Ca Nutrition Research Articles

478 Preharvest Calcium Application and Its Benefit on Vase Life of Lupinus havardii Watts Cut Flowers

Lupinus havardii has gained popularity as a potentially new and unique cut flower species, but its compound, ethylene-sensitive inflorescences (racemes) undergo rapid senescence and deterioration on cutting. The purpose of this study was to evaluate the influence of Ca culture solution applications on L. havardii cut-flower longevity. Four supplemental Ca treatments were incorporated into the nutrient solution (0, 2.5, 5.0, and 10.0 mM Ca using CaCl2), with four replications in a randomized complete-block design. Raceme Ca concentration increased with increasing Ca application, ranging from a low 5300 mg·kg-1 dry weight (0 mM supplemental Ca) to a high of 7500 mg·kg-1 (10.0 mM supplemental Ca). Calcium application deferred the daily loss in raceme fresh weight (FW) for up to 10 days of vase life in a concentration-dependent manner (P < 0.01), with the effect most pronounced between 5 and 9 days following cutting (average FW of 72% and 83% of day zero values for the control and 10.0 mM Ca, respectively, with 2.5 and 5.0 mM treatments intermediate). The cut racemes of L. havardii are model organs for spatially and sequentially organized postharvest development, with continued, 6-day postcutting life including 4-fold increases in cell permeability of basal, most mature flowers, marginal but significant increases in cell permeability of the most recently expanded flowers, and a 50% increase in total flowers number resulting from inflorescence expansion. Preliminary data indicate that manipulation of Ca nutrition may be a viable, inexpensive, and environmentally safe alternative to silver-based compounds currently in use for the vase life extension of L. havardii inflorescences.

Manganese and calcium nutrition of Pinus sylvestris and Pinus nigra from two different origins. II. Calcium

Summary Seedlings of Scots pine (Pinus sylvestris L.) of Greek and British origins and of black pine of Greek origin (Pinus nigra var. nigricans Host.) and Corsican pine (Pinus nigra var. maritima (Ait.) Melville) from seed collected in Britain were used to establish the growth response to both increasing levels of Ca supply in nutrient solution and to varying levels of Ca and Mn supply. Solution and tissue calcium requirements of all growth components of the pines were assessed. Maximum growth for Scots pine from British and Greek origins and for black pine from British origin were obtained at foliage Ca concentration ranges of 0.34‐1.00, 0.43‐0.87 and 0.30‐0.73 per cent respectively whereas for black pine from Greek origin no upper limit was obtained but the lower limit was 0.27 per cent. The Greek derived pines, in particular the black pine, showed higher tolerance to low and high calcium availability than the British ones. It is postulated that the difference between Greek and British pines in Ca nutrition reflects the differing dominant soil characteristics between the two countries.

Yield and nitrogen uptake of peanuts as affected by lime, cobalt, and molybdenum

Peanut response to lime has been associated to calcium (Ca) nutrition, but a higher nitrogen (N) Uptake has been observed in limed plots probably due to an increase in molybdenum (Mo) availability. A two‐year experiment was conducted to study the effects of Mo, cobalt (Co), and liming on peanut yields and N nutrition. Peanut seeds were treated with Mo and/or Co and grown in soil with base saturation about 13, 41, 57, and 71%. There was no effect of seed treatment with Co on peanut yields or N nutrition. Liming and Mo application increased N contents in the leaves. Nitrogen uptake was increased by Mo and liming in cv. Tatu and only by liming in cv. Tupã. Manganese (Mn) contents in the leaves were decreased by liming. The higher yields were observed when the Ca/Mn ratio in the leaves was above 25. In acid soils, low availability of Mo and Mn toxicity can impair N acquisition by peanut plants and decrease grain yields.

