Low Calcium Treatment Research Articles

Similar zooplankton responses to low pH and calcium may impair long-term recovery from acidification.

Throughout much of the 20th century, unprecedented industrial emissions have led to widespread acidification of regions in North America and Europe and, as lake water pH dropped, aquatic ecosystems have experienced dramatic declines in biodiversity. International emission-control agreements have led to sweeping increases in lake pH, however acid-structured zooplankton communities still persist in many lakes. Concomitantly, calcium concentrations have been declining as a legacy of acidification and are approaching or have reached concentrations that could represent a barrier to the re-establishment of zooplankton communities similar to those in non-acidified or circumneutral reference lakes. To understand how declining calcium may influence the re-establishment of zooplankton in acid-damaged lakes we manipulated calcium and pH using a factorial in-lake mesocosm experiment and assessed their individual and combined effects on a regionally diverse zooplankton assemblage. We found that the impacts of low calcium on zooplankton species were similar to those of acidification and, consequently, may prevent the recovery of acid-structured communities. Abundance of the larger bodied and acid-sensitive Daphnia pulex/pulicaria increased in high pH treatments, albeit nonsignificantly yet, by the end of our experiment, only two individuals were sampled among our 10 low calcium enclosures. In contrast, small acid-tolerant cladocerans, such as Daphnia catawba, Daphnia ambigua, and eubosminids maintained significantly higher abundances in low calcium treatments relative to all other treatment combinations. Although we did not detect an effect of calcium on mean body size, the disproportionately high abundance of small cladocerans in low calcium treatments resulted in low calcium communities with higher overall abundance and lower cladoceran evenness. Our results, along with a landscape comparison demonstrating parallel changes in zooplankton relative abundance from 34 historically acidified lakes, suggests that declining calcium will be an important, on-going factor that may limit the recovery of zooplankton, despite regional improvements in lake pH.

Research on the variation of the inclusion and sulfur content in Pipeline steel

Pipeline steel is widely used in various industries, and the sulfur content and inclusions in steel have a significant impact on performance, which determines whether the steel quality is qualified. The experiments were carried out to explore the sulfur content and inclusion evolution of pipeline steel which was deoxidized by Si–Mn–Al with “EAF-LF-VD-T-CC”. The samples of molten steel and slag were taken during the process of LF-VD-Tundish after EAF tapping. The kinetics model was established to simulate the desulfuration process of molten steel in actual production, obtaining a result which the error is within 3 ppm. It can be summarized that proper calcium treatment can transform the inclusion into a liquid inclusion, the value of [Ca] ranges from 25 to 45 ppm. Too high and lower calcium treatment can cause the compositions of inclusions to deviate from the liquid phase area, while too low calcium treatment will increase the overall size and density of the inclusions. In addition, the evolution of inclusion in steel at refining temperature and during solidification process was comprehensively calculated, considering all types of inclusions such as calcium oxide, magnesium oxide, aluminum oxide, calcium sulfide, spinel, calcium aluminate and liquid inclusion. The thermodynamic calculations are in good agreement with experimental results, which can predict the formation of the inclusions in Si–Mn–Al deoxidized pipeline steel.

Root-mediated acidification and resistance to low calcium improve wheat (Triticum aestivum) performance in saline-sodic conditions

Salinity represents a medium with high soluble salts where as sodicity represents a medium with high exchangeable sodium, low calcium and highly alkaline pH. Salinity and sodicity commonly occur together in salt-affected soils however physiological studies have mostly considered salinity alone ending up in poor field success of the selected genetic resources. Similarly, the role of root-mediated acidification in salt resistance is not known in wheat. Here six wheat genotypes were exposed to salinity (NaCl: 125 mM), low calcium (25% of non-treated control) and salinity + low calcium in solution culture. There were significant differences among the wheat genotypes for growth and leaf ionic composition under salinity, low calcium and salinity + low calcium treatments. The wheat genotypes SARC-1, 25-SAWSN-42 and Pasban-90 accumulated higher K+ and Ca2+ and lower Na+ and Cl− and were resistant to the combined stress of low calcium and salinity.These genotypes also showed higher root-mediated acidification under stress conditions. The wheat genotypes resistant to salinity + low calcium supply in solution culture also performed better in the saline-sodic soil in a lysimeter study. A genotype resistant to salinity alone accumulated lower Ca2+ and showed lower rhizosphere acidification potential and did not perform good in saline-sodic soil conditions. Therefore, root-mediated acidification potential and resistance to low calcium supply improves resistance of wheat to saline-sodic conditions. It is further suggested that screening of the wheat germplasm for saline-sodic soils should be carried out at salinity + low calcium to better simulate saline-sodic field conditions.

Spindly leg syndrome in Atelopus varius is linked to environmental calcium and phosphate availability.

