Effect of Soil pH on Growth and Cation Deposition in the Root Tip of <Emphasis Type="BoldItalic">Zea mays</Emphasis> L.

Abstract The effects of sandy soil pH on the distribution of growth velocities and on cation concentrations and deposition rates in root growth zones of Zea mays L. seedlings were investigated. The pH values of the rooting medium varied between 4.2 and 8.6 in sand culture (70% saturated) without external supply of nutrients. At all pH values, densities (in 7moles per g fresh weight) of potassium, magnesium, and calcium increased toward the root tip. Lower pH in the medium increased calcium tissue density fivefold and magnesium density 1.7-fold, whereas the density of potassium, the overall elongation rate, and the growth velocity distribution did not show any significant pH dependence. Throughout the growth zone the deposition rates of the divalent cations, as calculated on the basis of the continuity equation, increased with lower pH. The data are consistent with the hypothesis that the effects of pH on the cation deposition rates are due to the increase in the divalent cation concentration of the soil solution at low pH and that the abundant uronic acid residues of the young walls of the meristem provide a reservoir of storage capacity for Ca and Mg under conditions of low nutrient availability.     

INFLUENCE OF SUPPLEMENTAL INORGANIC NUTRIENTS ON GROWTH,SURVIVORSHIP, AND MYCORRHIZAL RELATIONSHIPS OF SCHIZACHYRIUM SCOPARIUM (POACEAE) GROWN IN FUMIGATED AND UNFUMIGATED SOIL

Little bluestem grass Schizachyrium scoparium ([Michx.] Nash) plants were grown under field conditions for 2 years in soils fumigated with methyl bromide and chloropicrin, or in unfumigated soil, and treated with supplemental inorganic nutrients (bases calcium and magnesium) phosphorus, nitrogen, and potassium. Most differences in measured plant responses were due to interactions between fumigation and nutrient treatments. These included biomass production, root mass per unit length (μg/cm), root lengths, flowering culm production, percent colonization, colonized root length, and spore production in rhizosphere soil. Plants generally responded to mycorrhizal fungal colonization by reducing total root length and producing thicker roots. Treatment of plants with bases appeared to profoundly affect the mycorrhizal association by reducing sporulation of vesicular-arbuscular mycorrhizal fungi and increasing colonization. When fumigated or unfumigated soils were considered separately, base-treated plants produced more biomass than other treatments. Base-treated plants grown on unfumigated soil had more flowering culms and longer colonized root lengths than all other plants. Percent colonization by mycorrhizal fungi and colonized root length were positively correlated with phosphorus/nitrogen ratios, but the ratio was not correlated with plant biomass production. This suggests that phosphorus is not a limiting nutrient in our soil and investment in a mycorrhizal association may not result in enhanced plant growth. The base-nutrient effects may indicate a need to reevaluate earlier studies of macro nutrient effects that did not take into account the role played by calcium and magnesium in assessing fungus-host plant interactions.     

Mineral uptake and transport in xylem and phloem of the proteaceous tree,Banksia prionotes

Xylem sap of sinker (tap) root, cluster feeding roots, lateral roots and from an age series of main stem extensions of 6-year trees of Banksia prionotes was collected and analyzed for principal organic and inorganic solutes. During the phase of root uptake activity in winter and spring, cluster roots were principal xylem donors of malate, phosphate, chloride, sodium, potassium and amino acid N whereas other parts of the root served as major sources to the shoot of other cations, nitrate and sulphate. Sinker root xylem sap was at all times less concentrated in solutes than that of lateral roots into which cluster roots were voiding exported solutes. Phosphate was abstracted from xylem by stem tissue during winter and it and a range of other solutes released back to xylem immediately prior to extension growth of the shoot in summer. Phloem sap collected from mid regions of stems was unusually low in potassium and phosphate relative to chloride and sulphate in comparison with phloem sap of other species, and its low potassium: sodium ratio relative to xylem indicated poor discrimination against sodium during phloem loading. Data are discussed in relation to the asynchronous seasonal cycles of nutrient uptake and shoot growth.     

