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Abstract
Development of rice cultivars with low phytic acid (lpa) is considered as a primary strategy for biofortification of zinc (Zn) and iron (Fe). Here, two rice genotypes (XS110 and its lpa mutant) were used to investigate the effect of P supplies on accumulations and distributions of PA, Zn and Fe in rice grains by using hydroponics and detached panicle culture system. Results showed that higher P level increased grain PA concentration on dry matter basis (g/kg), but it markedly decreased PA accumulation on per grain basis (mg/grain). Meanwhile, more P supply reduced the amounts and bioavailabilities of Zn and Fe both in milled grains and in brown grains. Comparatively, lpa mutant was more susceptive to exogenous P supply than its wild type. Hence, the appropriate P fertilizer application should be highlighted in order to increase grain microelement (Zn and Fe) contents and improve nutritional quality in rice grains.
... NH4NO3 was used as N source, and five N levels were designed, 0 (N0), 0.1% (N1, M/V), 0.2% (N2, M/V), 0.3% (N3, M/V), and 0.6% (N4, M/V). All other basic nutrient concentrations were kept the same except for N, namely 1. 50 [31]. ...
... Grains used for determining grain protein, PA, and Pi analysis were dehusked by a laboratory de-husker (Model: JLGJ China) and ground using a portable grinder (Model JFSJ100, China) fitted with a 0.25 mm screen. For further investigating the influence of different N levels on PA and protein's grain positional distribution, the aleurone fractions and milled rice of XS110 in 2016 were further separated using a milled rice polisher (Model JNMJ3, Taizhou Grain Industry Instrument Crop, Zhejiang, China) based on the degree of milling (DOM, defined as the weight percentage of grain fractions removed) [31,32]. In the current study, rice grain with DOM ≤ 6.5% and >12% is considered as aleurone fraction and milled rice. ...
... Total protein concentration was calculated as the sum of four protein fractions (albumin, globulin, prolamin, glutelin). PA concentration was quantified spectrophotometrically as described by Su et al. (2018) [31]. Inorganic phosphorus (Pi) concentration was determined as described by Jiang et al. (2019) [34], and total grain P was estimated as the sum of phytic acid-phosphorus (PA-P) and Pi. ...
Nitrogen (N) fertilization has been recognized as improving the grain beneficial micronutrients, including Zn and Fe, in rice. However, only a few studies have explicitly focused on N-induced variation in anti-nutritional components such as phytic acid (PA), PA synthesis-related gene expression, and variation in grain protein fractions. Therefore, in this study, two culture systems (hydroponic and detached panicle culture systems) were used to elucidate the influence of N application on PA concentration and its relation to the grain protein fractions, such as albumin, globulin, prolamin, and glutelin, and total protein in rice. Results showed that N application generally decreased the grain PA concentration in brown rice and down-regulated the PA synthesis-related genes in the lipid-independent pathway. In contrast, total grain protein and its fractions concentrations increased significantly. For grain positional distribution, PA and protein concentration were generally higher in the aleurone fraction than in the milled rice, regardless of N application. However, higher N application decreased the PA in both aleurone fraction and milled rice, while increased the grain protein fractions mainly in milled rice. These findings imply that N application could substantially improve the rice nutrition by reducing the PA while increasing the protein concentration. Hence, these findings may provide critical bases for rice nutritional improvement through optimal N management.
... Phosphorus (P) is an essential element for plant growth and development. Phosphorus fertilizers are widely used to increase yield, especially for intensive agricultural production in P-deficient soils (Wang, Sikand, and Wong 2016;Su et al. 2018). Although P fertilizers can significantly increase plant yield and development (Banaj et al. 2006), excessive use of P fertilizers limit yield increases (Bai et al. 2013), and causes environmental pollution (Guo et al. 2010;Le et al. 2010) and some microelement deficiencies such as Zn, Fe, and Cu in plants (Cakmak 2002;Stein 2010;Zhang et al. 2012). ...
... Under other P rates, micronutrient applications made no significant changes in the Fe concentrations of lettuce. In a study, Su et al. (2018) reported no effect on Fe content but a decrease in Fe concentration in rice grain with high P. On the other hand, in the present study, Zn application under low P conditions decreased the Fe content of lettuce. Foliar applied Fe, Zn or Fe plus Zn and soil applied P increased the Fe content of cowpea (Fouda and Abd-Elhamied 2017). ...
Interaction between phosphorus (P), zinc (Zn), and iron (Fe) alters plant nutrient concentrations and nutritional quality. In this regard, there are a limited number of studies on P and micronutrient relations in lettuce plants. In this study, the effects of Zn and Fe applications on plant growth, concentrations, and contents of P, Zn, Fe, copper (Cu), and manganese (Mn) were determined in lettuce plants grown under increasing P rates. Lettuce plants grown under increasing P rates (0, 100, 200, and 400 mg kg −1 P) were treated with either sole or combined applications of 20 mg kg −1 Zn and 30 mg kg −1 Fe. Fresh and dry weights, P concentrations, and contents of lettuce were increased by P fertilization. With Zn and Fe applications , lettuce Fe contents were increased by medium P rates. Plant Zn contents were increased by P fertilization when the plant supplied Zn alone. Besides the highest P rate, Zn and Fe increased plant Zn content through P fertilization. Under no micronutrient condition, Cu concentration revealed insignificant changes, but its content was significantly increased by P application. Plant Mn concentration only increased by low P when the plant supplied Zn however Mn contents of lettuce were increased by P fertilization. In conclusion, even high P doses had no significant impact on Fe, Zn, Cu, and Mn concentrations in lettuce plants. Plant Zn concentrations increased when Zn was applied with Fe. Likewise, Cu increased but manganese declined. This emphasizes the importance of simultaneous Zn and Fe fertilizer application, especially in Zn biofortification research. ARTICLE HISTORY
... Concentrations of micronutrients such as B, Mn, and Cu in rice grain were also shown to be increased by mineral fertilizer use (Hao et al., 2007;Kuppusamy et al., 2017). In addition, mineral N, P and K fertilizers use could enhance Fe accumulation in rice grain (Kuppusamy et al., 2017;Stangoulis and Knez, 2022), but excessive applications of these nutrients have been reported to cause the opposite effect (Panda et al., 2012;Su et al., 2018). In SSA, how significant specifically soil physical and chemical properties and mineral fertilizer application as crop management factors would contribute to the variation of nutrient concentrations in rice grain remains to be further evaluated. ...
... Last, some studies have not reported any effect of fertilizer use on Fe accumulation in rice grain (Chandel et al., 2010;Rakotoson et al., 2019), which is somehow in line with the non-significant coefficients of P and K application rates in our study. However, we found that N application rates were negatively affecting Fe accumulation and such can be because of the high rates (~200 kg N ha − 1 ) considered as possibly excessive (Panda et al., 2012;Su et al., 2018). The implication of this on Fe fortification of rice grain would be about the balance of N fertilization rates with yields. ...
Context or problem:
Quantification of nutrient concentrations in rice grain is essential for evaluating nutrient uptake, use efficiency, and balance to develop fertilizer recommendation guidelines. Accurate estimation of nutrient concentrations without relying on plant laboratory analysis is needed in sub-Saharan Africa (SSA), where farmers do not generally have access to laboratories.
Objective or research question:
The objectives are to 1) examine if the concentrations of macro- (N, P, K, Ca, Mg, S) and micronutrients (Fe, Mn, B, Cu) in rice grain can be estimated using agro-ecological zones (AEZ), production systems, soil properties, and mineral fertilizer application (N, P, and K) rates as predictor variables, and 2) to identify if nutrient uptakes estimated by best-fitted models with above variables provide improved prediction of actual nutrient uptakes (predicted nutrient concentrations x grain yield) compared to average-based uptakes (average nutrient concentrations in SSA x grain yield).
Methods:
Cross-sectional data from 998 farmers' fields across 20 countries across 4 AEZs (arid/semi-arid, humid, sub-humid, and highlands) in SSA and 3 different production systems: irrigated lowland, rainfed lowland, and rainfed upland were used to test hypotheses of nutrient concentration being estimable with a set of predictor variables among above-cited factors using linear mixed-effects regression models.
Results:
All 10 nutrients were reasonably predicted [Nakagawa's R2 ranging from 0.27 (Ca) to 0.79 (B), and modeling efficiency ranging from 0.178 (Ca) to 0.584 (B)]. However, only the estimation of K and B concentrations was satisfactory with a modeling efficiency superior to 0.5. The country variable contributed more to the variation of concentrations of these nutrients than AEZ and production systems in our best predictive models. There were greater positive relationships (up to 0.18 of difference in correlation coefficient R) between actual nutrient uptakes and model estimation-based uptakes than those between actual nutrient uptakes and average-based uptakes. Nevertheless, only the estimation of B uptake had significant improvement among all nutrients investigated.
Conclusions:
Our findings suggest that with the exception of B associated with high model EF and an improved uptake over the average-based uptake, estimates of the macronutrient and micronutrient uptakes in rice grain can be obtained simply by using average concentrations of each nutrient at the regional scale for SSA.
Implications:
Further investigation of other factors such as the timing of fertilizer applications, rice variety, occurrence of drought periods, and atmospheric CO2 concentration is warranted for improved prediction accuracy of nutrient concentrations.
... At present, reports on the effects of phosphate fertilizer on microelements concentrations in crops are not consistent, particularly with regard to Zn in grains. Most studies have shown that exogenous phosphorus supply reduced Zn uptake by roots and inhibited Zn transport into paddy grains Su et al. 2018). However, some researchers found that phosphorus had a slight synergistic effect on Zn concentration in grains (Naeem et al. 2018). ...
Rice is the main food crops with the higher capacity for cadmium (Cd) uptake, necessitating the urgent need for remediation measures to address Cd in paddy soil. Reasonable agronomic methods are convenient and favorable for fixing the issue. In this study, a pot experiment was employed to evaluate the effects of two foliar (NaH2PO4, SDP; KH2PO4, PDP) and two solid phosphate fertilizers (double-superphosphate, DSP; calcium-magnesium phosphate, CMP) on uptake and remobilization of Cd in rice plants under the low-P and rich-Cd soil. The results revealed that these four phosphorus fertilizer significantly down-regulated the relative expression of OsNRAMP5 involved in Cd absorption, while up-regulated OsPCS1 expression and increased distribution of Cd into the cell wall in roots. Furthermore, phosphorus fertilizer resulted in a significant decrease in the relative expression of OsLCT1 in stems and OsLCD in leaves, decreased the transfer factor of Cd from shoots to grains, and ulterior reduced the Cd accumulation in three protein components of globulin, albumin, and glutelin, making the average Cd concentration of brown rice decreased by 82.96%. These results comprehensively indicate that in situations with similar soil backgrounds, the recommended application of solid CMP and foliar PDP can alleviate the toxicity of Cd by reducing its absorption and remobilization.
... The activation of P means a series of methods aimed at facilitating the conversion of insoluble P in soil to the plantavailable state, involving the main mechanisms such as dissolution/precipitation, adsorption/desorption, and mineralization/immobilization (Mao et al. 2017;Su et al. 2018;Yamamoto et al. 2018;Zhu et al. 2018). The studies on P activation are focused on materials such as organic acids (OA), biofertilizers, and zeolites. ...
Purpose
Phosphorus, an essential limiting nutrient for plant growth, has been a significant challenge due to its low utilization efficiency in recent years. The application of organic acids has become one of the most effective means to activate insoluble soil phosphorus. This study aims to elucidate the global mechanism of soil phosphorus activation by organic acids and provide guidance for maximizing its effectiveness.
Methods
A meta-analysis of 7870 samples from 37 studies worldwide was done. The structural equation model was used to test two hypotheses based on meta-analysis results.
Results
Our study demonstrates that organic acids enhance soil phosphorus availability, primarily by promoting the transformation of phosphorus into plant-available forms. This transformation process is collectively influenced by organic acid types, soil properties, and treatment conditions (ranging from −14.58 to 185.77%). Acetic acid exhibits the strongest effect, increasing available phosphorus by 185.77%. Furthermore, soil and treatment conditions are found to have significant impacts on the transformation of available phosphorus by organic acids through the structural equation model, and excess organic acids are detrimental to this process.
