change on photosynthesis, and physiological and biochemical processes is much more complex and unknown in most crops, especially in cultivars with high photosynthetic efficiency under the assumption of concomitant global warming and atmospheric CO2 concentration increase. In this study, soybean cultivar HN41 with high photosynthetic efficiency ( ≥ 17.64 μmol [CO2] m-2s-1) and three varieties ZD16, ZD35, and GHD2 with normal photosynthetic efficiency (10.75-15.48 μmol [CO2] m-2s-1) were selected to study morphological traits and yield of soybean under elevated levels of CO2 (650 μL/L vs. ambient CO2) and temperature (± 0.5-0.6℃ vs. ambient temperature). The results indicated that CO2 levels significantly affected plant height and stem diameter, as well as dry weight and seed weight per plant. Temperature levels and the interaction between CO2 concentration and soybean cultivars significantly affected seed weight per plant. Relative to ambient CO2 concentration, elevated levels of CO2 promoted plant height, stem diameter, and dry weight and seed weight per plant, particularly under higher temperature. Moreover, elevated CO2 significantly increased plant height in HN41, ZD16, and GHD2 at high temperature (18.9%, 24.4%, and 31.5%, respectively) and significantly enhanced dry weight per plant in HN41, ZD16, ZD35, and GHD2 at ambient temperature (7.3%, 4.7%, 16.0%, and 18.8%, respectively), in contrast to ambient CO2 levels. Compared with ambient temperature, higher temperature significantly increased only the stem diameter of HN41 under elevated CO2 levels and significantly enhanced the grain weight per plant in HN41 under ambient CO2 levels. In addition, stem diameter, root/shoot ratio, and grain weight per plant in HN41 were significantly greater than those in normal cultivars (ZD16, ZD35, and GHD2) under the same conditions of atmospheric CO2 levels and temperature, whereas dry biomass per plant in HN41 was significantly increased compared with that in ZD16 and GHD2. In conclusion, increase of both atmospheric CO2 levels and temperature significantly affected plant growth of the highly photosynthesis-efficient soybean. Elevated CO2 concentration can promote plant growth particularly at high temperature, whereas elevated CO2 favors accumulation of photosynthetic products at ambient temperature especially for the highly photosynthesis-efficient soybean. 参考文献 相似文献 引证文献

The effects of elevated atmospheric CO2 concentration on the biological control of invasive aquatic weeds

SummaryIn this study, we used Parthenium hysterophorus and one of its biological control agents, the winter rust (Puccinia abrupta var. partheniicola) as a model system to investigate how the weed may respond to infection under a climate change scenario involving an elevated atmospheric CO2 (550 μmol mol−1) concentration. Under such a scenario, P. hysterophorus plants grew significantly taller (52%) and produced more biomass (55%) than under the ambient atmospheric CO2 concentration (380 μmol mol−1). Following winter rust infection, biomass production was reduced by 17% under the ambient and by 30% under the elevated atmospheric CO2 concentration. The production of branches and leaf area was significantly increased by 62% and 120%, under the elevated as compared with ambient CO2 concentration, but unaffected by rust infection under either condition. The photosynthesis and water use efficiency (WUE) of P. hysterophorus plants were increased by 94% and 400%, under the elevated as compared with the ambient atmospheric CO2 concentration. However, in the rust‐infected plants, the photosynthesis and WUE decreased by 18% and 28%, respectively, under the elevated CO2 and were unaffected by the ambient atmospheric CO2 concentration. The results suggest that although P. hysterophorus will benefit from a future climate involving an elevation of the atmospheric CO2 concentration, it is also likely that the winter rust will perform more effectively as a biological control agent under these same conditions.

