Adsorption and exchange of Ca,Mg and K-ions on the root cell walls of clover and rye-grass

Summary The ion exchange properties of clover and rye-grass root cell walls were studied quantitatively. Three sets of experiments were performed: adsorption of Ca, Mg and K ions versus pH, adsorption versus cation concentration and exchange isotherms Ca–Mg and Mg–K. A model has been developed. It allows the satisfactory prediction of results (except for pH curves) with the adjustment of a minimum of parameters. The total charge (RT), on its own, accounts for the difference between the ion exchange properties of the clover and rye grass cell walls. The selectivities observed on root material are very different from those observed on soil exchange complexes. The decreasing affinities of cell walls for cations follow the sequence: Ca>MgK for cell walls. These differences of selectivity are much larger than those usually observed for soil exchange complexes.     

Effect of soil acidity and saturating cation on adsorption of urea in soil

Summary Elevating the pH of two extremely acid tropical soils from an initial pH of 4 to 5 with Ca(OH)₂ and NaOH solutions resulted in a sharp decrease in urea adsorption. Further increases in pH to 9 caused only slight further decrease in urea adsorption. Ca treatment resulted in slightly higher adsorption than Na treatment over the full range of pH values studied for a clay soil with high smectite content, and for a loam with kaolinite mineralogy below pH 7. Above pH 7 a kaolinitic loamy soil gave slightly higher adsorption with Na treatment than with Ca.     

Effects of forest clear-cutting on the sulphur, phosphorus and base cations fluxes through podzolic soil horizons

Clear-cutting considerably alters the flow of nutrients through the forest ecosystem. These changes are reflected in soil solution concentrations and fluxes. The effects of clear-cutting (stems only) on the fluxes of water soluble phosphorus (P), sulphur (S) and base cations (Ca, Mg and K) through a podzolic soil were studied in a Norway spruce dominated mixed boreal forest in eastern Finland. Bulk deposition, total throughfall (throughfall + stemflow) and soil percolate from below the organic (O), eluvial (E) and illuvial (B) horizons were collected for 4 years before and for 3 years after cutting. Annual deposition loads (kg ha^–1) to the forest floor were less after clear-cutting, averaging 1.7 S, 0.84 Ca, 0.14 Mg, 0.64 K and 0.10 P. Before cutting, the loads were 4.6 S, 2.7 Ca, 0.70 Mg, 6.2 K and 0.20 P. Annual fluxes of total S and sulphate (SO ₄ ^2– ) from below the O-horizon were also lower (33%) after clear-cutting, total S averaging 2.0 kg ha^–1, the flux from below the B-horizon also diminished after clear-cutting. The flux of total P (mainly inorganic) from below the O-horizon increased threefold (6.9 kg ha^–1; sum over the 3-year period) compared to period before cutting. The fluxes of base cations from below the O-horizon increased twofold. The flux of K⁺ from below the O- and E-horizons was most strongly correlated with that of phosphate (PO ₄ ^3– ) and those of Ca²⁺ and Mg²⁺ with the DOC flux. Increased fluxes of P and base cations to the mineral soil generated only slightly increased fluxes from below the B-horizon. The retention of base cations and P in the mineral soil indicates there was little change in leaching to ground and surface waters after clear-cutting.     

Content and deposition of major mineral elements in different tissues and empty body of growing bulls of the german simmental breed

54 bulls of the German Simmental breed were fed either on a high energy level (maize silage ad libitum and 1.8 kg concentrate) or on a low energy level (maize silage restrictively and 1.0 kg concentrate). In dependence on feeding intensity a mean daily weight gain of 870 or 1210 g was obtained. Animals were slaughtered with a live mass of 200 kg, 350 kg, 500 kg, 575 kg and 650 kg. Empty body was divided into 13 cuts and afterwards separated into lean, bone and adipose tissues and tendons. Major mineral element content was determined in these tissues as well as in the noncarcass parts.