The Distribution of Mg, P and K in the Split Roots of Subterranean Clover

The aim of these experiments was to determine whether uninhibitedroot growth is possible in a soil lacking Mg, provided thatthe plant is adequately supplied with Mg from another regionwithin the soil. Two experiments were undertaken using splitroot systems in free-draining sand or gravel irrigated dailywith nutrient solution. Magnesium supply to one half of theroot system was varied and root growth in the deficient partof the system was measured. Magnesium redistribution was comparedto that of calcium, phosphorus and potassium. Magnesium content of the roots grown in the compartment withno Mg supply increased, but only when the shoots had an adequateto luxury Mg status. Even under these conditions root growthwas inhibited compared to roots with an adequate external supplyin both compartments. Similarly potassium was transferred tothe roots with no external supply, but root growth was retardedin this compartment. Roots proliferated in the compartment suppliedwith phosphate and did so at the expense of growth in the non-supplycompartment. The shoots had a barely adequate phosphorus statusand there was no transfer of phosphorus to the root with noexternal supply. Magnesium, phosphorus, potassium, root growth, split root systems, subterranean clover, Trifolium subterraneum L.     

Caclium uptake and associated adenosine triphosphatase activity in fragmented sarcoplasmic reticulum. Requirement for potassium ions.

The effects of monovalent cations on calcium uptake by fragmented sarcoplasmic reticulum have been clarified. Homogenization of muscle tissue in salt-containing solutions leads to contamination of this subcellular fraction with actomyosin and mitochondrial membranes. When, in addition, inorganic cations are contributed by the microsomal suspension and in association with nucleotide triphosphate substrates there is an apparent inhibition of the calcium transport system by potassium and other cations. However, when purified preparations were obtained after homogenization in sucrose medium followed by centrifugation on a sucrose density gradient in a zonal rotor, calcium uptake and the associated adenosine triphosphatase activity were considerably activated by potassium and other univalent cations. When plotted against the log of the free calcium concentration there was only a slight increase in calcium uptake and ATPase activity in the absence of potassium ions but sigmoid-shaped curves were obtained in 100 mM K+ with half-maximal stimulation occurring at 2 muM Ca2+ for both calcium uptake and ATPase activity. The augmentation in calcium uptake was not due to an ionic strength effect as Tris cation at pH 6.6 was shown to be inactive in this respect. Other monovalent cations were effective in the order K+ greater than Na+ greater than NH4+=Rb+=Cs+ greater than Li+ with half-maximal stimulation in 11 mM K+, 16 mM Na+, 25 mM NH4+, Rb+, and Cs+ and in 50 mM Li+. There was nos synergistic action between K+ AND Na+ ions and both calcium uptak and associated ATPase were insensitive to ouabain. Thallous ions stimulate many K+-requiring enzymes and at one-tenth the concentration were nearly as effective as K+ ions in promoting calcium uptake. The ratio of Ca2+ ions transported to P1 released remained unchanged at 2 after addition of K+ ions indicating an effect on the rate of calcium uptake rather than an increased efficiency of uptake. In support of this it was found that during the stimulation of calcium uptake by Na+ ions there was a reduction in the steady state concentration of phosphorylated intermediate formed from [gamma-32P]ATP. It is considered that there is a physiological requirement for potassium ions in the relaxation process.     

Effect of acid irrigation and liming on root growth of Norway spruce

The effect of acid irrigation and liming on fine root growth of Norway spruce (Picea abies [L.] Karst.) was studied in an approximately 80-year-old forest stand in southern Germany (Höglwald). Root growth was measured mainly on root windows and in addition by soil core sampling. Root growth rate showed a typical pattern in the course of a year with a maximum in August. Acid irrigation depressed root growth rate, whereas liming, particularly in combination with acid irrigation, markedly increased root growth in the humic layer and the upper 0–5 cm of the mineral soil. The treatment effects on root growth in the mineral soil below 5 cm were small and not significant. Root growth rate was not correlated with the concentration of aluminium (Al) or the molar ratio of calcium (Ca) to Al in the soil solution. The results suggest that inhibition of root growth by acid irrigation is a direct effect of high proton concentrations in the irrigation water, and that enhancement of root growth by liming is caused by an improved supply of mineral nutrients and higher biological activity.     