Dissolution Rate of Fluor-Apatite Crystals Inserted in Acid Soils of a Forested Catchment (Vosges Mountains, NE France)

In the Strengbach catchment (Vosges Mountain, NE France), the Ca and Mg nutrition of spruce and beech stands is very poor. Water and mineral fluxes through beech and spruce stands have been monitored at these sites since 1987. Ca supply is limited because its amount in the granite bedrock (CaO = 0.15-0.30 wt.%), in the bulk soil (CaO = 0.01-0.30 wt.%) and on the cation exchange capacity (CaO = 0.01-0.3 creole kg -1) is very low. Total and exchangeable Ca in the fine earth (< 2mm) of the layer soil (0-120 cm) is respectively about 8.4-9.6 t.ha -1 and 130-140 kg ha l . The rate of calcium release by weathering of soil primary minerals has been computed from detailed quantitative mineralogical data and mineral fluxes monitored at these two sites using steady state soil chemistry model PROFILE (Sverdrup and Warfvinge; 1993). Obtained values were extremely low (0.1-1.2 kg ha i yr l ) (Fichter et al., 1998a). Ca-bearing minerals in soils are albite and apatite. Although, apatite is the trace mineral in soil, Ca is principally located in this mineral because Ca content in albite is very low (CAO:0.45-0.53 wt.%) (Fichter et al., 1998b). Only few data of fluorapatite dissolution rate of fluor-apatite were published. In the aim to determinate the dissolution rate of fluor-apatite in these soils, the mineral test technique was used.

Effect of Calcium Nutrition on Disease Development and Latent Infection of Bacterial Wilt in Grafted Tomato Seedlings

To control bacterial wilt of tomato, grafting with resistant rootstocks widely prevails in Japan, but the disease has recently occurred even on grafted plants. Concerning this breakdown of resistance, the experiments were conducted to investigate the effect of Ca nutrition on disease development and latent infection of bacterial wilt in grafted tomato seedlings. Three levels of Ca (0.4, 4.4, or 20.4 mm) in a nutrient solution were applied to grafted seedlings (scion: `Momotarou', resistant rootstock: `Hawaii 7998') grown in a phytotron. One week after the Ca treatment, seedlings were inoculated with a 108 cfu/ml suspension of Ralstonia solanacearum by a stem puncture at the basal stem of the rootstock. The disease incidence was recorded for 21 days. In a second experiment, xylem exudates were collected from decapitated scions of the Ca-treated seedlings 5 days after inoculation. Populations of the pathogen in the exudates were counted by plating on a selective medium. Colonies isolated were reinoculated to susceptible seedlings to check the virulence. The high Ca treatment increased leaf and stem Ca contents, and significantly reduced the disease incidence. While Ca concentrations in the xylem exudates increased with the high Ca treatment, the populations of the pathogen in the exudates were high (&gt;109 cfu/ml) even at the high Ca treatment. All the colonies isolated were virulent. These results showed that grafted tomato seedlings treated with a high Ca concentration were highly resistant to bacterial wilt, but latently infected.

Fungus incidence on peanut grains as affected by drying method and Ca nutrition

An experiment was conducted to study the effects of liming and drying method on Ca nutrition, fungus infection and aflatoxin production potential on peanut ( Arachis hypogea) grains. Peanut cv. Botutatu was grown in the absence or presence of liming to raise the base saturation of the soil from 20 to 56%. Calcium contents of the soil were increased from 5.5 to 14.6 mmol (c)kg −1 and pH from 4.2 to 4.9. After harvest, plants and pods were dried in (1) shade, (2) field down to 100 g water kg −1, (3) field down to 250 g water kg −1 and transferred to a forced-air oven at 30°C, (4) field down to 360 g water kg −1 and transferred to a forced-air oven at 30°C. Calcium contents were analyzed in the grains, pericarps and seed coats. The incidence of Aspergillus spp., Penicillium spp., Rhizopus spp. and potential aflatoxin production in vitro were evaluated, as well as the seed coat thickness. The seed coat was thicker when peanut was grown in the presence of lime, leading to a decrease in seed infection by Aspergillus spp. and Penicillium spp. When plants were dried in shade, the growth of aflatoxinogenic fungi was independent of liming. However, in plants dried in the field or field + oven, the development of these fungi was decreased and even suppressed when the Ca content of the seed coat was increased from 2.2 to 5.5 g kg −1.

