The acquisition of phosphate by higher plants: Effect of carboxylate release by the roots. A critical review.

Phosphorus is one of the most limiting macronutrients for plant productivity in agriculture worldwide. The main reasons are the limited rock phosphate reserves and the high affinity of phosphate (P) to the soil solid phase, restricting the P availability to the plant roots. Plants can adapt to soils low in available P by changing morphological or/and physiological root features. Morphological changes include the formation of longer root hairs and a higher root : shoot ratio both parameters increasing the root surface which provides the shoot with P. This may be successful if the P availability in soil, i.e., the P concentration of the soil solution is not extremely low (> 1–2 µM P). If the P concentration of the soil solution is lower, the diffusive flux to the root surface will be very low and may not satisfy the P demand of the shoots. Under these conditions plants have developed strategies to increase the rhizosphere soil solution concentration by secreting mobilizing agents. The most effective way of P mobilization is the release of di‐ and tricarboxylic acid anions, especially oxalate and citrate. Citrate can accumulate in the rhizosphere up to concentrations up to 80 µmol g^?1 soil. Cluster root formation is an efficient way of carboxylate accumulation in the cluster root rhizosphere improving P mobilization. Cluster roots strongly improve the acquisition of the mobilized P. Considering a single root, around 80–90% of the mobilized P diffuses away from the root. From the rhizosphere of cluster roots, most of the mobilized P is taken up by the cluster roots. Both, the strong accumulation of carboxylates in and the effective P uptake from the cluster‐root rhizosphere are the basis of the unique ability of P acquisition by cluster root‐forming plants. Plants that do not form cluster roots, e.g., red clover, can also accumulate carboxylates in the rhizosphere. Red clover accumulates high quantities of citrate in the rhizosphere soil. Model calculations show that the release of citrate by red clover roots and its accumulation in the rhizosphere strongly improve P acquisition by this plant species in various soils. Similar results are obtained with alfalfa. In sugar beet, oxalate release can strongly contribute to P acquisition. In summary, P acquisition can be strongly improved by the release of carboxylates and should be taken as a challenge for basic and applied research.     

Fulvic acid in foliar spray is more effective than humic acid via soil in improving coffee seedlings growth

ABSTRACT

Humic (HA) and fulvic (FA) acids improve the nutrient availability and uptake by plants but some aspects of their agronomic use still need to be clarified. The effects of HA soil application and FA foliar application on the growth, Zn and B uptake by coffee seedlings were evaluated. HA was added to an Oxisol at concentrations 0, 10, 25, 50, 75 and 100 mg kg^?1 (C-HA), in both limed (pH 6.2) and overlimed (pH 7.2) conditions. FA (0, 0.2, 0.5 and 1 g L^?1 C-FA) was applied to coffee leaves in three different application modes (M): with 0.3% Zn and 0.6% B supplied via foliar (M₁), 0.6% B and 1.2% Zn supplied via foliar (M₂) and 1.2 mg kg^?1 B and 6 mg kg^?1 Zn supplied via soil (M₃). HA addition in soil significantly (p < 0.05) reduced leaf B and Zn accumulation and coffee growth in both pH conditions. In the M₁ and M₂, FA application significantly (p < 0.05) increased the shoot growth at 0.59 and 0.45 g L^?1 and B accumulation at 0.96 and 0.45 g L^?1 C-FA. Foliar application of C-FA, instead soil application of C-HA, is a suitable practice to improve coffee seedlings growth and nutrition on Oxisol.     