Conclusion
This study unequivocally demonstrates that organic acids significantly enhance soil phosphorus availability. The application of organic acids, particularly acetic acid, promotes the conversion of phosphorus into plant-available forms. Low concentrations of organic acids in neutral loam maximize this effect. This research contributes to the advancement in identifying more effective ways of utilizing organic acids as phosphorus activators and improving nutrient management strategies, ultimately paving the way for sustainable agricultural practices.
Graphical bstract
... Otherwise, the application of ammonium fertilizer can improve the availability of soil Fe and promote the absorption and utilization of Fe by rice. In contrast, nitrate fertilizer can inhibit the reduction of Fe 3+ and reduce the absorption of Fe by rice [79] . ...
Functional rice has a broad market prospect and represents one of the vital developmental directions for future rice production. This paper summarizes the types, breeding and cultivation technologies of functional rice, as well as prevention and control of pests and diseases. We conclude the following: (1) breeding for functional rice should focus on breeding rice varieties with an endosperm that is enriched with multiple active components and broad-spectrum resistance to pests and diseases; (2) moderate water stress and optimized fertilizer management practices of low nitrogen, low phosphorus, high potassium, high silicon, and moderate micronutrient fertilization, as well as timely and early harvest, are conducive to improving the yield and quality of functional rice. In addition, we stress the need to focus on the development and application of polymerization breeding technologies for the advancement of the functional rice industry, and future research in these areas should be reinforced.
... Therefore, a cropping system's first crop's average nitrogen-15 fertilizer recovery rate was 44% (Whittaker et al. 2023), and in the first five harvests, there was an overall recovery of nitrogen-15 fertilizer of around 50%. The remaining 50% of nitrogen-15 fertilizer would contribute to a sizable soil nitrogen pool, some of which may be lost from the cropping system, assuming that nitrogen-15 in roots had diminished by the sixth growing season (Su et al. 2018). Soil organic carbon will influence crop yields and nitrogen losses to the environment since nitrogen is bonded to capacity in soil organic matter, which is not only the primary source of nitrogen for crops but also the main sink of nitrogen fertilizer input in current cereal cropping systems (Quan et al. 2020). ...
Traditional fertilizers are highly inefficient, with a major loss of nutrients and associated pollution. Alternatively, biochar loaded with phosphorous is a sustainable fertilizer that improves soil structure, stores carbon in soils, and provides plant nutrients in the long run, yet most biochars are not optimal because mechanisms ruling biochar properties are poorly known. This issue can be solved by recent developments in machine learning and computational chemistry. Here we review phosphorus-loaded biochar with emphasis on computational chemistry, machine learning, organic acids, drawbacks of classical fertilizers, biochar production, phosphorus loading, and mechanisms of phosphorous release. Modeling techniques allow for deciphering the influence of individual variables on biochar, employing various supervised learning models tailored to different biochar types. Computational chemistry provides knowledge on factors that control phosphorus binding, e.g., the type of phosphorus compound, soil constituents, mineral surfaces, binding motifs, water, solution pH, and redox potential. Phosphorus release from biochar is controlled by coexisting anions, pH, adsorbent dosage, initial phosphorus concentration, and temperature. Pyrolysis temperatures below 600 °C enhance functional group retention, while temperatures below 450 °C increase plant-available phosphorus. Lower pH values promote phosphorus release, while higher pH values hinder it. Physical modifications, such as increasing surface area and pore volume, can maximize the adsorption capacity of phosphorus-loaded biochar. Furthermore, the type of organic acid affects phosphorus release, with low molecular weight organic acids being advantageous for soil utilization. Lastly, biochar-based fertilizers release nutrients 2–4 times slower than conventional fertilizers.
... Otherwise, the application of ammonium fertilizer can improve the availability of soil Fe and promote the absorption and utilization of Fe by rice. In contrast, nitrate fertilizer can inhibit the reduction of Fe 3+ and reduce the absorption of Fe by rice [79] . ...
... Zn bioavailability in grains was estimated by two methods: i) using the molar ratio of PA to Zn ([PA]/[Zn]) (Morris and Ellis, 1989), and ii) using a model that calculates the total daily absorbed Zn bioavailability (TAZ, mg Zn day −1 ) (Miller et al., 2007). Fe bioavailability in grains was also estimated by two methods: i) using the molar ratio of PA to Fe ([PA]/[Fe]) and ii) using a factor of 17.2% as the dietary Fe absorption in food, and the index of available Fe (TAF, mg Fe day −1 ) in grains was evaluated (Saha et al., 2017;Su et al., 2018). ...
Introduction
Lower phosphorus (P) availability limits crop productivity in agroecosystems. The remobilization of P from the source to the sink organs plays an important role in enhancing the P-utilization efficiency of crops. During the grain filling stage, phosphorus flow to the developing grains, the primary sink, determines crop yield. However, the specific contributions of different organs to grain P throughout the post-silking period in maize remain unclear.
Methods
In our study, three maize inbred lines (CIMBL89, Ji846, and CML118) with contrasting P statuses were selected and grown in a field with high P (HP, 150 kg ha–1 P2O5) and low P (LP, 0 kg ha–1 P2O5) conditions.
Results
The grain yield of CIMBL89 was 69% and 169% greater under HP supply, and 83% and 309% greater than those of Ji846 and CML118 under LP supply, respectively. The ear length, ear diameter, and kernel row number of CML118 were lower than those of CIMBL89 and Ji846 under HP conditions. Most of the P (87%) in the grains of CIMBL89 came from P uptake at the LP supply, while almost all P (95%) came from P remobilization in various organs at the HP supply after silking. In contrast, 91% of the P found in the grain of CML118 came from P remobilization under LP supply, while 76% came from P uptake under HP supply after silking.
Discussion
In conclusion, our findings suggest that CIMBL89, with greater P acquisition efficiency, contributes to grain formation and production during the post-silking period under LP conditions. Additionally, CIMBL89 can fully remobilize P and avoid the extravagant absorption of P in P-sufficient soil, which sets it apart from Ji846 and CML118.
... 65 As a result, lpa mutations have minimal effect on the nutritional value of white grain but primarily affect the chemistry of the bran fraction, where lpa sources have considerable potential in providing more nutritious feed for animals. 66 Furthermore, the lpa trait is still of great value for human consumption, where rice is consumed as brown rice. Thus, the benefits of lpa crops for both human food and animal feed should be comprehensively considered in policy and research strategies. ...
... However, the effect of phytic acid on binding toxic elements in the human intestine is still unclear (Kumar et al., 2017;Liu, Zheng, & Chen, 2017;Su, Zhou, Zhao, Pan, & Cheng, 2018). To the best of our knowledge, no specific work has been published in the literature on the phytic acid-As binding in the human intestine. ...
Twenty-two brown rice varieties available in the Qatari market were analyzed for essential and toxic elements by ICP-MS. Found concentrations (µg/kg) were: As: 171±78 (62-343), Cd: 42±60 (4-253), Cr: 515±69 (401-639), Pb: 6±7 (<MDL-26), and U: 0.1±0.5 (<MDL-2). One third of the samples contained high levels of arsenic. Significant differences (p<0.008) in concentrations were observed for many elements based on the grains’ country of origin and size. Calculated carcinogenic risk based on published speciation data of inorganic arsenic and chromium(VI) available in the literature for rice is >1 in million, may possibly be >1 in 10,000 based on conservatively high brown rice consumption rates of 200 g/d or 400 g/d in Qatar. These elevated risks may be applicable to specific population subgroups with diabetic conditions who consume only brown rice. Non-cancer risks are mainly derived from Mn, V, Se, and Cd with a hazard index >1 from some brown rice samples.
... Concerning Zn-P crosstalk, their relations have a negative correlation. The higher inorganic phosphate (Pi) content in soil increases Zn adsorption on soil particles (Su et al. 2018). The application of Pi fertilizers has an interesting impact on the soil pH. ...
Zinc (Zn) is a vital micronutrient in both plants and humans for healthy growth and development. The lesser Zn accessibility causes about 20% yield loss along with low Zn content in grains. About 30% of the human population in the world rely on Zn deficient diets. Dietry Zn deficiency causes impairment of physical growth, immune system functioning, reproductive health, and neurobehavioral development in humans. In various physiological processes, Zn plays a key role and serves as a cofactor for various enzymes and proteins in numerous essential biochemical pathways in both plant and animal. Consequently, it is important to increase Zn content of cereal grains such as rice, maize and wheat. Many investigations have been accomplished to improve Zn deficiency tolerance and improving Zn content in grains. In this regard, improving Zn use efficiency is the most meaningful approach that involves modifying root system architecture, solubilization of Zn complex by organic acids, root exudates, and Zn uptake and translocation mechanism in plants. Here we present an outlook of different biotechnological approaches to improve Zn use efficiency and producing cereals with superior grain quality.
... Ferti-fortification of rice with Zn through foliar application showed 1.6 times more Zn in brown rice than in its husk part (Dhaliwal et al. 2010). Appropriate phosphorus fertilizer application is also found to increase Zn and Fe in rice grain (Su et al. 2018). The use of zinc-solubilizing bacteria, Enterobacter cloacae strain ZSB14, is also found to be beneficial in rice Zn fortification (Krithika and Balachandar 2016). ...
Milled rice is an essential part of the regular diet for approximately half of the world’s population. Its remarkable commercial value and consumer acceptance are mostly due to its promising cooking qualities, appealing sensory properties, and longer shelf life. However, the significant loss of the nutrient-rich bran layer during milling makes it less nutritious than the whole grain. Thus, enhancing the nutritive value of milled rice is vital in improving the health and wellbeing of rice consumers, particularly for those residing in the low-economic zones where rice is the primary source of calories and nutrition. This article provides a critical review on multiple frontiers of recent interventions, such as (1) infusing the genetic diversity to enrich amylose and resistant starch to reduce glycaemic index, (2) enhancing the minerals and vitamins through complementary fortification and biofortification as short and long-term interventions, and (3) developing transgenic solutions to improve the nutrient levels of milled rice. Additionally, the review highlights the benefits of functional ingredients of milled rice to human health and the potential of enhancing them in rice to address the triple burden of malnutrition. The potential merit of milled rice concerning food safety is also reviewed in this article.
... In previous studies, low phytate (lpa ) mutants have been generated by random mutagenesis in various crops. Such mutants are most often associated with lower thousand seed weight and viability than the wild type, reducing breeding value Oltmans et al., 2005;Raboy, 2007;Su et al., 2018). In our study, some low phytate cultivars had a higher germination rate, and some high phytate cultivars showed low germination rate. ...
Phytate is the storage form of phosphorus in angiosperm seeds and plays vitally important roles during seed development. However, in crop plants phytate decreases bioavailability of seed-sourced mineral elements for humans, livestock and poultry, and contributes to phosphate-related water pollution. However, there is little knowledge about this trait in oilseed rape B. napus (oilseed rape). Here, a panel of 505 diverse B. napus accessions was screened in a genome-wide association study (GWAS) using 3.28 x 106 single nucleotide polymorphisms (SNPs). This identified 119 SNPs significantly associated with phytate concentration (PA_Conc) and phytate content (PA_Cont) and six candidate genes were identified. Of these, BnaA9.MRP5 represented the candidate gene for the significant SNP chrA09_5198034 (27kb) for both PA_Cont and PA_Conc. Transcription of BnaA9.MRP5 in a low -phytate variety (LPA20) was significantly elevated compared with a high -phytate variety (HPA972). Association and haplotype analysis indicated that inbred lines carrying specific SNP haplotypes within BnaA9.MRP5 were associated with high- and low-phytate phenotypes. No significant differences in seed germination and seed yield were detected between low and high phytate cultivars examined. Candidate genes, favorable haplotypes and the low phytate varieties identified in this study will be useful for low-phytate breeding of B. napus.
... The conclusions regarding the P-Zn relationship have sometimes been quite different. Besides finding an antagonistic effect of P on cereal grain Zn concentrations, researchers have found a non-effect (Su et al. 2018) or a slightly synergistic effect (Iqbal et al. 2017;Naeem et al. 2018), and these differences might be due to variation in soil texture, pH, or other soil properties (Haldar and Mandal 1981;Goh et al. 1997;Grant et al. 2002;Gao et al. 2011;Ghasemi-Fasaei and Mayel 2012;Hagh et al. 2016). In recent years, a number of studies on the effects of P application on cereal grain Zn have greatly increased. ...