EPIDEMIOLOGY OF PEPPER STIP

Pepper stip is a physiological disorder manifested as gray-brown to greenish spots occurring on fruit of bell, pimento, Anaheim, and other types of peppers, most noticeably on red fruit produced under fall conditions. The spots, ≈0.5 cm in diameter, occur singly or in groups; marketability for either fresh market or processing use is severely affected. The factors controlling the occurrence or severity of the disorder are not well understood; to date, control has been achieved primarily by the use of resistant cultivars. In 1995 replicated plots of susceptible (`Yolo Wonder L' and `Grande Rio') and resistant (`Galaxy' and `King Arthur') cultivars were grown in seven commercial fields in central California. `Galaxy' and `King Arthur' were essentially free of symptoms, while `Yolo Wonder L' and `Grande Rio' showed significant damage at all sites, with 23% to 88% of fruits affected at the mature-red stage. Petiole tissue analysis showed that resistant cultivars consistently had lower N and K, and higher Ca concentrations than susceptible cultivars; the same trend was apparent in fruit tissue. Stip was most severe at sites with low soil Ca and/or very high N and K fertilization rates. It is hypothesized that Ca nutrition significantly influences stip expression.

Effects of Calcium on Yield and Incidence of Blossom-end Rot of Three Tomato Cultivars

An experiment was conducted to investigate the effect of Ca nutrition on yield and incidence of blossom-end rot (BER) in tomato. Three levels of Ca (low = 20 ppm, medium = 200 ppm, and high = 1,000 ppm; selected to represent very deficient, normal, and very high levels of calcium) were applied to three cultivars of tomatoes (`Mountain Supreme', `Celebrity', and `Sunrise'; selected to represent genetic differences in susceptibility to BER) grown in modified Hoagland solutions using a greenhouse hydroponic system. The experiment was constructed in a randomized complete-block design with three blocks, two replications, three cultivars, and three calcium treatments. The source of basic nutrients was a 5–11–26 soluble fertilizer containing micronutrients. The ratio of N–P–K was adjusted to 1.0–1.3–3.0 by adding NH4NO3 (34% N). Calcium was added as CaCl2. Nitrogen concentrations were maintained at 30 (first month), 60 (second month), and 90 ppm (during fruit growth), while the concentration of other nutrients followed proportionally. Cultivars differed significantly in yield and average fruit weight but not in incidence of BER or leaf Ca concentration. There was no cultiva × calcium treatment interaction. Leaf Ca content across cultivars was increased by 34% and 44%, respectively, by the medium and high Ca treatments. Average fruit weight and total yield per plant were not significantly different between the low and medium Ca treatments, however, both were reduced by the high Ca treatment. Incidence of BER was 95% higher in the low rather than in the medium Ca treatment. There was no significant difference in BER between the medium and high Ca treatments.

The calcium nutrition of bambara groundnut (Vigna subterranea (L.) Verdc.)

It is known that the calcium (Ca) requirement of the pods of groundnut (Arachis hypogaea (L.)) will be met by direct uptake of this element by the subterrean pods from the soil. In bambara groundnut (Vigna subterranea (L.) Verdc.), however, some plants have been found to develop some of their pods above-ground. This suggests that the Ca supply of bambara groundnut pods deviates from that in groundnut. Therefore, to elucidate the Ca nutrition of bambara groundnut, with particular emphasis on the supply and internal distribution of Ca within the pod, three experiments were conducted consecutively, in which Ca supply to the roots and pods of bambara groundnut was varied independently using a “double-pot technique”. It appeared that calcium supplied to the podding medium was not taken up by the pods. Hence the pods are completely dependent on Ca taken up by the roots. The total Ca accumulated in hull and seed was found to be related to the dry matter mass of each of the two pod compartments. It was found that the amount of Ca accumulated in the pods was low compared with that of leaves. Within the pods, the calcium concentration in hulls was significantly higher than that of the seed. In all cases calcium concentrations in the seed were extremely low, even when external Ca supply was abundant. This suggests that in bambara groundnut, Ca transport from the hull to the seed is the most limiting step in the supply of Ca to the seed.

Calcium Nutrition Affects Resistance of Tomato Seedlings to Bacterial Wilt

The relationship between Ca nutrition and bacterial wilt development was studied on three tomato (Lycopersicon esculentum Mill.) cultivar seedlings with various degrees of resistance to the disease. Seedlings were transplanted into nutrient solutions with Ca at 0.4, 4.4, or 20.4 mm. One week after initiating the Ca treatment, tomato seedlings were inoculated by wounding the stem with scissors dipped in a suspension of the pathogen (Pseudomonas solanacearum E.F. Smith). Disease development was rapid in `Ponderosa' (a susceptible cultivar) at all Ca concentrations. Increased Ca concentration in the nutrient solution reduced disease severity in `Zuiei' (a moderately resistant cultivar). Resistance was negated at the low Ca concentration in `Hawaii 7998' (a highly resistant cultivar). Pathogen populations in stems decreased with increased Ca concentrations and degrees of resistance.