Nutrient element balance in citrus nutrition

Summary The inter-relationships between the leaf contents of 4 major nutrients, nitrogen, calcium, magnesium and potassium, are discussed within the context of a nutrient-element balance in citrus leaves. It was found that there was an unequal 3-way competition between the cations, potassium being perhaps the strongest antagonist of the three bases. There was also a reciprocative relationship between nitrogen and calcium, the data so far suggests a one-way phenomenon in favour of calcium. Furthermore the nitrogen/calcium ratio appears to have a significant effect on the leaf content of potassium, but not on the leaf content of magnesium.     

Certain aspects of the mechanism of intestinal transport of sodium, potassium, calcium and magnesium in rats

Intestinal absorption of sodium, potassium, calcium and magnesium was studied in rats by the method of intestinal perfusion using ouabain as an inhibitor of sodium-potassium dependent ATPase. At the same time the activity of ATPase and phosphatase were determined in homogenates of intestinal mucosa. A significant effect on the concentration of the determined ions was demonstrated in the transport of these ions, and also an unquestionable participation of intestinal ATPase in the direction and intensity of this transport. It was found that the multidirectional effect of ouabain on the transport of cations depended on their concentration. In the case of concentrations of cations similar to those in the mean food rations it has been demonstrated that ouabain increased the absorption of sodium, potassium and calcium and inhibited the absorption of magnesium. With a threefold higher ions concentration the absorption of potassium and magnesium was inhibited, without changing the transport of sodium and calcium. The possible explanation of the mechanism of these effects is discussed.     

Changes in the extractability of cations (Ca,Mg and K) in the rhizosphere soil of Norway spruce (Picea abies) roots

Nutrient concentrations in the rhizosphere soil can be higher, lower or remain unchanged compared to the bulk soil, but relatively little is known about such changes for basic cations in the rhizosphere of tree roots. A modified root container technique of studying rhizosphere processes was employed. Plexiglas cylinders were horizontally split by a membrane with 30 M mesh size into an upper compartment for root growth and a root-free lower compartment, each with an inner diameter of 5 cm and a height of 10 cm. One 2-year-old Norway spruce (Picea abies) seedling was transplanted from a nursery into each cylinder. Plants were not specifically inoculated, but roots were colonised by a mix of ectomycorrhizal fungi originating from the nursery. The nutrient poor mineral soil used in the experiment was taken from a forest site in Bayerischer Wald, southern Germany. The soil was either supplied with a mix of Ca, Mg and K, or not supplied with these cations. Plants were harvested 30 weeks after transplanting. The nylon membrane between the root compartments restricted root growth to the upper compartment, so that by the end of the experiment a root mat was formed at the top side of the membrane. In the lower compartment, soil nearest to the root mat was regarded as rhizosphere soil while soil in a distance from the root mat was regarded as bulk soil. In the upper compartment, rhizosphere soil was obtained at the end of the experiment by gently shaking the roots. The soils were analysed for Ca, Mg and K contents following two different soil extraction methods. In the fertilised treatment, H₂O-extractable Ca and Mg were accumulated in the rhizosphere. In contrast, K (NH₄Cl-extraction) was depleted in the rhizosphere. In the bottom tube, the depletion of K (NH₄Cl-extraction) was restricted to 1 cm distance from the root mat. In unfertilised soil, Ca, Mg and K concentrations did not differ clearly between rhizosphere and bulk soils. The results indicated that the occurrence of cation gradients in the rhizosphere depended on the level of soil nutrient supply. Distinct rhizosphere effects were measured by conventional soil extraction methods only when the soil was freshly fertilised with mineral elements prior to the experiment. In this case, K depletion in the rhizosphere reflected higher K uptake by the fertilised Norway spruce plants. For low-nutrient soils, novel techniques are required to follow subtle changes in the rhizosphere.     

Experimental Articles

Volcanic ash (Karymskii Volcano, Kamchatka) stimulated growth of the bacterium Rhodovulum sp. A-20s. The interaction between ash, water, media, and bacteria resulted in changes in the chemical composition of the solutions and ash. The ash-water interaction resulted in release of calcium to the solution, as well as in an increase in the proportions of sodium and calcium among the exchange cations of ash. As a result of the ash-medium interaction, calcium and copper were released to the solution; the exchange sodium cations were substituted by calcium and potassium. As a result of the ash-bacteria interaction, the content of copper in the solution decreased, and the exchange cations of calcium and sodium were actively substituted by potassium and magnesium. An increase in the magnesium content among the exchange cations of ash was especially apparent. The products of bacterial metabolism formed mineral-organic complexes with the ash substrate. The data obtained indicate the biogenic transformation of ash, which may lead to the initial phase of formation of clay minerals from volcanic ashes.     

