Cadmium concentrations in the phloem sap of rice plants (Oryza sativa L.) treated with a nutrient solution containing cadmium

To obtain direct evidence for the translocation of cadmium (Cd) via the phloem, we measured the Cd concentrations in the phloem sap of 5-week-old rice plants (Oryza sativa L. cv. Kantou) treated with a nutrient solution containing Cd. The phloem sap was collected from the leaf sheaths through the cut ends of stylets of the brown planthopper (Nilaparvata lugens Stål.). Cd concentrations in the phloem sap from the plants treated with 10 and 100 µM Cd for 3 d were 4.6 ± 3.4 and 17.7 ± 9.8 µM, respectively. Detection of Cd in the phloem sap indicated that Cd was translocated via sieve tubes in rice plants. Cd concentrations in the xylem exudate collected from the cut basis of the leaf sheaths of the plants treated with 10 and 100 µM Cd for 3 d were 18.9 ± 6.4 and 64.2 ± 14.6 µM, respectively. Cd concentrations in the phloem sap were significantly lower than those in the xylem exudate, indicating that Cd is not concentrated during the transfer from xylem to phloem. To our knowledge, this is the first determination of Cd concentrations in the phloem sap of plants, and the first direct proof that Cd is translocated via sieve tubes in rice plants.     

Sulfur deficiency of rice plants in the Lower Volta area,Ghana

Abstract

It is well known that stem nodules are formed on the aerial parts of Aeschynomene spp. and Sesbania rostrata grown in the field (Yatazawa and Yoshida 1979; Dreyfus and Dommergues 1981; Yoshida et al. 1985). We have reported that stem nodules were successfully formed by inoculation of Rhizobium isolates derived from both stem and root nodules of A. indica (Yoshida et al. 1985; Sasakawa et al. 1986). The specific activity of nitrogen fixation in stem nodules is comparable to that of root nodules (Sasakawa et al. 1986; Sasakawa 1990). A red pigment, which suggests the presence of leghemoglobin, was detected in stem nodules as well as in root nodules (Yatazawa and Yoshida 1979; Yatazawa and Susilo 1980; Sasakawa et al. 1986).     

Cytosolic glutamine synthetase is present in the phloem sap of rice (Oryza sativa L.)

The presence of glutamine synthetase (GS) in the rice sieve tube was examined. Proteins in the rice phloem sap from leaf sheaths were separated by sodium dodecylsulfate–polyacrylamide gel electrophoresis, transferred to polyvinylidine difluoride membranes and immunoblotted with anti-GS1 antibody. A cross-reacting band, thought to be GS1, was detected in the phloem sap. Moreover, the phloem sap contained a significant amount of GS transferase activity. Previous studies have shown that the concentrations of substrates and cofactors in the rice phloem sap are sufficient for cytosolic GS reaction. These data suggest that physiologically active GS1 is present in rice phloem sap, which might convert glutamate to glutamine in vivo .     

Noticeable increase in cadmium absorption by zinc deficient rice plants

The uptake and transport of cadmium were studied using zinc deficient rice plants. As a result, these plants absorbed and transported cadmium more rapidly than normal rice plants. A zinc deficiency might bring about physiological changes which significantly increase the cadmium accumulation in the roots and its transport into the shoots.     

外源谷胱甘肽喷施对缺硫胁迫下小白菜谷胱甘肽代谢的影响

[目的]硫是植物生长发育过程中所必需的营养元素,缺硫会阻碍植物生长发育,研究外源谷胱甘肽(GSH)对缺硫胁迫下小白菜GSH代谢的影响,为利用外源GSH减轻缺硫胁迫对植物造成的伤害提供理论依据.[方法]以小白菜为试验材料,采用营养液栽培方法,设正常供硫并喷施蒸馏水对照(CK)、缺硫喷施蒸馏水(H2O)、缺硫喷施25 mg...     

Upregulation of the genes for ferritin,RNase, and DnaJ in leaves of rice plants in response to sulfur deficiency

Microarray analysis was carried out with mRNAs isolated from aerial portions of rice plants subjected to sulfur deficiency. Among the candidate clones regulated by sulfur deficiency, three genes were identified by northern analysis that showed altered levels of mRNA accumulation. Genes similar to those for ferritin, S-like ribonuclease, and DnaJ-like protein were down-, down-, and upregulated by sulfate deficiency, respectively. These genes were found for the first time to be responsive to sulfur nutrition in the present study.     