Aluminum Effects on Calcium Uptake and Translocation in Wheat Forages

AbstractThe effects of Al on Ca transport could influence Ca accumulation in plants. Low forage Ca concentrations may cause hypocalcemia, a Ca deficiency syndrome of ruminants. Solution culture experiments were conducted in a growth chamber to examine the effects of Al (5–50 μM on uptake and translocation of Ca (45Ca) in winter wheat (Triticum aestivum L.) cultivars (Al‐tolerant Atlas 66 and Al‐sensitive Scout 66). Three‐day‐old seedlings, grown either in a CaCl2 solution (0.1 or 1.0 mM) or in a complete‐nutrient solution, were used. For plants grown in CaCl2 solution, addition of 5 μM Al significantly decreased Ca uptake and translocation in Scout 66, but not in Atlas 66. Higher levels of Al (20 and 50 μM) decreased Ca uptake and translocation much more in Scout 66 than in Atlas 66. For plants grown in complete‐nutrient solution, Al (5–50 μM) exposure for up to 6 h had little effect on Ca uptake and translocation in either cultivar. This may be due to the reduction in Al3+ activities in the external solution, as well as lowered Al3+ activities near the root‐cell plasmalemma. When roots were exposed to Al for 24 h, Ca uptake and translocation were decreased significantly in Scout 66, but were little affected in Atlas 66. The percentage of Ca translocated to the shoots was significantly decreased by Al in Scout 66, but not in Atlas 66. These results suggest that Al inhibits both Ca uptake and translocation in Scout 66, but inhibits primarily root Ca uptake in Atlas 66 (and only at higher Al levels). It appears that the use of Al‐tolerant cultivars of wheat forages on acid soils could be important for maintaining proper Ca nutrition of grazing animals.

Foliar response of red spruce saplings to fertilization with Ca and Mg in the Great Smoky Mountains National Park

The objective of this field study was to test whether Ca and (or) Mg was deficient in two red spruce (Picearubens Sarg.) sites located at 1720 and 1950 m in elevation in the Great Smoky Mountains National Park near Clingmans Dome, North Carolina. Initial current needle Ca and Mg concentrations were, respectively, 1700 and 620 μg/g at the upper site, and 1940 and 670 μg/g at the lower site, suggesting poorer nutrient conditions at the upper site. Twenty-eight saplings at each site stratified by height were involved in an individual-tree fertilization trial. Within each stratum four treatments were applied randomly: (i) no fertilization, (ii) 200 kg/ha Ca as CaCl2, (iii) 100 kg/ha Mg as MgCl2, and (iv) 200 kg/ha Ca as CaCl2 plus 100 kg/ha Mg as MgCl2. Fertilizer was applied in April 1989 and 1990, and needles that subsequently formed in the 1989 and 1990 growing seasons were sampled in November 1989 and 1990, respectively. Post-fertilization nutrient concentrations, needle weights, and nutrient contents were compared through analysis of covariance with the pre-treatment needle weight as covariate. Vector analysis suggested an improvement in Ca nutrition and potential growth response with Ca and Ca + Mg fertilization at the upper site in the 1st year but not at the lower site. Neither site appeared to be Mg deficient. Magnesium fertilization had an antagonistic effect on Ca uptake at both sites, whereas Ca addition seemed to improve Mg uptake. Our study suggests that foliar Mg concentrations of 600 μg/g are well within the sufficiency range, but that red spruce saplings may experience incipient Ca deficiency in the field when Ca concentrations in the current needles are &lt;1700 μg/g.