Meeting the Iron Needs of Infants and Young Children

Elevated CO2 improves assimilation rate and growth of tomato plants under progressively higher soil salinity by decreasing abscisic acid and ethylene levels

Growth under elevated atmospheric CO2 concentration accelerates leaf senescence in sunflower (Helianthus annuus L.) plants

Despite a plethora of papers, reports and consensus statements during the last 25 years concerning the high prevalence and complications of iron deficiency (ID), the problem is still with us. A recent national study in Britain showed that 12% of 2-year-olds were anaemic, rising to 29% in Asian immigrant groups (Lawson et al, 1998). What can be done about it? This paper reviews detection and prevention of iron deficiency anaemia (IDA) referring mainly to studies published in the last 5 years. Earlier substantial reviews of iron nutrition are available (Brock et al, 1994; British Nutrition Foundation, 1995; Hallberg & Asp, 1996). Reviews specifically related to children include those by Oski (1993) and Wharton (1999a). Detection is divided into indications for investigation, which investigations to apply, and their interpretation. There are obvious indications for determining iron status in some clinical presentations. An example is suspected malabsorption. One study found that an oral iron absorption test was more sensitive as a screening test for upper intestinal absorption than the commonly used D-xylose method (Stahlberg et al, 1991; De Vizia et al, 1992). Other deficiencies often coexist with ID partly because a poor diet may have many deficiencies but also because of micronutrient interaction, e.g. ID with deficiencies of vitamin A or D (Gujral & Gopaldesas, 1995; Underwood & Arthur, 1996; Wharton, 1999b). ID may play a role in or complicate such diverse disorders as ischaemic stroke, apparent asthma, cyanotic heart disease and gastric trichobezoar (Hartfield et al, 1997; Hetzel & Losek, 1998; Olcay et al, 1996; Phillips et al, 1998). In my view any child reaching hospital as an outpatient or inpatient should have their haemoglobin level and RBC indices determined. Some specialities argue this is unnecessary since the haemoglobin distribution in their patients is no different to that in the general population (e.g. in otolaryngology; Heaton et al, 1991). This seems a lost occasion for opportunistic screening for a common disorder. Clinical signs are helpful only in severe anaemia, but surveys show that pale conjunctivae (sensitivity 74%) and nail beds (specificity 96%) are useful signs (Thaver & Baig, 1994). Blue sclerae might be an extra sign (Beghetti et al, 1993). The highest prevalence of iron deficiency anaemia (IDA) occurs in toddlers and adolescents because the increment in haemoglobin iron per unit body weight is greatest at these ages (see Fig 1). . Changes in body iron during development: (a) total body iron and haemoglobin iron (mg) in males except where shown; (b) daily increment in body iron (mg/d): —-, male; - - - -, female; ...., female plus menstrual loss; (c) proportional daily increment in body iron (μg/kg/d); symbols as for (b). Two points should be noted. There is little increase in total body iron in the first 4 months or so of life. As the haemoglobin falls from around 18 g/dl at birth to 14 g/dl during the first 2 weeks of life the liberated iron is stored and then gradually reused as the total mass of circulating haemoglobin begins to increase with growth. Between 4 and 12 months total body iron increases by about 130 mg, and an external source of iron is necessary. If not met, ID occurs and frank anaemia develops usually after the first birthday. Note also that boys need more iron at adolescence because of the increase of muscle and myoglobin. Subsequently these increased requirements due to changes in body composition subside, but increased requirements continue in girls following menarche. Infants who continue to receive only breast milk after the first 6 months of life are at increased risk. Breast feeding may continue after 6 months without difficulty so long as other foods providing available iron are introduced. Also at risk are infants who, despite current policy, are changed from an infant formula to whole cows' milk before the age of 1 year. It is not clear whether the higher prevalence of IDA in these infants is mainly the effect of an inadequate intake of dietary iron or due in addition to increased intestinal iron loss (Ziegler et al, 1990; Fuchs et al, 1993a, b). In toddlers attending well child facilities in Cleveland, U.S.A., a simple dietary history predicted microcytic anaemia (sensitivity 71%, specificity 79%), but a quarter of the anaemic children were not identified (Boultry & Needlman, 1996). A community study in Sydney found a low consumption of meat (i.e. haem iron) and introduction of whole cows' milk before the first birthday were significant indicators of ID (Mira et al, 1996). Many adolescent girls try to control their weight and inadvertently limit iron intake. This was particularly marked 10 years ago in British girls who bought snacks from local shops rather than eating school