Zinc (Zn) deficiency is a well-documented worldwide problem for crops and humans. Although phosphorus (P) fertilizer application achieves high grain yield in intensive agricultural systems, it can reduce Zn availability in cereal grains. Therefore, a quantitative evaluation of the P–Zn antagonism is needed. A global meta-analysis of 51 publications with wheat, maize, and rice was performed to quantitatively analyze the effect of P application on grain Zn concentration. Phosphorus application reduced grain Zn concentration by 16.6% for wheat, 20.2% for maize, and 0% for rice. Phosphorus application did not affect soil available Zn concentration but, averaged across the three crops, significantly decreased root Zn concentration by 9.94%; the reduction was associated with a reduction in colonization of roots by arbuscular mycorrhizal fungi. Phosphorus application did not affect shoot-to-root or grain-to-straw ratios of Zn concentration, indicating that Zn translocation and remobilization within the plant were not reduced by P application. Especially for wheat and maize, the P–Zn antagonism was explained by a “dilution effect” and the suppression of Zn uptake efficiency by roots rather than by a suppression of translocation and remobilization. In addition to partially explaining the cause of the P–Zn antagonism, this is the first study using meta-analysis method to quantitatively demonstrate a P–Zn antagonism for Zn concentration in wheat and maize. Biofortification for increasing the grain Zn concentration may benefit from an increased understanding of how P application affects rhizosphere and root processes.
... We suggest that P toxicity is triggered by the accumulation of phytic acid in leaves. In seeds, phytic acid synthesis is stimulated in response to Pi accumulation for storing P and metals (Hawkesford et al., 2012;Su, Zhou, Zhao, Pan, & Cheng, 2018). In line with this observation, we found that phytic acid synthesis occurs substantially with an increase in Pi accumulation in the leaves due to the upregulated mRNA expression of genes involved in phytic acid synthesis (Table 1; Figure 8). ...
Phosphorus (P) is an essential mineral nutrient for plants. Nevertheless, excessive P accumulation in leaf mesophyll cells causes necrotic symptoms in land plants; this phenomenon is termed P toxicity. However, the detailed mechanisms underlying P toxicity in plants have not yet been elucidated. This study aimed to investigate the molecular mechanism of P toxicity in rice. We found that under excessive inorganic P (Pi) application, Rubisco activation decreased and photosynthesis was inhibited, leading to lipid peroxidation. Although the defence systems against reactive oxygen species (ROS) accumulation were activated under excessive Pi application conditions, the Cu/Zn‐type superoxide dismutase activities were inhibited. A metabolic analysis revealed that excessive Pi application led to an increase in the cytosolic sugar phosphate concentration and the activation of phytic acid synthesis. These conditions induced mRNA expression of genes that are activated under metal‐deficient conditions, although metals did accumulate. These results suggest that P toxicity is triggered by the attenuation of both photosynthesis and metal availability within cells mediated by phytic acid accumulation. Here, we discuss the whole phenomenon of P toxicity, beginning from the accumulation of Pi within cells to death in land plants.
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The hidden hunger caused by grain zinc (Zn) deficiency in crop poses a potential threat to the health of nearly two bil-
lion people worldwide, especially in developing countries. In this study, the long-term phosphorus fertilizer experiment and in
vitro detached rice panicle culture systems with varied phosphorus levels were conducted to investigate the effect of phosphorus
on rice grain Zn bioavailability and its relation of grain inositol phosphates profiles (phytic acid related metabolic derivatives)
concentration. In our results, compared with low phosphorus level, high phosphorus supply increased grain phytic acid phospho-
rus and total phosphorus concentration (mg g–1). Moreover, high phosphorus supply also increased different grain inositol
phosphate profile concentrations (InsP1-6), especially for InsP4-6. On the contrary, grain Zn concentration decreased with
phosphorus supply. Both the decrement of Zn and increment of phytic acid phosphorus induced by the higher phosphorus supply
in rice grain led to the significant decrement of grain Zn bioavailability. In in vitro detached panicle culture system, the Zn
bioavailability in P12 treatment decreased by 81.3% relative to P0 treatment. In conclusion, higher phosphorus input could
significantly decrease grain Zn bioavailability through increased grain phytic acid phosphorus and inositol phosphates derivatives
concentration, in addition to the decrement of grain Zn concentration.
... The applied P is absorbed from the root and remobilized to the shoot, and then PA is synthesized in developing seeds using the transported P [25]. It has been reported that the PA content is affected by the amount of supplied P in various crops [26][27][28], including rice [29]. In a low-phytate soybean line, which derived from a cross of the normal-phytate Japanese cv. ...
Phytic acid (PA) prevents the absorption of minerals in the human intestine, and it is regarded as an antinutrient. Low PA rice is beneficial because of its higher Zn bioavailability and it is suggested that the gene expression level of myo-inositol 3-phosphate synthase 1 (INO1) in developing grain is a key factor to explain the genotypic difference in PA accumulation among natural variants of rice. P fertilization is also considered to affect the PA content, but it is not clear how it affects INO1 gene expression and the PA content in different genotypes. Here, we investigated the effect of P fertilization on the PA content in two contrasting rice genotypes, with low and high PA accumulation, respectively. Based on the results of the analysis of the PA content, inorganic P content, INO1 gene expression, and xylem sap inorganic P content, we concluded that the effect of P fertilization on PA accumulation in grain differed with the genotype, and it was regulated by multiple mechanisms.
... Phytic acid (PA), as a storage form of phosphorus (P) in plants, accounts for 65-80% of total P accumulation in cereal grains (Su, Zhou, Zhao, Pan, & Cheng, 2018). The high PA concentration in wheat grains reduces the Zn bioavailability by forming a complex with Zn and inhibiting Zn solubility, digestibility and absorption in the human body (Imran & Rehim, 2017). ...
Dietary zinc (Zn) deficiency is a common micronutrient deficiency in humans. Zinc fertilization has been proved to be an effective approach to improve grain Zn concentration in wheat and alleviate Zn deficiency in humans. To maximize the potential of Zn fertilization, it is necessary to select appropriate Zn fertilizer forms and application methods. Here, combined soil and foliar application of ZnSO4, rather than Zn‐EDTA, effectively increased grain Zn concentration in winter wheat (Triticum aestivum L. cv. “Xiaoyan 22”) grown in a calcareous soil. However, neither ZnSO4 nor Zn‐EDTA, when applied to the soil or the foliage alone, had any significant effect on grain Zn concentration. The fractions of Zn loosely bound to organic matter, carbonate‐bound Zn and manganese oxide‐bound Zn in the rhizosphere soil changed dynamically over the course of the wheat growth period, with the highest levels found at the jointing stage. The residual ZnSO4 fertilizer had a positive effect on grain Zn concentration in the subsequent wheat crop due to increased storage of phytic acid in wheat grains and high concentrations of Zn loosely bound to organic matter and carbonate‐bound Zn in the soil. In comparison, Zn‐EDTA applied to the soil only increased the exchangeable‐Zn fraction, and had little residual effect on any other Zn fraction. Repeated soil applications of Zn‐EDTA would be effective to improve grain Zn concentration in wheat plants in subsequent years.
Highlights
• Effects of Zn fertilization in a calcareous soil were tested by a 3‐year field experiment.
• Combined soil and foliar application of ZnSO4 improved grain Zn concentration in wheat.
• Foliar ZnSO4 or Zn‐EDTA application alone had no significant effects on grain Zn concentration.
• Soil ZnSO4 application had a long‐term positive effect on grain Zn concentration in the subsequent wheat crop.
... Previous studies showed that this finding may be related to the increased P uptake in grain with the increase in available soil P because P storage in grain was mainly in the form of phytic acid, which was able to aid crop loading Zn into grains in the form of phytate-Zn (Bohn et al. 2008;Liu et al. 2014). In addition, an in vitro culture with detached panicles recently found that the grain Zn uptake of wild-type rice (XS110) did not decrease, but that of the corresponding mutant (lpa-XS110) was decreased by P supplementation, implying that Zn remobilization and its distribution to grains were associated with crop varieties (Su et al. 2018). Therefore, apart from the suitable available soil P, an appropriate wheat variety should also be considered to increase Zn remobilization and distribution to grains to gain higher Zn levels at harvest. ...
Background and aims
The decrease in cereal grain zinc (Zn) caused by phosphorus (P) application has attracted wide attention. However, optimizing P fertilization for both satisfactory grain yield and grain Zn concentration is still a problem due to a poor understanding of the relationship between P application rates and available soil P, and that of available soil P and soil Zn availability, relevant soil factors, and plant Zn uptake and utilization.
Methods
A location-fixed field experiment was initiated in 2004 with winter wheat (Triticum aestivum L.) grown at five P rates of 0, 50, 100, 150, and 200 kg P2O5 ha⁻¹, and soil and plant samples were collected during the three growing seasons of 2013–2016.
Results
Winter wheat grain yield increased, and the grain Zn concentration decreased with increasing available soil P in a linear-plus-plateau manner. The grain yield plateau, averaging 6009 ± 155 kg ha⁻¹, was reached at an available soil P concentration of 10.2 ± 2.5 mg kg⁻¹, and the grain Zn plateau, averaging 22.4 ± 0.9 mg kg⁻¹, was reached at an available soil P of 14.2 ± 1.8 mg kg⁻¹. Shoot Zn uptake after flowering was not affected, while Zn remobilization from vegetative parts to grains and the Zn harvest index increased with P application at available soil P levels below 11.6 mg kg⁻¹. The available soil Zn increased, and root mycorrhizal colonization was unaffected at lower available soil P levels.
Conclusions
The decrease in wheat grain Zn concentration with increasing P application at lower available soil P levels was primarily explained by yield dilution effects, not the changes in available soil Zn and root mycorrhizal colonization. Under the experimental conditions, the available soil P would have to be as low as 0.7 ± 0.4 mg kg⁻¹ to achieve the target grain Zn concentration of 40 mg kg⁻¹, and at this level, the grain yield would only be 4127 ± 252 kg ha⁻¹.
Optimal nutrition is crucial for human health and well-being. Hence, understanding the nutrient requirements of humans is important for researchers, healthcare givers, and policymakers to tackle the problem of nutritional deficiencies and associated health issues. In general, the human body has the ability to adjust to natural fluctuations in dietary intakes by regulating the absorption and excretion of nutrients, in a process called homeostasis that help optimize the utilization of nutrients. Under healthy conditions or balance, the amount of nutrient absorbed is equal to that of its excretion. Therefore, nutrient requirements are factorially computed by summing the losses through all possible routes along with its associated variation in healthy population (specific age and physiological groups), resulting in a distribution of physiological requirements. These are adjusted for absorption/bioavailability to derive the dietary requirement distribution. The mean of this distribution is estimated average requirement (EAR) and the upper 97.5th centile is referred to as recommended dietary allowance (RDA). These metrics are applied in measuring dietary inadequacies, developing dietary guidelines and diet plans, and regulating the food industry. The goal is to achieve nutrient intakes above the EAR (for population) or RDA (for individuals) to reduce the risk of deficiencies. Nutrient requirements are important in food fortification including crop biofortification as they help in setting the target nutrient levels in foods. In this chapter an attempt was made to simplify various aspects related to nutrient homeostasis, requirements, and their applications particularly in the context of fortification.
The breeding of low phytic acid (LPA) crops is widely considered an effective strategy to improve crop nutrition, but the LPA crops usually have inferior seed germination performance. To clarify the reason for the suboptimal seed performance of LPA rice, this study investigated the impact of reduced seed phytic acid (InsP 6 ) content in rice ins(3)P synthase1 (EC 5.5.1.4, RINO1), one of the key targets for engineering LPA rice, knockouton cellular differentiation in seed embryos and its relation to myo ‐inositol metabolism and auxin signalling during embryogenesis. The results indicated that the homozygotes of RINO1 knockout could initiate differentiation at the early stage of embryogenesis but failed to form normal differentiation of plumule and radicle primordia. The loss of RINO1 function disrupted vesicle trafficking and auxin signalling due to the significantly lowered phosphatidylinositides (PIs) concentration in seed embryos, thereby leading to the defects of seed embryos without the recognizable differentiation of shoot apex meristem (SAM) and radicle apex meristem (RAM) for the homozygotes of RINO1 knockout. The abnormal embryo phenotype of RINO1 homozygotes was partially rescued by exogenous spraying of inositol and indole‐3‐acetic acid (IAA) in rice panicle. Thus, RINO1 is crucial for both seed InsP 6 biosynthesis and embryonic development. The lower phosphatidylinositol (4,5)‐bisphosphate (PI (4,5) P 2 ) concentration and the disorder auxin distribution induced by insufficient inositol supply in seed embryos were among the regulatory switch steps leading to aberrant embryogenesis and failure of seed germination in RINO1 knockout.