Fruit Cracking in Tomato

The environmental and physiological causes of cracking or splitting of soft fruits and citrus as they ripen are not well understood. This paper explores factors contributing to radial cracking in tomatoes, gives suggestions for prevention of cracking, and suggests directions for future research. Fruit cracking occurs when there is a rapid net influx of water and solutes into the fruit at the same time that ripening or other factors reduce the strength and elasticity of the tomato skin. In the field, high soil moisture tensions suddenly lowered by irrigation or rains are the most frequent cause of fruit cracking. Low soil moisture tensions reduce the tensile strength of the skin and increase root pressure. In addition, during rain or overhead irrigation, water penetrates into the fruit through minute cracks or through the corky tissue around the stem scar. Increases in fruit temperature raise gas and hydrostatic pressures of the pulp on the skin, resulting in immediate cracking in ripe fruit or delayed cracking in green fruit. The delayed cracking occurs later in the ripening process when minute cracks expand to become visible. High light intensity may have a role in increasing cracking apart from its association with high temperatures. Under high light conditions, fruit soluble solids and fruit growth rates are higher. Both of these factors are sometimes associated with increased cracking. Anatomical characteristics of crack-susceptible cultivars are: 1) large fruit size, 2) low skin tensile strength and/or low skin extensibility at the turning to the pink stage of ripeness, 3) thin skin, 4) thin pericarp, 5) shallow cutin penetration, 6) few fruits per plant, and 7) fruit not shaded by foliage. Following cultural practices that result in uniform and relatively slow fruit growth offers some protection against fruit cracking. These practices include maintenance of constant soil moisture and good Ca nutrition, along with keeping irrigation on the low side. Cultural practices that reduce diurnal fruit temperature changes also may reduce cracking. In the field, these practices include maintaining vegetative cover. Greenhouse growers should maintain minimal day/night temperature differences and increase temperatures gradually from nighttime to daytime levels. For both field and greenhouse tomato growers, harvesting before the pink stage of ripeness and selection of crack-resistant cultivars probably offers the best protection against cracking. Areas for future research include developing environmental models to predict cracking and exploring the use of Ca and gibberellic acid (GA) sprays to prevent cracking.

Salinity-induced calcium deficiencies in wheat and barley

Salinity-calcium interactions, which have been shown to be important in plants grown in dryland saline soils of the Canadian prairies, were studied in two species differing in salt tolerance. In solution culture, wheat showed a greater reduction in growth and a higher incidence of foliar Ca deficiency symptoms than barley when grown under MgSO4 or Na2SO4 plus MgSO4 salt stress. Amendment of the saline solution with Ca to increase the Ca/(Na+Mg) ratio ameliorated the effects of salt, but more so in wheat than in barley. At least part of the difference in salt tolerance between the two species must therefore relate to species differences in the interaction of salinity and Ca nutrition. The greater response of wheat to Ca was not due to a lower Ca status in leaf tissue; on the contrary, although Ca amendments improved tissue Ca/(Na+Mg) ratios in both species, salinized wheat had equivalent or higher Ca content, and higher Ca/(Na+Mg) ratios than did barley. The higher Ca requirement of wheat is apparently specific to a saline situation; at low salinity, wheat growth was not reduced as extensively as that of barley as Ca/(Na+Mg) ratio was decreased. High night-time humidity dramatically improved wheat growth under saline conditions, but increasing the Ca concentration of the saline solution had no effect on growth in the high humidity treatment. Membrane leakage from leaf tissue of wheat grown under saline conditions was increased compared to tissue from non-saline plants. Plants grown in Ca-amended saline solutions showed no increase in membrane leakage. These results confirm the importance of Ca interaction with salinity stress, and indicate differences in species response.

Effects of gypsum on growth and mineral content of Brussels sprouts, and soil properties of Orthic Podzols

Studies of crop response to Ca fertilizers are generally few as well as information concerning the Ca nutrition of Brussels sprouts (Brassica oleracea var.gemmifera). Six field studies were conducted, over three years, to determine yield response of Brussels sprouts to soil applied gypsum (CaSO4.2H2O), lime (calcite), and elemental S on sandy loam to loamy sand Orthic Podzols in Prince Edward Island. Relative yield of marketable (0–32mm) Brussels sprouts were related to soil ammonium acetate extractable Ca (r = 0.71). The highest yields (11 to 13 t ha−1) were associated with an extractable Ca of above 400µg g−1 soil, while a Ca level below 400µg reduced yield by 20%. Highest marketable yields were associated with a Ca level in the leaf tissue (in upper mature leaves at sprout formation) of above 2.2% (w/w) (r = 0.55), this in turn was associated (r = 0.87) with an extractable soil Ca above 400µg g−1 soil. Calcite and elemental S did not influence yield or mineral content. Gypsum, as expected increased leaf S content, but leaf tissue S levels were not related to marketable yield. Slight decreases in soil pH due to increasing gypsum rate (0.5–4.3 t ha−1) were associated with changing accumulations of B, Mn, Fe, Ca, and Zn in the leaf tissue. Gypsum had little effect on soil porosity and structure indices, but changing pH (in both gypsum and lime treatments) significantly influenced soil microbial biomass.