间作对植株生长及养分吸收和根际环境的影响

通过盆栽实验研究了线辣椒和玉米间作对其植株生长、矿质养分吸收、根际环境以及铁载体分泌的影响,以探索间作促进铁、磷等养分吸收利用的可能生理机制.结果表明:(1)与单作相比,间作线辣椒地上部干重降低23.0%,根系干重增加44.2%,玉米地上部和根系的干重分别增加8.7%和22.9%;间作线辣椒根冠比和根系活力分别显著提高86.4%和29.8%;间作线辣椒、玉米叶绿素含量分别显著提高12.6%和7.8%.(2)与单作相比,间作线辣椒的铁、锌、锰含量分别增加1.50倍、1.39倍和1.34%,而间作玉米则无显著变化;间作线辣椒和玉米的钙含量都显著低于相应单作,氮含量没有显著变化,但磷、钾含量显著增加.(3)间作线辣椒和玉米的根际土、非根际土的酸性磷酸酶活性及根系酸性磷酸酶活性都显著高于相应单作,而其根际土和非根际土的pH值无显著变化;间作玉米根系的铁载体分泌比单作减少32.8%,间作线辣椒根系的铁还原酶活性是单作的1.10倍.研究发现,线辣椒/玉米间作能通过影响根际生物学特征和化学过程提高植株的铁、锌、磷和钾养分水平,缓解养分胁迫,是一种很有推广价值的种植模式.     

The development of waterlogging damage in wheat seedlings (Triticum aestivum L.)

Summary Decreases in the concentrations of nitrogen, phosphorus, potassium, calcium and magnesium, in the shoots of wheat seedlings soon after the start of waterlogging were mainly attributed to an inhibition of ion uptake and transport by roots in the oxygen deficient soil. There was a small net accumulation of nitrogen, phosphorus and potassium by the aerial tissues, principally the tillers rather than the main shoot. By contrast, calcium and magnesium accumulated in both tillers and main shoot. With waterlogging, nitrogen, phosphorus and potassium were translocated from the older leaves to the younger growing leaves, and in the case of nitrogen this was associated with the onset of premature senescence. Calcium and magnesium were not translocated from the older leaves, the younger leaves acquiring these cations from the waterlogged soil. The promotion of leaf senescence by waterlogging was counteracted by applications of nitrate or ammonium to the soil surface, or by spraying the shoots with solutions of urea, but the beneficial effects on shoot growth were small.The role of mineral nutrition in relation to waterlogging damage to young cereal plants is discussed.     

Effects of varied soil nitrogen supply on Norway spruce (Picea abies [L.] Karst.)

During a seven-month period the effect of different nitrogen (N) availability in soil on growth and nutrient uptake was studied in three-year-old Norway spruce (Picea abies [L.] Karst.) trees. The plants were grown in pots on N-poor forest soil supplied with various amounts and forms (inorganic and organic) of N. Increasing supply of inorganic N (as NH₄NO₃) increased the formation of new shoots and shoot dry weight. The root/shoot dry weight ratio of new growth was drastically decreased from 1.6 in plants without N supply to 0.5 in plants supplied with high levels of NH₄NO₃. This decrease in root/shoot dry weight ratio was associated with distinct changes in root morphology in favour of shorter and thicker roots. The addition of keratin as organic N source did neither affect growth nor root morphology of the trees. The amount of N taken up by plants was closely related to the supply of inorganic N, and trees supplied with highest levels of NH₄NO₃ also had the highest N contents in the dry matter of needles and roots. In contrast, N contents in needles of trees grown without additional N, or with keratin supply, were in the deficiency range. Supply of NH₄NO₃ decreased the contents of phosphate (P) and potassium (K) and therefore markedly increased N/P and N/K ratios in the needles. On the other hand, the contents of calcium (Ca), magnesium (Mg), and manganese (Mn) in the needles were increased in the plants supplied with inorganic N, suggesting high soil availability and promotion of uptake of these divalent cations by high nitrate uptake. The observed effects on root/shoot dry weight ratio, root morphology, and mineral nutrient composition of the needles indicated that high inorganic N supply may increase above-ground productivity but at the same time decrease the tolerance of trees against soil-borne (e.g. deficiency of other mineral nutrients) stress factors. Deceased 21 September 1996 Deceased 21 September 1996     