Spindly leg syndrome (SLS) is a relatively common musculoskeletal abnormality associated with captive-rearing of amphibians with aquatic larvae. We conducted an experiment to investigate the role of environmental calcium and phosphate in causing SLS in tadpoles. Our 600-tadpole experiment used a fully-factorial design, rearing Atelopus varius tadpoles in water with either high (80mg/l CaCO3), medium (50mg/l CaCO3), or low calcium hardness (20mg/l CaCO3), each was combined with high (1.74 mg/l PO4) or low (0.36 mg/l PO4) phosphate levels. We found that calcium supplementation significantly improved tadpole survival from 19% to 49% and that low calcium treatments had 60% SLS that was reduced to about 15% at the medium and high calcium treatments. Phosphate supplementation significantly reduced SLS prevalence in low calcium treatments. This experimental research clearly links SLS to the calcium: phosphate homeostatic system, but we were unable to completely eliminate the issue, suggesting an interactive role of other unidentified factors.

Does water chemistry limit the distribution of New Zealand mud snails in Redwood National Park?

New Zealand mud snails (NZMS) are exotic mollusks present in many waterways of the western United States. In 2009, NZMS were detected in Redwood Creek in Redwood National Park, CA. Although NZMS are noted for their ability to rapidly increase in abundance and colonize new areas, after more than 5 years in Redwood Creek, their distribution remains limited to a ca. 300 m reach. Recent literature suggests that low specific conductivity and environmental calcium can limit NZMS distribution. We conducted laboratory experiments, exposing NZMS collected from Redwood Creek to both natural waters and artificial treatment solutions, to determine if low conductivity and calcium concentration limit the distribution of NZMS in Redwood National Park. For natural water exposures, we held NZMS in water from their source location (conductivity 135 μS/cm, calcium 13 mg/L) or water from four other locations in the Redwood Creek watershed encompassing a range of conductivity (77–158 μS/cm) and calcium concentration ( 4 months) in the lowest conductivity waters from Redwood Creek and all but the lowest-conductivity treatment solutions, regardless of calcium concentration. However, reproductive output was very low in all natural waters and all low-calcium treatment solutions. Our results suggest that water chemistry may inhibit the spread of NZMS in Redwood National Park by reducing their reproductive output.

Significance of zoledronic acid on survival in patients with bone metastases from renal cell carcinoma.

374 Background: It remains unclear whether zoledronic acid (ZOL) improves overall survival (OS) for renal cell carcinoma (RCC) patients with bone metastases. We retrospectively investigated the clinical benefit of ZOL for OS in RCC patients with bone metastases. Methods: Between 1978 and 2010, 77 patients who had RCC metastatic to bone were treated in our hospital. Of them, 36 were treated with ZOL and their OS was significantly better than that of the other 41 patients (1- and 3-year survival, 84% and 73% vs. 49% and 27%, respectively, p < 0.001). OS rates were clearly discriminated according to MSKCC model stratification: 3-year survival rates in the favorable, intermediate and poor risk groups were 83% (n = 12), 49% (n = 45), and 19% (n = 20), respectively (p=0.0033). To match characteristics in our retrospective study, we selected 45 patients conforming to MSKCC intermediate risk group criterion. In this cohort, 23 patients received ZOL (ZOL-treated group) whereas the other 22 did not (non-ZOL-treated group). The primary endpoint was OS and the secondary endpoint was the skeletal-related event (SRE) rate defined as the total number of SREs divided by the total years on study. Results: For the cohort of 45 patients, the median OS from diagnosis of bone metastases was 27.2 months. Multivariate analysis showed that low serum calcium (hazard ratio [HR]: 2.58, 95% confidence interval [CI]: 1.31 to 4.69; p = 0.0083) and ZOL treatment (HR: 1.89, 95% CI: 1.27 to 2.96; p = 0.0013) were independent factors predicting longer survival. The ZOL-treated group had significantly longer OS (1-year survival: 80.8%) than the non-ZOL-treated group (1-year survival: 59.1%, p = 0.0034). A difference in OS between the two groups still was present (p = 0.012) when the duration of molecular-targeted therapy was excluded from the OS period. Patients in the ZOL-treated group experienced a lower SRE rate (0.87/year) than patients in the non-ZOL-treated group (1.82/year, p = 0.0453). In particular, none of the patients in the ZOL-treated group developed spinal compression whereas 6 (28%) in the non-ZOL-treated group did (p = 0.0479). Conclusions: The current study indicates that ZOL not only reduces SREs but possibly improves OS in these patients.

Significance of zoledronic acid on survival in patients with bone metastases from renal cell carcinoma.