lunch or food from home, but there has been evidence of improvement since then (Department of Health, 1989; Moynihan et al, 1994; Southon et al, 1994; Doyle et al, 1994). Many adolescents pass through a temporary period of vegetarianism because of concerns with animal welfare. Although adequate iron nutrition is achievable on a vegetarian diet it must provide iron sources (such as pulses) and enhancers of absorption (e.g. vitamin C and fish or poultry if acceptable), and the temporary amateur vegetarianism may not ensure sufficient absorbed iron. Preterm babies are born with a lower concentration of haemoglobin, so any physiological haemolysis liberates less iron for stores; erythropoietin, if given, increases iron requirements, and so does catch up growth. Light for gestational age babies often have a raised haemoglobin at birth reflecting intrauterine hypoxia, and so initially, post haemolysis iron stores are higher but the rapid catch-up growth increases demands. In a normal term baby the total haemoglobin mass doubles during the first year of life (from 180 mg at birth to 340 mg at 1 year). In a preterm 1 kg baby the increase is 6-fold (50–300 mg). In a 2 kg baby born at term the increase is 3-fold (110–330 mg). Children of immigrants or refugees have a higher prevalence of iron deficiency, presumably due to such factors as socio-economic deprivation (living in inner city areas with overcrowding and limited parental income), language difficulties (health education is difficult), unfamiliarity with foods available in the new environment (often a tendency to rely on milk and puddings), food customs which are difficult to follow (e.g. halal meat for Muslims may not be easily available and so children are given a meat-free diet by a mother inexperienced in providing a balanced vegetarian diet). In a nationally representative survey of British 1.5–2.5-year-olds 12% had IDA but among children of immigrant families it was higher: India (20%), Pakistan (27%) and Bangladesh (29%) (Lawson et al, 1998). Other recent reports describe the problem in children from South-East Asia, Latin America and Eastern Europe living in U.S.A., Norway and Switzerland (Graham et al, 1997; Sargent et al, 1996). Athletic performance, particularly endurance sport, may lead to blood loss from the gut and urinary tract (Robertsson et al, 1987; Haymes & Lamanca, 1989). Therefore athletic girls who have passed menarche and are trying to slim may be at particular risk of iron deficiency. The staging of iron status by Oski et al (1983) is a useful concept and various measurements can be used to define the stages. Iron stores and erythropoiesis normal. Erythropoiesis normal but iron stores reduced (serum ferritin <12 μg/l) indicating a reduction of iron in the bone marrow, liver and other parts of the reticuloendothelial system (note that the exact cut-off point for normal/abnormal ferritin depends on the method used; a reference ferritin preparation to calibrate the assay is recommended). (i) Abnormal RBC biochemistry (free erythrocyte protoporphyrin (EPP) >99 mmol/mol haem; serum transferrin receptor raised, e.g. >8.5 mg/l but exact cut-off depends on age and the assay used); (ii) abnormal RBC morphology (microcytosis, MCV <80 fl, varying with age; anisocytosis, RDW > 15%); (iii) transport iron reduced (transferrin saturation <10%). The above plus haemoglobin <11 g/dl. There is no evidence that iron depletion or iron-deficient erythropoiesis alone have any adverse clinical effects, whereas iron deficiency anaemia is associated with alterations of immunological, gut and mental function. In the recent NHANES survey in the U.S.A. (Dallman et al, 1996) ID was defined as the presence of two or more abnormal measurements as shown in Table I. Although one can argue about the exact cut-off points used and the need for two abnormal characteristics, this battery of tests was applied to a large number of children and the haemoglobin ranges produced (i.e. after excluding children with more than one abnormal test) are suitable reference standards (see Table I). A recent survey in Bristol has suggested a cut-off point for haemoglobin concentration in 12- and 18-month-olds as low as 10 g/dl, but no attempt was made to exclude iron-deficient children and the haemoglobin method used was the Hemocue B-Hb photometer (Sherriff et al, 1999). It would be impractical, however, to use initially the whole battery of investigations shown in Table I and simpler approaches for population and individual studies have been suggested. Yip et al (1996) suggested that haemoglobin concentrations alone could be used in populations. The distributions of haemoglobin are determined in children and adults. If the distribution is moved to the left, in both children and women of child bearing age but not in men, then iron deficiency is likely. If the distribution is moved to the left in men as well, then probably other factors are operating as well, e.g. malaria or hookworm. This approach has been used to diagnose dietary ID in Pakistan, iron losses from hookworm in Zanzibar, and iron losses (from undetermined causes) in Alaskan natives (Petersen