Quantification of zinc transport via the phloem to the grain in rice plants (Oryza sativa L.) at early grain-filling by a combination of mathematical modeling and 65Zn tracing

Zinc (Zn) is an essential nutrient for human beings, and most Zn intake occurs through vegetables or cereals such as rice (Oryza sativa L.) grains. Recently, we detected Zn as well as cadmium, which may be partitioned to rice grains, in the phloem saps from the uppermost internodes of rice and in the xylem saps from the cut stems at early grain-filling. To quantify Zn transport to the grains via the phloem and xylem, a mathematical model previously developed for cadmium transport to rice grains was applied. We examined the translocation of zinc into the grains of rice plants at early grain-filling by feeding zinc-65 (⁶⁵Zn) via a root-bathing medium, through culm cuts above and below the flag-leaf nodes, and through the flag leaves. The estimate made using the mathematical model and experimental data for three types of ⁶⁵Zn transport suggests that the grain Zn may be accumulated predominantly via the phloem through two means of transport, phloem transport of stored Zn from the leaves and, more importantly, xylem-to-phloem transfer at the nodes from Zn as it is being absorbed. The Zn transport via the phloem to the grains is more selective than that of cadmium, a non-nutrient element, as also evidenced by the greater transport of cadmium to the glumes via the xylem.     

不同硼效率棉花品种木质部和韧皮部汁液中矿质养分的差异

溶液培养条件下研究硼对2个硼效率不同的棉花品种木质部、韧皮部中硼及其它矿质养分运输的影响。结果表明,缺硼使2个棉花品种木质部汁液硼含量及溢出量明显降低,低效品种降低幅度大于高效品种。供硼充足(0.5mg/L)时,2个棉花品种木质部汁液中硼浓度均小于培养液中硼浓度;缺硼(0.002mg/L)时,高效品种与低效品种木质部汁液硼浓度分别是培养液硼浓度的32.0和20.5倍。缺硼使2个棉花品种木质部汁液中钾、锰、铜、锌含量均升高,高效品种升高幅度较大;钙含量均降低,低效品种降低幅度较大;高效品种镁含量增高,低效品种降低。而2个棉花品种木质部各养分(钾、镁、钙、锰、铜、锌)溢出量均降低,低效品种降低更明显。无论在缺硼或供硼充足时,2个棉花品种韧皮部中硼浓度均极低,但韧皮部溢泌液中其它养分受缺硼影响品种间表现不同,高效品种韧皮部钾、镁、锰、铜溢出量升高,低效品种则降低;2个品种钙、锌溢出量均降低,低效品种降低幅度更大。     

Cloning of the phloem-specific small heat-shock protein from leaves of rice plants

The N-terminal amino-acid sequence of a major rice phloem-sap protein, designated as RPP23, was determined. The complete amino-acid sequence of RPP23 was deduced from the corresponding rice EST- clone and contained an extra 46 amino acids at the N-terminus, that was apparently cleaved off to form mature RPP23 in sieve tubes. RPP23 shared a similarity to plant small heat-shock proteins (smHSPs), though the N-terminal region of RPP23 was distinct from that of known smHSPs. Immunocytological analyses using leaf sections showed that RPP23 was located only in the phloem regions of leaves, and was present in non-stressed plants. In mature leaves, stronger immunocytological signals were detected in sieve elements than in companion cells.     

不同通风量下城市污泥堆肥过程中硫素的转化特征

  【目的】  研究通风量对城市污泥堆肥过程中硫素转化和挥发性硫化物释放的影响,为有效控制挥发性含硫恶臭物质,保留污泥堆肥产品中的硫素营养提供理论依据和方法。  【方法】  城市污泥和调理剂 (锯末) 以3∶1 (湿重) 的比例混合后,采用自动好氧堆肥控制装置进行15天的堆肥试验,通过改变鼓风机频率实现不同堆体的通风量调节。设置鼓风机工作频率10、13、16 Hz 3个处理,相应的通风量为2.5、3.0和3.5 L/min。在堆肥的第0、1、2、3、5、7、9、11、13、15天进行堆体内部多点混合采样,进行挥发性硫化物的浓度测定,研究城市污泥不同堆肥阶段硫素的转化特征。  【结果】  相较于低通风量 (10 Hz),高通风量 (16 Hz) 下H₂S的峰值浓度下降了约50%,但其累积释放量增加了45.4%;甲硫醚的累积释放量提高了398%,峰值浓度增加了490.8%;CS₂的累积释放量下降了57.8%,其峰值浓度下降了77%。堆肥产品中有效硫浓度在低、中、高通风量条件下相较于堆肥前分别上升了19.5%、19.1%、36.1%。  【结论】  城市污泥堆肥过程中,提高通风量可以降低H₂S的浓度峰值,但增加了H₂S的累积释放量,甲硫醚的峰值浓度和累积释放量均显著增加;提高通风量可以抑制城市污泥堆肥过程中CS₂的释放。在低、中、高3种通风量条件下,堆肥产品的有效硫浓度相较于堆肥前都明显升高。高通风处理虽然全量硫的损失最大,但更有利于提高堆肥产品中可直接被植物吸收的有效硫含量。     