Kinetic aspects of calcium metabolism in lactating sheep offered herbages with different Ca concentrations and the effect of protein supplementation.

1. Two experiments are described in which kinetic aspects of calcium metabolism were studied in housed lactating sheep consuming different fresh herbage species. The importance of protein supply was also investigated. 2. In Expt. 1, two groups (n 4) were offered, ad lib., a freshly cut ryegrass (Lolium perenne L.)-white clover (Trifolium repens L.) pasture containing 5.48 g Ca/kg dry matter (DM). One group was supplemented daily with 100 g protected casein. A third group (n 4) was offered, ad lib., freshly cut oats-Tama ryegass (Lolium multiflorum L.) herbage which had a lower Ca content of 3.07 g Ca/kg DM. Stable Ca and nitrogen balances were carried out during the first 7 weeks of lactation. At this stage 180 microCi 45Ca were administered for Ca kinetic studies. 3. In Expt 2, eight sheep were offered, ad lib., a fresh ryegrass-white clover pasture, and paired on the basis of their udder size. One member of each pair was supplemented daily with 100 g casein via the abomasum and the amount of milk removed was equalized between pairs. Ca and N balance (12 d) and) and Ca kinetic studies (280 microCi 45Ca) were carried out during weeks 2 and 5 of lactation. 4. Rate of absorption of Ca increased, while rate of Ca secretion in milk and resorption from bone decreased as lactation progressed. Ca balances changed from negative to positive as lactation progressed in sheep offered ryegrass-white clover, but, while improving, were always negative in sheep offered oats-Tama ryegrass. Protein supplementation increased (18%) milk production of the ewes in Expt 1 and their retention of N in Expt 2. 5. The proportion of utilized Ca derived from the diet, as opposed to the skeleton, tended to increase as a result of protein supplementation. 6. Availability of Ca from ryegrass-white clover ranged from 0.19 to 0.32, even though only 50% of the net Ca requirement was derived from the diet. Availability of Ca from the oats-Tama ryegrass diet was similar, though in this case less than 20% of the net Ca requirement was derived from the diet. It was concluded that availability of Ca from forage diets may be lower than previously anticipated. 7. Faecal endogenous loss ranged from 16 to 40 mg Ca/kg body-weight per d, and was similar on both diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Control of stomatal aperture by calcium in isolated epidermal tissue and whole leaves of Commelina communis L.

SUMMARYPlants of Commelina communis L. were grown in media containing different concentrations of calcium from 1 to 8 mol m −3. After 4 weeks' growth stomatal behaviour was studied both on the intact plants and on isolated abaxial epidermis. The effect of Ca nutrition on stomatal opening was apparently different according to these two methods of observation. The apertures measured in light and in absence of CO2 were smaller on abaxial epidermal strips from plants grown at larger Ca concentrations than those grown at smaller concentrations. The inhibition of opening was thought to be due to the presence of free Ca2+ ions because inhibition was not found when EGTA was included in the medium used for incubating the isolated epidermis, and significant quantities of Ca were lost to the medium by epidermal tissue from plants grown on high concentrations of Ca.Studies on the leaves of intact plants were made with a diffusion porometer and by gas exchange techniques using a leaf cuvette in which the environment was closely controlled. A/c1 curves were used to partition non‐stomatal and stomatal limitations to gas exchange. Porometer measurements of stomatal conductance, determined within the growth room, indicated reduced values for plants grown at low Ca compared with those grown at high Ca, i.e. the observations contradicted those obtained with isolated epidermis.Biomass production increased with Ca up to 4 mol m −3. Analysis of A/c1 curves indicated that plants grown at the larger Ca concentration showed significantly greater values for carboxylation efficiency (dA/dc1). Partitioning of stomatal and non‐stomatal limitations to carbon fixation indicated that the gas‐phase limitations of CO2 were similar at different Ca concentrations. Differences in carboxylation efficiency could account for the greater biomass accumulation found at the larger Ca concentration.Calcium analysis indicated that plants grown at high Ca contained greater bulk leaf Ca concentrations, and a difference in Ca concentration was also evident in epidermal tissue, but the relative distribution of fractionated epidermal Ca was similar. Xylem sap Ca analysis also revealed more Ca in the apoplast of high Ca grown plants.The differences in stomatal behaviour in isolated epidermis and in the intact leaves suggest that in Ca‐rich plants, the level of free Ca2+ ions in the vicinity of guard cells is controlled, thus preventing inhibition of stomatal opening and interference with gas exchange. The loss of this control when epidermis is detached implies that the presence of the mesophyll tissue is important.

