Bioenergy grass [Erianthus ravennae (L.) Beauv.] secretes two members of mugineic acid family phytosiderophores which involved in their tolerance to Fe deficiency

Ravenna grass, Erianthus ravennae (L.) Beauv. (E. ravennae) is a potential high biomass-energy crop with low input requirements. Iron (Fe) deficiency in calcareous soils is a widespread agronomic problem which reduces crop yields. Fe is sparingly soluble under aerobic conditions at high soil pH, such as in calcareous soils; therefore, plants cannot take up enough Fe. Increasing crop productivity of giant grasses, such as Ravenna grass in calcareous soil, has a positive effect by alleviating environmental problems. However, the growth character in calcareous soil and Fe homeostatic trait of Ravenna grass are largely unknown. In this study, we analyzed characteristics of Ravenna grass. The growth of E. ravennae plants were impaired in calcareous soil compared to those in the normal soil. In calcareous soil, the growth of E. ravennae plants differ among the water and fertilizer conditions; E. ravennae plants were grown better in the submerged condition adding micronutrient among conditions. These results suggested that impaired growth of E. ravennae in calcareous soil might be micronutrient shortage. We found that E. ravennae roots possess Fe reductase activities which were upregulated under Fe-deficient conditions. E. ravennae produced and secreted mugineic acid (MA) and deoxymugineic acid (DMA) to acquire Fe from the soil. The amount of MA was higher than that of DMA. Thus, E. ravennae might have both partial Strategy-I and Strategy-II Fe uptake systems. E. ravennae intercropped with transgenic rice plants producing and secreting MA through the introduction of the barley MA synthase gene showed improved growth compared to monocropped E. ravennae plants, suggesting that the increased amounts of MA enhanced their tolerance to Fe deficiency. Our results suggest that there is a considerable potential to improve the growth of E. ravennae plants in calcareous soils by enhancement of their Fe uptake systems through increase of MA production.     

Co-situs application of controlled-release fertilizers to alleviate iron chlorosis of paddy rice grown in calcareous soil

Abstract

Co-situs is the placement with one application of a sufficient amount of controlled-release fertilizer for an entire growing season at any site, together with seeds or seedlings, without causing fertilizer salt injury. An experiment was conducted to find an efficient method for ameliorating Fe deficiency in two rice cultivars (cv. Tsukinohikari and cv. Sasanishiki) grown in a calcareous soil (pH 9.2, CaCO₃ 384 g kg^?1), which was poor in organic matter (0.1 g kg^?1) and available Fe (3.0 μg g^?1 soil). The field treatments consisted of co-situs application of the following fertilizers: 1) controlled-release NPK fertilizer (CRF-NPK) containing no micronutrients; 2) controlled-release NPK fertilizer containing micronutrients (CRF-M1); and 3) controlled-release NPK fertilizer containing micronutrients (CRF-M2). The main difference between CRF-M1 and CRF-M2 was that the former had larger granules than the latter. All the fertilizers were placed in contact with the roots of rice seedlings at transplanting time. Plants in the CRF-M1 and CRF-M2 treatments had similar lengths, number of stems, leaf age, and leaf color (SPAR value) during the cultivation period. By contrast, plants from the CRF-NPK treatments grew poorly, showed severe chlorosis symptoms of Fe deficiency, and all died on 30 DAT. Plants of both cultivars accumulated more macroand micronutrients with the CRF-M2 treatment than with the CRF-M1 treatment. The grain yield of cv. Tsukinohikari was 0.0, 1,910, and 2,160 kg ha^?1 for the CRF-NPK, CRF-M1, and CRF-M2 treatments, respectively, and 0.0, 2,490, and 2,860 kg ha^?1 for the same treatments for cv. Nihonbare. Chlorosis due to iron deficiency was successfully ameliorated and world-average grain yields were obtained with the co-sites application of both controlled-release fertilizers.     

石灰性水稻土中磷酸铁对水稻磷营养的贡献

A study was carried out on contribution of iron phosphate to phosphorus nutrition of rice plant under waterlogged and moist conditions,respectively,by use of synthetic Fe^32 PO4.nH2O,tagging directly the iron phophate in calcareous paddy soils.Results showed that under waterlogged condition,similar to iron phosphate in acidic paddy soils.that in clacareous paddy soils was an important source of phosphorus to rice plant ,and the amount of phosphorus originated from it generally constituted 30-65% of the total phosphorus absorbed by rice plant.     