et al, 1996). The strategy has been questioned in Thailand for children >5 years of age in whom anaemia was rarely associated with a low plasma ferritin (Linpisarn et al, 1996). Electronic counters based on impedence or light scattering are in common use in developed countries. The likelihood of iron deficiency may then be assessed from the indices. Increasing use is now made of histogram distributions of red blood cell volume rather than using only arithmetic summaries of size and variation in size such as mean corpuscular volume (MCV) and red cell distribution width (RDW). With some methods 'red cell cytograms' are also available in which red cell volume is plotted against red cell haemoglobin concentration for all red cells counted. Walters & Abelson (1996) have described the interpretation of full blood count and indices, possible artefacts (due to cold agglutinins, high white cell counts, and hyperosmolar plasma), crude checks for internal consistency (haemoglobin in g/dl about 3 × RBC; calculated and correct PCV about 3 × haemoglobin) and its interpretation in children. Hinchcliffe & Helliwell (1993) have described the use of distribution histograms and cell cytograms in children. Typically in iron deficiency anaemia Hb and MCV are reduced, RDW is increased (i.e. microcytosis and anisocytosis), red cell haemoglobin distribution width (HDW) is increased (i.e. anisochromia), and the 'shape' of the cell cytogram scatter is moved down and to the left with a large proportion of cells in the hypochromic microcytic zone. During a response to iron treatment double peaks are seen in the histograms for red cell volume and red cell haemoglobin and the cytogram shows more cells in the normocytic normochromic zone. The application of these more sophisticated methods to population screening has not been evaluated. Mates et al (1995) argued that a full electronic counter blood screen is a 'watchdog of community health'. In their Israeli series including adults as well as children, 1% had microcytosis, mostly due to iron deficiency (58%) and thalassaemia minor (35%). Similarly Kim et al (1996) recommend that MCV and RDW be routinely determined, and this increases the predictive value for iron deficiency to 98%. Choi & Reid (1998) found RDW a useful predictor of red cell disease in the well baby clinic. EPP alone (or zinc protoporphyrin, ZPP) has been used for screening and as an indication for a therapeutic trial of iron in some American paediatric practices (Benjamin et al, 1991; Siegal & Lagrone, 1994). In iron deficiency zinc fills the iron pocket in the protoporphyrin molecule. ZPP determination requires only 20 μl of blood and is easily measured in a haematofluorimeter. It also remains abnormal for a week or so, even if iron therapy commenced before the test. However, it is also abnormal in the anaemias of inflammation and in lead poisoning. Serum ferritin may also be determined on small blood samples, but careful standardization of methods and use of a reference ferritin preparation for calibration are necessary (Worwood, 1997). It is raised during acute infections, chronic disease and liver disease irrespective of the iron stores, but iron deficiency is the only cause of a low concentration. Serum transferrin receptor concentration has raised considerable interest. The concentration reflects the number of transferrin receptors on immature red cells and so in most instances also reflects the rate of bone marrow erythropoiesis. Iron deficiency, however, also results in an 'unproportional' increase in the concentration (Heubers et al, 1990). An increased concentration provides an early and sensitive indicator of functional iron deficiency, sometimes before the plasma ferritin has fallen (Skikne et al, 1990; Worwood, 1995, 1997). A major advantage is that it remains normal in many chronic disorders if iron deficiency is not present. However, it is raised in the thalassaemias even though iron deficiency is not present. As in adults, in infants and 11–12-year-old boys higher concentrations of the receptor were associated with a lower serum ferritin even within the normal physiological range for ferritin (Virtanen et al, 1999). However, its use as an index of iron deficiency in infancy and adolescence has been questioned (Kuiper-Kramer et al, 1998; Kling et al, 1998; Kivivuori et al, 1993; Kuizon et al, 1996). It would be unwise to use the test alone without other measurements of ID as well. Hereditary causes of microcytosis, inflammation and various chronic diseases, and occasionally lead poisoning, may cause difficulties of interpretation. Apart from the thalassaemias, hereditary causes of microcytosis are quite rare. Most are associated with iron overload of tissues, but a small number of children have been described with ID because of a defect in absorption (Table II). The RBC in IDA and the thalassaemias have similar indices. The degree of anisocytosis and hence the RDW is usually higher in IDA, particularly in relation to the degree of microcytosis. Various mathematical ratios of red cell indices have been suggested to help the differentiation. Using cytometry plots, the