A projection of ozone‐induced wheat production loss in China and India for the years 2000 and 2020 with exposure‐based and flux‐based approaches

Using a high‐resolution (40 × 40 km) chemical transport model coupled with the Regional Emission inventory in Asia (REAS), we simulated surface ozone concentrations ([O₃]) and evaluated O₃‐induced wheat production loss in China and India for the years 2000 and 2020 using dose–response functions based on AOT40 (accumulated [O₃] above 40 ppb) and POD_Y (phytotoxic O₃ dose, accumulated stomatal flux of O₃ above a threshold of Y nmol m^?2 s^?1). Two O₃ dose metrics (90 days AOT40 and POD₆) were derived from European experiments, and the other two (75 days AOT40 and POD₁₂) were adapted from Asian studies. Relative yield loss (RYL) of wheat in 2000 was estimated to be 6.4–14.9% for China and 8.2–22.3% for India. POD₆ predicted greater RYL, especially for the warm regions of India, whereas the 90 days AOT40 gave the lowest estimates. For the future projection, all the O₃ dose metrics gave comparable estimates of an increase in RYL from 2000 to 2020 in the range 8.1–9.4% and 5.4–7.7% for China and India, respectively. The lower projected increase in RYL for India may be due to conservative estimation of the emission increase in 2020. Sensitivity tests of the model showed that the POD_Y‐based estimates of RYL are highly sensitive to perturbations in the meteorological inputs, but that the estimated increase in RYL from 2000 to 2020 is much more robust. The projected increase in wheat production loss in China and India in the near future is substantially larger than the uncertainties in the estimation and indicates an urgent need for curbing the rapid increase in surface [O₃] in these regions.     

Concentration‐ and flux‐based dose–responses of isoprene emission from poplar leaves and plants exposed to an ozone concentration gradient

Concentration‐ and flux‐based O₃ dose–responses of isoprene emission from single leaves and whole plants were developed. Two poplar clones differing in O₃ sensitivity were exposed to five O₃ levels in open‐top chambers for 97 d: charcoal‐filtered ambient air (CF), non‐filtered ambient air (NF) and NF plus 20 ppb (NF + 20), 40 ppb (NF + 40) and 60 ppb (NF + 60). At both leaf and plant level, isoprene emission was significantly decreased by NF + 40 and NF + 60 for both clones. Although intra‐specific variability was found when the emissions were up‐scaled to the whole plant, both leaf‐ and plant‐level emissions decreased linearly with increasing concentration‐based (AOT40, cumulative exposure to hourly O₃ concentrations >40 ppb) and flux‐based indices (POD_Y, cumulative stomatal uptake of O₃ > Y nmol O₃ m^?2 PLA s^?1). AOT40‐ and POD₇‐based dose–responses performed equally well. The two clones responded differently to AOT40 and similarly to POD_Y (with a slightly higher R² for POD₇) when the emission was expressed as change relative to clean air. We thus recommend POD₇ as a large‐scale risk assessment metric to estimate isoprene emission responses to O₃ in poplar.     

Rate and duration of grain filling in relation to flag leaf senescence and grain yield in spring wheat (Triticum aestivum) exposed to different concentrations of ozone