Comparison of the functions of the barley nicotianamine synthase gene HvNAS1 and rice nicotianamine synthase gene OsNAS1 promoters in response to iron deficiency in transgenic tobacco

Barley ( Hordeum vulgare L.) nicotianamine synthase gene ( HvNAS1 ) expression in barley is strongly induced by Fe deficiency in the roots and rice ( Oryza sativa L.) nicotianamine synthase gene ( OsNAS1 ) expression in rice is induced by Fe deficiency both in the roots and in the shoots. In dicots, NAS genes are not strongly induced by Fe deficiency, and they function to maintain Fe homeostasis. Rice OsNAS1promoter::GUS or barley HvNAS1promoter::GUS was introduced into tobacco ( Nicotiana tabacum L.) and tissue specificities and systemic regulation of their expression were compared. A split-root experiment revealed that the HvNAS1 promoter exhibited functions similar to those of Fe-acquisition-related genes in tobacco roots, suggesting that this promoter responded to certain Fe-deficiency systemic signals and to the Fe concentration in the rhizosphere. The HvNAS1 promoter might harbor a type of universal system of gene expression for Fe acquisition. However, the OsNAS1 promoter did not respond to local application of Fe to the roots and induced GUS activities in mature leaves in response to Fe deficiency. This promoter might possess numerous types of cis -acting sequences that are involved in Fe metabolism.     

Physiological basis of iron chlorosis tolerance in rice (Oryza sativa) in relation to the root exudation capacity

Micronutrient deficiency in cultivable soil, particularly that of iron (Fe) and zinc (Zn), is a major productivity constraint in the world. Low Fe availability due to the low solubility of the oxidized ferric forms is a challenge. An experiment was, thus, executed to assess the performance of eight genetically diverse rice genotypes on Fe-sufficient (100 µM) and Fe-deficient (1 µM) nutrient solution, and their ability to recover from Fe deficiency was measured. Fe efficiency under Fe deficiency in terms of biomass production showed a significant positive correlation with the root release of phytosiderophore (PS) (R² = 0.62*). This study shows that the Fe deficiency tolerance of Pusa 33 was related to both a high release of PS by the root and an efficient translocation of Fe from the root to the shoot as the Fe–PS complex, which could be useful for improving the Fe nutrition of rice particularly under aerobic conditions.     

Responses of earlirose rice to iron,zinc, and BPDS when grown on calcareous soil

Abstract

The Earlirose cultivar of rice (Oryza sativa L.) grown in calcareous Hacienda loam soil was extremely Fe deficient. The Fe deficiency was corrected by premixing 40 ppm Fe (as FeSO₄) into the soil before transplanting plants. The Fe deficiency appeared to be induced by high plant levels of Cu and Mn. Addition of Zn (40 ppm as ZnSO₄) intensified the Fe deficiency. The Fe addition did not overcome the effect of the Zn. BPDS (bathophenanthroline disulfonate), a chelator of Fe⁺⁺, had little effect on the results.     

Barley responses to copper foliar spray concentrations when grown in a calcareous soil

This study was designed to determine the adequate copper (Cu) foliar spray concentration to correct Cu deficiency on barley (Hordeum vulgare L.) when grown in a calcareous soil. Five Cu foliar spray solution levels were tested (0% or control; 0.03%, 0.06%, 0.13%, and 0.33%). Copper was applied in the sulfate form at the early boot stage. The results showed that Cu flag leaf concentration was increased with the highest Cu application (0.33%), while Cu concentration in the grain was increased with a spray of 0.03%. An antagonism between Cu, Zn, and Fe leaf concentration was observed. Grain yield and harvest index showed a linear positive response to Cu foliar spray concentrations. A significant increase of 19.6% on grain yield was recorded with a foliar spray 0.33% of Cu.     

