Water chemistry and nutrient budgets in an undisturbed evergreen rainforest of southern Chile

In a pristine evergreen rainforest of Nothofagus betuloides, located at the Cordillera de los Andes in southern Chile (41 °S), concentrations and fluxes of nutrients in bulk precipitation, cloud water, throughfall water, stemflow water, soil infiltration and percolation water and runoff water were measured. The main objectives of this study were to investigate canopy-soil-atmosphere interactions and to calculate input-output budgets. From May 1999 till April 2000, the experimental watershed received 8121 mm water (86% incident precipitation, 14% cloud water), of which the canopy intercepted 16%. Runoff water volume amounted 9527 mm. Bulk deposition of inorganic (DIN) and organic (DON) nitrogen amounted 3.6 kg ha^–1 year^–1 and 8.2 kg ha^–1 year^–1 respectively. Occult deposition (clouds + fog) contributes for 40% to the atmospheric nitrogen input (bulk + occult deposition) of the forest. An important part of the atmospheric ammonium deposition is retained within the canopy or converted to nitrate or organic nitrogen by epiphytic bacteria or lichens. Also the export of inorganic (0.9 kg ha^–1 year^–1) and organic (5.2 kg ha^–1 year^–1) nitrogen via runoff is lower than the input to the forest floor via throughfall and stemflow water (3.2 kg DIN ha–1 year^–1 and 5.6 kg DON ha^–1 year^–1). The low concentrations of NO ₃ ^– and NH ₄ ⁺ under the rooting depth suggest an effective biological immobilization by vegetation and soil microflora. Dry deposition and foliar leaching of base cations (K⁺, Ca²⁺, Mg²⁺) was estimated using a canopy budget model. Bulk deposition accounted for about 50% of the total atmospheric input. Calculated dry and occult deposition are both of equal value (about 25%). Foliar leaching of K⁺, Ca²⁺, and Mg²⁺ accounted for 45%, 38% and 6% of throughfall deposition respectively. On an annual basis, the experimental watershed was a net source for Na⁺, Ca²⁺ and Mg²⁺.     

The effect of forest type on throughfall deposition and seepage flux: a review

Converting deciduous forests to coniferous plantations and vice versa causes environmental changes, but till now insight into the overall effect is lacking. This review, based on 38 case studies, aims to find out how coniferous and deciduous forests differ in terms of throughfall (+stemflow) deposition and seepage flux to groundwater. From the comparison of coniferous and deciduous stands at comparable sites, it can be inferred that deciduous forests receive less N and S via throughfall (+stemflow) deposition on the forest floor. In regions with relatively low open field deposition of atmospheric N (<10 kg N ha⁻¹ year⁻¹), lower NH₄⁺ mean throughfall (+stemflow) deposition was, however, reported under conifers compared to deciduous forest, while in regions with high atmospheric N pollution (>10 kg N ha⁻¹ year⁻¹), the opposite could be concluded. The higher the open field deposition of NH₄⁺, the bigger the difference between the coniferous and deciduous throughfall (+stemflow) deposition. Furthermore, it can be concluded that canopy exchange of K⁺, Ca²⁺ and Mg²⁺ is on average higher in deciduous stands. The significantly higher stand deposition flux of N and S in coniferous forests is reflected in a higher soil seepage flux of NO₃⁻, SO₄²⁻, K⁺, Ca²⁺, Mg²⁺ and Al(III). Considering a subset of papers for which all necessary data were available, a close relationship between throughfall (+stemflow) deposition and seepage was found for N, irrespective of the forest type, while this was not the case for S. This review shows that the higher input flux of N and S in coniferous forests clearly involves a higher seepage of NO₃⁻ and SO₄²⁻ and accompanying cations K⁺, Ca²⁺, Mg²⁺ and Al(III) into the groundwater, making this forest type more vulnerable to acidification and eutrophication compared to the deciduous forest type.     