Effects of different concentrations of ozone on grain filling, flag leaf senescence and final grain yield in field‐grown spring wheat (Triticum aestivum L. cv. Dragon) were studied using open‐top chambers. The hypothesis tested was that an ozone‐induced reduction in grain yield is mainly related to an enhanced senescence and a shortening of the grain‐filling period. The plants were exposed to filtered air (F), non‐filtered air without extra ozone (NF) or non‐filtered air with 3 different levels of ozone added (NF1+, NF2+ and NF3+). The mean daytime (08.00–20.00 h) ozone concentrations during the exposure period (31 days) were 7, 20, 34, 48 and 62 nmol mol?1 in F, NF, NF1+, NF2+ and NF3+, respectively. The corresponding ozone doses, expressed as the accumulated exposure over a concentration threshold of 40 nmol mol?1 (AOT40), were 0, 12, 1 989, 5 881 and 10 375 nmol mol?1 h, respectively, and 884, 2 594, 4 557, 6 188 and 7 900 μmol m?2, respectively, expressed as the calculated cumulative flag leaf ozone flux (CFO30). The flag leaves senesced earlier and the grain‐filling duration was significantly shorter at higher ozone exposure compared to F (?5, ?13 and ?18% in NF1+, NF2+ and NF3+, respectively). The relative grain‐filling rate did not differ between the treatments. The 1000‐grain weights were 10, 28 and 37% lower, and the grain yields were 15, 29 and 46% lower than F in NF1+, NF2+ and NF3+, respectively. Ozone exposure had no significant effect on the number of grains per unit ground area or on straw yield, but significantly reduced the harvest index and increased the grain protein concentration in NF2+ and NF3+ compared to F. The grain yield was negatively correlated with the ozone dose, expressed either as AOT40 or as CFO3 with or without an ozone flux threshold. The 1000‐grain weight was positively correlated with the grain‐filling duration (R2=0.998), which in turn was positively correlated with the leaf area duration (R2=0.989).     

Effects of nutrient solution zinc activity on net uptake,translocation, and root export of cadmium and zinc by separated sections of intact durum wheat (Triticum turgidum L. var durum) seedling roots

Cd accumulation in durum wheat presents a potential health risk to consumers. In an effort to understand the physiological mechanisms involved with Cd accumulation, this study examined the effects of Zn on Cd root uptake and phloem translocation in a split– root system. Durum wheat seedlings were grown in chelate-buffered nutrient solution with intact root systems divided into two sections. Each root section grew in a separate 1 l pot, one of which contained 0.2 μM CdSO₄. In addition, each two-pot system contained ZnSO₄ in the following combinations (in μm) (for -cd root system: +cd root system): 1:1, 1:10, 10:1,10:10, 1:19, and 19:1. Harvested plant material was analyzed for Cd and Zn. In addition, rates of Cd and Zn net uptake, translocation to the shoot, and root export (translocation from one root segment to the other) between days 8 and 22 were calculated. Results show that Zn was not translocated from one root section to its connected root section. Uptake rates of Cd increased as solution Zn concentrations increased. Cd translocation from one root section to the other decreased significantly when the Zn concentration in either pot was greater than 1 μM. These results show the potential of Zn to inhibit movement of Cd via the phloem, and suggests that providing adequate Zn levels may limit phloem loading of Cd into wheat grain. Increasing the rhizosphere activity of Zn²⁺ in Cd-containing soils may therefore result in reduced Cd accumulation in grain even while net Cd uptake is slightly enhanced. This revised version was published online in June 2006 with corrections to the Cover Date.     

Comparison of crop yield sensitivity to ozone between open‐top chamber and free‐air experiments

Assessments of the impacts of ozone (O₃) on regional and global food production are currently based on results from experiments using open‐top chambers (OTCs). However, there are concerns that these impact estimates might be biased due to the environmental artifacts imposed by this enclosure system. In this study, we collated O₃ exposure and yield data for three major crop species—wheat, rice, and soybean—for which O₃ experiments have been conducted with OTCs as well as the ecologically more realistic free‐air O₃ elevation (O₃‐FACE) exposure system; both within the same cultivation region and country. For all three crops, we found that the sensitivity of crop yield to the O₃ metric AOT40 (accumulated hourly O₃ exposure above a cut‐off threshold concentration of 40 ppb) significantly differed between OTC and O₃‐FACE experiments. In wheat and rice, O₃ sensitivity was higher in O₃‐FACE than OTC experiments, while the opposite was the case for soybean. In all three crops, these differences could be linked to factors influencing stomatal conductance (manipulation of water inputs, passive chamber warming, and cultivar differences in gas exchange). Our study thus highlights the importance of accounting for factors that control stomatal O₃ flux when applying experimental data to assess O₃ impacts on crops at large spatial scales.     