Lotus japonicus CASTOR and POLLUX Are Ion Channels Essential for Perinuclear Calcium Spiking in Legume Root Endosymbiosis

The mechanism underlying perinuclear calcium spiking induced during legume root endosymbioses is largely unknown. Lotus japonicus symbiosis-defective castor and pollux mutants are impaired in perinuclear calcium spiking. Homology modeling suggested that the related proteins CASTOR and POLLUX might be ion channels. Here, we show that CASTOR and POLLUX form two independent homocomplexes in planta. CASTOR reconstituted in planar lipid bilayers exhibited ion channel activity, and the channel characteristics were altered in a symbiosis-defective mutant carrying an amino acid replacement close to the selectivity filter. Permeability ratio determination and competition experiments reveled a weak preference of CASTOR for cations such as potassium over anions. POLLUX has an identical selectivity filter region and complemented a potassium transport–deficient yeast mutant, suggesting that POLLUX is also a potassium-permeable channel. Immunogold labeling localized the endogenous CASTOR protein to the nuclear envelope of Lotus root cells. Our data are consistent with a role of CASTOR and POLLUX in modulating the nuclear envelope membrane potential. They could either trigger the opening of calcium release channels or compensate the charge release during the calcium efflux as counter ion channels.     

Exploitation of K near roots of cotton,maize, upland rice,and soybean grown in an Ultisol

Native soil potassium (K) has received increased attention as a K source for plants to reduce fertiliser input. Our objective was to compare the ability of different crops to utilise native K. We also wanted to study the exploitation and transport pattern of soil K influenced by plant uptake. Cotton, maize, soybean, and upland rice were cultivated in rhizoboxes. The system permitted sampling of 1-mm-thin soil layers at increasing distances from the plant roots. Both exchangeable and nonexchangeable K was determined and compared with plant uptake of K. The upland rice was superior in K uptake, and took up some nonexchangeable K. Soybean and cotton grew poorly, and K was accumulated in the root zone due to excess supply by mass flow. The importance of mass flow over diffusion of K was verified by calculations and is contrary to accepted principles of K transport in soil. The reasons were high transpiration and restricted root growth. This indicates that mass flow of K in some situations is more important than generally assumed. Mass flow also caused the accumulation of Ca and Na in the root zone, especially that of rice. Accumulation of K in the root zone of rice did not cause K fixation, possibly due to an unknown K-releasing mechanism of upland rice. This revised version was published online in July 2006 with corrections to the Cover Date.     

复合菌剂调控连作当归根围土壤养分及对产量的影响

【背景】连作可引起微生物群落结构失调,导致土壤环境恶化、养分循环不畅、当归[Angelica sinensis (Oliv.) Diels]产量降低,通过现代微生物技术改良土壤、消减连作障碍势在必行。【目的】于大田条件下,研究施用复合菌剂对当归根围土壤酶活、速效养分及产量的影响,明确增产机制,改进增产措施。【方法】利用溶磷圈法检测不同菌株溶磷活性、乙炔还原法检测固氮活性、试剂盒法检测过氧化物酶和硝化能力;复合菌剂T1[荧光假单胞菌(Pseudomonas fluorescens)CBS5、产碱假单胞菌(Pseudomonas alcaligenes) CBS7、嗜冷假单胞菌(Pseudomonas extremaustralis)CBSB、生枝动胶菌(Zoogloea ramigera) CBS4]和T2 (荧光假单胞菌CBS5、产碱假单胞菌CBS7、嗜冷假单胞菌CBSB)及对照CK (无菌马铃薯葡萄糖肉汤培养基)分别处理连作当归,分光光度法测定根围土壤及根中养分循环、转化相关酶活,氮、磷、钾速效养分含量;常规方法测产量;统计软件进行相关数据方差分析和主成分分析。【结果】产碱假单胞菌C...     