In the lean tissue the mean content (200 kg) of 0.3 g calcium, 10 g phosphorus, 1 g magnesium, 2.3 g sodium and 14.8 g potassium/kg dry matter decreased slightly with rising live mass (200–650 kg). The contents of major mineral elements were much higher in bone tissue. For the fattening period from 200 to 650 kg of live mass mean contents of 151.5 g calcium, 71.3 g phosphorus, 3.2 g magnesium, 5.1 g sodium and 1.1 g potassium per kg DM were analysed. Mineral element content of bone tissue increased with rising live mass as well as animals on low feeding intensity showed a higher mineral content than on high energy level. In all, major mineral element content in fat tissue was very low. In noncarcass parts head and legs calcium and phosphorus had analogous to bone tissue the highest concentration. Hide showed a high content of sodium, whereas organs and digestive tract had a high content of potassium and phosphorus. Total mass of major mineral elements in the different tissues increased above all in the fattening period of 200 to 350 kg. In carcass as well as in empty body, mass of calcium and phosphorus was much higher than magnesium, sodium and potassium. Also animals on low feeding intensity showed a higher mass of major mineral elements in carcass and empty body than animals on high energy feeding intensity. The intensively fed bulls had a mean deposition of 12.7 g calcium, 6.9 g phosphorus, 0.37 g magnesium, 1.2 g sodium and 2.1 potassium per 1000 g of empty body weight gain, whereas restrictively fed bulls deposited in average 15.0 g calcium, 7.8 g phosphorus, 0.4 g magnesium, 1.2 g sodium and 2.4 g potassium per 1000 g of empty body weight gain.     

Influence of soil type and potassium and magnesium fertilization on the release of potassium and magnesium by electro-ultrafiltration and ammonium acetate-lactate extraction

Summary The effect of increasing potassium and magnesium fertilization during 15 years on the amounts of K and Mg extracted by AL-solution and desorbed by Electro-Ultrafiltration (EUF) was determined in four Swedish soils. In all soils, with increasing potassium fertilization the amounts of K extracted by AL and desorbed by EUF increased, and the amounts of Mg-AL and Mg-EUF decreased. Magnesium fertilization had no significant effect on the K values but increased both Mg-AL and Mg-EUF. The EUF-values were lower than the corresponding AL-values, but the ratio of EUF-desorbed to AL-extracted amounts of K and Mg varied depending on soil type as well as on fertilization rate. The ratio of K-EUF to K-AL increased and the ratio of Mg-EUF to Mg-AL decreased with increasing potassium fertilization, whereas magnesium fertilization decreased the ratio of Mg-EUF to Mg-AL.     

A cytochemical study on the role of ATPases during pollen germination in Agapanthus umbelatus L'Her.

Summary Cytochemical detection of ATPase activity in the pollen grain (PG) and pollen tube (PT) of Agapanthus umbelatus showed that the enzymes concerned presented specific patterns of membrane distribution according to their ionic dependencies and to the timecourse of germination and tube growth. In the pollen tubes Ca²⁺-ATPases were mainly localized in mitochondria and ER membranes, while Mg²⁺-ATPases were found especially in the tonoplast and in the membrane of the P-particles. K⁺-ATPases showed a high activity at the plasma membrane. In the pollen grain similar patterns of ATPase activity were observed. The highest activity of all three types was observed at the plasma membrane of the grain and at the intine and inner exine layers of the cell wall. The activity observed in the pollen grain cell wall decreased with germination time. In vivo germination studies in the presence of specific inhibitors of the ATPases showed patterns of inhibition that could be correlated with the corresponding ATPase putative role.The results are discussed in terms of the ultrastructural organization of the PG and PT, especially those correlated with (1) formation and maintenance of ionic gradients throughout the PT, (2) polarized growth and (3) hydrodynamics of PT elongation.Abbreviations PT Pollen tube - PG pollen grain - PTW pollentube wall - PGW pollen-grain wall - ER endoplasmic reticulum - NEM N-ethylmaleimide     

