Comparison of Iron Availability in Leaves of Barley and Rice

Iron (Fe) is an essential trace element in all eukaryotes. In higher plants, Fe deficiency causes interveinal chlorosis in young leaves. However, in barley and rice, both of which are “Strategy II” plants, the degree and the pattern of Fe-deficiency symptoms differ. In the present study, barley and rice plants were grown in the same container, i.e., by “coculturing,” to compensate for the amount of mugineic acids in rice in the nutrient solution. We examined the differential availability of Fe for distribution and retranslocation in shoots between barley and rice without considering the difference in the iron acquisition ability, which is affected by the differential mugineic acid secretion between barley and rice. Although the Fe concentration of young barley leaves had decreased under the coculture conditions, the SPAD value was similar to that in monocultured barley. In contrast, although there was an increase in the Fe concentration of the young leaves of cocultured rice, the SPAD value decreased, as in the case of monocultured rice. Rice accumulated Fe in old leaves, whereas in barley Fe was efficiently distributed to young leaves. Therefore, the SPAD value of the second leaf in rice remained constantly high. The Fe concentration of the second leaf in barley decreased under Fe-deficient coculture conditions, the SPAD value decreased and the senescence of the second leaf become accelerated. ⁵⁹Fe pulse-labeling experiments suggested that in barley Fe was more efficiently retranslocated from old leaves to young leaves than that in rice. As a result, the level of Fe present in the fraction with a molecular weight lower than the 10,000/water-soluble Fe ratio was higher in the old leaves of barley than in the old leaves of rice under Fe-deficient conditions. Based on the results obtained, we suggest that the distribution and retranslocation characteristics of internal Fe in barley may be well adapted to Fe deficiency.     

Comparison of Iron Availability in Leaves of Barley and Rice

Iron (Fe) is an essential trace element in all eukaryotes. In higher plants, Fe deficiency causes interveinal chlorosis in young leaves. However, in barley and rice, both of which are "Strategy II" plants, the degree and the pattern of Fe-deficiency symptoms differ. In the present study, barley and rice plants were grown in the same container, i.e., by "coculturing," to compensate for the amount of mugineic acids in rice in the nutrient solution. We examined the differential availability of Fe for distribution and retranslocation in shoots between barley and rice without considering the difference in the iron acquisition ability, which is affected by the differential mugineic acid secretion between barley and rice. Although the Fe concentration of young barley leaves had decreased under the coculture conditions, the SPAD value was similar to that in monocultured barley. In contrast, although there was an increase in the Fe concentration of the young leaves of cocultured rice, the SPAD value decreased, as in the case of monocultured rice. Rice accumulated Fe in old leaves, whereas in barley Fe was efficiently distributed to young leaves. Therefore, the SPAD value of the second leaf in rice remained constantly high. The Fe concentration of the second leaf in barley decreased under Fe-deficient coculture conditions, the SPAD value decreased and the senescence of the second leaf become accelerated. ⁵⁹Fe pulse-labeling experiments suggested that in barley Fe was more efficiently retranslocated from old leaves to young leaves than that in rice. As a result, the level of Fe present in the fraction with a molecular weight lower than the 10,000/water-soluble Fe ratio was higher in the old leaves of barley than in the old leaves of rice under Fe-deficient conditions. Based on the results obtained, we suggest that the distribution and retranslocation characteristics of internal Fe in barley may be well adapted to Fe deficiency.     

花生缺铁黄化的敏感时期及耐低铁品种的筛选指标

采用盆栽试验,系统研究了石灰性土壤上16个花生品种在各个生育时期新叶的黄化度、叶绿素值、活性铁含量的差异及其动态变化。结果表明,缺铁胁迫下花生耐低铁和铁敏感品种间叶片的黄化程度存在着显著差异,大多数铁敏感品种在出苗后50～65 d时黄化度最高。供试16个品种顶部新展开叶片的叶绿素值（SPAD值）和活性铁含量在整个生育期的变幅分别为4.5～34.6和8.0～36.3 mg/kg, FW,随生长时间的延长两者均呈高―低―高的动态变化趋势。在生长前期,耐低铁品种新叶的叶绿素值和活性铁含量均显著高于铁敏感品种;开花期是花生对缺铁胁迫最为敏感的时期,此阶段黄化现象最严重、各品种新叶的叶绿素值和活性铁含量最低。相关分析表明,在生长前期叶绿素值与黄化度、活性铁及荚果产量之间均呈极显著的相关关系。新叶叶绿素值可作为花生耐低铁品种筛选的一可靠指标。     