High temperatures (HT) cause pollen abortion and poor floret fertility in rice, which is closely associated with excessive accumulation of reactive oxygen species (ROS) in the developing anthers. However, the relationships between accumulation of abscisic acid (ABA) and ROS, and their effects on tapetum‐specific programmed cell death (PCD) in HT‐stressed anthers are poorly characterized. Here, we determined the spatiotemporal changes in ABA and ROS levels, and their relationships with tapetal PCD under HT exposure. Mutants lacking ABA‐activated protein kinase 2 (SAPK2) functions and exogenous ABA treatments were used to explore the effects of ABA signaling on the induction of PCD and ROS accumulation during pollen development. HT‐induced pollen abortion was tightly associated with ABA accumulation and oxidative stress. The higher ABA level in HT‐stressed anthers resulted in the earlier initiation of PCD induction and subsequently abnormal tapetum degeneration by activating ROS accumulation in developing anthers. Interactions between SAPK2 and DEAD‐box ATP‐dependent RNA helicase elF4A‐1 (RH4) were required for ABA‐induced ROS generation in developing anthers. The OsSAPK2 knockout mutants showed the impaired PCD responses in the absence of HT. However, the deficiency of SAPK2 functions did not suppress the ABA‐mediated ROS generation in HT‐stressed anthers. This article is protected by copyright. All rights reserved.
High temperature (HT) at meiosis induces heat injury to pollen viability and floret fertility, which is closely associated with HT-induced endoplasmic reticulum (ER) stress and ROS damage in developing anthers. Disulfide isomerase like proteins (PDILs) play an essential role in the formation, reduction, and isomerization of disulfide bonds in nascent secretory proteins for the maintenance of cell viability and ER homeostasis. However, the underlying mechanism by which HT induces ROS burst in rice anthers and its relation to ER stress for the varying existence of PDILs is largely unknown. In this paper, we investigated the action of PDILs in the regulation of heat injury to floret fertility and its association with HT-induced ROS generation in developing anthers under well-controlled climatic conditions. Results showed that knock-down of OsPDIL1-1 by RNAi enhanced the activity of NADPH oxidase and caused the excessive ROS accumulation in developing anthers, consequently the up-grading sensitivity of pollen viability and floret fertility to heat stress. RBOHb is the primary site where HT exposure affected NADPH oxidase activity and triggered ROS generation in rice anthers because OsPDIL1-1 was found to interact with RBOHb in the ER-PM junction. Furthermore, HT exposure triggered the RBOHb-mediated ROS generation in a Ca²⁺-dependent manner, while the induction of HT exposure to ER stress was not necessarily associated with ROS generation derived from NADPH oxidase.
Phytic acid (PA) is the most prevalent storage form of grain phosphorus (P) and acts as an anti-nutrient by lowering mineral bioavailability. Genotypic variation of grain PA and its relation to mineral bioavailability, and their nutritional fortification potential with zinc (Zn) supply has not been fully investigated in pigmented rice. Here, we compared the differences in grain PA concentration and mineral bioavailability among 13 pigmented rice (red, yellow, and green rice) and six non-pigmented rice cultivars (three common white rice and their corresponding low-PA (lpa) mutant). Pigmented rice was enriched with micronutrients, especially Zn and Fe, on an average of 39.1 and 44.8 mg kg−1 as compared with 31.9 and 33.1 mg kg−1 in non-pigmented rice respectively. The lpa cultivars showed the highest bioavailability for most of the minerals. However, no significant difference was observed for mineral bioavailability between pigmented and common white rice, owing to higher anti-nutritional PA in pigmented rice (9.25 g kg−1) than in common white rice (8.29 g kg−1). However, a large difference in grain PA was found among green rice (11.19 g kg−1), yellow rice (9.82 g kg−1) and red rice (8.56 g kg−1) cultivars. Therefore, foliar Zn was used to investigate PA concentration and Zn bioavailability. Foliar Zn application increased grain Zn but decreased grain PA concentration, which ultimately increased grain Zn bioavailability. Zn application had a remarkable effect on Zn bioavailability for red rice (an average of 82%) as compared with common white rice (48%). These findings could provide helpful knowledge for pigmented rice fortification.
【Objective】This study was aimed to elucidate the spatial distribution of phytic acid (PA), mineral concentration and their availabilities in pomelo fruits, and these findings could provide theoretical bases for biofortification of mineral nutrition and comprehensive nutritional evaluation of pomelo fruit. 【Method】Five representative pomelo cultivars (white-fleshed pomelo, golden-pomelo, red-fleshed pomelo, three-red pomelo, and red-albedo pomelo) grown in Pinghe County, Fujian Province, were used in the present study. At the ripening stage, the representative fruits from each cultivar were selected and divided the whole fruit into four spatial parts, i.e. flavedo, albedo, segment membrane and juice sac. The PA, mineral concentration and their availabilities were analyzed by iron precipitation spectrometry, inductively coupled plasma mass spectrometry (ICP-MS) and molar ratio of phytic acid to minerals in different spatial locations of pomelo fruit. In addition, Zn bioavailability was also evaluated by the ternary model, a mathematical model of zinc absorption in human intestine. 【Result】The concentration of phosphorus (total phosphorus) and inorganic phosphorus was highest in juice sac, but the concentration of PA was the lowest in juice sac. The PA concentration decreased persistently from the outer (flavedo) to the inner (pulp), i.e. flavedo > albedo > segment membrane > juice sac. The concentration of phytate-phosphorus in juice sac was only 4% of total phosphorus, while that in peel was 30%. In addition, the significant cultivar differences of PA were recorded in juice sac. The concentration of PA in juice sac of different pomelo cultivars was the highest in red-fleshed pomelo, while which was the lowest in three-red pomelo and white-fleshed pomelo, with 2.6-fold difference. However, non-significant difference was found in phosphorus and inorganic phosphorus among different pomelo cultivars. From the perspective of mineral distribution in pomelo, the higher concentration of calcium (Ca) was recorded in peel (flavedo, albedo, and segment membrane), while the higher concentration of phosphorus was found in juice sac. Iron (Fe) in peel was significantly higher than that in juice sac, and the variation was the largest in flavedo and juice sac. Influenced by both PA and minerals in different spatial location of pomelo fruit, [PA]/[Mg] and [PA]/[Fe] was the highest in flavedo, [PA]/[Zn] and [PA]/[Mn] was the highest in albedo, whereas [PA]/[Ca] was the highest in the juice sac. There were also significant cultivar differences in the mineral availability in juice sac. The [PA]/[Fe] of golden-pomelo was nearly six times higher than that of red-albedo pomelo. The [PA]/[Zn] of red-albedo pomelo was 3.6 times higher than that of white-fleshed pomelo and three-red pomelo. Generally, among the five pomelo cultivars, three-red pomelo and white-fleshed pomelo had the relatively low PA while high mineral availabilities. 【Conclusion】Significant cultivar and spatial positional differences existed in PA, minerals and their availabilities in pomelo fruits. Phosphorus in the pomelo juice sac mainly existed in the form of inorganic phosphorus, rather than PA. The results suggested that the inhibitory effect of PA on mineral availability was relatively small and limited in the juice sac. However, the concentration of PA in peel (flavedo, albedo) was relatively higher. Therefore, it is necessary to pay attention to the minerals availabilities during pomelo peel related deep food processing. © 2021 Editorial Department of Scientia Agricultura Sinica. All rights reserved.
The role of cereal grain zinc (Zn) in human health has been intensively studied in dietary structure, but limited information is available on the transfer of Zn from soil to crop grain for wheat grown in the intensive production system, especially the effect from management practices such as applications of fertilizer Zn, nitrogen (N) and phosphorus (P). Using wheat as a model crop in the intensive agriculture system, we have found that more Zn supply is needed to achieve the high yield goal. The critical levels for soil DTPA-Zn and shoot Zn concentration at anthesis for maximum grain yield are identified as 1.98 and 29.4 mg kg− 1, which were greater than those of the previous reports. Increasing N supply improved wheat Zn uptake due to increased root length and surface area. In contrast, fertilizer P application significantly decreased wheat Zn uptake, which was mainly attributed to the reduction of root colonization by arbuscular mycorrhizal fungi. Applying strategies such as foliar and soil application of Zn fertilizers can enhance grain Zn bioavailability, depending on the application method and the amount of available soil Zn. For Zn biofortification, foliar application of Zn has great superiority due to its benefits on grain Zn, low cost, and high adaptation to environment and crop production systems. In conclusion, N and P fertilizations can be optimized to combine with Zn fertilizer application as a double-win strategy to simultaneously achieve high grain yield and grain Zn bioavailability for wheat grown in the intensive production system.
Mineral phosphorus (P) fertilizers support high crop yields and contribute to feeding the teeming global population. However, complex edaphic processes cause P to be immobilized in soil, hampering its timely and sufficient availability for uptake by plants. The resultant low use efficiency of current water-soluble P fertilizers creates significant environmental and human health problems. Current practices to increase P use efficiency have been inadequate to curtail these problems. We advocate for the understanding of plant physiological processes, such as physiological P requirement, storage of excess P as phytate, and plant uptake mechanisms, to identify novel ways of designing and delivering P fertilizers to plants for improved uptake. We note the importance and implications of the contrasting role of micronutrients such as zinc and iron in stimulating P availability under low soil P content, while inhibiting P uptake under high P fertilization; this could provide an avenue for managing P for plant use under different P fertilization regimes. We argue that the improvement of the nutritional value of crops, especially cereals, through reduced phytic acid and increased zinc and iron contents should be among the most important drivers toward the development of innovative fertilizer products and fertilization technologies. In this paper, we present various pathways in support of this argument. Retuning P fertilizer products and application strategies will contribute to fighting hunger and micronutrient deficiencies in humans. Moreover, direct soil P losses will be reduced as a result of improved P absorption by plants.
Legacy phosphorus (P) in soil, accumulated over several years of fertilizer application in excess of crop demand, represents a huge and largely untapped resource. P activators can increase the availability of this P to plants by accelerating its transformation into soluble P fractions. In this study, we evaluated the potentials of four "P activators" (oxalic acid, lignin, phytase and ascorbic acid) to increase plant available P in a laboratory incubation experiment with two P-deficient calcareous soils used for wheat production. Samples were analysed for Olsen P, phosphomonoesterase and with Hedley sequential P fractionation. All four treatments had significant effects on different soil P fractions. Oxalic acid mainly enhanced inorganic P (Pi) solubility from the HCl-extractable P pool. Lignin enhanced P lability from the NaOH-, HCl- and residual-P pools. Phytase and ascorbic acid principally affected the organic P fractions (Po). Oxalic acid and lignin showed most potential to improve P (H2O-P, NaHCO3-Pi and NaHCO3-Po) availability, which increased by 110-419% and 4.1-122%, respectively. These findings illustrated the potential mechanisms responsible for P release associated with different P activators and reinforced the case for their use in increasing legacy P availability for agriculture in calcareous soils.
Purpose
Phosphate (P) fertilizers are being widely used to increase crop yield, especially in P-deficient soils. However, repeated applications of P could influence trace element bioaccumulation in crops. The effects of 5-year P enrichment on trace element (Cu, Zn, Cd, Pb, As, and Hg) accumulation in Oryza sativa L. were thus examined.
Materials and methods
Two paddy soils with different initial P availabilities were amended with and without P fertilizer from 2009 to 2013. Trace elements and P levels in rice and soils were analyzed.
Results and discussion
In soil initially with limited P, P amendment enhanced grain Pb, As, and Hg concentrations by 1.8, 1.5, and 1.4-fold, respectively, but tended to decrease the grain Cd level by 0.73-fold, as compared to the control. However, in soil initially with sufficient P, P amendment tended to reduce accumulation of all examined elements in rice grain.