‘On-farm’ seed priming with zinc in chickpea and wheat in Pakistan

A series of on-station trials was implemented between 2002 and 2006 to assess the response of wheat (Triticum aestivum L.) and chickpea (Cicer arietinum) to zinc (Zn) added by soaking seeds (priming) in solutions of ZnSO₄ before sowing. Wheat seed was primed for 10 h in 0.3% Zn and chickpea for 6 h in 0.05% Zn. Seed treatments increased the seed concentration in wheat from 27 to 470 mg/kg and in chickpea from 49 to 780 mg/kg. Priming wheat seeds with 0.3% Zn significantly increased the mean shoot dry mass, Zn concentration and Zn uptake of 15-day-old seedlings relative to non-primed controls and seeds primed with water alone. Using 0.4% Zn further increased shoot Zn concentration but depressed shoot dry mass to the level of the non-primed control. In seven trials, mean grain yield of wheat was significantly increased from 2.28 to 2.42 t/ha (6%) by priming with water alone and to 2.61 t/ha (14%) by priming with 0.3% Zn. Mean grain yield of chickpea in seven trials was increased significantly from 1.39 to 1.65 t/ha (19%) by priming seeds with 0.05% Zn. The effect of priming chickpea seeds with water was intermediate (1.49 t/ha) and not statistically separable from the non-primed and zinc-primed treatments. Increased grain yield due to priming in both crops was associated with increases in total biomass but there was no significant effect of priming on harvest index. In addition to increasing yield, priming seeds with Zn also significantly increased grain zinc concentration, by 12% in wheat (mean of three trials) and by 29% in chickpea (one trial) and the total amount of Zn taken up by the grain (by 27% in wheat and by 130% in chickpea). Using ZnSO₄ to prime seeds was very cost-effective, with net benefit-to-cost ratios of 75 for wheat and 780 for chickpea. An erratum to this article can be found at     

Effects of elevated carbon dioxide, ozone and water availability on spring wheat growth and yield

Spring wheat (Triticum aestivum L. cv. Dragon) was exposed to elevated carbon dioxide (CO₂), alone (1995) or in combination with two levels of increased ozone (O₃) (1994) or increased irrigation (1996) during three successive growing seasons as part of the EU ESPACE‐wheat programme and conducted in open‐top chambers (OTCs) and ambient air (AA) plots at Östad, 50 km north‐east of Göteborg, Sweden. Doubling the CO₂ concentration had a positive effect on grain yield in all 3 years (+21, +7 and +11%, respectively), although only statistically significant in 1994. That year was characterised by a warm and dry summer in comparison with 1995 and 1996, in which the summers were more humid and typical for south‐west Sweden. In 1994, the CO₂‐induced increase in grain yield was associated with an increase in the duration of the green leaf area, a positive effect on straw yield and on the number of ears per square metre and a negative effect (?13%) on grain protein concentration. Harvest index was unaffected by the elevated CO₂ concentration. The only statistically significant effect of elevated CO₂ in 1995 was a decrease in the grain protein concentration (?11% in both CO₂ concentrations), and in 1996 an increase (+21%) in the straw yield. In 1996 the soil water potential was less negative in elevated CO₂, which is likely to reflect a lower water consumption of these plants. Addition of extra O₃ significantly affected the grain yield (?6 and ?10%, respectively) and the 1 000‐grain weight negatively (?3 and ?6%). Statistically significant interactions between CO₂ and O₃ were obtained for the number of ears per unit area and for the 1 000‐grain weight. The 1 000‐grain weight was negatively affected by O₃ in low CO₂, but remained unaffected in the high CO₂ treatment. There was a significant decrease (?6%) in the grain protein concentration induced by elevated irrigation. The chambers, compared with AA plots, had a positive effect on plant development and on grain yield in all 3 years.     