Boron nutrition and mobility,and its relation to the elemental composition of greenhouse grown root crops I. Rutabaga

Abstract

The nutrition and mobility of B, and its relation to the elemental composition of two cultivars of rutabaga (Brassica napus ssp. rapifera cv. Laurentian and Wilhelmsberger) plants were investigated in greenhouse experiments. Laurentian exhibited a greater response than Wilhelmsberger to continuing B deficiency as indicated by the severity in the roots of brown heart, of external roughness and elongation and of the decrease in B concentration. Signs of B deficiency were not found when the B contents of the root and young leaves were 27 and 56 ug g‐1 DM respectively. Root B levels of 14 and 17–20 μg g^‐1 gave moderate and slight internal signs of brown discoloration. Foliar applications of B partially restored the B concentrations of the roots; however, the mechanism of movement was unclear. The Mg, Mn and Zn contents of roots were the only elements that consistently increased and accumulated under B deficiency. The relative element composition of the root compared to the mature leaves is consistent with the root being supplied predominantly with nutrients by the phloem. Nutrient retranslocation was assessed from the ratio of element concentration in the roots or young leaves to that in the mature leaves. Although Mg, Mn and B exhibited limited mobility under adequate B nutrition they were translocated from mature leaves to younger tissues under B starvation. It is concluded that Wilheimsberger is by virtue of its greater capacity for the retranslocation of B to roots, less sensitive to B deficiency and the brown heart disorder.     

Intensification of arsenic toxicity to paddy rice by hydrogen sulfide and ferrous iron

Abstract

The phytotoxicity of arsenic to paddy rice was examined by the pot culture method using Utsunomiya grey lowland soil which had received nutrient salts including ammonium sulfate with or without additional rice straw powder as a reducing agent.

By treatment with 50 ppm of arsenic and straw, plant growth was retarded from the beginning of culture, and about 6 weeks later, at the middle of July, small reddish black spots emerged near the tips of expanded green leaves. The spots then increased and spread over the whole leaves resulting in bronzing and final dieback in about the mid-August. On treatment with higher concentrations of arsenic and straw, the plants were more severely injured and died through bronzing at earlier stages. All such dead plants were found to have accumulated abnormally high iron in their leaf tissues. On treatment with lower concentrations of arsenic and straw or in the case of higher arsenic without straw, plant growth and grain yield were reduced with the occurrence of partial bronzing or oranging of leaves and the iron content of the plants was somewhat increased.

These results indicate that arsenic may induce ferrous iron toxicity which intensifies the toxicity of arsenic to paddy rice.     

双季早稻氮素亏缺补偿效应的形成及其生理机制初探

为探明双季早稻氮素亏缺补偿效应的形成及其生理机制,采用桶栽方式,以超级杂交早稻品种淦鑫203为试验材料,于氮素亏缺敏感期分蘖期,设置5个氮肥处理:T0(各生育阶段均不施用氮肥,即空白对照)、T1(各生育阶段氮肥按常量分配)、T2(分蘖期氮肥亏缺后幼穗分化期不恢复供氮)、T3(分蘖期氮肥亏缺后幼穗分化期常量恢复供氮)和T4(分蘖期氮肥亏缺后幼穗分化期倍量补偿供氮),比较各氮肥处理稻株产量及其构成因素、单株分蘖数、成穗率和净光合速率、SPAD值、氮代谢酶(硝酸还原酶NR和谷氨酰胺合成酶GS)活性、内源激素含量、根系伤流量等有关生理指标的差异性。结果表明,T4单株产量与T1十分接近,补偿指数CI=0.99,无显著差异,呈现出等量补偿效应。与T1相比,T4叶片净光合速率、SPAD值、NR和GS活性均能维持在较高水平,而且随着生育推进,至补偿后期,T4该4项生理指标仍维持在较高水平,表现出较为明显的氮素亏缺补偿效应。至补偿后期,氮素补偿处理的T4和T3稻株叶片脱落酸(ABA)含量显著低于T0、T1和T2,以T4最低,生长促进类激素之和(GA3+IAA+ZR)与生长抑制类激素(ABA)比值则显著高于T0、T1和T2。氮素亏缺补偿后第10天根系伤流量以T0最低,T4、T3均高于T1,且T4与T1间差异达显著水平。至补偿后期,T4单株分蘖数及成穗率高于T1、T3。本研究结果进一步明确了双季超级杂交早稻分蘖期氮素亏缺补偿效应的形成,有助于诠释水稻氮素亏缺补偿效应形成的生理机制,为水稻氮肥施用不当时进行追补及双季早稻高产稳产栽培提供了科学依据。     