proportion (%) of hypochromic cells is greater than the proportion of microcytic cells in iron deficiency, whereas the reverse is true in thalassaemia (d'Onofrio et al, 1992). In thalassaemia there also may be an increase in hypochromic macrocytes. When there is any possibility of a thalassaemia, however, it is usually better to proceed directly to haemoglobin electrophoresis and A2 determination, but iron deficiency in association with thalassaemia may temporarily mask the characteristic changes in A2 and HbF. In a United States study a half of people (aged 15–49 years) with beta thalassaemia trait, had a raised ZPP, and so did a quarter of those with haemoglobin E or alpha-thalassaemia trait, suggesting that ZPP may be abnormal in thalassaemia traits, but the exact iron status of the subjects was not defined (Graham et al, 1996). The anaemias of infection and chronic diseases are classically normochromic and normocytic, but hypochromia and microcytosis occur in about a third of infected children. Even after a mild infection many measurements move in the same direction as occurs in ID, but ferritin rises and serum transferrin receptor remains normal (see reviews by Abshire, 1996, and Walter et al, 1997). On the other hand, tropical infection such as malaria did not interfere with the use of EPP and ferritin in the diagnosis if ID of Zanzibari schoolchildren (Stoltzfus et al, 1997). In chronic disease such as rheumatoid arthritis interpretation is difficult. Although measurements suggesting ID may be due to cytokine activity true ID by bone marrow may also serum transferrin receptor is raised in a number of suggesting iron erythropoiesis which may to iron et al, 1996). The anaemia is classically normocytic and but ID is often as well, the RBC ZPP is raised, not because of iron to protoporphyrin to haem but because which the is by There is evidence iron deficiency with an increased risk of lead et al, 1995; et al, 1996). Some years ago anaemia with would for both but as lead has the diagnosis is less If in the blood lead should be determined and the response to iron noted. and reduction in blood lead following treatment are less in iron-deficient children et al, 1996; et al, 1997). is a of and the early before If at the age of 18 many children would have been anaemic for some If e.g. months at the of a number of children not anaemic then so some months In Bristol a quarter of children found to be anaemic at the age of 2 years had not been so at months et al, 1993). An age for screening is not children in particular groups might be if the prevalence of IDA is high in the e.g. in inner city children of immigrant or and toddlers in whom cows' milk was the before 12 months of Various have suggested e.g. the for (1998) in of in such as the British and Nutrition many individual and & 1996). loss should be with which as the usually The of may In infants in whom the was not had had a higher at 2 months of age; this had no effect on serum ferritin at 3 months of age in children et al, 1997; et al, 1997). of iron at birth is in haemoglobin, blood loss is a cause of anaemia in early and the other stores in show little to the iron some studies in both the developed and have shown Two have shown that iron status in is associated with a iron status in the infants at 1 year of age 1996; et al, 1990). This could a effect of reduced iron stores or that both mother and child have an iron-deficient babies there is little because total body iron does not increase during this If ID occurs then abnormal blood loss should be This may occur in the period or (e.g. from gastric in a rarely of Breast feeding is or that a infant formula is the age 6 months a dietary source of iron is necessary. babies this is easily by use of an infant formula which is iron or introduction of a all of which are iron Breast milk alone not the extra iron but absorption of the small of iron is This is less in babies formula or a and babies to receive foods from an age than et al, 1990). Although there is evidence that early an introduction of foods with iron absorption from breast milk et al, should be from 6 months of because of its haem is an providing zinc as well, which may also a in breast A study showed that an intake of of meat a from the age of months to an intake of 10 to lower falls of haemoglobin in there were no on serum ferritin or transferrin receptor concentrations et al, 1998). many who continue to breast their infants vegetarian foods from which iron is less foods are available in the and some are with iron. use of these foods a more diet less and than a diet alone & et al, in questioned the possibility of iron to children from about 4 months rather than the risk of which have low iron et al, 1998). In Britain of the total iron intake of children years is by as haem by such as and and This diet the for most ages but not for toddlers age years intake was of is for girls of (Department of Health, 1989; et al, However, the total intake is only of the The absorption of iron is determined by the composition of the the of the and of haem iron increases anaemia is but is little by other of the of iron