Leaf-applied sodium chloride promotes cadmium accumulation in durum wheat grain

Cadmium (Cd) accumulation in durum wheat grain is a growing concern. Among the factors affecting Cd accumulation in plants, soil chloride (Cl) concentration plays a critical role. The effect of leaf NaCl application on grain Cd was studied in greenhouse-grown durum wheat (Triticum turgidum L. durum, cv. Balcali-2000) by immersing (10 s) intact flag leaves into Cd and/or NaCl-containing solutions for 14 times during heading and dough stages. Immersing flag leaves in solutions containing increasing amount of Cd resulted in substantial increases in grain Cd concentration. Adding NaCl alone or in combination with the Cd-containing immersion solution promoted accumulation of Cd in the grains, by up to 41%. In contrast, Zn concentrations of grains were not affected or even decreased by the NaCl treatments. This is likely due to the effect of Cl complexing Cd and reducing positive charge on the metal ion, an effect that is much smaller for Zn. Charge reduction or removal (CdCl₂⁰ species) would increase the diffusivity/lipophilicity of Cd and enhance its capability to penetrate the leaf epidermis and across membranes. Of even more significance to human health was the ability of Cl alone to penetrate leaf tissue and mobilize and enhance shoot Cd transfer to grains, yet reducing or not affecting Zn transfer.     

Influence of Pak choi plant cultivation on Se distribution,speciation and bioavailability in soil

Background and aims

The combination of plant breeding and agronomic biofortification is the most reasonable approach to minimize zinc (Zn) deficiency-related problems in humans, but also in crop production. However, its efficiency and suitability under Mediterranean conditions and its effects on the grain yield and quality parameters are not well known.

Methods

Field experiments were conducted over two years in south-eastern Portugal, where soils are deficient in Zn. Ten advanced breeding lines and three commercial varieties of bread-making wheat were fertilized with four Zn treatments as following: i) control, ii) soil Zn application, iii) foliar Zn application and iv) both soil and foliar Zn application.

Results

Low rainfall produced 46 % more of grain Zn concentration but about 67 % less of grain yield. Grain Zn concentration varied greatly across treatments and cultivars with INIAV-1, INIAV-6, INIAV-9 and the commercial varieties being the most efficient. There were no significant increases in Zn concentrations due to soil Zn application, but gains higher than 20 mg kg^?1 were obtained both with foliar and soil+foliar Zn applications. Grain yield was not significantly higher in foliar application, but increased to about 10 % in soil, and about 7 % in soil+foliar applications, respectively.

Conclusions

In soils with low Zn availability, the best strategy to improve grain Zn concentrations has been to select the most efficient cultivars for Zn accumulation with the added application of Zn in soil+foliar form.

     

Evidence of widespread effects of ozone on crops and (semi‐)natural vegetation in Europe (1990–2006) in relation to AOT40‐ and flux‐based risk maps

Records of effects of ambient ozone pollution on vegetation have been compiled for Europe for the years 1990–2006. Sources include scientific papers, conference proceedings, reports to research funders, records of confirmed ozone injury symptoms and an international biomonitoring experiment coordinated by the ICP Vegetation. The latter involved ozone‐sensitive (NC‐S) and ozone‐resistant (NC‐R) biotypes of white clover (Trifolium repens L.) grown according to a common protocol and monitored for ozone injury and biomass differences in 17 European countries, from 1996 to 2006. Effects were separated into visible injury or growth/yield reduction. Of the 644 records of visible injury, 39% were for crops (27 species), 38.1% were for (semi‐) natural vegetation (95 species) and 22.9% were for shrubs (49 species). Owing to inconsistencies in reporting effort from year to year it was not possible to determine geographical or temporal trends in the data. Nevertheless, this study has shown effects in ambient air in 18 European countries from Sweden in the north to Greece in the south. These effects data were superimposed on AOT40 (accumulated ozone concentrations over 40 ppb) and POD3_gen (modelled accumulated stomatal flux over a threshold of 3 nmol m^?2 s^?1) maps generated by the EMEP Eulerian model (50 km × 50 km grid) that were parameterized for a generic crop based on wheat and NC‐S/NC‐R white clover. Many effects were found in areas where the AOT40 (crops) was below the critical level of 3 ppm h. In contrast, the majority of effects were detected in grid squares where POD3_gen (crops) were in the mid‐high range (>12 mmol m^?2). Overall, maps based on POD3_gen provided better fit to the effects data than those based on AOT40, with the POD3_gen model for clover fitting the clover effects data better than that for a generic crop.     