Responses of aerobically grown iron chlorosis tolerant and susceptible rice (Oryza sativa L.) genotypes to soil iron management in an Inceptisol

Iron deficiency is a serious nutritional disorder in aerobic rice, causing chlorosis, poor yields and reduced grain nutritional quality. The problem can be managed by complementing the use of Fe-efficient plant type with a suitable Fe management strategy. In the present paper, we report the effect of eight iron management practices to resolve the problem of iron (Fe) chlorosis through the use of an iron deficiency tolerant (IDTR) and iron deficiency susceptible (IDSR) rice genotype, i.e. Pusa 33 and ADT 39, respectively. Fe deficiency tolerance of these genotypes was related to the root release of PS which enabled a higher uptake of Fe in the IDTR than the IDSR under Fe deficiency. In general, IDTR performed better than the IDSR as evident from a significant increase in total iron, active iron, chlorophyll content and grain and straw yield. IDSR produced the highest grain and straw yield under slow iron release nano clay complex source. Grain Fe content of the IDTR and IDSR increased by 18.9 and 13.4%, respectively, under recommended dose of Fe. The results identified the most effective soil management strategies for the alleviating Fe deficiency chlorosis and improving Fe nutrition of both IDTR and IDSR genotypes.     

Depressed growth of non‐chlorotic vine grown in calcareous soil is an iron deficiency symptom prior to leaf chlorosis

The development of iron deficiency symptoms (growth depression and yellowing of the youngest leaves) and the distribution of iron between roots and leaves were investigated in different vine cultivars (Silvaner, Riparia 1G and SO4) grown in calcareous soils. As a control treatment all cultivars were also grown in an acidic soil. Only the cultivars Silvaner and Riparia 1G showed yellowing of the youngest leaves under calcareous soil conditions at the end of the cultivation period. All cultivars including SO4 showed severe shoot growth depression, by 50 % and higher, before yellowing started or without leaf yellowing in the cultivar SO4. Depression of shoot growth occurred independently from that of root growth. In a further treatment the effect of Fe‐EDDHA spraying onto the shoot growth of the cultivar Silvaner after cultivation in calcareous soil was investigated. Prior to Fe application plants were non‐chlorotic, but showed pronounced shoot growth depression. Spraying led to a significant increase in shoot length, though leaf growth was not increased. Accordingly, depression of shoot growth of non‐chlorotic plants under calcareous soil conditions and with ample supply of nutrients and water has been evidenced to be at least partly an iron deficiency symptom. We suggest that plant growth only partially recovered because of dramatic apoplastic leaf Fe inactivation and/ or a high apoplastic pH which may directly impair growth. Since growth was impaired before the youngest leaves showed chlorosis we assume that meristematic growth is more sensitively affected by Fe deficiency than is chlorophyll synthesis and chloroplast development. In spite of high Fe concentrations in roots and leaves of the vines grown in calcareous soils plants suffered from Fe deficiency. The finding of high Fe concentrations also in young, but growth retarded green leaves is a further indication that iron deficiency chlorosis in calcareous soils is caused by primary leaf Fe inactivation. However, in future, only a rigorous study of the dynamic changes of iron and chlorophyll concentration, leaf growth and apoplastic pH at the cellular level during leaf development and yellowing will provide causal insights between leaf iron inactivation, growth depression, and leaf chlorosis.<?show $6#>     

The Function of a Maize-Derived Phosphoenol pyruvate Carboxylase (PEPC) in Phosphorus-Deficient Transgenic Rice

Transgenic rice ( Oryza sativa L., a C₃ plant) lines carrying a complete phospho enol pyruvate carboxylase (PEPC) gene from maize (a C₄ plant) were tested for their performance in terms of organic acid synthesis and organic acid exudation into the rhizosphere under phosphorus (P)-deficient conditions. High PEPC activity increased the fraction of photosynthetically fixed carbon allocated to the organic acid pool, and P deficiency enhanced oxalate exudation from the roots of the transgenic plants. There was no evidence that the transformed PEPC was involved in internal P recycling in the plant. However, the root PEPC activity was positively correlated with the oxalate exudation and negatively correlated with the root P concentration, and a higher root PEPC activity led to a higher oxalate exudation. Thus, it is suggested that C₄-PEPC transgenic rice plants had acquired the ability to exude oxalate, which enhanced their capacity to adapt to low P soil conditions.     

Comparison of phospholipid fatty acid composition in percolating water,floodwater, and the plow layer soil during the rice cultivation period in a Japanese paddy field

Azolla has been used as a green manure for rice in Vietnam and southern China (3). Recently it was adopted by farmers in the Koronadal area in South Cotabato Province, the Philippines (2). In that area Azolla pinnata grows reasonably well without phosphate fertilizer, which is generally used for stimulating Azolla growth (3, 5).     