花桥早熟板栗实生选种研究

1996~2005年,我们对花桥早熟板栗开展了实生选种研究,初步选育出花桥1号和花桥2号两个优良早熟新品种。研究结果表明:花桥1号和花桥2号两个新品种确实具有成熟期早、果粒大、抗性强、栽培管理容易、丰产性好、商品价值高等优良性状,在湘中丘岗山地具有广阔的开发前景,属地方名特优新品种。     

Oral bovine serum albumin immune‐stimulating complexes improve the immune responses and resistance of large yellow croaker (Pseudosciaena crocea,Richardson, 1846) against Vibrio alginolyticus

This study aimed to investigate effects of bovine serum albumin immune‐stimulating complexes (BSA ISCOMs) on immune‐related genes expression, serum nonspecific immunity and disease resistance of large yellow croaker (Pseudosciaena crocea). Fish were fed diets containing 3.5 ml of BSA ISCOMs per kg feed (experimental group) or 3.5 ml of phosphate‐buffered saline per kg feed (control group) for 1 week. The liver, spleen, head‐kidney tissues were sampled for determining gene expression of myxovirus‐resistant protein (Mx), major histocompatibility complex class II alpha chain (MHC II α), tumour necrosis factor‐alpha (TNF‐α) and interleukin‐10 (IL‐10) 30 and 90 days after feeding. Also, blood samples were collected for determining activities of serum superoxide dismutase (SOD), interferon alpha (IFN‐α), TNF‐α and alkaline phosphatase (ALP). TNF‐α and MHCⅡα gene expression in the liver, spleen, head‐kidney, as well as IFN‐α, TNF‐α and ALP activities in the serum, of experimental fish were significantly higher 30 days after feeding; while only TNF‐α and MHC II gene expression in the head‐kidney remained upregulated 90 days after feeding. The cumulative mortality of the experimental fish was significantly lower than control. This study indicated that BSA ISCOMs improved the immune response and induced protective immunity in large yellow croaker.     

潜根线虫侵染对水稻早衰的影响

接种试验表明,水稻潜根线虫(Hirschmanniella oryzae)侵染的稻株,由于生长后期根系腐烂和衰败导致植株早衰.水稻品种间对线虫侵染存在抗性和耐病性差异,耐病水稻品种在较高侵染虫量条件下根生长量和稻谷产量损失较小.潜根线虫侵染能诱发稻株体内的过氧化物酶(POD)、酪氨酸解氨酶(TAL)、多酚氧化酶(PPO...     

Eisenmenger's complex in a Holstein-Friesian cow

A 4.5-year-old, Holstein-Friesian cow presented with a 1-month history of severe exercise intolerance. Rectal examination and transrectal ultrasonography revealed a large mass in the left retroperitoneum. The heart rate was 70 to 80/min. Premature ventricular complexes and ventricular bigeminy were present on an electrocardiogram. Erythrocytosis was present and blood gas analysis revealed marked hypoxaemia. An echocardiogram demonstrated a large ventricular septal defect, a partially dextroposed aorta, and concentric hypertrophy of the right ventricular free wall. Colour flow Doppler echocardiography and a contrast echocardiographic study demonstrated a right-to-left shunt through the ventricular septal defect. Eisenmenger's complex was diagnosed. The patient was euthanased. Necropsy confirmed the gross cardiac lesions identified by echocardiography and an abscess in the apex of the left ventricle. Severe pulmonary arterial lesions were present, consistent with a marked increased in pulmonary vascular resistance. Actinomyces pyogenes was cultured from abscesses of the retroperitoneum and the ventricular apex.     

Distraction osteogenesis to treat premature distal radial growth plate closure in a dog

A 4-month-old Labrador was presented for forelimb lameness and elbow pain. Radiography revealed asymmetric premature closure of the distal radial physis resulting in humeroradial and humero-ulnar subluxation. A four-ring circular external fixator applied to the antebrachium was used to perform distraction osteogenesis. After a 4 day latency period, varying rates of linear distraction were used to lengthen the radius by 50% of its original length, which is significantly longer than has been previously reported. By 69 days after performing the radial osteotomy, the distraction callus had achieved clinical union and the fixator was removed. One year postoperatively, mild lameness was present after exercise and minimal elbow osteo-arthritis was evident radiographically. Complications observed included pin tract drainage, transient carpal contracture and radio-ulnar synostosis.     