Soil solution dynamics and plant uptake of cadmium and zinc by durum wheat following phosphate fertilization

A growth chamber study was conducted to evaluate the effect of application of phosphate fertilizer on soil solution dynamics of cadmium (Cd) and Cd accumulation in durum wheat (Triticum turgidum L. var. durum). Treatments consisted of three phosphate fertilizer sources containing 3.4, 75.2, and 232 mg Cd kg^?1 applied at three rates (20, 40 and 80 mg P kg^?1) plus a no fertilization control. An unplanted treatment at 40 mg P kg^?1 was included to separate the effects on soil solution Cd dynamics of the crop from that of the fertilizer. Soil solution samples were obtained using soil moisture samplers every 10 days after germination. The experimental results indicated that plant biomass significantly increased with P application rates and decreased with increased Cd concentration in the phosphate fertilizers. Total cadmium concentration in soil solution was not consistently affected by phosphate fertilization rate and fertilizer sources, and therefore Cd concentration in the fertilizer. Application of phosphate fertilizer, however, increased the concentration and accumulation of Cd and shoot Cd/Zn ratio, and decreased shoot Zn concentration in durum wheat. Phosphate sources had a marginally significant effect (P?=?0.05) on shoot Cd concentration and did not affect Cd accumulation in durum wheat. Concentration of Cd in soil solution was unrelated to Cd concentration in durum wheat. These results suggest that the immediate increase in Cd concentration and Cd accumulation in durum wheat with phosphate application is due more to competition between Zn and Cd for absorption into plants, enhanced root to shoot translocation and enhanced root development, than to a direct addition effect from Cd contained in phosphate fertilizer. In the short term, application of phosphate fertilizers can increase Cd concentration in the crops, regardless of the Cd concentration of the fertilizer. An optimal P fertilization, possibly in combination with Zn application, may offer an important strategy for decreasing Cd concentration and accumulation in crops.     

<Emphasis Type="Bold">Zinc nutrition in wheat-based cropping systems</Emphasis>

Background

Zinc (Zn) deficiency is one of the most important micronutrient disorders affecting human health. Wheat is the staple food for 35% of the world’s population and is inherently low in Zn, which increases the incidence of Zn deficiency in humans. Major wheat-based cropping systems viz. rice–wheat, cotton–wheat and maize–wheat are prone to Zn deficiency due to the high Zn demand of these crops.

Methods

This review highlights the role of Zn in plant biology and its effect on wheat-based cropping systems. Agronomic, breeding and molecular approaches to improve Zn nutrition and biofortification of wheat grain are discussed.

Results

Zinc is most often applied to crops through soil and foliar methods. The application of Zn through seed treatments has improved grain yield and grain Zn status in wheat. In cropping systems where legumes are cultivated in rotation with wheat, microorganisms can improve the available Zn pool in soil for the wheat crop. Breeding and molecular approaches have been used to develop wheat genotypes with high grain Zn density.

Conclusions

Options for improving grain yield and grain Zn concentration in wheat include screening wheat genotypes for higher root Zn uptake and grain translocation efficiency, the inclusion of these Zn-efficient genotypes in breeding programs, and Zn fertilization through soil, foliar and seed treatments.

     

O3浓度升高和太阳辐射减弱对小麦根际土壤微生物功能多样性的影响

采用开顶箱(OTC)法和遮光网技术,设置100 n L/L臭氧熏气与3个辐射减弱梯度结合,模拟臭氧浓度升高和太阳辐射减弱的复合大气背景。用BIOLOG生态测试板,采用孔平均颜色变化率法(AWCD)测定冬小麦根际土壤微生物利用不同碳源的能力,计算微生物群落多样性指数,对不同碳源的利用率进行了主成分分析。两年试验结果显示,臭氧熏气与太阳辐射减弱复合作用,降低了土壤微生物对碳源的利用速度和利用总量;除了聚合物以外其它碳源利用率显著降低;对土壤微生物多样性没有直接的影响;对碳源降解的抑制效应大于增强的O3与减弱的太阳辐射两因素各自的单独作用。太阳辐射减弱20%,一定程度上增加了对聚合物类的分解。O3熏气条件下太阳辐射减弱,糖类、胺类代谢变异度较高,受环境影响较大。     