Dual transport properties of anion exchanger 1: the same transmembrane segment is involved in anion exchange and in a cation leak

Previous results suggested that specific point mutations in human anion exchanger 1 (AE1) convert the electroneutral anion exchanger into a monovalent cation conductance. In the present study, the transport site for anion exchange and for the cation leak has been studied by cysteine scanning mutagenesis and sulfhydryl reagent chemistry. Moreover, the role of some highly conserved amino acids within members of the SLC4 family to which AE1 belongs has been assessed in AE1 transport properties. The results suggest that the same transport site within the AE1 spanning domain is involved in anion exchange or in cation transport. A functioning mechanism for this transport site is proposed according to transport properties of the different studied point mutations of AE1.     

Characterization of a high-conductance,voltage-dependent cation channel from the plasma membrane of rye roots in planar lipid bilayers

Plasma-membrane vesicles were purified by aqueous-polymer two-phase partitioning of a microsomal membrane fraction from rye (Secale cereale L.) roots and incorporated into planar 1-palmitoyl-2-oleoyl phosphatidylethanolamine bilayers. A high-conductance cation channel (a maxi cation channel) was characterized from single-channel electrical recordings. The channel was incorporated into the bilayer with its cytoplasmic surface facing the trans compartment and voltages were referenced cis with respect to trans. The channel was permeable to both monovalent and divalent cations. The unitary conductance was 451 pS in symmetrical 100 mM KCl and 213 pS in symmetrical 100 mM BaCl₂. The permeability ratio P_KP_Ba was 1.002.56. Unitary conductances declined in the order K⁺Rb⁺>Cs⁺>Na⁺> Li⁺ (monovalent cations) and Ba²⁺>Sr²⁺>Ca²⁺> Mg²⁺>Co²⁺>Mn²⁺ (divalent cations). The relative permeabilities of monovalent cations mirrored their conductivity sequence, whereas the permeabilities of all divalent cations were similar. The maxi cation channel showed complex kinetics, exhibiting both voltage- and time-dependent inactivation and voltage-dependent gating. The voltage dependence of the kinetics shifted in parallel with changes in the reversal potential of the channel. In symmetrical 100 mM KCl, following a voltage step from zero to the test voltage, the channel inactivated and the active-channel lifetime ( _i) shortened exponentially as the test voltage was increased. The channel always opened immediately upon depolarization to zero volts, indicating that inactivation of the channel did not result from the loss of any intrinsic factor. The probability of finding an active channel in the open state (P₀) exhibited a bell-shaped relationship with membrane potential. At voltages between -40 and 80 mV, P₀ exceeded 0.99, but p₀ declined abruptly at more extreme voltages. Under ionic conditions which approximated physiological conditions, in the presence of 100 mM KCl on the trans (cytoplasmic) side and 1 mM KCl plus 2 mM CaCl₂ on the cis (extracellular) side, the reversal potential was 15.6 mV and the kinetics approximated those observed in symmetrical 100 mM KCl. Thus, the channel would open upon depolarization of the plasma membrane in vivo. If the channel functioned physiologically as a Ca²⁺ channel it might be involved in intracellular signalling: the channel could open in response to a variety of environmental, developmental and pathological stimuli which depolarize the plasma membrane, allowing Ca²⁺ into the cytoplasm and thereby initiating a physiological response.Abbreviations E_K Nernst (equilibrium) potential for potassium - E_rev zero-current (reversal) potential - I/V current/voltage - _c apparent mean lifetime of the activated-channel closed state - _i apparent mean lifetime of the activated channel following a voltage step from zero volts - ₀ apparent mean lifetime of the activated-channel open state - PE 1-palmitoyl-2-oleoyl phosphatidylethonlamine - P₀ probability of finding the activated channel in an open state - TEA⁺ tetraethylammonium This work was supported by the Agriculture and Food Research Council and by a grant from the Science and Engineering Research Council Membrane Initiative (GR/F 33971) to Prof. E.A.C. MacRobbie (University of Cambridge, UK).     