Immunostimulatory complexes containing Eimeria tenella antigens and low toxicity plant saponins induce antibody response and provide protection from challenge in broiler chickens

Immunostimulating complexes (ISCOMs) are unique multimolecular structures formed by encapsulating antigens, lipids and triterpene saponins and are one of the most successful antigen delivery systems for microbial antigens. In the current study, both the route of administration and the antigen concentration of ISCOMs, containing Eimeria tenella antigens and saponins from native plants, were evaluated in their ability to stimulate humoral immunity and to protect chickens against a challenge infection with E. tenella. Broiler chickens were immunized with ISCOM preparations containing E. tenella antigens and the purified saponins Gg6, Ah6 and Gp7 isolated from Glycyrrhiza glabra, Aesculus hippocastanum and Gipsophila paniculata, respectively. The effects of the route of administration, dose of antigen and type of saponin used for construction of ISCOMs were evaluated for ability to stimulate serum IgG and IgM and to protect chickens against a homologous challenge. A single intranasal immunization was the most effective route for administering ISCOMs although the in ovo route was also quite effective. Dose titration experiments demonstrated efficacy after single immunization with various ISCOM doses but maximum effects were observed when ISCOMs contain 5–10 μg antigen. Immunization of birds by any of the three routes with E. tenella antigens alone or antigens mixed with alum hydroxide adjuvant resulted in lower serum antibody and reduced protection to challenge relative to immunization with ISCOMs. Overall the results of this study confirm that significant immunostimulation and protection to challenge are achieved by immunization of chickens with ISCOMs containing purified saponins and native E. tenella antigens and suggest that ISCOMs may be successfully used to develop a safe and effective vaccine for prevention of avian coccidiosis.     

Podzol: Soil of the Year 2007. A review on its genesis,occurrence, and functions

The Podzol has been elected “Soil of the year 2007” in Germany. This article reviews the present knowledge on the development, functions, and threats of Podzols. The main theories on mobilization and transport of organic matter, Fe, Al, and Si are (1) metal‐organic migration, (2) metal reduction, and (3) inorganic sol migration. Immobilization theories include precipitation or polymerization due to increasing pH/abundance of base cations with depth, mechanical filtering in soil pores, oxidation of metal‐organic complexes, biodegradation of the organic part, decreasing C‐to‐metal ratios during translocation, adsorption to soil particles, and flocculation at the point of zero charge. Podzolization is discussed also on the catena scale, where vertical and lateral translocation processes (across pedon boundaries) need to be considered to understand Podzol patterns in landscapes. Chronosequence studies show that incipient podzolization usually becomes visible between 100 and 500 y and mature Podzols develop in 1,000–6,000 y. The occurrence of Podzols worldwide is concentrated mainly on the boreal zone and mountain regions within the humid temperate zone. Smaller Podzol areas are found in some perhumid tropical and subtropical regions. In Germany, Podzols occur in the Alps, in the glaciofluvial valleys and heathlands of N Germany, and in the mountain ranges. They fulfil several ecological functions, especially for groundwater recharge. Main threats for these mostly sandy soils are wind erosion and surface mining of sand. Two pedons which were chosen to represent the “Soil of the year 2007” are presented. Finally, some conclusions about podzolization processes are drawn, which may explain the diverse observations reported in the literature.     

玉米(Zea mays L.)中单14号及亲本叶绿体的组分和功能比较

玉米中单１４号的叶绿体在叶绿素含量、光能吸收、电子传递速率、激发能分配和色素蛋白复合体组成等方面均优于两亲本。其叶绿素ａ、ｂ和总含量提高了３１％￣３６％；对光能吸收强度较大；光还原活力超过双亲２５．５％；分配到ＰＳＩ的激发能比亲本多１４７．１％；叶绿素蛋白复合体分析结果说明，其捕光色素蛋白复合体含量高于亲本。因而中单１４号比亲本在叶绿体的光合功能上显示优势。