A simple method to evaluate genetic variation in grain zinc concentration by correcting for differences in grain yield

Increasing the grain zinc (Zn) concentration of staple food crops will help alleviate chronic Zn deficiency in many areas of the world. Significant variation in grain Zn concentration is often reported among collections of cereals, but frequently there is a concomitant variation in grain yield. In such cases grain Zn concentration and grain yield are often inversely related. Without considering the influence of the variation in grain yield on Zn concentration, the differences in grain Zn concentration may simply represent a yield dilution effect. Data from a series of field and glasshouse experiments was used to illustrate this effect and to describe an approach that will overcome the yield dilution effect. In experiments with a wide range of bread wheat, synthetic hexaploids and accessions of durum wheat, variation in grain yield among the genotypes accounted for 30–57% of the variation in grain Zn concentration. Variation in kernel weight also occurred, but was poorly correlated with grain Zn concentration. To account for the influence of variation in grain yield on grain Zn concentration grain Zn yield was plotted against grain yield. By defining the 95% confidence belt for the regression genotypes that have inherently low or high grain Zn concentrations at a given yield level can be identified. This method is illustrated using two data sets, one consisting of bread wheat and one comprising a collection of synthetic hexaploids.     

The effect of rate and Cd concentration of repeated phosphate fertilizer applications on seed Cd concentration varies with crop type and environment

Background and aims

Limited information is available on how cadmium (Cd) applied in phosphate fertilizer interacts with soil and environmental conditions over time to affect crop Cd concentrations.

Methods

Field studies from 2002 to 2009 at seven locations evaluated the cumulative effects of P fertilizer rate and Cd concentration on seed Cd concentration of durum wheat (Triticum turgidum L.) and flax (Linum usitatissiumum L.).

Results

Soil characteristics and environment affected Cd availability. Durum wheat grain Cd increased with P fertilizer rate but effect on flaxseed Cd concentration was smaller. Cadmium concentration in fertilizer had a greater effect on flaxseed than durum wheat Cd concentration. Seed Cd concentration of both crops was greatest with the highest rate P fertilizer containing the highest Cd concentration. There was not a strong cumulative effect of fertilization over the 8 years of the study, indicating attenuation of Cd availability over time.

Conclusions

Cadmium in phosphate fertilizer increases Cd available for crop uptake, but crop Cd concentration is also affected by soil characteristics and annual environmental conditions. Type of crop produced and soil and environmental characteristics that affect phytoavailability must be taken into account when assessing the Cd risk from P fertilization.     

Impact of elevated ozone concentration on growth,physiology, and yield of wheat (Triticum aestivum L.): a meta‐analysis

We quantitatively evaluated the effects of elevated concentration of ozone (O₃) on growth, leaf chemistry, gas exchange, grain yield, and grain quality relative to carbon‐filtered air (CF) by means of meta‐analysis of published data. Our database consisted of 53 peer‐reviewed studies published between 1980 and 2007, taking into account wheat type, O₃ fumigation method, rooting environment, O₃ concentration ([O₃]), developmental stage, and additional treatments such as drought and elevated carbon dioxide concentration ([CO₂]). The results suggested that elevated [O₃] decreased wheat grain yield by 29% (CI: 24–34%) and aboveground biomass by 18% (CI: 13–24%), where CI is the 95% confidence interval. Even in studies where the [O₃] range was between 31 and 59 ppb (average 43 ppb), there was a significant decrease in the grain yield (18%) and biomass (16%) relative to CF. Despite the increase in the grain protein content (6.8%), elevated [O₃] significantly decreased the grain protein yield (?18%). Relative to CF, elevated [O₃] significantly decreased photosynthetic rates (?20%), Rubisco activity (?19%), stomatal conductance (?22%), and chlorophyll content (?40%). For the whole plant, rising [O₃] induced a larger decrease in belowground (?27%) biomass than in aboveground (?18%) biomass. There was no significant response difference between spring wheat and winter wheat. Wheat grown in the field showed larger decreases in leaf photosynthesis parameters than wheat grown in < 5 L pots. Open‐top chamber fumigation induced a larger reduction than indoor growth chambers, when plants were exposed to elevated [O₃]. The detrimental effect was progressively greater as the average daily [O₃] increased, with very few exceptions. The impact of O₃ increased with developmental stages, with the largest detrimental impact during grain filling. Both drought and elevated [CO₂] significantly ameliorated the detrimental effects of elevated [O₃], which could be explained by a significant decrease in O₃ uptake resulting from decreased stomatal conductance.     