Conclusions
Phosphate amendment in initially P-limited and P-sufficient soils had different effects on trace element availability in soil (as reflected by extractable element) and plant physiology (growth and metal translocation), resulting in contrasting patterns of trace element accumulation in rice between the two types of soils. Our study emphasized the necessity to consider the promoting effects of P on Pb, As, and Hg accumulation in grain in initial P-deprived soil.
Most of the phosphorus in seeds is accumulated in the form of phytic acid (myo-inositol-1,2,3,4,5,6-hexakisphosphate, InsP6). This molecule is a strong chelator of cations important for nutrition, such as iron, zinc, magnesium, and calcium. For this reason, InsP6 is considered an antinutritional factor. In recent years, efforts to biofortify seeds through the generation of low phytic acid (lpa) mutants have been noteworthy. Moreover, genes involved in the biosynthesis and accumulation of this molecule have been isolated and characterized in different species. Beyond its role in phosphorus storage, phytic acid is a very important signaling molecule involved in different regulatory processes during plant development and responses to different stimuli. Consequently, many lpa mutants show different negative pleitotropic effects. The strength of these pleiotropic effects depends on the specific mutated gene, possible functional redundancy, the nature of the mutation, and the spatio-temporal expression of the gene. Breeding programs or transgenic approaches aimed at development of new lpa mutants must take into consideration these different aspects in order to maximize the utility of these mutants.
Aims
Phosphorus (P)-induced zinc (Zn) deficiency is one of the most commonly studied antagonistic interactions in plant nutrition. However, there are many controversial reports about P–Zn interaction, possibly related to growth conditions. In this study, the effects of P supply on the root uptake and tissue concentrations of Zn as well as the development of Zn deficiency were investigated in wheat (Triticum aestivum) grown in different media.
Methods
Plants were grown under greenhouse and growth chamber conditions in native soil, autoclaved soil and nutrient solution with different P and Zn supplies. In the soil experiment, the shoot biomass and grain yield were measured whereas in the nutrient solution experiment, the root and shoot biomass were determined. Development of Zn deficiency symptoms was examined. Concentrations of Zn, P and other elements were measured in harvested tissues. Mycorrhizal colonization of roots was scored in soil-grown plants. Root uptake of stable Zn isotope (70Zn) was investigated at different P rates in a separate nutrient solution experiment.
Results
Higher P rates caused substantial decreases in shoot and grain Zn concentrations in native soil but not in autoclaved soil. Treatment of native soil with increasing P significantly reduced mycorrhizal colonization. At low Zn, P applications aggravated Zn deficiency symptoms in both soil and solution culture. In solution culture, root and shoot Zn concentrations were not lowered by higher P rates. Root uptake of 70Zn from nutrient solution was even depressed at low P.
Conclusions
The negative effect of increasing P supply on root Zn uptake and tissue Zn concentrations in wheat is mycorrhiza-dependent and may completely disappear in a mycorrhiza-free environment.
Increasing nitrogen supply can increase Fe and Zn concentrations in wheat grain, but the underlying mechanisms remain unclear. Size-exclusion chromatography coupled with inductively coupled plasma mass spectrometry was used to determine Fe and Zn speciation in the soluble extracts of grain pearling fractions of two wheat cultivars grown at two N rates (100 and 350 kg of N ha −1). Increasing N supply increased the concentrations of total Fe and Zn and the portions of Fe and Zn unextractable with a Tris−HCl buffer and decreased the concentrations of Tris−HCl-extractable (soluble) Fe and Zn. Within the soluble fraction, Fe and Zn bound to low molecular weight compounds, likely to be Fe−nicotianamine and Fe−deoxymugineic acid or Zn−nicotianamine, were decreased by 5−12% and 4−37%, respectively, by the high N treatment, whereas Fe and Zn bound to soluble high molecular weight or soluble phytate fractions were less affected. The positive effect of N on grain Fe and Zn concentrations was attributed to an increased sink in the grain, probably in the form of water-insoluble proteins. ■ INTRODUCTION Iron and zinc deficiencies are widespread nutritional disorders, affecting over two billion people in the world. 1,2 Insufficient dietary intakes of Fe and Zn and limited dietary diversity are thought to be responsible for human micronutrient deficiencies, especially in developing countries, where high proportions of cereal grains with inherently low concentrations of Fe and Zn, such as wheat and rice, are consumed as staple foods. 1,3 The bioavailability of Fe and Zn in cereal grains is also relatively low due to the presence of antinutritional compounds such as phytic acid and phenolic compounds. 1 Additionally, milling of wheat grain into white flour further results in reduced concentrations of Fe and Zn, because they are enriched in the outer parts of the grains, consisting mainly of the aleurone layer, embryo, pericarp, and testa. 4−6 Therefore, increasing Fe and Zn concentrations and/or their bioavailability in white flour is desirable for tackling the problem of micronutrient malnutrition. Recent studies have shown that nitrogen supply is an important factor affecting the concentrations of Fe and Zn in wheat grain. For example, under both field and glasshouse conditions, increasing N supply generally enhances Fe and Zn concentrations in wheat grain. 5,7−9 It has been reported that N increases Zn uptake by roots, Zn translocation from roots to shoots and Zn remobilization from leaves to grain in wheat, 4,10
Inositol hexaphosphate (Ins P6 or “phytic acid”) typically accounts for 75 (± 10%) of seed total phosphorus (P). In some cases, genetic blocks in seed Ins
P6 accumulation can also alter the distribution or total amount of seed P. In nonmutant barley (Hordeum vulgare L.) caryopses, ~80% of Ins P6 and total P accumulate in the aleurone layer, the outer layer of the endosperm, with the remainder in the germ. In barley
low phytic acid 1-1 (Hvlpa1-1) seed, both endosperm Ins P6 and total P are reduced (~45% and ~25%, respectively), but germs are phenotypically wild type. This translates into a net
reduction in whole-seed total P of ~15%. Nutrient culture studies demonstrate that the reduction in endosperm total P is not
due to a reduction in the uptake of P into the maternal plant. Genetic tests (analyses of testcross and F2 seed) reveal that the Hvlpa1-1 genotype of the filial seed conditions the seed total P reduction; sibling seed in the same head of barley that differ
in their Hvlpa1-1 genotype (heterozygous vs. homozygous recessive) differ in their total P (normal vs. reduced, respectively). Therefore,
Hvlpa1 functions as a seed-specific or filial determinant of barley endosperm total P.
Cereal Chem. 87(1):10–20 Micronutrient malnutrition affects over 2 billion people in the develop-ing world. Iron (Fe) deficiency alone affects >47% of all preschool aged children globally, often leading to impaired physical growth, mental development, and learning capacity. Zinc (Zn) deficiency, like iron, is thought to affect billions of people, hampering growth and development, and destroying immune systems. In many micronutrient-deficient regions, wheat is the dominant staple food making up >50% of the diet. Biofortifi-cation, or harnessing the powers of plant breeding to improve the nutri-tional quality of foods, is a new approach being used to improve the nutrient content of a variety of staple crops. Durum wheat in particular has been quite responsive to breeding for nutritional quality by making full use of the genetic diversity of Fe and Zn concentrations in wild and synthetic parents. Micronutrient concentration and genetic diversity has been well explored under the HarvestPlus biofortification research pro-gram, and very positive associations have been confirmed between grain concentrations of protein, Zn, and Fe. Yet some work remains to ade-quately explain genetic control and molecular mechanisms affecting the accumulation of Zn and Fe in grain. Further, evidence suggests that nitrogen (N) nutritional status of plants can have a positive impact on root uptake and the deposition of micronutrients in seed. Extensive research has been completed on the role of Zn fertilizers in increasing the Zn density of grain, suggesting that where fertilizers are available, making full use of Zn fertilizers can provide an immediate and effective option to increase grain Zn concentration, and productivity in particular, under soil conditions with severe Zn deficiency.
This paper reviews the possibility and limits for increasing the content and bioavailability of iron (Fe), zinc (Zn) and calcium (Ca) in edible parts of staple crops, such as cereals, pulses, roots and tubers as a way to combat mineral deficiencies in human populations. Theoretically, this could be achieved by increasing the total level of Fe, Zn and Ca in the plant foods, while at the same time increasing the concentration of compounds which promote their uptake (ascorbic acid), and/or by decreasing the concentration of compounds which inhibit their absorption (phytic acid or phenolic compounds). The content of Zn and Ca in grains and fruits can in some cases be increased through soil and/or foliar applications of Zn and Ca fertilisers. Plant breeding and genetic engineering techniques, however, have the greatest potential to increase Fe and Zn content in grains, roots and tubers. The possibility of enhancing Ca and ascorbic acid content in plant foods by plant breeding and genetic engineering remained to be explored. The critical factor is to ensure that the extra minerals have an adequate bioavailability for man. Given the important role of phytic acid and polyphenols in plant physiology, reducing the levels of these compounds in the edible parts of plants does not appear to be wise although introduction of phytases which are active during digestion is an exciting possibility.© 2000 Society of Chemical Industry
This paper reviews the possibility and limits for increasing the content and bioavailability of iron (Fe), zinc (Zn) and calcium (Ca) in edible parts of staple crops, such as cereals, pulses, roots and tubers as a way to combat mineral deficiencies in human populations. Theoretically, this could be achieved by increasing the total level of Fe, Zn and Ca in the plant foods, while at the same time increasing the concentration of compounds which promote their uptake (ascorbic acid), and/or by decreasing the concentration of compounds which inhibit their absorption (phytic acid or phenolic compounds). The content of Zn and Ca in grains and fruits can in some cases be increased through soil and/or foliar applications of Zn and Ca fertilisers. Plant breeding and genetic engineering techniques, however, have the greatest potential to increase Fe and Zn content in grains, roots and tubers. The possibility of enhancing Ca and ascorbic acid content in plant foods by plant breeding and genetic engineering remained to be explored. The critical factor is to ensure that the extra minerals have an adequate bioavailability for man. Given the important role of phytic acid and polyphenols in plant physiology, reducing the levels of these compounds in the edible parts of plants does not appear to be wise although introduction of phytases which are active during digestion is an exciting possibility. (C) 2000 Society of Chemical Industry.
The application of phosphorus (P) and crop residues (CR) to acid sandy soils of the Sahel has been shown to increase yields of pearl millet (Pennisetum glaucum L.) several-fold. Information is lacking, however, about possible detrimental effects of such yield-enhancing amendments on grain quality, in particular the bioavailability of zinc (Zn) as defined by the phytate:zinc molar ratio (PZMR) and the concentrations of calcium, micronutrients, and protein. To determine the effects of CR and P on grain quality, millet seeds taken from the grain stores of 14 farmers and from a 2-yr on-station fertilizer experiment were analyzed for macronutrients, Zn, copper, iron, and phytate-P. The on-station experiment comprised four millet lines, P applied at 0 and 13 kg ha−1, and CR applied at 500 and 2000 kg ha−1 as surface mulch or ash. Grain from farmers' unfertilized millet had PZMRs ranging from 15 to 30. Application of P increased the concentrations of phytic acid in the grain between 25 and 29% and decreased Zn concentrations between 6 and 11%. The reasons for this were greater P uptake and a dilution of Zn by the large yield increases after P application. Phosphorus application decreased protein concentrations in both years, and increased the PZMRs from 20 to 28 in 1992 and from 21 to 29 in 1993. Although CR markedly increased millet yield, their application had little effect on PZMRs. While PZMRs above 15 are generally considered critical for Zn nutrition of humans, meat consumption and traditional practices of millet processing may increase Zn bioavailability in local dishes. Further studies of full diets are therefore needed, particularly among rural groups at particularly high risk of Zn deficiency such as nursing women and small children before definitive conclusions can be drawn about the effects of P fertilizer application to millet on the nutritional status of farmers in the Sahel.