Effects of a soil fulvic acid on the growth and nutrient content of cucumber (Cucumis sativus) plants

Summary Cucumber (Cucumis sativus) plants were grown in Hoagland solution to which 20 to 2000 ppm of a soil fulvic acid (FA) were added. The addition of 100 to 300 ppm of FA produced highly significant increases in the growth and development of above and below ground plant parts, in the uptake of nutrient elements (N, P, K, Ca, Mg, Cu, Fe and Zn), and in the formation of numbers of flowers per plant. Effects of adding 500 and more ppm of FA were less beneficial.     

The possible role of hydrogen sulfide on the pathogenesis of spontaneous hypertension in rats

Hydrogen sulfide (H(2)S) is a newly found modulator in vascular system. This work showed that gene expression of cystathionine gamma-lyase (CSE), a H(2)S generating enzyme, and the activity of CSE in thoracic aorta were suppressed in hypertension rats. The plasma level of H(2)S also decreased in those rats. Exogenous administration of H(2)S could increase the plasma level of H(2)S and enhance the CSE activity of aorta. Exogenous administration of H(2)S also attenuated the elevation of pressure and lessened the aorta structural remodeling during the development of hypertension. In WKY rats, the gene expression and activity of CSE also decreased when the endogenous production of H(2)S was deprived by administration of DL-propargylglycine (specific inhibitor of CSE), accompanying the elevated pressure and the development of vascular remodeling. The results showed that endogenous H(2)S system was involved in both the maintenance of basal blood pressure and the development of hypertension. Exogenous H(2)S could exert beneficial effect on the pathogenesis of spontaneous hypertension.     

外源多胺对水稻萌发和前期生长的作用及其在土壤中的滞留

研究了不同浓度的多胺（尸胺、腐胺和亚精胺）对水稻种子萌发幼苗生长的化感作用结果表明．外源多肢对水稻种子萌发和幼苗生长均有抑制作用,尤其是对根的抑制,其作用程度依次为亚精胺＞腐胺＞尸胺,但是外源多胺能显著地提高水稻幼苗的抗冷性．使用灭菌土壤和用蒸馏水、Ｎａ２ＥＤＴＡ和盐酸水溶液浸取的实验结果表明,尸胺进入土壤后,大部分被土壤吸附和络合而滞留,少部分自由存于土壤中,在络合剂和酸存在下,尸胺可从土壤中解脱     

施用生物炭对华北平原农田土壤容重、阳离子交换量和颗粒有机质含量的影响

以华北平原高产农田3年定位试验为基础,研究了生物炭与矿质肥配施对土壤容重、阳离子交换量和颗粒有机质组分中碳、氮含量的影响.试验共设4个处理：单施氮磷钾肥（CK）;氮磷钾肥+2250 kg·hm^-2生物炭（C₁）;氮磷钾肥+4500 kg·hm^-2生物炭（C₂）;炭基缓释肥（750 kg·hm^-2,CN）.结果表明： 与CK相比,C₁和C₂处理显著降低了0～7.5 cm土层容重,降低幅度分别为4.5%和6.0%;施用生物炭增加了0～15 cm土层的阳离子交换量,其中C₂处理增加了24.5%;在0～7.5 cm土层,C₁处理土壤颗粒有机质组分中的碳、氮浓度较CK处理分别增加了250%和85%,C₂处理分别增加了260%和120%.施用生物炭3年后土壤理化特性得到明显改善,并在碳增汇和温室减排方面具有潜在积极效应.     