拉杰沙希大学校园药用植物菌根研究

Forty different medicinal plants were investigated for arbuscular mycorrhizal association in the Rajshahi University Campus in Bangladesh. The results indicated that 35 different plants were infected by AM (arbuscular mycorrhizal) fungi as found by trypan blue staining procedure. The percentage of root colonization by AM fungi varied from 13.3% to 100%. Mangifera indica and Morus indica have maximum percentage of colonization (100%). The intensity of root colonization were abundant in the plants belonging to the families Anacardiaceae, Asclepiadaceae, Moraceae, Leguminosae and Apocynaceae whereas the intensity of colonization of crop roots were moderate and poor belonging to Gramineae and Leguminosae. The presence of greater number of spore in soil was always associated with the incidence of abundant mycelia. In plant roots the formation of spore and mycelia was restricted by low pH. Number of mycorrhizal fungus spores ranged between 35 to100 per 100g air dried soil in different family respective soils. The frequency of mycorrhizal fungus infection showed positive correlation with soil pH, moisture, water holding capacity, texture, total nitrogen, organic carbon, phosphorus, calcium, potassium, and magnesium. Especially phosphorus and nitrogen in the soil greatly influenced the plant root infection by AM fungi.     

Response of Douglas fir seedlings to phosphorus fertilization and influence of temperature on this response

Summary Effects of P fertilizers on growth of Douglas fir (Pseudotsuga menziesii var.menziesii (Mirb.) Franco.) seedlings were examined in pots and nursery beds. In pot experiments levels of P equivalent to 300 kg/ha were adequate for maximum growth over 14–18 weeks and resulted in available soil P levels of 80 ppm after 15 weeks' growth. Maximum growth in pots was obtained with shoot P concentrations of 0.18%–0.20%, with higher values at lower temperatures, but the optimum concentration for one-year old (1-0) nursery seedlings was 0.16% P. Growth of seedlings was greatly restricted at a soil temperature of 5°C and an air temperature of 12°C. At a soil temperature of 10°C and an air temperature of 14°C seedling P requirement was greater than at soil and air temperatures of 20°C.Comparison showed that monammonium phosphate was more effective than calcium superphosphate in stimulating growth in pots and nursery. Triple superphosphate was also effective in the nursery. Diammonium phosphate, potassium dihydrogen phosphate and phosphoric acid had no advantages as P sources in the nursery. Available P levels of 100–130 ppm, in the loamy sand and sandy loam nurseries studied, and needle P concentrations of 0.18%, when sampled in October, were associated with maximum growth of two-year old (2-0) seedlings.P fertilization decreased root/shoot ratio, but did not alter the allometric relationship of shoot to root. Improving P status from a low level increased root growth capacity in 2-0 seedlings and P fertilization of potted seedlings increased dry weight/height ratio. Uptakes per seed bed ha of 236 kg N, 31 kg P, 81 kg K and 73 kg Ca by 2-0 seedlings were comparable with, or greater than, uptake rates of agricultural crops. Recoveries of 6–11% of P from fertilizer were recorded in the nursery.     

夜间增温对冬小麦根系生长和土壤养分有效性的影响

气候变暖存在明显的昼夜不对称性,夜间气温升高幅度显著高于白天.本研究采用夜间被动式增温系统,于2009-2010年在我国冬小麦主产区（石家庄、徐州、许昌和镇江）进行全生育期田间增温试验,研究了土壤pH值、速效养分和抽穗期冬小麦根系对夜间增温的响应.结果表明： 与不增温对照相比,夜间增温显著降低了土壤pH值和速效养分含量,并在一定程度上提高了根系干质量和根冠比.冬小麦整个生育期,夜间增温分别使石家庄、徐州、许昌和镇江试验点土壤pH值平均降低0.4%、0.4%、0.7%和0.9%,碱解氮含量平均降低8.1%、8.1%、7.1%和6.0%,速效磷含量平均降低15.7%、12.1%、19.6%和25.8%;速效钾含量平均降低11.5%、7.6%、7.6%和10.1%.增温处理下,石家庄、徐州和镇江试验点抽穗期冬小麦根系干质量分别平均增加31.5%、27.0%和14.5%;石家庄、许昌和镇江试验点抽穗期冬小麦根冠比分别平均提高23.8%、13.7%和9.7%.夜间增温可能通过改变土壤化学特性影响土壤养分供应和冬小麦生长