Water and element input into native, agri- and silvicultural ecosystems of the Brazilian savanna

The interaction of rain water with the vegetation canopy results in changes of the water quantity and quality. We examined these canopy effects in different ecosystems of the Brazilian savanna, the Cerrado. The ecosystems were 20 yr-old Pinus caribaea Morelet plantations (PI), productive (PP) and degraded Brachiaria decumbens Stapf pastures (DP), continuous corn-soybean rotation (CC), and native typical cerrado (CE). We collected rainfall, throughfall, and, in PI and CE, stemflow from three plots of each ecosystem. Dry deposition and canopy leaching were estimated with a Na-tracer method. Between May 1997 and April 1999, the mean annual rainfall was 1656 mm of which 145 mm fell during the dry season (May–September). The throughfall percentage of the rainfall increased in the order, PI (75–85%) < CC (76–89%) < CE (89–100%) < PP (90–100%) < DP (99–100%); stemflow was < 1% of the rainfall. The volume-weighted mean (VWM) pH in rainfall was higher in the dry (6.5) than in the rainy season (5.4). The VWM pH in throughfall decreased in the order, CC (rainy season: 5.9/dry season: 6.2) > PP (5.5/6.0) > CE (5.2/6.0) > DP (5.2/5.6) > PI (4.8/5.7). The rainfall deposition of the dry season contributed one third of the annual element input with rainfall because of higher element concentrations than in the rainy season. The mean Na deposition ratios, i.e. the ratio of throughfall (+ stemflow) to rainfall deposition as a measure for dry deposition, increased in the order, CE (1.5) = CC (1.5) < PP (1.7) < PI (1.9) < (DP 2.1). Total deposition (rainfall + dry deposition) accounted for 104–164% of the K and Ca fertilizer application in PP and for 6.1–12% of the K, Ca, and Mg fertilizer application in CC. The P concentrations were below the detection limit of 0.2 mg L^–1 in all samples. Net canopy uptake, i.e. a smaller throughfall(+ stemflow) than rainfall + dry deposition, of Ca, K, Mg, S, Cu, and Zn in at least one of CE, PI, DP, and PP indicate that plant growth may be limited in part by these nutrients. During the vegetation period, between 28 and 50% of the applied K and Ca were leached from the canopy in PP and between 8.7 and 17% of the applied K, Ca, Mg, and S in CC. Our results demonstrate that PI causes larger water losses and enhanced acid inputs to the soil compared with all other ecosystems. However, the PI and pasture canopies scavenge more nutrients from the atmosphere than CE and CC.     

杨树人工林生态系统降水再分配及主要离子特征

大气降水是森林生态系统养分输入的主要途径之一,对养分的生物地球化学循环有着重要的意义。对13年生杨树人工林林外雨、树干流、林内雨和地表径流等水文过程中的养分特征进行了调查分析,旨在了解该生态系统的养分输入与输出规律,为杨树人工林可持续经营提供依据。结果表明,从2013年11月至2014年10月,杨树人工林生态系统林外雨量为1154.1 mm,树干流量仅占大气降水量的2.3%,15.4%的大气降水被杨树人工林的冠层截留;林内雨、树干流与大气降水量(林外雨)的动态变化规律相似。各类降水年加权平均pH值表现为林内雨林外雨树干流;各类降水的离子浓度动态变化规律基本一致,即在降水量较小的11月至次年1月份,各阴阳离子的浓度普遍较高,在降水量较大的2—9月份,阴阳离子浓度普遍较低。SO_4~(2-)-S和Ca~(2+)分别是各类降水中的主要阴离子和阳离子;整体上,树干流的离子浓度林内雨大气降水;林内雨是养分输入的主要形式,通过林内雨输入林地较多的养分离子是Ca~(2+)和K~+,分别为70.83 kg hm~(-2)a~(-1)和63.31 kg hm~(-2)a~(-1);地表径流和土壤渗漏是养分输出的主要形式,输出林地较多的离子是Cl~-和Ca~(2+),分别为196.47 kg hm~(-2)a~(-1)和123.09 kg hm~(-2)a~(-1),其次为SO_4~(2-)-S、Mg~(2+)、Na~+、K~+;NH_4~+-N和NO_3~--N的输出量不足输出离子总量的1%。所以,从水文过程看,杨树人工林生态系统无机氮(NH_4~+-N和NO_3~--N)和K~+表现为净积累,净积累量分别为10.9 kg hm~(-2)a~(-1)和56.4 kg hm~(-2)a~(-1),其他离子表现为净损失,其中Cl~-的净损失量达179.8 kg hm~(-2)a~(-1)左右,其他离子损失量50 kg hm~(-2)a~(-1)。     