Huntingtin regulates Ca chemotaxis and K-facilitated cAMP chemotaxis,in conjunction with the monovalent cation/H exchanger Nhe1, in a model developmental system: Insights into its possible role in Huntington׳s disease

Huntington?s disease is a neurodegenerative disorder, attributable to an expanded trinucleotide repeat in the coding region of the human HTT gene, which encodes the protein huntingtin. These mutations lead to huntingtin fragment inclusions in the striatum of the brain. However, the exact function of normal huntingtin and the defect causing the disease remain obscure. Because there are indications that huntingtin plays a role in Ca²⁺ homeostasis, we studied the deletion mutant of the HTT ortholog in the model developmental system Dictyostelium discoideum, in which Ca²⁺ plays a role in receptor-regulated behavior related to the aggregation process that leads to multicellular morphogenesis. The D. discoideum htt⁻-mutant failed to undergo both K⁺-facilitated chemotaxis in spatial gradients of the major chemoattractant cAMP, and chemotaxis up a spatial gradient of Ca²⁺, but behaved normally in Ca²⁺-facilitated cAMP chemotaxis and Ca²⁺-dependent flow-directed motility. This was the same phenotypic profile of the null mutant of Nhel, a monovalent cation/H⁺exchanger. The htt⁻-mutant also failed to orient correctly during natural aggregation, as was the case for the Nhel mutant. Moreover, in a K⁺-based buffer the normal localization of actin was similarly defective in both htt⁻ and nhe1⁻ cells in a K⁺-based buffer, and the normal localization of Nhe1 was disrupted in the htt⁻ mutant. These observations demonstrate that Htt and Nhel play roles in the same specific cation-facilitated behaviors and that Nhel localization is directly or indirectly regulated by Htt. Similar cation-dependent behaviors and a similar relationship between Htt and Nhe1 have not been reported for mammalian neurons and deserves investigation, especially as it may relate to Huntington?s disease.     

Soil textural class plays a major role in evaluating the effects of land use on soil quality indicators

Inappropriate land use that negatively affects ecological processes and soil quality is generally considered to be the primary cause of soil degradation in tropical agroecosystems. We hypothesized that in addition to land use, soil textural class also has an important effect on ecological processes and soil quality. To test our hypothesis, effects of land use change on soil organic fractions as well as microbial and biochemical indicators were quantified for clayey and sandy-clay-loam soils within the native Cerrado biome, pasture (Brachiaria brizantha) and sugarcane (Saccharum officinarum) agroecosystems in southwestern Brazil (Minas Gerais state). Labile carbon, humic substances, soil microbial respiration (SMR), microbial biomass carbon (MBC), metabolic quotient (qCO₂), hydrolysis of fluorescein diacetate (FDA), beta-glucosidase, urease, phosphatase and arylsulphatase activities were measured for each sample. Labile carbon concentrations were not affected by land use but were lower in sandy-clay-loam soil than clayey soil. Humic substances were at the highest concentrations in the native Cerrado and the lowest in sugarcane agroecosystems. Sandy-clay-loam soil had lower humic acid concentrations than clayey soil. Soil microbial indicators (SMR, MBC and FDA) showed lower values in pasture and sugarcane agroecosystems than in the native Cerrado. FDA was a more sensitive microbial indicator than SMR and MBC for detecting land use and textural class differences. The qCO₂ indices were greater in sugarcane systems than in either pasture or native Cerrado systems. The activity of exocellular hydrolytic enzymes, such as beta-glucosidase, urease, phosphatase and arylsulphatase, was smaller in sugarcane and pasture agroecosystems than in native Cerrado ecosystems. Within the same land use, the activity of these enzymes was always greater in clayey soil than in sandy-clay-loam soil, indicating a higher impact of land uses on enzyme activities in clayey soils. Results for the measured indicators support the hypothesis that soil textural class plays a major role in assessing differences between land use systems in the Brazilian Cerrado biome.     