is by vitamin other in and such as and and animal is by and reviews specifically for children, and The of iron absorption is also by body stores, the rate of and The receive from these factors to absorption are not In foods are less available at and and are higher et al, 1998). On the other hand, some foods are in iron to better iron status than if are used & 1998). is used as a source of iron in et al, 1997). The role of cows' milk in intestinal blood loss has been to In many parts of the hookworm is the most common cause of blood There are control at control of of use of simple for schoolchildren and should be applied to children as well, with iron (Stoltzfus et al, 1998; et al, 1997). is less as a cause of anaemia, and have been as less causes of iron deficiency as a population problem et al, 1996). With a clear strategy should be a simple of is but of eating customs and is difficult. education have been e.g. in a in Bristol prevalence of microcytic anaemia at months from to during a but because it had to a 2 years et al, 1993). have not been In a reaching about children in a of about of children in both the and control groups were anaemic at 18 months of age et al, 1997). of suitable foods may be if their to the is reduced of by from a or a The example is the and Infants and Children in the U.S.A. infant and are of to about a quarter of all the was the prevalence of iron deficiency anaemia has fallen and is less than in many other (e.g. in U.S.A. the prevalence of IDA among is Britain et al, 1997; et al, A recent showed that those within the had less anaemia and a better iron status than those who were not & 1997). The British to families on or the mother to an infant formula of which are in or whole cows' milk which little iron. are not are Many other have but many are based on milk for and does little to iron The in iron of infant is Most in the U.S.A. about 12 mg/l and most in Europe up to mg/l In both without iron are by the current and in are around 4 mg There are to little or no iron to in the first months of life 1996). (a) body iron increases little during this breast milk only small of and iron may have adverse on the & Wharton, 1991; et al, (b) With higher the absorbed is only a little more iron in the gut (c) infants an infant formula with no or small of iron in the first 4 months of life not ID et al, 1993; & 1996). all infant used at this age iron. about 6 months of age more dietary iron and a of a intake The usually a formula but the level of is e.g. use of a infant formula or an American infant formula or introduction of a of these is to the early introduction of cows' is that even in in infancy a level of lower than used can be in adequate absorption iron e.g. mg et al, 3 mg et al, 2 mg et al, but the of were for months only and did not follow infants into the year of life anaemia is most Using iron infant in adults, the suggested of mg/l to provide 1 mg of absorbed iron et al, 1998). A is which of an infant formula iron Many studies have shown the effect of using of cows' milk on iron status in infants months and in toddlers in the year of life. It is not however, to this reflects the effect of a greater intake of or is due also to of an formula such as the greater absorption of iron because of the higher vitamin C less of absorption because of the lower concentrations of and one study found that the addition of did not iron et al, or less milk and iron both the iron and the are British studies of the use of or cows' milk from the age of 6 months that ID was in those an iron

A significant increase in atmospheric CO2 concentration and associated climate aridization and soil salinity are factors affecting the growth, development, productivity, and stress responses of plants. In this study, the effect of ambient (400 ppm) and elevated (800 ppm) CO2 concentrations were evaluated on the C4 xero-halophyte Kochia prostrata treated with moderate salinity (200 mM NaCl) and polyethylene glycol (PEG)-induced osmotic stress. Our results indicated that plants grown at elevated CO2 concentration had different responses to osmotic stress and salinity. The synergistic effect of elevated CO2 and osmotic stress increased proline accumulation, but elevated CO2 did not mitigate the negative effects of osmotic stress on dark respiration intensity and photosystem II (PSII) efficiency. This indicates a stressful state, which is accompanied by a decrease in the efficiency of light reactions of photosynthesis and significant dissipative respiratory losses, thereby resulting in growth inhibition. Plants grown at elevated CO2 concentration and salinity showed high Na+ and proline contents, high water-use efficiency and time required to reach the maximum P700 oxidation level (PSI), and low dark respiration. Maintaining stable water balance, the efficient functioning of cyclic transport of PSI, and the reduction of dissipation costs contributed to an increase in dry shoot biomass (2-fold, compared with salinity at 400 ppm CO2). The obtained experimental data and PCA showed that elevated CO2 concentration improved the physiological parameters of K. prostrata under salinity.