Low phytic acid (LPA) barley (Hordeum vulgare L.) cultivars partition phosphorus (P) in seed tissue differently than conventional wild-type (WT) barley cultivars. A reduction in seed phytic acid (myo-inositol-1,2,3,4,5,6-hexkisphosphate) is coupled with an increase in inorganic phosphorus (Pi). The response of the LPA characteristic to phosphate fertilization has not been previously investigated; therefore the effect of phosphate fertility on barley seed yield, and concentrations of seed total P, seed Pi, and flag leaf P was investigated at four locations over two years. The LPA cultivars were hypothesized to behave similarly to WT cultivars, therefore two WT cultivars, Baronesse and Colter, were compared to one LPA cultivar, Herald (lpa1-1 mutation), and one LPA advanced breeding line, 01ID451H (mutation 640). At three locations, phosphate fertilizer (P2O5) was applied in the form of triple superphosphate (0-45-0) at rates of 0, 56, 112, and 168 kg ha-1. Increased P fertilization was associated with increased flag leaf P concentration, but no changes were observed for other measured characteristics. At a fourth location, differential soil P fertility was provided via previously established plots varying from very low to adequate P fertility. Inadequate levels of P were associated with delayed maturity, and reductions in yield, test weight, height, and total seed P concentration. The responses of LPA and WT barleys were similar, indicating the LPA traits in barley originating from the lpa1-1 and 640 mutations are stable under a wide range of soil P fertility.
Commercialization of soybean [Glycine max (L.) Merr.] varieties with low seed phytic acid will depend on the stability of the trait when grown in soils with a wide range of P availabilities and on the impact of altered P composition on seed protein and oil concentrations. Impacts of deficient (0.05 mmol L⁻¹) to excessive (0.9 to 1.2 mmol L⁻¹) levels of external P on seed P composition of normal and low phytic acid lines and of altered seed P composition on seed protein and oil synthesis were evaluated. Soybean lines homozygous recessive (pha/pha) at one of two loci with genes that condition the low seed phytic acid trait had the same greater‐than‐threefold increase in phytic acid in response to increasing external P as their normal phytic acid parent, ‘AGS Prichard‐RR’ (Pha/Pha). This supports the conclusion from previous inheritance studies that the low seed phytic acid trait in CX1834‐1‐2 is controlled by epistatic interaction between two independent recessive genes. The seed phytic acid concentration in the low phytic acid line G03PHY‐443 (derived from CX1834‐1‐2) was <2 g phytic acid P kg⁻¹ dry wt. when grown under deficient to excessive external P. As the P supply increased, seed inorganic P concentrations for this line increased from 0.8 to 4.0 g kg⁻¹ dry wt., compared to an increase of 0.2 to 0.6 g kg⁻¹ dry wt. for the normal phytic acid lines. Seed protein and oil concentrations did not differ significantly between normal and low phytic acid lines. These results support continued development of varieties with low seed phytic acid and high yields.
The lpa1 mutations in maize are caused by lesions in the ZmMRP4 (multidrug resistance-associated proteins 4) gene. In previous studies (Raboy et al. in Plant Physiol 124:355-368, 2000; Pilu et al. in Theor Appl Genet 107:980-987, 2003a; Shi et al. Nat Biotechnol 25:930-937, 2007), several mutations have been isolated in this locus causing a reduction of phytic acid (myo-inositol-1,2,3,4,5,6-hexakisphosphate, or InsP(6)) content and an equivalent increasing of free phosphate. In particular, the lpa1-241 mutation causes a reduction of up to 90% of phytic acid, associated with strong pleiotropic effects on the whole plant. In this work, we show, for the first time to our knowledge, an interaction between the accumulation of anthocyanin pigments in the kernel and the lpa mutations. In fact the lpa1-241 mutant accumulates a higher level of anthocyanins as compared to wild type either in the embryo (about 3.8-fold) or in the aleurone layer (about 0.3-fold) in a genotype able to accumulate anthocyanin. Furthermore, we demonstrate that these pigments are mislocalised in the cytoplasm, conferring a blue pigmentation of the scutellum, because of the neutral/basic pH of this cellular compartment. As a matter of fact, the propionate treatment, causing a specific acidification of the cytoplasm, restored the red pigmentation of the scutellum in the mutant and expression analysis showed a reduction of ZmMRP3 anthocyanins' transporter gene expression. On the whole, these data strongly suggest a possible interaction between the lpa mutation and anthocyanin accumulation and compartmentalisation in the kernel.
Over three billion people are currently micronutrient (i.e. micronutrient elements and vitamins) malnourished, resulting in egregious societal costs including learning disabilities among children, increased morbidity and mortality rates, lower worker productivity, and high healthcare costs, all factors diminishing human potential, felicity, and national economic development. Nutritional deficiencies (e.g. iron, zinc, vitamin A) account for almost two-thirds of the childhood death worldwide. Most of those afflicted are dependent on staple crops for their sustenance. Importantly, these crops can be enriched (i.e. 'biofortified') with micronutrients using plant breeding and/or transgenic strategies, because micronutrient enrichment traits exist within their genomes that can to used for substantially increasing micronutrient levels in these foods without negatively impacting crop productivity. Furthermore, 'proof of concept' studies have been published using transgenic approaches to biofortify staple crops (e.g. high beta-carotene 'golden rice' grain, high ferritin-Fe rice grain, etc). In addition, micronutrient element enrichment of seeds can increase crop yields when sowed to micronutrient-poor soils, assuring their adoption by farmers. Bioavailability issues must be addressed when employing plant breeding and/or transgenic approaches to reduce micronutrient malnutrition. Enhancing substances (e.g. ascorbic acid, S-containing amino acids, etc) that promote micronutrient bioavailability or decreasing antinutrient substances (e.g. phytate, polyphenolics, etc) that inhibit micronutrient bioavailability, are both options that could be pursued, but the latter approach should be used with caution. The world's agricultural community should adopt plant breeding and other genetic technologies to improve human health, and the world's nutrition and health communities should support these efforts. Sustainable solutions to this enormous global problem of 'hidden hunger' will not come without employing agricultural approaches.
The quantities of zinc and phytate in the diet are the primary factors determining zinc absorption. A mathematical model of zinc absorption as a function of dietary zinc and phytate can be used to predict dietary zinc requirements and, potentially, enhance our understanding of zinc absorption. Our goal was to develop a model of practical and informative value based on fundamental knowledge of the zinc absorption process and then fit the model to selected published data to assess its validity and estimate parameter values. A model of moderate mathematical complexity relating total zinc absorption to total dietary zinc and total dietary phytate was derived and fit to 21 mean data from whole day absorption studies using nonlinear regression analysis. Model validity, goodness of fit, satisfaction of regression assumptions, and quality of the parameter estimates were evaluated using standard statistical criteria. The fit had an R(2) of 0.82. The residuals were found to exhibit a normal distribution, constant variance, and independence. The parameters of the model, A(MAX), K(R), and K(P), were estimated to have values of 0.13, 0.10, and 1.2 mmol/d, respectively. Several of these estimates had wide CI attributable in part to the small number and the scatter of the data. The model was judged to be valid and of immediate value for studying and predicting absorption. A version of the model incorporating a passive absorption mechanism was not supported by the available data.
Zinc biofortification in rice can be improved by altering Zn application timing and placement and cultivar choice. We made a comprehensive assessment on this, analysing Zn, Fe and phytic acid in whole grains and processed brown, white and cooked rice obtained from six cultivars raised with Zn applied through soil and/or foliar supply at different phenological stages of the crop and measuring Zn bioavailability in cooked rice. Pathways for Zn enrichment (27.4–92.6% over control) by Zn fertilization with different application protocols and cultivars were elucidated. Such enrichment of Zn was associated with depletion in Fe (6.5–29.4%) and phytic acid (14.8–30.4%). However, the loss of Zn on processing of rice grains increased on Zn fertilization (12.6–28.7 mg kg⁻¹) because of a preferential allocation of applied Zn into bran and aleurone of the grains. Despite such loss, application of Zn caused a net increase in Zn bioavailability (52.2% over control) in the cooked product. Using the ranksum scoring technique, we found cultivar GB 1 and Zn supply through soil (basal) + 2 foliar applications achieved the most effective biofortfication of Zn in rice by optimizing grain yield, and enriching Zn and its bioavailability in cooked grain with least antagonism of Fe availability.
To supplement human dietary nutrition, it is necessary to evaluate the effects of phosphorus (P) fertilizer application on grain and flour protein and especially on the bioavailability of zinc (Zn). A field experiment of winter wheat with six P application rates (0, 25, 50, 100, 200, 400 kg/ha) was conducted from 2013 to 2015. The grain yield increased with P application but did not further enhance when P rates exceeded 50 kg/ha. As P application increased, the protein concentration in grain and standard flour and the viscosity of standard flour decreased. Phosphorus and phytic acid (PA) concentration in grain and flours increased and then plateaued, while Zn concentration decreased and then plateaued as P application increased from 0 to 100 kg/ha. Estimated Zn bioavailability in grain and flours decreased as P application increased from 0 to 100 kg/ha and then plateaued. Estimated Zn bioavailability was greater in standard flour, bread flour, and refined flour than in grain or coarse flour. Phosphorus supply in the intensive cropping of wheat can be optimized to simultaneously obtain high grain yields, high grain and flour protein, and high Zn bioavailability.
Rice is known to accumulate methylmercury (MeHg) in the rice grains. MeHg as a neurotoxin impacts on
the human central nervous systems and especially on the developing brain. In this exploratory study, 87
commercial rice products sold in Europe, including nine baby-rice products, were analyzed for total Hg
and MeHg content. MeHg concentration in all rice products investigated range from 0.11 to 6.45 ug/kg
with an average value of 1.91 ± 1.07 ug/kg and baby-rice is not significantly different from other rice
products. Total Hg ranges from 0.53 to 11.1 ug/kg1 with an average of 3.04 ± 2.07 ug/kg1. MeHg concentrations in all rice products studied in this work would not exceed the provisional tolerable weekly intake
(PTWI). 30% of all commercial market rice products exceeded 10% of the PTWI calculated for toddlers or
13% of products for adults with rice based diet.
Developing seeds store reserve levels of phosphorus and minerals, mobilization of which during germination provides the mineral nutrition essential for optimal early seedling growth. This process also functions as a component of the inorganic P and mineral homeostasis mechanisms necessary for nominal cellular function. The storage and resup-ply of phosphorus centers around the synthesis and breakdown of phytic acid (myo-inositol 1,2,3,4,5,6-hexakisphosphate). Phytic acid is often deposited as a mixed, ‘phytin’ salt, primarily of potassium and magnesium. Thus phytin deposition and re-mobilization also represents an important component of mineral cation storage. Exceptions to this may include iron and calcium storage and homeostasis, for which non-phytin mechanisms may play major roles. There has been recent progress in the molecular biology of several components of phosphorus and mineral storage pathways. These include studies of myo-inositol synthesis, some aspects of myo-inositol phosphate metabolism, protein body transport functions, and calcium and iron storage proteins. Recent genetic studies bring into question the paradigm that phytic acid synthesis is essential to phosphorus storage or inorganic P homeostasis. Much additional progress is required, particularly concerning the synthetic pathway to phytic acid, before a thorough or truly detailed understanding of the molecular biology of P and mineral storage processes is obtained.
The effect of milling degree in three oat cultivars was determined to illustrate the milling characteristics as well as the distribution of phytic acid and some nutritional components in oats. According to the results, to obtain the same milling degree (12%), Baiyan2 (naked oat) required the longest milling (60 s), while Linna (hulled oat) and Bayou1 (naked oat) required shorter milling of 50 s. The milling process could effectively decrease the level of phytic acid, whose distribution was found to be uneven and highly concentrated in the oat bran (27%-53% phytic acid). As for the content of phytic acid in oat, Bayou1 showed a much higher value (52.92 ± 10.27%) in oat bran than Baiyan2 (31.38 ± 0.31%) and Linna (27.81 ± 4.62%). Generally, it took 50-60 s to remove oat bran by milling, which resulted in a 19.7% decrease in hardness of cooked oat. Besides, for naked oat Baiyan2, the marked decline of iron and lipid as well as the constant levels of calcium, zinc, protein, starch and β-glucan was also detected during the milling process.
The method of culturing detached ears of wheat in a liquid medium has been modified to provide for the culture of ears from anthesis to maturity. For prolonged culture of ears, the presence of the peduncular node was beneficial. Grains developing in ears cultured from 2 days after anthesis until they had ripened germinated normally. By comparison with ammonium or nitrate, glutamine was the better source of nitrogen particularly at low levels of sucrose in the medium; inorganic forms of nitrogen inhibited grain-filling. Setting of grains was apparently dependent upon the availability of carbohydrate and there was no evidence from treatments involving shading for a photomorphogenetic response to reduced light intensity. While grain-filling was sustained by the provision of sucrose supplied artificially, light did nevertheless affect the accumulation of dry matter in the grains.