Use of a D-optimal design with constrains to quantify the effects of the mixture of sodium,potassium, calcium and magnesium chloride salts on the growth parameters of <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

The combined effect of NaCl, KCl, CaCl(2), and MgCl(2) on the water activity (a (w)) and the growth parameters of Saccharomyces cerevisiae was studied by means of a D-optimal mixture design with constrains (total salt concentrations < or = 9.0%, w/v). The a (w) was linearly related to the concentrations of the diverse salts; its decrease, by similar concentrations of salts, followed the order NaCl > CaCl(2) > KCl > MgCl(2), regardless of the reference concentrations used (total absence of salts or 5% NaCl). The equations that expressed the maximum specific growth (mu (max)), lag phase duration (lambda), and maximum population reached (N (max)) showed that the values of these parameters depended on linear effects and two-way interactions of the studied chloride salts. The mu (max) decreased as NaCl and CaCl(2) increased (regardless of the presence or not of previous NaCl); however, in the presence of a 5% NaCl, a further addition of KCl and MgCl(2) markedly increased mu (max). The lambda was mainly affected by MgCl(2) and the interactions NaCl x CaCl(2) and CaCl(2) x MgCl(2). The further addition of NaCl and CaCl(2) to a 5% NaCl medium increased the lag phase while KCl and MgCl(2) had negligible or slightly negative effect, respectively. N (max) was mainly affected by MgCl(2) and its interactions with NaCl, KCl, and CaCl(2); MgCl(2) stimulated N (max) in the presence of 5% NaCl while KCl, NaCl, and CaCl(2) had a progressive decreasing effect. These results can be of interest for the fermentation and preservation of vegetable products, and foods in general, in which this yeast could be present.     

Dual role of CO2/HCO3(-) buffer in the regulation of intracellular pH of three-dimensional tumor growths

Intracellular pH (pH(i)), a major modulator of cell function, is regulated by acid/base transport across membranes. Excess intracellular H(+) ions (e.g. produced by respiration) are extruded by transporters such as Na(+)/H(+) exchange, or neutralized by HCO(3)(-) taken up by carriers such as Na(+)-HCO(3)(-) cotransport. Using fluorescence pH(i) imaging, we show that cancer-derived cell lines (colorectal HCT116 and HT29, breast MDA-MB-468, pancreatic MiaPaca2, and cervical HeLa) extrude acid by H(+) efflux and HCO(3)(-) influx, largely sensitive to dimethylamiloride and 4,4'-diisothiocyanatostilbene-2,2'-disulfonate (DIDS), respectively. The magnitude of HCO(3)(-) influx was comparable among the cell lines and may represent a constitutive element of tumor pH(i) regulation. In contrast, H(+) efflux varied considerably (MDA-MB-468 > HCT116 > HT29 > MiaPaca2 > HeLa). When HCO(3)(-) flux was pharmacologically inhibited, acid extrusion in multicellular HT29 and HCT116 spheroids (～10,000 cells) was highly non-uniform and produced low pH(i) at the core. With depth, acid extrusion became relatively more DIDS-sensitive because the low extracellular pH at the spheroid core inhibits H(+) flux more than HCO(3)(-) flux. HCO(3)(-) flux inhibition also decelerated HCT116 spheroid growth. In the absence of CO(2)/HCO(3)(-), acid extrusion by H(+) flux in HCT116 and MDA-MB-468 spheroids became highly non-uniform and inadequate at the core. This is because H(+) transporters require extracellular mobile pH buffers, such as CO(2)/HCO(3)(-), to overcome low H(+) ion mobility and chaperone H(+) ions away from cells. CO(2)/HCO(3)(-) exerts a dual effect: as substrate for membrane-bound HCO(3)(-) transporters and as a mobile buffer for facilitating extracellular diffusion of H(+) ions extruded from cells. These processes can be augmented by carbonic anhydrase activity. We conclude that CO(2)/HCO(3)(-) is important for maintaining uniformly alkaline pH(i) in small, non-vascularized tumor growths and may be important for cancer disease progression.     