Grain zinc, iron and protein concentrations and zinc-efficiency in wild emmer wheat under contrasting irrigation regimes

Micronutrient malnutrition, and particularly deficiency in zinc (Zn) and iron (Fe), afflicts over three billion people worldwide, and nearly half of the world’s cereal-growing area is affected by soil Zn deficiency. Wild emmer wheat [Triticum turgidum ssp. dicoccoides (Körn.) Thell.], the progenitor of domesticated durum wheat and bread wheat, offers a valuable source of economically important genetic diversity including grain mineral concentrations. Twenty two wild emmer wheat accessions, representing a wide range of drought resistance capacity, as well as two durum wheat cultivars were examined under two contrasting irrigation regimes (well-watered control and water-limited), for grain yield, total biomass production and grain Zn, Fe and protein concentrations. The wild emmer accessions exhibited high genetic diversity for yield and grain Zn, Fe and protein concentrations under both irrigation regimes, with a considerable potential for improvement of the cultivated wheat. Grain Zn, Fe and protein concentrations were positively correlated with one another. Although irrigation regime significantly affected ranking of genotypes, a few wild emmer accessions were identified for their advantage over durum wheat, having consistently higher grain Zn (e.g., 125 mg kg^?1), Fe (85 mg kg^?1) and protein (250 g kg^?1) concentrations and high yield capacity. Plants grown from seeds originated from both irrigation regimes were also examined for Zn efficiency (Zn deficiency tolerance) on a Zn-deficient calcareous soil. Zinc efficiency, expressed as the ratio of shoot dry matter production under Zn deficiency to Zn fertilization, showed large genetic variation among the genotypes tested. The source of seeds from maternal plants grown under both irrigation regimes had very little effect on Zn efficiency. Several wild emmer accessions revealed combination of high Zn efficiency and drought stress resistance. The results indicate high genetic potential of wild emmer wheat to improve grain Zn, Fe and protein concentrations, Zn deficiency tolerance and drought resistance in cultivated wheat.     

Differential response of rye,triticale, bread and durum wheats to zinc deficiency in calcareous soils

Field and greenhouse experiments were carried out to study the response of rye (Secale cereale L. cv. Aslim), triticale (× Triticosecale Wittmark. cv. Presto), two bread wheats (Triticum aestivum L, cvs. Bezostaja-1 and Atay-85) and two durum wheats (Triticum durum L. cvs. Kunduru-1149 and C-1252) to zinc (Zn) deficiency and Zn fertilization in severely Zn-deficient calcareus soils (DTPA-Zn=0.09 mg kg^-1 soil). The first visible symptom of Zn deficiency was a reduction in shoot elongation followed by the appearance of whitish-brown necrotic patches on the leaf blades. These symptoms were either absent or only slight in rye and triticale, but occurred more rapidly and severely in wheats, particularly in durum wheats. The same was true for the decrease in shoot dry matter production and grain yield. For example, in field experiments at the milk stage, decreases in shoot dry matter production due to Zn deficiency were absent in rye, and were on average 5% in triticale, 34% in bread wheats and 70%, in durum wheats. Zinc fertilization had no effect on grain yield in rye but enhanced grain yield of the other cereals. Zinc efficiency of cereals, expressed as the ratio of yield (shoot dry matter or grain) produced under Zn deficiency compared to Zn fertilization were, on average, 99% for rye, 74% for triticale, 59% for bread wheats and 25% for durum wheats.These distinct differences among and within the cereal species in susceptibility to Zn deficiency were closely related to the total amount (content) of Zn per shoot, but not with the Zn concentrations in shoot dry matter. For example, the most Zn-efficient rye and the Zn-inefficient durum wheat cultivar C-1252 did not differ in shoot Zn concentration under Zn deficiency, but the total amount of Zn per whole shoot was approximately 6-fold higher in rye than the durum wheat. When Zn was applied, rye and triticale accumulated markedly more Zn both per whole shoot and per unit shoot dry matter in comparison to wheats.The results demonstrate an exceptionally high Zn efficiency of rye and show that among the cereals studied Zn efficiency declines in the order rye>triticale>bread wheat>durum wheat. The differences in expression of Zn efficiency are possibly related to a greater capacity of efficient genotypes to acquire Zn from the soil compared to inefficient genotypes.     