黑河天涝池流域典型林分生态水文化学特征

采集了黑河天涝池流域典型林分林外雨、穿透雨、树干径流和枯透水,并检测水体pH值和12种离子(K~+、Ca~(2+)、Na~+、Mg~(2+)、NH_4~+、Cu~(2+)、Zn~(2+)、Pb~(2+)、Cd~(2+)、Cl~-、SO_4~(2-)、NO_3~3)的质量浓度。结果表明:天涝池流域大气降水pH均值为7.74,呈碱性,降水中离子绝对质量浓度较低,最高的是NO_3~-,质量浓度为1.1111 mg/L,最低的为Na~+,质量浓度为0.0108 mg/L;两种林分冠层有降低降雨pH值的作用,青海云杉林冠层对NH_4~+有升高作用,祁连圆柏林冠层对NH_4~+有降低作用,两种林冠层对NO_3~-和Cu~(2+)质量浓度有降低作用,对其它离子质量浓度均表现为升高作用;两种林分树干径流有提高穿透雨pH值的作用,与穿透雨相比,两种林分树干径流中阴离子均有升高,圆柏树干径流中所有阳离子质量浓度均有下降,云杉树干径流中Ca~(2+)、K~+、Mg~(2+)和Na~+减少,NH_4~+和Cu~(2+)增加;典型林分枯透水有提升穿透雨pH值的作用,与穿透雨相比,两种林分枯透水中阴离子质量浓度均有升高,云杉枯透水各阳离子均有降低,圆柏枯透水中Ca~(2+)、K~+和Mg~(2+)质量浓度升高,NH_4~+、Na~+和Cu~(2+)质量浓度下降;在采集的所有样本中,Pb~(2+)和Cd~(2+)均未检出,而Zn~(2+)仅在云杉树干径流中检出。     

Ca2+ pump and Ca2+/H+ antiporter in plasma membrane vesicles isolated by aqueous two-phase partitioning from corn leaves

Summary Plasma membrane vesicles, which are mostly right side-out, were isolated from corn leaves by aqueous two-phase partitioning method. Characteristics of Ca²⁺ transport were investigated after preparing inside-out vesicles by Triton X-100 treatment.⁴⁵Ca²⁺ transport was assayed by membrane filtration technique. Results showed that Ca²⁺ transport into the plasma membrane vesicles was Mg-ATP dependent. The active Ca²⁺ transport system had a high affinity for Ca²⁺(K _m (Ca²⁺)=0.4 m) and ATP(K _m (ATP)=3.9 m), and showed pH optimum at 7.5. ATP-dependent Ca²⁺ uptake in the plasma membrane vesicles was stimulated in the presence of Cl^– or NO ₃ ^– . Quenching of quinacrine fluorescence showed that these anions also induced H⁺ transport into the vesicles. The Ca²⁺ uptake stimulated by Cl^– was dependent on the activity of H⁺ transport into the vesicles. However, carbonylcyanidem-chlorophenylhydrazone (CCCP) and VO ₄ ^3– which is known to inhibit the H⁺ pump associated with the plasma membrane, canceled almost all of the Cl^–-stimulated Ca²⁺ uptake. Furthermore, artificially imposed pH gradient (acid inside) caused Ca²⁺ uptake into the vesicles. These results suggest that the Cl^–-stimulated Ca²⁺ uptake is caused by the efflux of H⁺ from the vesicles by the operation of Ca²⁺/H⁺ antiport system in the plasma membrane. In Cl^–-free medium, H⁺ transport into the vesicles scarcely occurred and the addition of CCCP caused only a slight inhibition of the active Ca²⁺ uptake into the vesicles. These results suggest that two Ca²⁺ transport systems are operating in the plasma membrane from corn leaves, i.e., one is an ATP-dependent active Ca²⁺ transport system (Ca²⁺ pump) and the other is a Ca²⁺/H⁺ antiport system. Little difference in characteristics of Ca²⁺ transport was observed between the plasma membranes isolated from etiolated and green corn leaves.     

Throughfall chemistry in a loblolly pine plantationunder elevated atmospheric CO2 concentrations

Accelerated tree growth under elevatedatmospheric CO₂ concentrations may influencenutrient cycling in forests by (i) increasingthe total leaf area, (ii) increasing the supplyof soluble carbohydrate in leaf tissue, and (iii) increasing nutrient-use efficiency. Here wereport the results of intensive sampling andlaboratory analyses of NH ₄ ⁺ , NO ₃ ^– , PO ₄ ^3– , H⁺, K⁺, Na⁺,Ca²⁺, Mg²⁺, Cl^–, SO ₄ ^2– , and dissolved organic carbon (DOC) in throughfallprecipitation during the first 2.5+ years of the DukeUniversity Free-Air CO₂ Enrichment (FACE)experiment. After two growing seasons, a largeincrease (i.e., 48%) in throughfall deposition of DOCand significant trends in throughfall volume and inthe deposition of NH ₄ ⁺ , NO ₃ ^– , H⁺, and K⁺ can be attributed to the elevatedCO₂ treatment. The substantial increase indeposition of DOC is most likely associated withincreased availability of soluble C in plant foliage,whereas accelerated canopy growth may account forsignificant trends toward decreasing throughfallvolume, decreasing deposition of NH ₄ ⁺ ,NO ₃ ^– , and H⁺, and increasing deposition of K⁺ under elevated CO₂. Despiteconsiderable year-to-year variability, there wereseasonal trends in net deposition of NO ₃ ^– ,H⁺, cations, and DOC associated with plant growthand leaf senescence. The altered chemical fluxes inthroughfall suggest that soil solution chemistry mayalso be substantially altered with continued increasesin atmospheric CO₂ concentrations in the future.     