Studies on the behaviour and substratum preference in juveniles of the marine prawn,Metapenaeus monoceros (Fabricius)

Circadian rhythmicity in the behaviour of the marine prawn, Metapenaeus monoceros (Fab) and its substratum preference has been observed under laboratory conditions. In the morning at 9. a.m. 80% prawns remain buried and in the afternoon at 3 p.m. 60% burrowing was observed. A contrasting situation was observed in the night i.e. 17% burrowing at 9 p.m. and 30% burrowing at 3 a.m. was registered. In the second set of experiments juveniles were subjected to four types of substrata viz. mud, black fine sand, white coarse sand and stones. It was noted that M. monoceros showed more affinity towards the mud and less preference to other substrata. The obtained results are discussed to provide clues for prawn fishing.This work was supported by I.C.A.R., New Delhi through a project on Reprod. Endocr. Edible prawns.     

The effects of pH and calcium on the growth ofLeucaena leucocephala in an oxisol and ultisol soil

Leucaena was grown for eleven weeks in a pH and calcium amended oxisol and ultisol to determine whether poor growth in acid soils is related to calcium deficiency or low pH induced effects, such as aluminium toxicity. Soil pH was ameliorated by the addition of either CaCO₃, or SrCO₃, while CaCO₃ or Ca(NO₃)₂ were used to modify calcium supply. In both soils, CaCO₃, and SrCO₃ application resulted in an increase in pH and a reduction in exchangeable aluminium although the response of leucaena to the applied amendment varied between the two soils. In the oxisol there was little effect of increased pH on growth, but a marked response to Ca application. In the ultisol, growth was improved by increasing pH but there was no response to increased calcium. The effects of liming on these soils are discussed in relation to alternative strategies available for utilising leucaena and other tree legumes.     

Studies on the possible role of protein phosphorylation in the transduction of the ethylene signal

Previous work in our laboratory has demonstrated the existence of high affinity binding sites for the plant growth regulator ethylene. The ethylene binding protein (EBP), from Phaseolus cotyledons, shows many of the characteristics of a functional receptor for ethylene, has been purified on SDS-PAGE and polyclonal antibodies raised in rabbits. Current work involves the investigation of the ethylene transduction signal in a number of ethylene-responsive tissues.In peas, it has been shown that ethylene promotes the phosphorylation of specific proteins of similar molecular weight to the EBP from Phaseolus. Such ethylene-induced phosphorylation can be inhibited by the ethylene antagonist, 2,5-NBD. The antibodies raised to the EBP from Phaseolus have been shown to immunoprecipitate ³²P-labelled proteins from membrane protein preparations obtained from pea tissue. Studies on ethylene binding in pea have also shown that the binding of ethylene may be regulated by phosphorylation. Thus, under conditions which promote phosphorylation, binding is inhibited, whereas the reverse is true under conditions which enhance dephosphorylation.Further work is described which examines the effect of protein kinase, protein phosphatase and calcium channel inhibitors on ethylene-induced phosphorylation in peas, together with wild-type (WT) and ethylene insensitive (eti) mutants of Arabidopsis thaliana. The effects of these treatments can be monitored in vivo using the ethylene-induced triple response as a screen. Furthermore, the protein profiles of such treated seedlings can then be compared by labelling protein extracts with ³²P and subjecting the samples to SDS-PAGE followed by autoradiography.     

腾格里沙漠3种土壤有机质和碳酸钙特征

为了揭示干旱区成土碳酸钙的形成机制,在内蒙古阿拉善左旗境内的腾格里沙漠东缘,选择半固定风沙土上的油蒿群落、固定风沙土上的油蒿+冷蒿群落和淡棕钙土上的猫头刺群落为研究对象,3个样地面积均为80 m × 80 m,每个样地内含400个4 m × 4 m的样方,研究了沙丘固定过程中表层土壤碳酸钙与有机质的特征.研究结果表明,3个样地中,有机质的分布格局与碳酸钙的分布格局大体相同;土壤碳酸钙含量与土壤有机质含量均呈显著的正相关关系,且变化趋势相同;土壤碳酸钙空间异质性的变化与有机质空间异质性的变化具有一致性.这些结果说明土壤碳酸钙与土壤有机质之间存在一定的关联性,这同时说明在沙丘固定过程中土壤有机质可能参与了成土碳酸钙的形成.