RELATIONSHIP BETWEEN CHLOROPHYLL CONTENT IN LEAVES OF SORGHUM AND PIGEONPEA DETERMINED BY EXTRACTION METHOD AND BY CHLOROPHYLL METER (SPAD-502)

ABSTRACT

The estimation of chlorophyll content in leaves by the chlorophyll meter (SPAD 502) is more convenient than by the extraction method for studies on photosynthesis or senescence where the total chlorophyll is estimated on the same leaf over time. This study was to test hypothesis that specific leaf weight (SLW) appears to be one of the factors determining SPAD index under different conditions. The influence of SLW on SPAD index and an improved simple method to determine chlorophyll content of sorghum and pigeonpea by a chlorophyll meter was studied. The results indicated that regression lines were significantly different between sorghum and pigeonpea, and at the vegetative and physiological maturity stages in each crop. Residuals of simple regressions calculated from all data of each crop were correlated with SLW. Multiple-regression with SPAD index as the dependent variable, and chlorophyll content and SLW as the independent variables gave the best estimation of chlorophyll content in leaves of sorghum and pigeonpea. These results suggest that SLW is an important factor affecting SPAD index and the influence of SLW on SPAD index can vary with crop species. Devices for estimating SLW could be incorporated into the chlorophyll meter to provide SPAD values adjusted for SLW. Further investigation is required on the influence of SLW on SPAD index for other crops.     

酸性根际肥对石灰性土壤pH和铁有效性的影响研究

在无植物栽培的条件下通过肥料在土壤中的扩散试验研究酸性根际肥对石灰性土壤 pH值、有效铁含量的影响 ,利用盆栽试验验证对石灰性土壤上花生缺铁失绿黄化症的矫正效果。结果表明 ,酸性根际肥 (pH 1.0～ 2 .0 )中的酸在土壤中扩散的影响半径可达 6cm ,但对土壤pH降低作用最显著的是在距肥料 2cm内 ;在施肥 2 8d内 ,距肥料 2cm处 ,土壤 pH值降低了 0 .9个单位 ,土壤铁有效性 (DTPA浸提量 )增加了 5 .9mg kg ;施用酸性根际肥可使花生叶绿素SPAD值与叶片活性铁含量显著提高 ,克服了花生缺铁黄化症状 ,使施肥区 (肥料周围 2cm内 )土壤pH值显著降低 ,并显著提高了该区土壤铁的有效性和花生对土壤Fe的吸收量。     

Iron-deficiency response and expression of genes related to iron homeostasis in poplars

Iron (Fe) deficiency is a serious agricultural problem, especially in calcareous soils, which are distributed worldwide. Poplar trees are an important biomass plant, and overcoming Fe deficiency in poplars will increase biomass productivity worldwide. The poplar Fe-deficiency response and the genes involved in poplar Fe homeostasis remain largely unknown. To identify these genes and processes, we cultivated poplar plants under Fe-deficient conditions, both in calcareous soil and hydroponically, and analyzed their growth rates, leaf Soil and Plant Analyzer Development (SPAD) values, and metal concentrations. The data clearly showed that poplars have notable growth defects in both calcareous soil and a Fe-deficient hydroponic culture. They exhibited serious chlorosis of young leaves after 3 weeks of Fe-deficient hydroponic culture. The Fe concentrations in old leaves with high SPAD values were markedly lower in Fe-deficient poplars, suggesting that poplars may have good translocation capability from old to new leaves. The Zn concentration in new leaves increased in Fe-deficient poplars. The pH of the hydroponic solution decreased in the Fe-deficient culture compared to the Fe-sufficient culture. This finding shows that poplars may be able to adjust the pH of a culture solution to better take up Fe. We also analyzed the expression of Fe homeostasis-related genes in the roots and leaves of Fe-sufficient and Fe-deficient poplars. Our results demonstrate that PtIRT1, PtNAS2, PtFRO2, PtFRO5, and PtFIT were induced in Fe-deficient roots. PtYSL2 and PtNAS4 were induced in Fe-deficient leaves. PtYSL3 was induced in both Fe-deficient leaves and roots. These genes may be involved in the Fe uptake and/or translocation mechanisms in poplars under Fe-deficient conditions. Our results will increase a better understanding of the Fe-deficiency response of poplars and hence improve the breeding of Fe-deficiency-tolerant poplars for improved biomass production, the greening of high pH soils, and combatting global warming.     