Water chemistry and nutrient budgets in an undisturbed evergreen rainforest of Southern Chile

In a pristine evergreen rainforest of Nothofagus betuloides, located at the Cordillera de los Andes in southern Chile (41?°S), concentrations and fluxes of nutrients in bulk precipitation, cloud water, throughfall water, stemflow water, soil infiltration and percolation water and runoff water were measured. The main objectives of this study were to investigate canopy–soil–atmosphere interactions and to calculate input–output budgets. From May 1999 till April 2000, the experimental watershed received 8121?mm water (86% incident precipitation, 14% cloud water), of which the canopy intercepted 16%. Runoff water volume amounted 9527?mm. Bulk deposition of inorganic (DIN) and organic (DON) nitrogen amounted 3.6?kg?ha^?1?year^?1 and 8.2?kg?ha^?1?year^?1 respectively. Occult deposition (clouds?+?fog) contributes for 40% to the atmospheric nitrogen input (bulk?+?occult deposition) of the forest. An important part of the atmospheric ammonium deposition is retained within the canopy or converted to nitrate or organic nitrogen by epiphytic bacteria or lichens. Also the export of inorganic (0.9?kg?ha^?1?year^?1) and organic (5.2?kg?ha^?1?year^?1) nitrogen via runoff is lower than the input to the forest floor via throughfall and stemflow water (3.2?kg?DIN?ha^?1?year^?1 and 5.6?kg?DON?ha^?1?year^?1). The low concentrations of NO-₃ and NH+₄ under the rooting depth suggest an effective biological immobilization by vegetation and soil microflora. Dry deposition and foliar leaching of base cations (K⁺, Ca²⁺, Mg²⁺) was estimated using a canopy budget model. Bulk deposition accounted for about 50% of the total atmospheric input. Calculated dry and occult deposition are both of equal value (about 25%). Foliar leaching of K⁺, Ca²⁺, and Mg²⁺ accounted for 45%, 38% and 6% of throughfall deposition respectively. On an annual basis, the experimental watershed was a net source for Na⁺, Ca²⁺ and Mg²⁺.     

Composition and deposition of throughfall in a flooded forest archipelago

The sources of spatial and temporal variation and rates of nutrient deposition via throughfall were studied for 9 months in the Anavilhanas archipelago of the Negro River, Brazil. A total of 30 events was sampled individually for rain and throughfall chemistry in a 1-ha plot of flooded forest. Throughfall samples were collected in 40 collectors distributed in five parallel transects in the study plot, while rain was collected in 4 collectors in an adjacent channel. Volume-weighted mean (VWM) concentrations of solutes in rain were consistently lower than in throughfall, except for H⁺, NO ₃ ^– and NH ₄ ⁺ . Ratios of VWM concentrations of rain to throughfall indicated that K⁺, followed by Mg²⁺ and PO ₄ ^3– , were the most enhanced solutes as rain passed through the forest canopy. The deposition of solutes varied significantly among transects, except for Na⁺ and Ca²⁺, and was significantly correlated with maximum flooding depth, foliar nutrient content, soil fertility and canopy closure for most solutes. The concentrations of PO ₄ ^3– and most major ions were higher in throughfall compared to those in rain due to canopy exchange and dry deposition. In contrast, NO ₃ ^– , NH ₄ ⁺ and H⁺ were retained due to immobilization by leafy canopy and ion exchange processes. Solute inputs via throughfall (not including stemflow) to a floodplain lake (Lake Prato) of the archipelago accounted for 30 to 64% of the total for most solutes in the lake at high water, which indicates that throughfall is an important source of nutrients to the aquatic ecosystem of the Anavilhanas archipelago.     