Increasing nitrogen supply can increase Fe and Zn concentrations in wheat grain, but the underlying mechanisms remain unclear. Size-exclusion chromatography coupled with inductively-coupled plasma mass spectrometry was used to determine Fe and Zn speciation in the soluble extracts of grain pearling fractions of two wheat cultivars grown at two N rates (100 and 350 kg N ha-1). Increasing N supply increased the concentrations of total and the portions of Fe and Zn unextractable with a Tris-HCl buffer, and decreased the concentrations of Tris-HCl-extractable (soluble) Fe and Zn. Within the soluble fraction, Fe and Zn bound to low molecular weight compounds, likely to be Fe-nicotianamine (Fe-NA) and Fe-deoxymugineic acid (Fe-DMA) or Zn-NA, were decreased by 5-12% and 4-37%, respectively, by the high N treatment, whereas Fe and Zn bound to soluble high molecular weight or soluble phytate fractions were less affected. The positive effect of N on grain Fe and Zn concentrations was attributed to an increased sink in the grain, probably in the form of water-insoluble proteins.
A pathway of phytic acid (PA) synthesis in plants has been revealed via investigations of low phytic acid mutants. However, the regulation of this pathway is not well understood because it is difficult to control the environments of cells in the seeds, where PA is mainly synthesized. We modified a rice suspension culture system in order to study the regulation of PA synthesis. Rice cells cultured with abscisic acid (ABA) accumulate PA at higher levels than cells cultured without ABA, and PA accumulation levels increase with ABA concentration. On the other hand, higher concentrations of sucrose or inorganic phosphorus do not affect PA accumulation. Mutations in the genes RINO1, OsMIK, OsIPK1 and OsLPA1 have each been reported to confer low phytic acid phenotypes in seeds. Each of these genes is upregulated in cells cultured with ABA. OsITPK4 and OsITPK6 are upregulated in cells cultured with ABA and in developing seeds. These results suggest that the regulation of PA synthesis is similar between developing seeds and cells in this suspension culture system. This system will be a powerful tool for elucidating the regulation of PA synthesis.
This study was conducted to assess the role of increasing N supply in enrichment of whole grain and grain fractions, particularly the endosperm, with Zn and Fe in wheat. The endosperm is the most widely consumed part of wheat grain in many countries. Plants were grown in the greenhouse with different soil applications of N and Zn and with or without foliar Zn spray. Whole grain and grain fractions were analyzed for N, P, Zn and Fe. Increased N supply significantly enhanced the Zn and Fe concentrations in all grain fractions. In the case of high Zn supply, increasing N application enhanced the whole grain Zn concentration by up to 50% and the endosperm Zn by over 80%. Depending on foliar Zn supply, high N elevated the endosperm Fe concentration up to 100%. High N also generally decreased the P/Zn and P/Fe molar ratios in whole grain and endosperm. The results demonstrate that improved N nutrition, especially when combined with foliar Zn treatment, is effective in increasing Zn and Fe of the whole grain and particularly the endosperm fraction, at least in the greenhouse, and might be a promising strategy for tackling micronutrient deficiencies in countries where white flour is extensively consumed.
The Constant Capacitance model provided a quantitative description of o-phosphate adsorption by 44 noncalcareous soils whose pH values ranged from 4. 9 to 7. 6. The intrinsic surface protonation-dissociation constants, capacitance density, and phosphate packing area parameters required by the model were adopted from model calculations on reference hydrous oxide minerals. The intrinsic phosphate surface complexation constants were calculated through the application of a nonlinear least squares fitting program to the soil o-phosphate adsorption data. Two of these intrinsic constants were found to be independent of pH over the range investigated, as required by the model. The Constant Capacitance model was best able to describe o-phosphate adsorption by noncalcareous soils, including pH effects, if a soil-specific set of intrinsic phosphate surface complexation constants was employed.
Nutrient inputs in crop production systems have come under increased scrutiny in recent years because of the potential for environmental impact from inputs such as N and P. The benefits of nutrient inputs are often minimized in discussions of potential risk. The purpose of this article is to examine existing data and approximate the effects of nutrient inputs, specifically from commercial fertilizers, on crop yield. Several long-term studies in the USA, England, and the tropics, along with the results from an agricultural chemical use study and nutrient budget information, were evaluated. A total of 362 seasons of crop production were included in the long-term study evaluations. Crops utilized in these studies included corn (Zea mays L.), wheat (Triticum aestivum L.), soybean [Glycine max (L.) Merr.], rice (Oryza sativa L.), and cowpea [Vigna unguiculata (L.) Walp.]. The average percentage of yield attributable to fertilizer generally ranged from about 40 to 60% in the USA and England and tended to be much higher in the tropics. Recently calculated budgets for N, P, and K indicate that commercial fertilizer makes up the majority of nutrient inputs necessary to sustain current crop yields in the USA. The results of this investigation indicate that the commonly cited generalization that at least 30 to 50% of crop yield is attributable to commercial fertilizer nutrient inputs is a reasonable, if not conservative estimate.
The residual value of ordinary (single) superphosphate (SP) and Queensland (Duchess) apatite rock phosphate was measured in a pot experi- ment using yields of three legume species (serradella, Ornithopus compressus; medic, Medicago polymorpha var. brevispina; clover, Trifolium subterraneum) fertilized with mineral nitrogen (N) grown in rotation with wheat (Triticum aestivum). The plants were grown in a glasshouse in a sandy soil (pH in CaCl2- 5.8) for 30 to 34 days. There were four crops: Legume, wheat, legume, and wheat. The phosphate (P) requirement of the plant species was determined from the amount of P required to produce 90% of the maximum yield. Soil samples were taken before sowing each crop to measure bicarbonate-extractable soil P (soil test P) which was related to the yields of that crop.
Summary In a field experiment, more than 22% increase in the grain yield of corn was obtained by the application of 50 kg ZnSO4/ha. Grain yields were also increased by increasing the level of applied phosphorus. Positive relationship was obtained between
Zn and P, the phosphorus treatment increased Zn uptake by grains and vice versa.
Iron (Fe) deficiency in human caused by inadequate dietary intake is a global nutritional problem. A glass house pot experiment was conducted to evaluate the effect of foliar FeSO4 containing applications on concentrations of Fe, Zn and Fe bioavailability in polished rice among five rice cultivars. The results showed that foliar application of FeSO4, FeSO4 plus nicotianamine (NA), and FeSO4 plus NA with ZnSO4 increased the grain Fe concentration by 16.97%, 29.9% and 27.08%, respectively. The grain Fe bioavailability also increased by foliar application of FeSO4, FeSO4 plus NA, and FeSO4 plus NA with ZnSO4, these represent increases of 12.63%, 20.86% and 18.75%, respectively. Foliar FeSO4 containing applications improved the Fe bioavailability, might be attributed from the reduction of phytic acid, meanwhile the increase of Fe concentration in polished rice. Addition of ZnSO4 to foliar Fe application increase both Fe and Zn content without altering Fe content and bioavailability. In addition, cultivar difference in Fe and Zn concentration was observed might be come from genetic control on ability in leaf absorption and seed deposition of foliar application. Furthermore, cultivar difference in Fe bioavailability was observed might be attributed from the variation of grain Fe, phytic acid and total phenolics contents among the five rice cultivars. The results suggested that foliar FeSO4 containing applications represent a promising agricultural approach to reduce Fe deficiency in countries where polished rice is extensively consumed.
In addition to the formation of insoluble lead (Pb) compounds, adsorption is another potentially important process controlling the bioavailability of Pb in soils. Less attention has been given to manganese (Mn) oxides, even though they are known to adsorb Pb more strongly than any other metal (hydr)oxides. This study was conducted to evaluate the effects of P and Mn oxide on bioavailable Pb in five metal-contaminated soils or mine spoils from Kansas and Missouri. Cryptomelane was used as the representative Mn oxide. Nine treatments were used: zero P, 5000 mg of P as triple superphosphate (TSP) or phosphate rock (PR), 2500 and 5000 mg of Mn oxide/kg, and combinations of Mn oxide and P as TSP or PR. Changes in bioavailable Pb over time were measured using a modified physiologically based extraction procedure (PBET), and mineralogical changes were observed using X-ray diffraction. The addition of P or cryptomelane reduced bioavailable Pb in all five materials. The addition of P and cryptomelane together was more effective in reducing bioavailable Pb than the addition of either amendment alone in all materials. Reductions in bioavailable Pb in stomach phase extractions upon addition of P or P and cryptomelane ranged from 15 to 41% and 23 to 67%, respectively, compared to the unamended control. Similarly, a modified toxicity characteristic leaching procedure (TCLP) indicated less soluble Pb in materials receiving P and cryptomelane compared to the control, P- or cryptomelane-treated samples. X-ray diffractometry analysis supported the PBET and TCLP results, indicating that more “pyromorphite-like minerals” formed in the presence of both P and Mn oxide compared to the control. This new improved technique to remediate Pb-contaminated soil and mine wastes has advantages over standard methods.
The amount and distribution of major nutritionally relevant elements was determined in the grains of a low phytate rice (Oryza sativa L.) mutant line (HIPi1) and its parent variety Xieqingzao (XQZ). The concentration of phytate P (PA-P) was significantly reduced in HIPi1 grains. On brown rice basis, HIPi1 had a content of PA-P about 58.4% that of XQZ, while total P levels were not significantly different between the mutant and its parent. Significant location effects were observed on the amount of the major elements, i.e., Ca, K, Mg, Fe, Zn, in various parts of grains of both HIPi1 and XQZ. In milled rice, larger amounts of these elements were found, consistently and significantly across all three locations, in HIPi1 than XQZ, at rates on average of 32.6%, 31.2%, 44.8%, 52% and 71.3%, respectively. The results showed that the low phytate mutation could not only potentially increase the bioavailability but also the amount of most important micronutrient elements, i.e., Fe, Zn and Ca, in the edible part of rice grains, and thus provide an important added-value to this mutation.
Rice is an important staple food in Asian countries. In rural areas it is also a major source of micronutrients. Unfortunately, the bioavailability of minerals, e.g. zinc from rice, is low because it is present as an insoluble complex with food components such as phytic acid. We investigated the effects of soaking, germination and fermentation with an aim to reduce the content of phytic acid, while maintaining sufficient levels of zinc, in the expectation of increasing its bioavailability. Fermentation treatments were most effective in decreasing phytic acid (56-96% removal), followed by soaking at 10°C after preheating (42-59%). Steeping of intact kernels for 24h at 25°C had the least effect on phytic acid removal (<20%). With increased germination periods at 30°C, phytic acid removal progressed from 4% to 60%. Most wet processing procedures, except soaking after wet preheating, caused a loss of dry mass and zinc (1-20%). In vitro solubility, as a percentage of total zinc in soaked rice, was significantly higher than in untreated brown rice while, in steeped brown rice, it was lower (p<0.05). Fermentation and germination did not have significant effects on the solubility of zinc. The expected improvement due to lower phytic acid levels was not confirmed by increasing levels of in vitro soluble zinc. This may result from zinc complexation to other food components.
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Six japonica rice cultivars differing in phytic acid and protein content were used to investigate the effect of grain position in the panicle on grain weight, phytic acid and protein content. There were significant differences in grain weight, albumin, globulin, prolamin, glutelin, and total protein content among the grains within a panicle for all six cultivars, but no differences were found for phytic acid content. An effect of grain position between primary rachises on grain weight and protein content was clearly detected, while that among top, middle and bottom rachis showed a greater change, varying with the cultivar. Albumin and globulin contents tended to be lower in the grains on the primary rachis than in those on the secondary rachis, and glutelin and total protein contents showed the opposite trend in the three cultivars with lower protein content. There was no significant correlation between phytic acid and protein content in the different grain positions within a panicle. The accumulation of phytic acid and protein during grain development appears to be independent.
Thirty-one japonica cultivars with contrasting agronomic traits were used and 5 nitrogen (N) fertilizer treatments of level and timing were performed to determine the effects of N application on grain phytic acid and proteins including albumin, globulin, prolamin, and glutelin. Variance analysis showed a large effect of N and a smaller effect of cultivar on grain phytic acid and proteins. With increased N level, grain phytic acid concentrations progressively reduced whereas concentrations of the 4 proteins and ratios of glutelin to total protein increased, indicating that N level has a beneficial effect on rice nutritional quality. In addition, substantial genotypic differences in response of grain phytic acid and proteins to N treatments were detected. Some cultivars such as Xiushui09, Zhendao10, and Yanjing5 exhibited more stability of grain proteins under contrasting N treatments, and the significance of this stability is discussed in regard to its use in rice quality improvement.