主要粮食作物基于SPAD的氮素营养诊断方法研究进展

基于叶绿素计测定的SPAD值与植物叶片叶绿素和氮浓度的关系,详细综述了用叶绿素计在玉米、小麦、水稻以及其他作物上进行氮素营养诊断的研究进展.第一,"相对SPAD值"、"氮饱和指数"或"归一化SPAD"等指标能够消除或减小品种、生育期及区域年际间的误差;第二,不同生育期应选择理想指示叶作为诊断目标;第三,不同叶位间的SP...     

Relationship between spectroradiometric and chlorophyll measurements in green beans

Abstract

Individual linear relationships were established between total chlorophyll and SPAD readings, while a unique linear relationship was determined between chlorophyll a and SPAD readings for three green bean cultivars (Phaseolus vulgaris L.). Greening of young expanding leaves at the top of the canopy of all cultivars was associated with low transmittance and reflectance in the PAR region. However, transmittance and reflectance responses of young leaves were different between cultivars. Leaf senescence was associated with an increase in transmittance in the PAR region, but no changes were obtained in the Near‐InfraRed region (NIR). Top young leaves and middle canopy fully expanded leaves of the three green bean cultivars presented a similar transmittance in the Visible and NIR regions. Although the correlations between reflectance and SPAD values of young expanding leaves and that for the inverse‐log reflectance were relatively weaker than that obtained for transmittance either for the same leaf age or different leaf ages, the results suggest that the SPAD meter may be used to provide a rapid estimate of leaf transmittance and reflectance in the field.     

Effect of sewage sludge application to amelio‐rate iron deficiency of grain sorghum

Abstract

Recent research has indicated that land application of municipal sewage sludge to calcareous soils can be used to ameliorate iron (Fe) deficiency of grain sorghum [Sorghum bicolor (L.) Monech]. A greenhouse study was conducted to determine the response of grain sorghum grown on three different soils to application of sewage sludge. Sludge applied at rates of 0, 7.5, 15.0, and 25.0 g/kg soil did not completely ameliorate grain sorghum Fe deficiency. When FeEDDHA was soil applied, sewage sludge application significantly increased plant growth due to increases in soil phosphorus (P) availability. Application of sewage sludge at rates greater than 7.5 g/kg reduced dry matter production of grain sorghum in the FeEDDHA amended Orelia SC soil, the soil with the lowest total neutralizing potential. The decreases yield was possibly due to toxic levels of soil and plant copper (Cu) and zinc (Zn), and increased soil salinity.     

Boron nutrition and mobility,and its relation to the elemental composition of greenhouse grown root crops. II radish

Abstract

The elemental distribution between the leaves and roots of mature radish (Raphanus sativus cv Cherry Belle) plants grown in the greenhouse with various concentrations of nutrient solution B or Ca was determined to assess the role of phloem in the provision of nutrients to the root, and the retranslocation of B under deficient conditions. The relative composition and accumulation of elements in different parts, and the ratio of their concentrations in leaves:roots were used as a measure of their uptake, relative mobility and retranslocation. The data indicate that B, but not Ca is retranslocated in the phloem to the roots when that particular element was in short supply in the nutrient solution. B deficiency induced brown heart disorder in radish roots but the severity was dependent on the degree of deficiency below 28 μg g^‐l DM in the root. These symptoms were alleviated when the root B concentrations were enhanced by foliar applications of B. It is concluded that radish responded to B deficiency in a fashion similar to that reported previously for rutabaga and that it might serve as a time‐saving model system for examining the mechanisms responsible for brown heart in rutabaga.     