Paramecium Na+ channels activated by Ca2+-calmodulin: Calmodulin is the Ca2+ sensor in the channel gating mechanism

Paramecium Na⁺ channels, which were Ca²⁺-calmodulin activated, were studied in the inside-out mode of patch clamp. After excision of the membrane patch, they were active in the presence of 10^–5 to 10^–3 m Ca²⁺ in the bath. They became much less active in the presence of 10^–6 m Ca²⁺, and their activity subsided completely at 10^–8 m Ca²⁺. A Hill plot showed a dissociation constant of 6 m for Ca²⁺ binding. This dissociation constant shifted to a submicromolar range in the presence of 1 mm Mg²⁺. The channels also exhibited a mild voltage dependence. When exposed to 10^–8 m Ca²⁺ for an extended period of 2–4 min, channels were further inactivated even after bath Ca²⁺ was restored to 10^–4 m. Whereas neither high voltage (+100 mV) nor high Ca²⁺ (10^–3 m) was effective in reactivation of the inactive channels, addition of Paramecium wild-type calmodulin together with high Ca²⁺ to the bath restored channel activity without a requirement of additional Mg²⁺ and metabolites such as ATP. The channels reactivated by calmodulin had the same ion conductance, ion selectivity and Ca²⁺ sensitivity as those prior to inactivation. These inactivation and reactivation of the channels could be repeated, indicating that the direct calmodulin effect on the Na⁺ channel was reversible. Thus, calmodulin is a physiological factor critically required for Na⁺ channel activation, and is the Ca²⁺ sensor of the Na⁺-channel gating machinery.We thank C. Kung for his kind support, and A. Boileau for critical reading. Supported by grants from National Institutes of Health GM 22714-20 and 36386-09.     

The chemical composition of throughfall beneath oak, birch and pine canopies in Northwest Germany

The chemical composition of rainwater is altered upon its passage through tree canopies. In order to investigate how rainwater chemistry is affected by canopy-dependent processes in characteristic forest types of Northwest German sandy lowland regions – oak–birch-forests, Betula pubescens Ehrh. swamp forests, and stands of Pinus sylvestris L. – comparative studies on the chemical composition of throughfall were carried out at seven forest sites, situated in close proximity within a nature reserve. Additionally, rainwater was sampled at three heathland sites for analysis of open-field precipitation and at three sites along an oak–birch-forest edge. Throughfall concentrations of most of the parameters analysed were significantly higher than open-field concentrations, especially with regard to electric conductivity, NH₄-N, K⁺, and KMnO₄-index. Ion concentrations in throughfall were the lowest in a 10-year-old stand of Betula pendula Roth. and Pinus sylvestris and in a Betula pubescens swamp forest and were highest beneath a stand of Pinus sylvestris. Except for Na⁺, Cl⁻, and NO₃⁻, ion concentrations in both throughfall and open-field precipitation increased during the growing season (May–October). In throughfall, Ca²⁺, Mg²⁺, K⁺, and Mn²⁺ were strongly correlated. Enrichment ratios between throughfall and open-field deposition varied among sites and elements and were the highest for K^‰+, Mg^2‰+, and Mn^2‰+. Estimates of canopy leaching indicated high leaching rates of K^‰+ and Mn^2‰+ and moderate leaching of Mg^2‰+. The contribution of foliar leaching to throughfall deposition was higher at the deciduous than at the coniferous stands.     

Rainfall partitioning and related hydrochemical fluxes in a diverse and in a mono specific (Phenakospermum guyannense) secondary vegetation stand in eastern Amazonia