供硫水平对花生叶片硫素含量与形态的影响

采用盆栽方法研究了供硫水平对花生不同叶龄叶片的硫酸盐、谷胱甘肽和蛋白态硫含量及其形态的影响。结果表明,叶片谷胱甘肽含量随叶龄增大而减少,硫酸盐含量却相反。当硫素供应充足时,幼叶谷胱甘肽含量占总硫 4.6%,蛋白态硫含量占 91%,其余以硫酸盐形式存在;中龄叶及老叶的硫酸盐含量占总硫的60%~80%,而谷胱甘肽含量不到1%。当硫素供应不足时,幼叶和中龄叶含硫化合物总量减少,尤其是硫酸盐。因此,在缺硫时,谷胱甘肽不是植株硫的主要来源,且低氮加重缺硫症状发生。不同叶龄叶片对缺硫反应不同,幼叶对缺硫反应更为敏感。     

Predicting plant sulfur deficiency in soils: results from Ohio

We developed a model for plant available sulfur (S) in Ohio soils to predict potential crop plant S deficiency. The model includes inputs of plant available S due to atmospheric deposition and mineralization of soil organic S and output due to leaching. A leaching index was computed using data on annual precipitation; soil pH and clay content that influence sulfate adsorption; and pore water velocity based upon percent sand, silt, and clay. There are five categories of S status ranging from highly deficient to highly sufficient, and the categories are defined based on whether the crop S requirement was 15 or 30kg S ha⁻¹ year⁻¹. The final database derived from the model includes 1,473 soil samples representing 443 of the 475 soil series in Ohio. For a crop requiring 15kg S ha⁻¹ year⁻¹, most soils (68.6%) were classified as variably deficient, which implies that the response to S fertilization will be variable but often positive depending on specific crop conditions. For a crop requiring 30kg S ha⁻¹ year⁻¹, 43.2% of soils were classified as variably deficient, but 49.7% were classified as moderately or highly deficient, implying that a response to S fertilization will usually or always occur. The model predicts crop S status for a single state in the USA, but with proper inputs, it should be applicable to other areas.     

Growth and canopy structure of rice plants grown under field conditions as affected by Si application

Abstract

The ontogenetic changes of N, P, and K contents in leaves of rice, maize, soybean, adzuki bean, potato, and sugar beet were studied as the following results were obtained.

1. N content of rice and maize drastically changed at the primordia formation stage, while that of other crops did not show clear changes depending on the stage of growth.

2. P content of rice and maize was higher in upper leaves than lower leaves, but did not change appreciably in other crops.

3. K content of potato and sugar beet remained constant for a long period of time compared to other crops.

4. P-N relationship in rice and maize distinctly differed between upper and lower leaves; ratio of P content to N content of upper leaves was higher than that of lower leaves.

5. K-N relationship in potato and sugar beet was very different from that in other crops; K content remained constant regardless of the decrease in N content except for the lower leaves.

Thus, as the P-N balance of rice and maize (Gramineae crops) and K-N balance of potato and sugar beet (root crops) showed distinctive characteristics compared to other crops, the physiological significance of the mineral balance must be further investigated.     

Sulfonate S: A major form of forest soil organic sulfur

Summary Several forests of varying elevations, soils and vegetation were studied to evaluate the relative importance of sulfonate S, amino acid S, and ester sulfate as constituents of soil organic S. Suflonate S exceeded 40% of total S in the O1 horizon of all but one site examined, and comprised at least 50% of total S in the O2 horizons of 14 out of 18 study sites examined. Sulfonate pool sizes, on a percentage basis, tended to decrease with increasing sample depth within the mineral horizons, but sulfonate S was still a major form of organic S in the C horizon. Amino-acid S pool sizes were, as a general rule, lower than those for sulfonate in the O1 and O2 horizons, and lower than those for both ester sulfate and sulfonate when mineral soil horizons were considered. In no case did amino-acid S represent>25% of total S. Amino-acid S decreased with increasing depth at all but one site examined. Ester sulfate pool sizes were generally less than those of sulfonate S and greater than those of amino-acid S. This trend was observed with the O1, O2, and A horizons, but it was not apparent with samples from the intermediate and lowest soil horizons, where ester sulfate levels exceeded those for sulfonate S in 4 out of 8 and 5 out of 14 sites, respectively, in these latter horizons. Although there were some exceptions, collectively, the data suggest that sulfonate S is a major form of organic S in forest soils, irrespective of depth.     