Inhibition of iron-stress reactions in sunflower by bicarbonate

In pot culture experiments using a calcareous soil the growth rate of sunflowers was depressed by latent iron deficiency. Iron-stress reactions, reflected by enhanced uptake rate of Fe-59 after short-term supply of ⁵⁹FeEDDHA were observed under these conditions. These reactions, however, were delayed and much less distinct than those observed under latent iron deficiency in water culture experiments. Addition of MgCO₃ to this soil increased the iron deficiency of the plants and caused chlorosis, but prevented these iron-stress reactions. In contrast to the soil experiments, distinct iron-stress reactions could be observed with latent iron-deficiency in sand culture experiments in which varied amounts of inorganic Fe-III were supplied. These reactions were only observed, however, in absence of bicarbonate. Even 4 meq bicarbonate severely inhibited these iron-stress reactions which were almost totally inhibited at 10 meq bicarbonate. Bicarbonate depressed both short-term uptake of Fe-59 as well as total iron content of the leaves. There was no evidence for an additional “inactivation” of iron within the leaves due to bicarbonate treatment. Bicarbonate also strongly depressed the manganese content of the young leaves. The results demonstrate that the regulatory mechanism of so-called “iron-efficient” plant species like sunflower under iron-stress - increase in H⁺ efflux and reducing capacity of the roots and thus enhanced uptake of iron (and manganese) - is severely inhibited or even blocked by high bicarbonate concentrations. “Lime chlorosis”, caused by high bicarbonate concentrations on calcareous substrates is therefore also widespread in so-called “iron-efficient” species.     

水稻锰毒与铁素营养关系的研究

通过水培试验，研究了水稻锰毒与铁素营养关系，并探讨了过量锰对一些生理指标的影响。试验结果表明：地上部是生长介质中过量锰对水稻危害的主要部位；过量的锰增加铁在水稻根系的沉积，减少铁的吸收，改变体内铁的分布，降低铁的活性，诱发水稻缺铁胁迫；过量锰缺铁胁迫的水稻正常代谢受阻，叶片叶绿素、蛋白质含量减少，过氧化氢酶活性降低，而过氧化物酶活性增加     

2个超级杂交水稻剑叶主脉两侧SPAD值的差异表现

为探索水稻叶片SPAD值的分布特征,提高基于SPAD值水稻氮素营养诊断的精准度,以Q优6号和准两优527为材料,研究了6个不同施氮条件下超级杂交水稻主脉两侧SPAD值的差异表现。结果表明,2个超级杂交水稻剑叶两侧,一侧较为光滑,另一侧较为粗糙,光滑面或粗糙面居左或居右的概率接近50%,且光滑面SPAD值高于粗糙面SPAD值,粗糙面SPAD值的环比增长率绝对值一般高于光滑面。光滑面和粗糙面的SPAD差值主要集中在1.5~3.5之间,此范围内Q优6号和准两优527的次数分布率分别为40.67%和36.4%。SPAD归一化倒数值与施氮量、产量存在显著的线性相关关系,当Q优6号和准两优527的SPAD归一化倒数值为35~40和30~35时,施氮适宜,产量较高。本研究结果表明重视水稻叶片主脉两侧的差异可以提高诊断的精准性,为基于SPAD值的水稻氮素营养诊断提供了参考依据。     

INFLUENCE OF ELEVATED PHOSPHORUS LEVELS IN NUTRIENT SOLUTION ON MICRONUTRIENT UPTAKE AND DEFICIENCY SYMPTOM DEVELOPMENT IN STRAWBERRY CULTURED WITH FERTIGATION SYSTEM

The relationship between the total amount of micronutrients absorbed by the above-ground plant tissue and the occurrence of visible micronutrient deficiency symptoms in two strawberry cultivars as influenced by elevated phosphorus (P) levels in fertigation solution was investigated. The plants were cultured with a fertilizer solution containing 0, 0.5, 1, 2, 4, or 6 mM P and tissue nutrient content were determined at 120 days after transplanting. Young leaves of the plants grown with nutrient solution P levels higher than 4 mM and 2 mM, respectively, in ‘Keumhyang’ and ‘Seonhong’, developed interveinal chlorosis. Tissue concentrations (mg·kg^?1 dry weight) of metallic micronutrients [iron (Fe), copper (Cu), manganese (Mn), and zinc (Zn)] in both cultivars did not decrease, but the total amount absorbed by the aboveground plant tissue decreased in the treatments in which nutrient deficiencies were observed. These results indicate that total amount of micronutrients is a better indicator of P-induced micronutrient deficiency.     