Influence of Calcium and Magnesium Salts on Acid Soil Chemistry and Calcium Nutrition of Apple

AbstractField experiments were conducted in two Brazilian orchards to examine the effects of soil applications of calcitic lime (Ca‐lime), phosphogypsum, CaCl2, and magnesite (Mg‐lime) on soil chemistry and Ca nutrition of apple (Malus domestica Borkh. cv. Gala/MM 106). One orchard was on a low Ca, high Al Inceptisol; the second orchard was on a low Ca, low Al Oxisol. The resulting soil chemical changes were strongly influenced by the initial soil chemistry and the composition of the soil amendments. The effects of Ca‐lime, added at a rate calculated to neutralize the topsoil exchange acidity, were restricted primarily to the upper 20 cm of the soil, where it increased pH, increased total dissolved and exchangeable Ca, eliminated dissolved Al, and reduced exchangeable Al. Phosphogypsum, added at Ca rates equivalent to the Ca‐lime treatment, slightly reduced soil pH in the Inceptisol and slightly increased soil pH in the Oxisol. Phosphogypsum did not appreciably affect dissolved Al in the topsoil; however, it did reduce exchangeable Al but to a lesser degree than did Ca‐lime or Mg‐lime. Phosphogypsum increased exchangeable Ca and decreased exchangeable Al in the subsoil to a depth of 40 to 60 cm. Calcium chloride, added at Ca rates equivalent to the Ca‐lime treatment, produced dissolved and exchangeable Ca increases similar to the phosphogypsum treatment; however, soluble and exchangeable Al were increased and pH slightly decreased throughout the soil profiles. Mg‐lime, added at an acidity‐neutralizing rate equivalent to the Ca‐lime treatment, produced results similar to Ca‐lime except that soluble and exchangeable Mg rather than Ca were increased in the topsoil. Apple tree root densities were enhanced in the soil layers that were made simultaneously high in exchangeable Ca and low in exchangeable Al by the soil amendments. The trees with the more extensive root systems had higher leaf Ca concentrations and produced more and larger fruit. The Ca concentrations in these larger fruit were not reduced by fruit expansion, suggesting enhanced Ca supply from the soil

Calcium deficiency identified as an important factor limiting maize growth in acid ultisols of eastern Nigeria

Poor maize growth in unlimed acid soils of eastern Nigeria was investigated with a view to identify the main factors responsible for infertility in such soils. Surface soils collected from 4 sites in the region were amended with (i) CaSO4 (ii) Ca(OH)2 and (iii) MgCO3. Maize was grown in each soil, including an untreated check, in the greenhouse for 4 weeks and tops and roots dry matter were measured. Although CaSO4 depressed the pH of the soil, it caused a highly significant increase (p = 0.01) in the yield of dry matter of tops and roots and a non-significant increase in the uptake of P and Ca. Exchangeable Al was virtually eliminated when the soil was amended with MgCO3 but maize growth in this soil was drastically inhibited and symptoms of severe calcium deficiency were observed. Higher yield increases, arising from soil amendment with Ca(OH)2 relative to CaSO4 were ascribed to better Ca nutrition rather than reduction in the level of exchangeable Al. Uptake of P and Ca was significantly increased (p = 0.05) by liming with Ca(OH)2. The results suggest that Ca deficiency is a more serious growth-limiting factor than Al toxicity in the soils tested. The implication of this finding is that much money can be saved by using industrial wastes of relatively low neutralizing value, like cement fluke dust and basic slag, as soil amendments rather than the costly ocnventional liming materials.

Einfluß von Mineralstoffernährung, Ozon und saurem Nebel auf Peroxidase-Aktivitäten in Fichtennadeln,Picea abies (L.) Karst

As part of the first experiment of MAGL (Munich working group on air pollutants), peroxidase activity was investigated in spruce needles treated with ozone, acid mist, and differential Ca and Mg nutrition.