An automated turbidimetric method for total sulfur in plant tissue and sulfate sulfur in soils

Abstract

An automated turbidimetric method has been developed for the rapid and accurate determination of sulfate. The method is practical and useful for accurately measuring total sulfur in plant tissues, and extractable sulfate in soils. The principle of intermittent reagent addition is used which eliminates drift and sensitivity changes caused by coating of BaSO₄ on tubing and cell walls. Also, the appropriate chemistry is used to minimize interactions of the wash with the sample at a sampling rate of 30/H. The sensitivity of the method is excellent with a working range of 0 to 15 ppm sulfur for soils. For plant digests the sample solutions are diluted to 0–35 ppm S. The precision as determined by repeated analysis of a soil sample extract was 0.58% RSD with a mean of 9.26 pg/g extractable SO⁼ ₄‐S. On another soil sample using a different extractant and extraction procedure the RSD was 0.64%, mean of 9.26 μg/g. Multiple automated sulfur analyses on a plant tissue digest resulted in an RSD of 0.41% for a sample containing 0.21% S. The automated turbidimetric method for sulfate has excellent precision and sensitivity in plant tissue and soil analyses where gravimetric BaSO₄ assays are not practical.     

Effect of sulfur deficiency and excess on yield and sulfur accumulation in tomato plants

Abstract

Tomato (Lycopersicon esculentum Mill. var. hybrid 6C‐204) plants were grown for 95 days after germination until each one bore 6 ripe clusters in a greenhouse using nutrient solutions with nine added sulfate levels ranging from 0 to 105 me/1.

Sulfur‐deficiency symptoms and characteristics of plants growing under hign SO₄‐S levels were observed and described. Fruit yields were negatively affected by both S‐deficiency and high SO₄‐S concentrations. Top growth was affected more than root growth by changes in the amount of SO₄‐S supplied. The critical SO₄‐S concentration in the growth media ranged from 2 a 22.5 me/1.

Leaf sulfate‐S increased gradually in leaves and roots as SO₄‐S supply in the nutrient solution increased while organic‐S remained relatively constant. Leaf sulfate‐S critical value was growth stage dependent. Maximum yields at flowering were associated with leaf concentrations of 0.48–1.2% SO₄‐S and 0.25–0.35% organic‐S.     

外源稀土对水稻伤流组分的影响

应用微区试验和伤流测定法研究了外源稀土对水稻根系合成氨基酸和激素的效应,以及对伤流中无机营养离子的影响。结果表明,在本试验条件下,土施低浓度稀土能促进根系合成,显著增加氨基酸总量和激素在伤流中的含量,提高营养离子的吸收;但高浓度稀土却有着明显的抑制效应。应用数学模拟的方法计算出稀土抑制氨基酸合成的半效应值(或50值)约为350～500mg/kg。稀土提高了伤流液中钙的含量,而对磷、钾的含量起抑制效应。     

Organic sulfur forms in mineral top soils of the Marsh in Schleswig‐Holstein,Northern Germany

Little is known about the nature of organic sulfur (S) in soils of the Marsh in Schleswig‐Holstein, Northern Germany. In addition to total and inorganic S, we determined two organic S fractions (ester sulfate‐sulfur and carbon‐bonded sulfur) in 14 aerated mineral top horizons of two salt marshes and ten dyked polder soils of different age. All soils developed from marine sediments. Total S concen‐trations ranged from 153 to 950 mg kg^—1. Organic S was the main S constituent (range from 53 to 99% with a median of 97%). Higher inorganic S levels were found only in the salt marshes due to soluble sulfate (15 to 47%). The younger marsh soils (salt marshes and soils of a polder dyked in 1978) had unique high S contents of 0.9 to 2.4% in their organic matter, whereas the S contents of the organic matter in older marsh soils were at only 0.6%. This S‐rich organic matter is a heritage of a former anoxic marine environment. In most horizons the carbon‐bonded S was the dominant sulfur form. However, both carbon‐bonded S and ester sulfate‐S did not relate to soil age. This limits the benefit of the wet chemical fractionation procedure used for studying the fate of organic S in marsh soils.