水稻根表铁氧化物胶膜对水稻吸收磷的影响

本文采用营养液培养方法研究了根表铁氧化物胶膜对水稻吸收磷的影响。结果表明，水稻报表的铁氧化物胶膜随营养液中Fe2+浓度的增加而增加。铁氧化物胶膜可富集生长介质中的磷，根表铁膜数量越多，富集的磷量也越多。根表铁股可促进水稻对磷的吸收，但这种促进作用的大小依赖于根表铁膜数量。根表铁膜数量为24570mp／kg时，促进作用达到最大，此后随着铁膜数量的增加，水稻吸收磷的数量下降，但仍高于根表没有铁膜的水稻。因此，水稻根表形成的铁氧化物胶膜在一定程度上是一个磷富集库，对水稻吸收磷起促进作用。在此过程中，缺铁条件下水稻根分泌物中的植物铁载体对淀积铁氧化物胶膜的水稻根系吸收磷没有明显的作用。     

Effect of iron deficiency on the growth,development and grain yield of some selected upland rice genotypes in the rainforest

Abstract

Iron deficiency is a major production constraint of upland rice in the tropics despite is abundance in the soil. This investigation aimed to explicate the effect of iron deficiency on the growth, development, grain yield and its attributes of some selected upland rice in the rainforest. Field experiments were established at Africa Rice sub-Station, Ibadan, Nigeria. The treatments consisted of 35 upland rice genotypes and availability of iron in the soil (Fe-sufficient and Fe-deficient). The treatments were arranged in alpha lattice design with three replications. It was observed that upland rice sown in iron (Fe) deficient soils had significantly lower growth (plant height, number of tillers and seedling vigor), flowered later, with significantly lower yield attributes (1000 grain weight, filled grain) and grain yield than those sown in Fe-sufficient soils. Conversely, the number of unfilled grains were significantly higher in upland rice sown in Fe-deficient than those in sufficient soils. Percentage yield loss was in the range 98.00% to 22.95% for China best and Faro 65 respectively. Genotypes were identified to be tolerant (Faro 65, NERICA 3 and IRAT 109) and susceptible (Ofada 2, NERICA 5 and China Best) to Fe-deficiency based on their percentage grain yield loss. These evidences suggested that despite the increased phenology of upland rice sown in Fe-deficient soils their reproductive growth was suppressed through increased number of unfilled grains as witnessed in China Best and Faro 64.     

Association of soil properties and soil and plant iron to iron deficiency response in rice (Oryza Sativa L.)

Abstract

Problems are invariably encountered when attempts are made to explain the variability in Bray percent yields or plant response in terms of soil or plant iron (Fe). To resolve this inconsistency, the present investigation was initiated to identify a combination of soil extractable Fe, soil properties and form of plant Fe that may be used as a measure of Fe deficiency. The study involved 16 diverse soils, using upland rice (Oryza sativa L.) as the test crop and Fe‐EDDHA [ferric ethylenediamine di (o‐hydroxyl‐phenyl acetic acid)] as source of Fe. The results showed that Bray percent yields were neither related to DTPA (diethylenetriamine pentaacetic acid) or EDTA (ethylenediamine tetraacetic acid) extractable Fe nor with total plant Fe. Even the inclusion of pH, lime, organic carbon and clay data in the regression equations was of no value. However, Bray percent yields were significantly and positively (r = 0.57* ) associated with ferrous Fe (Fe²⁺) in 40‐day‐old rice plants. The explanation concerning variability in Bray percent yields obtained on diverse soils could be increased about one and half 2 times (R²= 0.59*) if the contribution of lime and soil pH was also incorporated in the stepwise regression analysis. The individual contribution to R of lime, pi respectively. Thus, it appears that Fe²⁺ concentration in plants (along with soil pH) may identify Fe deficiency. The critical limit to separate Fe deficient from green rice plants was set at 45 ug Fe²⁺/g in the leaves.