Rainfall partitioning into throughfall and stemflow was studied in a diverse and in a mono specific stand of secondary vegetation in Eastern Amazonia. The nutrient concentrations in the water were analysed in order to quantify the related hydrochemical fluxes. Secondary vegetation forms the fallow in the local shifting cultivation system and is usually dominated by shrubs and trees. Phenakospermum guyannense (Strelitziaceae), a banana-like herb, is one of the predominant non-woody species. The study was conducted during an 18-month period in a 2.5-year-old relatively species-rich stand and a 10-year-old stand dominated by P. guyannense. In a year with 1956 mm of rainfall 65% (1281 mm) of this quantity reached the soil as throughfall in the diverse stand and 38% (743 mm) in the mono specific stand. Stemflow was estimated to be 23% and 41% respectively. P. guyannense and Banara guianensis (Flacourtiaceae), a tree species, were causing these high funnelling effects. In the young diverse stand B. guianensis had a stemflow of more than 200 l year⁻¹ and P. guyannense had a median flux of 77 l year⁻¹ per pseudostem. In the older stand the taller plants of P.␣guyannense collected 644 l year⁻¹ per pseudostem on the median. The reason for these high values could be the banana-like growth form of P. guyannense and the crown morphology of B. guianensis, which has inclined branches. The low proportion of throughfall and the high stemflow values differ from all previous studies in Amazonian primary forests. The proximity to the Atlantic Ocean strongly influenced the nutrient fluxes via rainfall at our study site. This becomes obvious from the high Na and Cl fluxes with rainfall (19.7 kg Na ha⁻¹ year⁻¹, 37.2 kg Cl ha⁻¹ year⁻¹) which were approximately equal to the Na and Cl fluxes with the sum of throughfall and stemflow for both stands. K fluxes in throughfall and stemflow in both stands were higher than in rainfall by a factor of 8. The high K enrichment during the crown passage is assumed to be caused by a␣high K concentration in the leaf tissue resulting in enhanced leaching from the leaves. In months with low␣rainfall the concentrations of Ca, Mg, S and Cl in throughfall of the diverse stand were significantly higher than in months with high rainfall. This was mainly due to vegetation burns in the dry period, which resulted in ash deposition on the canopy and subsequent wash-off and solution of ash particles. Received: 11 May 1997 / Accepted: 2 November 1997     

Do storm synoptic patterns affect biogeochemical fluxes from temperate deciduous forest canopies?

The volumetric quantity and biogeochemical quality of throughfall and stemflow in forested ecosystems are influenced by biological characteristics as well environmental and storm meteorological conditions. Previous attempts at connecting forest water and nutrient cycles to storm characteristics have focused on individual meteorological variables, but we propose a unified approach by examining the storm system in its entirety. In this study, we use methods from synoptic climatology to distinguish sub-canopy biogeochemical fluxes between storm events to understand the response of forest ecosystems to daily weather patterns. For solute inputs tied to atmospheric deposition (NH₄ ⁺, NO₃ ^?, SO₄ ^2?, Na⁺, Cl^?), stagnant air masses resulted in high inputs in rainfall (273.42, 81.81, 52.30, 156.99, 128.70 μmol L^?1), throughfall (355.05, 130.66, 83.24, 239.55, 261.32 μmol L^?1), and stemflow (338.34, 182.75, 153.74, 125.75, 272.88 μmol L^?1). For inputs tied to canopy exchange (DOC, K⁺, Ca²⁺, Mg²⁺), a clear distinction was observed between throughfall and stemflow pathways. The largest throughfall concentrations were in the Great Lakes Low (1794.80, 352.96, 72.75, 74.37 μmol L^?1) while the largest stemflow concentrations were in the Weak Upper Trough (3681.78, 497.34, 82.36, 72.46 μmol L^?1). Stemflow leaching is likely derived from a larger reservoir of leachable cations in the tree canopy than throughfall, with stemflow fluxes maximized during synoptic types with greater rainfall amounts and throughfall fluxes diluted. For flux-based enrichment ratios, water volume, storm magnitude, antecedent dry period, and seasonality were important factors, further illustrating the influence of synoptic characteristics on wash-off, leaching and, ultimately, dilution processes within the canopy.     

Reduced external calcium or sodium stimulates calcium influx in Pelvetia eggs

The effect of external calcium and sodium ion concentrations on the calcium fluxes on the Pelvetia fastigiata De Toni egg was measured. Decreasing external [Ca²⁺] greatly increased the permeability of the eggs to Ca²⁺; at 1 mM external Ca²⁺ this permeability was 60 times as great as it was at the normal [Ca²⁺] of 10 mM. Lowering the external [Na⁺] also increased Ca²⁺ influx; at 2 mM Na⁺, the Ca²⁺ influx was 2–3 times as great as it was at the normal [Na⁺] if choline was used as a Na⁺ substitute. Lithium was less effective as a Na⁺ substitute in increasing Ca²⁺ influx. The extra Ca²⁺ influx in low [Na⁺] seemed to be dependent on internal [Na⁺]. The Ca²⁺ efflux increased transiently and then declined in low Na⁺ media.     