稻秸还田提高我国南方典型稻田冬绿肥产量和养分积累

  【目的】  提高冬绿肥的产量和养分积累量有利于轮作系统中主作物的高产稳产和光、温、养分资源的高效循环利用。研究稻秸还田对冬季豆科绿肥生长和养分积累及土壤性状的影响,为稻田豆科绿肥的高产栽培及稻秸资源化利用提供指导。  【方法】  在广西、四川和安徽,分别以盐渍水稻土、紫色土和黄棕壤为供试土壤,进行相同处理的豆科绿肥盆栽试验,供试品种均为当地主栽品种。稻秸添加量设 3个水平:0、3000、6000 kg/hm2 (S0、S1、S2),每个稻秸添加水平下设两个施氮水平:0和45 kg/hm2 (N0、N45),共包括6个处理。于豆科绿肥盛花期采集植株和土壤样品,测定鲜草产量和土壤理化性状。  【结果】  与稻秸不还田且不施氮肥处理(RS0N0)相比,盐渍水稻土、紫色土和黄棕壤上稻秸还田与氮肥配施处理的绿肥鲜草产量分别提高了63.0%～66.0%、35.2%～53.8%和103.6%～117.1%,植株氮累积量分别提高了19.1%～41.5%、43.7%～67.2%和65.1%～70.5%,磷累积量分别提高了12.1%～68.9%、31.4%～57.3%和37.9%～45.3%,钾累积量分别提高了22.0%～58.7%、30.7%～35.0%和89.2%～102.9%。在盐渍水稻土、紫色土,稻秸还田(S1、S2)均可提高绿肥鲜草产量和氮磷钾养分积累量,配合施氮没有进一步提高鲜草产量和氮磷钾养分积累量;而在黄棕壤与秸秆半量还田相比,稻秸全量还田降低了绿肥产量,但在一定程度上增加了绿肥地上部养分积累量,稻秸还田配合施用氮肥则显著增加了绿肥的产量和地上部养分积累量。盐渍水稻土稻秸还田与氮肥配施处理(RS1N45和RS2N45)提高了土壤有效磷含量;黄棕壤土壤有效磷含量、土壤速效钾含量随稻秸添加量增加先下降后上升,与不施肥对照相比,3种土壤上稻秸与氮肥配施处理均显著提高了土壤无机氮含量。偏最小二乘法路径模型分析表明,稻秸还田及土壤类型对豆科绿肥鲜草产量和地上部氮、磷、钾的累积量均有极显著正影响(P < 0.01),氮肥处理仅对豆科绿肥鲜草产量有极显著正影响(P < 0.01)。  【结论】  稻秸还田不同程度地促进了豆科绿肥对土壤速效养分的吸收,提高了豆科绿肥鲜草产量和地上部氮磷钾累积量。在肥力较高的盐渍水稻土和紫色土上,稻秸全量还田可显著增加豆科绿肥的鲜草产量,维持土壤有效养分,无需配合施用氮肥。在肥力较低的黄棕壤上,全量还田(6000 kg/hm2)需配施氮肥才可充分发挥稻秸还田的增产效果,缓解土壤中有效养分含量的下降。     

Effects of organic matter addition on phosphorus availability to flooded and nonflooded rice in a P‐deficient tropical soil: a greenhouse study

Addition of organic matter (OM) to flooded soils stimulates reductive dissolution of Fe(III) minerals, thereby mobilizing associated phosphate (P). Hence, OM management has the potential to overcome P deficiency. This study assessed if OM applications increases soil or mineral fertilizer P availability to rice under anaerobic (flooded) condition and if that effect is different relative to that in aerobic (nonflooded) soils. Rice was grown in P‐deficient soil treated with combinations of addition of mineral P (0, 26 mg P/kg), OM (0, ~9 g OM/kg as rice straw + cattle manure) and water treatments (flooded vs nonflooded) in a factorial pot experiment. The OM was either freshly added just before flooding or incubated moist in soil for 6 months prior to flooding; blanket N and K was added in all treatments. Fresh addition of OM promoted reductive dissolution of Fe(III) minerals in flooded soils, whereas no such effect was found when OM had been incubated for 6 months before flooding. Yield and shoot P uptake largely increased with mineral P addition in all soils, whereas OM addition increased yield and P uptake only in flooded soils following fresh OM addition. The combination of mineral P and OM gave the largest yield and P uptake. Addition of OM just prior to soil flooding increased P uptake but was insufficient to overcome P deficiency in the absence of mineral P. Larger applications of OM are unlikely to be more successful in flooded soils due to side effects, such as Fe toxicity.