Effects of Cadmium,Copper, Lead,and Zinc Contamination on Metal Accumulation by Safflower and Wheat

Accumulation of heavy metals (HMs) in cultivated soils is a continuing environmental problem in many parts of the world. An increase in HM concentration can enhance uptake of toxic metals by crops and enter the human food chain. In this study, the uptake behavior of wheat and safflower was evaluated in a calcareous soil by using 12 undisturbed columns in which half were artificially contaminated. Heavy metals in the form of CdCl₂ (15 mg Cd kg^{? 1}), CuSO₄ (585 mg Cu kg^{? 1}), Pb(NO₃)₂ (117 mg Pb kg^{? 1}), and ZnCl₂ (1094 mg Zn kg^{? 1}) were sprayed on the soil surface and completely mixed in the top 10 cm. The background total concentrations of Cd, Cu, Pb and Zn were 1.6, 29.5, 17.5 and 61.2 mg kg^{? 1}, respectively. After metal application, half of the columns (3 contaminated and 3 uncontaminated) were sown with wheat (Triticum aestivum) and the other half with safflower (Carthamus tinctorious) and grown for 74 days until maturity. After harvesting, soil columns were cut into 10-cm sections and analyzed for HNO₃- and DTPA-extractable metal concentrations. Metal concentrations were also measured in different plant tissues. The results showed that artificial contamination of topsoil decreased the transpiration rate of wheat by 12% and that of safflower by 6%. In contaminated columns, Cd, Cu, Pb, and Zn accumulation in wheat shoot was greater by 8.0-, 1.9-, 3.0-, and 2.1-fold than the control, respectively. Accordingly, these numbers were 46.0-, 1.3-, 1.7-, and 1.6-fold in safflower shoot. Soil contamination with HMs resulted in a 55% decrease in shoot dry matter yield of wheat while it had no significant effect on shoot dry matter of safflower. The normalized water consumption for safflower was therefore not affected by metal contamination (≈ 13 mm H₂O g^{? 1} of dry weight for all safflower and uncontaminated wheat treatments), while contaminated wheat was much less water efficient at about 27 mm H₂O g^{? 1} dry weight. It was concluded that although artificial contamination had a negative effect on wheat growth, it did not affect safflower's normal growth and water efficiency.     

臭氧胁迫冬小麦叶片高光谱特征和叶绿素含量估算

为无损、快速监测臭氧胁迫下冬小麦叶片叶绿素含量，建立叶绿素含量与光谱指标的定量关系，基于自由式臭氧浓度增加系统平台观测了臭氧浓度升高下拔节期、开花期及灌浆期冬小麦叶片的叶绿素含量和光谱特征。通过线性回归、人工神经网络(ANN)以及偏最小二乘回归(PLSR)模型对臭氧胁迫下叶片高光谱特征进行了叶绿素含量的估算。结果表明：臭氧胁迫冬小麦叶片的光谱曲线特征出现绿峰“红移”和红边位置“蓝移”现象。相比于拔节期和开花期，小麦叶片在灌浆期受到臭氧的影响更大。臭氧胁迫下叶绿素含量与部分光谱特征参数及遥感植被指数存在显著相关关系，所有模型均取得了较高的估算精度(R²>0.8),其中以光谱特征参数为建模参量的偏最小二乘回归模型精度最高。该方法可用于臭氧胁迫下冬小麦叶片叶绿素含量的估测，动态监测作物的臭氧胁迫。