Calcium absorption by fish intestine: The involvement of ATP-and sodium-dependent calcium extrusion mechanisms

Summary Measurements of unidirectional calcium fluxes in stripped intestinal epithelium of the tilapia,Oreochromis mossambicus, in the presence of ouabain or in the absence of sodium indicated that calcium absorption via the fish intestine is sodium dependent. Active Ca²⁺ transport mechanisms in the enterocyte plasma membrane were analyzed. The maximum capacity of the ATP-dependent Ca²⁺ pump (V _m :0.63 nmol·min^–1 mg^–1,K _m : 27nm Ca²⁺) is calculated to be 2.17 nmol·min^–1·mg^–1, correcting for 29% inside-out oriented vesicles in the membrane preparation. The maximum capacity of the Na⁺/Ca²⁺ exchanger with high affinity for Ca²⁺ (V _m :7.2 nmol·min^–1·mg^–1,K _m : 181nm Ca²⁺) is calculated to be 13.6 nmol·min^–1·mg^–1, correcting for 53% resealed vesicles and assuming symmetrical behavior of the Na⁺/Ca²⁺ exchanger. The high affinity for Ca²⁺ and the sixfold higher capacity of the exchanger compared to the ATPase suggest strongly that the Na⁺/Ca²⁺ exchanger will contribute substantially to Ca²⁺ extrusion in the fish enterocyte. Further evidence for an important contribution of Na⁺/Ca²⁺ exchange to Ca²⁺ extrusion was obtained from studies in which the simultaneous operation of ATP-and Na⁺-gradient-driven Ca²⁺ pumps in inside-out vesicles was evaluated. The fish enterocyte appears to present a model for a Ca²⁺ transporting cell, in which Na⁺/Ca²⁺ exchange activity with high affinity for Ca²⁺ extrudes Ca²⁺ from the cell.     

Elevation of Different Ion-Specific ATPase Activities by L-Thyroxine (T4) in Different Tissues of Tasar Silkworm, Antheraea mylitta (Lepidoptera: Saturniidae) during Developmental Stages

Tissue-specific age-dependent changes were observed in Na⁺K⁺-, Ca²⁺-, and Mg²⁺-ATPase activities in tropical tasar silkworm, Antheraea mylitta Drury. Maximum enzyme activity was recorded in all the tissues on day 12 (before spinning) in control group of animals. In testis, Na⁺K⁺-, Ca²⁺-, and Mg²⁺-ATPase activities gradually increased from day 2 to day 12 during fifth larval age and level was maintained up to adult eclosion while, in ovary, a marked decline was noted up to day of adult emergence. Further, a significant and sharp rise was found in ATPase activity in silk gland tissue up to day 12 and afterwards a drastic fall was noted on day 15 (end of spinning) during fifth larval age.Administration of T4 to fifth stage larvae (1 hr old) at doses 0.5–2.0 μg/g significantly elevated the Na⁺K⁺-, Ca²⁺-, and Mg²⁺-ATPase activities in larval and pupal gonads in a dose-dependent fashion. But, in moths, the enhancement was very much confined to Na⁺K⁺- and Ca²⁺-ATPase in testes and only Ca²⁺-ATPase in ovaries. Again, in silk glands thyroxine (0.5–2.0 μg/g) caused a significant rise in the all ion-dependent ATPase activities only during the fifth larval stage. Interestingly, higher doses of T4 (4.0 μg/g) caused a significant reduction in Na⁺K⁺-, Ca²⁺- and Mg²⁺-ATPase in all the tissues almost all the days studied so far. However, lower doses of T4 (0.1 and 0.25 μg/g) remained ineffective in altering the different ion-specific ATPase activities. This study suggests, that mammalian thyroxine has a metabolic influence showing biphasic nature of action in tasar silkworm ATPase system.     

Identification of the cardiac sarcolemmal Na+−Ca2+ exchanger using monoclonal antibodies

Summary We have previously partially purified the sarcolemmal Na⁺–Ca²⁺ exchange protein and produced rabbit polyclonal antibodies to the exchanger (Philipson, K. D., Longoni, S., Ward, R. 1988.Biochim. Biophys.Acta 945:298–306). We now describe the generation of three stable murine hybridoma lines which secrete monoclonal antibodies (MAb's) to the exchanger. These MAb's immunoprecipitate 50–75% of solubilized Na⁺–Ca²⁺ exchange activity. The MAb's appear to be reactive with native conformation-dependent expitopes on the Na⁺–Ca²⁺ exchanger since they do not react on immunoblots. An indirect method was used to identify Na⁺–Ca²⁺ exchange proteins. A column containing Na⁺–Ca²⁺ exchanger immobilized by MAb's was used to affinity purify the rabbit polyclonal antibody. The affinity-purified polyclonal antibody reacted with proteinsof, apparent molecular weights of 70, 120, and 160 kDa on immunoblots of sarcolemma. The data provide strong support for our prevous association of Na⁺–Ca²⁺ exchange with these proteins.     