Phytic acid (PA), found in cereal and legume staple foods, is considered an antinutrient for iron (Fe) and zinc (Zn). Amongst numerous factors, temperature has a substantial effect on PA synthesis in seeds of legumes. PA, Fe, and Zn concentrations were determined for mature seeds of eleven lentil genotypes grown under simulated long term temperature regimes representative of Saskatoon, Canada (decreasing temperatures) and Lucknow, India (increasing temperatures). PA and Zn concentrations in lentil seeds were significantly higher in the rising temperature regime (8.8 mg/g and 69 mg/kg, respectively) than in the decreasing temperature regime (6.7 mg/g and 61 mg/kg, respectively). Fe concentrations followed the same trend (116 vs. 113 mg/kg). The cooler temperatures of temperate summers might be an important factor in the production of seeds with lower PA concentrations. These results are relevant to the development of biofortification strategies aimed at lowering the PA content in staple crops.
The multifunctional position supplied by myo-inositol is emerging as a central feature in plant biochemistry and physiology. In this critique, attention is drawn to metabolic aspects and current assessment is made of manifold ways in which myo-inositol and its metabolic products impact growth and development. The fact that a unique enzyme, common to all eukaryotic organisms where such assessment has been undertaken, controls conversion of d-glucose-6-P to 1l-myo-inositol-1-P provides a useful point of departure for this brief metabolic survey. Some aspects such as biosynthesis, phosphate and polyphosphate ester hydrolysis, and O-methylation of myo-inositol have captured the consideration of molecular biologists, yet other aspects including oxidation, conjugation, and transfer to phospholipids remain virtually untouched from this viewpoint. Here, an attempt is made to enlist new interest in all facets of myo-inositol metabolism and its place in plant biology.
Low phytic acid (LPA) crops have recently been considered as a potential way to combat nutritional and environmental issues related to seed phytic acid phosphorus (PA-P). Although, a number of LPA mutant lines have been developed in various crops, they are often featured with lower grain yield and seed viability compared with wild type (WT) parents. We recently developed several LPA mutant lines in rice with PA-P reductions varying from 33.8% to 63.6%. In this study, the performance of grain yield and seed viability of these mutants were investigated. Four of the five mutant lines had 12.5–25.6% reductions in grain yield compared to the corresponding WT parental lines. The reduction in grain weight, varying from 5.4% to 10.7%, was found to be the main causative factor of yield reduction. Similarly, LPA mutants had inferior seed viability to their corresponding WT parent varieties; all mutant lines had a significantly lower simplified vigour index (seed germination rate × seedling dry weight) than their parents, with reductions of 7.8–26.3%, although some mutant lines had similar germination rates as their WT parents. The two mutant lines, which had similar germination rates as their WT parent, however, had significantly lower field emergence rates. More pronounced differences of simplified vigour index were observed after artificial aging treatments between four LPA lines from their WT parents, implying that LPA rice seeds were more susceptible to storage than WT. The yield and yield-related traits of F2 plants and F3 lines from three crosses were evaluated; the results showed that while LPA was associated with significantly lower grain yield and grain weight than WT sibs, there were also LPA plants and lines that out-performed WT controls. These results implied that the negative effect of LPA mutations on grain yield might be reduced or minimized through cross and selection breeding. The implications of these findings were discussed with regard to LPA rice breeding and potential commercial production.
Dietary phytic acid is a major causative factor for low Zn bioavailability in many cereal- and legume-based diets. The bioavailability of Zn in seed of low phytic acid (lpa) variants of maize ( Zea mays L.), rice ( Oryza sativa L.), and barley ( Hordeum vulgare L.) was evaluated using a suckling rat pup model. Suckling rat pups (14 days old, n = 6-8/treatment) were fasted for 6 h and intubated with (65)Zn-radiolabeled suspensions prepared using seed produced by either wild-type (normal phytic acid) or lpa genotypes of each cereal. Test solutions were radiolabeled overnight (all genotypes) or immediately prior to intubation (barley genotypes). Pups were killed 6 h postintubation and tissues removed and counted in a gamma counter. Zn absorption was low from wild-type genotypes of maize (21, 33%) and rice (26%), and phytic acid reduction resulted in significantly higher Zn absorption, 47-52 and 35-52%, respectively. Zn absorption from wild-type barley incubated overnight was high (86-91%), and phytate reduction did not improve Zn absorption (84-90%), which is likely due to endogenous phytase activity. When the wild-type barley solutions were prepared immediately before intubation, Zn absorption was significantly lower (63, 78%) than from the lpa cultivars (92, 96%). Variation in seed or flour phenolic acid levels did not affect Zn absorption. Differences in seed Zn levels did not substantially affect Zn absorption. Thus, when phytic acid is abundant in a diet, it has a larger effect on Zn absorption than the level of Zn. Therefore, reducing the phytic acid content of staple cereal grains may contribute to enhancing Zn nutrition of populations consuming these staple foods.
Phosphorous in soybean [Glycine max (L.) Merr.] seed is stored primarily as phytic acid, which is nutritionally unavailable to nonruminant livestock. The objective of this study was to isolate mutations that reduce soybean seed phytic acid P and increase seed inorganic P. Following treatment with ethyl methanesulfonate, M2 through M6 plants were screened for high seed inorganic P. Seeds of M2 plants high in inorganic P produced progenies high in inorganic P through the M6 generation. M6 progenies of one plant averaged 6.84 g kg-1 seed phytic acid and inorganic P varied from 2.34 to 4.41 g kg-1 or 60 to 66% of phytic acid P plus inorganic P. M6 progenies of a second plant averaged 10.89 g kg-1 phytic acid and varied from 1.21 to 3.84 g kg-1 inorganic P, representing from 47 to 51% of the sum of phytic acid P plus inorganic P. In contrast, nonmutant seeds of the check cultivar Athow contained 15.33 g kg-1 phytic acid and averaged 0.74 g kg-1 inorganic P, representing 15% of the sum of phytic acid P plus inorganic P. Low phytic acid and high inorganic P in these progenies should increase the nutritional value of soy meal and reduce excess P in livestock manure.
The influence of variety, location, growing year, and storage on the total phosphorus (total P), phytate-P, and phytate-P to total P ratio in Korean rice varieties was investigated. Experiment 1 investigated the influence of 9 rice varieties, 4 locations, and 2 growing years. In experiment 2, the effect of storage for 1, 6, and 12 months was examined. Results showed that locations, varieties, and their interactions had a significant effect on the total P and phytate-P contents in rice, whereas growing year did not. Location had a higher effect than variety. Rice grown at locations with higher precipitation levels and higher temperatures obtained lower total P, phytate-P, and phytate-P to total P ratio. Effect of variety and location showed the possibility of reducing phytate-P in rice. Storage of rice for up to 12 months did not affect the total P and phytate-P concentrations of rice.
A better understanding of the factors that contribute to the overall grain quality of rice (Oryza sativa) will lay the foundation for developing new breeding and selection strategies for combining high quality, with high yield. This is necessary to meet the growing global demand for high quality rice while offering producing countries additional opportunities for generating higher export revenues. Several recent developments in genetics, genomics, metabolomics and phenomics are enhancing our understanding of the pathways that determine several quality traits. New research strategies, as well as access to the draft of the rice genome, will not only advance our understanding of the molecular mechanisms that lead to quality rice but will also pave the way for efficient and targeted grain improvement.
myo-Inositol(1,2,3,4,5,6)hexakisphosphate (InsP(6) or 'phytic acid') was first known as the storage form of phosphorus in seeds. Seed-derived dietary InsP(6) can contribute to iron and zinc deficiency in human populations. Excretion of 'phytic acid phosphorus' by non-ruminants such as poultry, swine and fish can contribute to water pollution. Sustainable solutions to these important problems might depend on progress in the molecular biology and genetics of InsP(6) accumulation during seed development. The development of 'low phytate' grain and legume genotypes could help advance our understanding of this biology, and when used in foods and feeds might help to reduce human malnutrition and reduce animal waste phosphorus.
The relationships between nutrient P and Zn levels and the phytic acid, P, and Zn concentrations in soybean (Glycine max L. Merr. cv ;Williams 79') seed were studied. Phytic acid increased linearly from 4.2 to 19.2 milligrams per gram as nutrient P treatment was varied from 2.0 to 50 milligrams per liter and Zn was held constant at 0.05 milligrams per liter. Leaf P concentration during seed development was found to be closely related to the concentrations of seed P and phytic acid. Leaf and seed Zn concentrations both responded positively to increasing nutrient Zn treatment. The effects of P treatment on plant and seed P and phytic acid were largely independent of the effects of Zn treatment on leaf and seed Zn. Phytic acid to Zn molar ratios ranging from 3.6 to 33.8 were observed.The effects of nutrient P treatments on the concentrations of phytic acid, seed P, and leaf P were also studied in the P-sensitive (gene np) cultivars ;Harosoy' and ;Clark' and their respective P-tolerant (gene Np) near-isogenic lines L66-704 and L63-1677. In general, the positive relationships observed among nutrient P, leaf P, seed P, and phytic acid concentrations were similar to those observed in the studies with Williams 79. When fertilized with low or moderate nutrient P (2.5 and 25.0 milligrams P per liter, respectively) no significant differences in any parameter were observed between Harosoy or Clark and their respective P-tolerant isolines. When fertilized with high nutrient P (100 milligrams P per liter), Harosoy seed had a significantly higher concentration of phytic acid (30 milligrams per gram) than did seed of its P-tolerant near-isogenic line L66-704 (24.2 milligrams per gram phytic acid), whereas no significant difference was observed between Clark and its P-tolerant near-isogenic line L63-1677 (22.8 and 21.6 milligrams per gram, respectively). Variation in the phytic acid concentrations in the mature seed of the cultivars and isolines more closely paralleled leaf P concentrations observed during seed development (49 days after flowering), than those observed at the onset of seed development (14 days after flowering). Electrophoresis and ion-exchange chromatography revealed that partially phosphorylated intermediates do not appear when phytic acid accumulation is greatly reduced by limiting the nutrient P or when accumulation is greatly accelerated by excess P.
Phytic acid (PA, myo-inositol 1,2,3,4,5,6-hexakisphosphate), or its salt form, phytate, is commonly regarded as the major anti-nutritional component in cereal and legume grains. Breeding of low phytic acid (lpa) crops has recently been considered as a potential way to increase nutritional quality of crop products. In this study, eight independent lpa rice mutant lines from both indica and japonica subspecies were developed through physical and chemical mutagenesis. Among them, five are non-lethal while the other three are homozygous lethal. None of the lethal lines could produce homozygous lpa plants through seed germination and growth under field conditions, but two of them could be rescued through in vitro culture of mature embryos. The non-lethal lpa mutants had lower PA content ranging from 34 to 64% that of their corresponding parent and four of them had an unchanged total P level. All the lpa mutations were inherited in a single recessive gene model and at least four lpa mutations were identified mutually non-allelic, while the other two remain to be verified. One mutation was mapped on chromosome 2 between microsatellite locus RM3542 and RM482, falling in the same region as the previously mapped lpa1-1 locus did; another lpa mutation was mapped on chromosome 3, tightly linked to RM3199 with a genetic distance of 1.198 cM. The latter mutation was very likely to have happened to the LOC_Os03g52760, a homolog of the maize myo-inositol kinase (EC 2.7.1.64) gene. The present work greatly expands the number of loci that could influence the biosynthesis of PA in rice, making rice an excellent model system for research in this area.
Effect of nitrogen fertilizer application on grain phytic acid and protein concentrations in japonica rice and its variations with genotypes
- H Wang
- S H Ding
- Y Raboy
- V Cichy
H.; Wang, S. H.; Ding, Y. F. Effect of nitrogen fertilizer application on
grain phytic acid and protein concentrations in japonica rice and its
variations with genotypes. J. Cereal Sci. 2009, 50, 49−55.
(10) Raboy, V.; Cichy, K.; Peterson, K.; Reichman, S.; Sompong, U.;