Analysis of the Ca2+ domain in the Arabidopsis H+/Ca2+ antiporters CAX1 and CAX3

Ca²⁺ levels in plants are controlled in part by H⁺/Ca²⁺ exchangers. Structure/function analysis of the Arabidopsis H⁺/cation exchanger, CAX1, revealed that a nine amino acid region (87–95) is involved in CAX1-mediated Ca²⁺ specificity. CAX3 is 77% identical (93% similar) to CAX1, and when expressed in yeast, localizes to the vacuole but does not suppress yeast mutants defective in vacuolar Ca²⁺ transport. Transgenic tobacco plants expressing CAX3 containing the 9 amino acid Ca²⁺ domain (Cad) from CAX1 (CAX3-9) displayed altered stress sensitivities similar to CAX1-expressing plants, whereas CAX3-9-expressing plants did not have any altered stress sensitivities. A single leucine-to-isoleucine change at position 87 (CAX3-I) within the Cad of CAX3 allows this protein to weakly transport Ca²⁺ in yeast (less than 10% of CAX1). Site-directed mutagenesis of the leucine in the CAX3 Cad demonstrated that no amino acid change tested could confer more activity than CAX3-I. Transport studies in yeast demonstrated that the first three amino acids of the CAX1 Cad could confer twice the Ca²⁺ transport capability compared to CAX3-I. The entire Cad of CAX3 (87–95) inserted into CAX1 abolishes CAX1-mediated Ca²⁺ transport. However, single, double, or triple amino acid replacements within the native CAX1 Cad did not block CAX1 mediated Ca²⁺ transport. Together these findings suggest that other domains within CAX1 and CAX3 influence Ca²⁺ transport. This study has implications for the ability to engineer CAX-mediated transport in plants by manipulating Cad residues.     

Salinity induced differences in growth,ion distribution and partitioning in barley between the cultivar Maythorpe and its derived mutant Golden Promise

Dry matter changes and ion partitioning in two near isogenic barley cultivars Maythorpe (relatively salt sensitive) and Golden Promise (relatively salt tolerant) were studied in response to increasing salinity. Although the growth of both cultivars was significantly reduced by exposure to NaCl, the effect was greater in Maythorpe, whilst Golden Promise maintained an increased ratio of young to old leaf blade. Golden Promise maintained significantly lower Na⁺ concentrations in young expanding tissues compared with Maythorpe. Partitioning of Cl^– was evident in that both varieties maintained lower Cl^– concentrations in mesophyll than in epidermal cells. Golden Promise maintained higher K⁺/Na⁺ and Ca²⁺/Na⁺ ratios in young leaf blade and young sheath tissues than Maythorpe when exposed to salt. Differences in ion partitioning and the maintenance of higher K⁺ and Ca²⁺ to Na⁺ ratios, especially in young growing and recently expanded tissues, would appear to be important mechanisms contributing to the improved salt tolerance of Golden Promise.     

Epidermal solute concentrations and osmolality in barley leaves studied at the single-cell level

The solute relations of the upper epidermis of the third leaf of barley (Hordeum vulgare L. cv. Klaxon) were studied by analysing vacuolar saps extracted from individual cells. Their osmolality (nanolitre osmometry) and the concentrations of K, Na, Ca, Cl, P, S (energy dispersive X-ray analysis) and NO ₃ ^– (microfluorometry) were measured. All of the osmotically important solutes were accounted for. These were K⁺, NO ₃ ^– , Cl^–, and Ca²⁺. The concentration of each solute varied along the leaf blade and changed with leaf age. Calcium in particular increased during leaf ageing, exceeding concentrations of 50 mM. Plants starved of Ca²⁺ during this period accumulated epidermal K⁺ instead of Ca²⁺. Leaf ageing was accompanied by an increase in epidermal osmolalities by about 100 mosmol · kg^–1. When compared to the bulk leaf extract, epidermal cell extracts exhibited significantly higher concentrations of NO ₃ ^– , Cl^– and Ca²⁺, similar concentrations of K⁺ and Na⁺, and lower concentrations of P. In plants subjected to various levels of NaCl stress (up to 200 mM), epidermal concentrations of Cl^– always exceeded those of the bulk extract, while Na⁺ concentrations were similar. Epidermal cells osmotically adjusted to the increase in the external salt concentration.Abbreviations EDX analysis energy dispersive X-ray analysis We wish to thank Paul Richardson, Jeremy Pritchard, Peter Hinde, Eirion Owen and Andrew Davies (Banger) for their helpfull discussion and technical advice. This work was financed by a grant (UR5/ 521) from the Agricultural and Food Research Council.