e15038 Background: It remains unclear whether zoledronic acid (ZOL) improves overall survival (OS) for renal cell carcinoma (RCC) patients with bone metastases. We retrospectively investigated the clinical benefit of ZOL for OS in RCC patients with bone metastases. Methods: Between 1978 and 2010, 77 patients who had RCC metastatic to bone were treated in our hospital. Of them, 36 were treated with ZOL and their OS was significantly better than that of the other 41 patients (1- and 3-year survival, 84% and 73% versus 49% and 27%, respectively, p<0.001). OS rates were clearly discriminated according to MSKCC model stratification: 3-year survival rates in the favorable, intermediate and poor risk groups were 83% (n=12), 49% (n=45), and 19% (n=20), respectively (p=0.0033). To match characteristics in our retrospective study, we selected 45 patients conforming to MSKCC intermediate risk group criterion. In this cohort, 23 patients received ZOL (ZOL-treated group) whereas the other 22 did not (non-ZOL-treated group). The primary endpoint was OS and the secondary endpoint was the skeletal-related event (SRE) rate defined as the total number of SREs divided by the total years on study. Results: For the cohort of 45 patients, the median OS from diagnosis of bone metastases was 27.2 months. Multivariate analysis showed that low serum calcium (hazard ratio [HR]: 2.58, 95% confidence interval [CI]: 1.31 to 4.69; p=0.0083) and ZOL treatment (HR: 1.89, 95% CI: 1.27 to 2.96; p=0.0013) were independent factors predicting longer survival. The ZOL-treated group had significantly longer OS (1-year survival: 80.8%) than the non-ZOL-treated group (1-year survival: 59.1%, p=0.0034). A difference in OS between the two groups still was present (p=0.012) when the duration of molecular-targeted therapy was excluded from the OS period. Patients in the ZOL-treated group experienced a lower SRE rate (0.87/year) than patients in the non-ZOL-treated group (1.82/year, p=0.0453). In particular, none of the patients in the ZOL-treated group developed spinal compression whereas 6 (28%) in the non-ZOL-treated group did (p=0.0479). Conclusions: The current study indicates that ZOL not only reduces SREs but possibly improves OS in these patients.

The influence of environmental calcium concentrations on calcium flux, compensatory drinking and epithelial calcium channel expression in a freshwater cartilaginous fish

Calcium metabolism and mRNA levels of the epithelial calcium channel (ECaC) were examined in a freshwater cartilaginous fish, the lake sturgeon Acipenser fulvescens. Lake sturgeon were acclimated for ≥2 weeks to 0.1 (low), 0.4 (normal) or 3.3 (high) mmol l(-1) environmental calcium. Whole-body calcium flux was examined using (45)Ca as a radioactive marker. Net calcium flux was inward in all treatment groups; however, calcium influx was greatest in the low calcium environment and lowest in the high calcium environment, whereas efflux had the opposite relationship. A significant difference in the concentration of (45)Ca in the gastrointestinal tract (GIT) of fish in the low calcium environment led to the examination of drinking rate and calcium flux across the anterior-middle (mid) intestine. Drinking rate was not different between treatments; however, calcium influx across the mid-intestine in the low calcium treatment was significantly greater than that in both the normal and high calcium treatments. The lake sturgeon ECaC was 2831 bp in length, with a predicted protein sequence of 683 amino acids that shared a 66% identity with the closest sequenced ECaCs from the vertebrate phyla. ECaC mRNA levels were examined in the gills, kidney, pyloric caeca, mid-intestine and spiral intestine. Expression levels were highest in the gills, then the kidneys, and were orders of magnitude lower in the GIT. Contrary to existing models for calcium uptake in the teleost gill, ECaC expression was greatest in high calcium conditions and kidney ECaC expression was lowest in low calcium conditions, suggesting that cellular transport mechanisms for calcium may be distinctly different in these freshwater cartilaginous fishes.

Stop dietary calcium restriction in kidney stone-forming patients.

Epidemiologic studies have demonstrated an increased incidence of kidney stones in individuals with low calcium intake. More recently, a 5-year clinical study found the recurrence of kidney stones was higher in stone-formers on a low dietary calcium treatment. Considering these important new findings, and the known adverse effect on bone mass, dietary calcium restriction should be avoided in kidney stone-forming individuals.

Expression of Zonula Occludens and Adherens Junctional Proteins in Human Venous and Arterial Endothelian Cells: Role of Occludin in Endothelial Solute Barriers

The purpose of this study was to correlate the expression of occludin and VE-cadherin with the solute barrier properties of arterial and venous endothelial monolayers. Immunofluorescent confocal and traditional microscopy were used to determine junctional protein localization in endothelium in vivo and in vitro respectively, and western and northern analysis used to determine protein and gene expression levels. Permeability of endothelial monolayers was examined under normal, low calcium, and cytochalasin-D treatment conditions. Antisense oligonucleotide experiments for occludin were performed to determine the contribution of occludin to solute barrier. Occludin protein in endothelial monolayers is more concentrated in arterial junctions than in venous junctions both in vivo and in vitro. Arterial endothelial cells express 18-fold more occludin protein and nine times more occludin mRNA compared to venous endothelial cells. In vivo, both endothelial cells demonstrate VE-cadherin staining; and in vitro, only venous endothelial cells express VE-cadherin protein and mRNA. Occludin antisense experiments suggest that both arterial and venous barrier properties are due to these different amounts of occludin expression. Venous barrier was remarkably sensitive to low extracellular calcium, while arterial barrier was more sensitive to cytochalasin-D. These findings suggest strongly that arterial and venous endothelial barrier reflects the level of expression of different adhesion molecules and that modulation of these proteins, especially occludin, may regulate the level of endothelial solute barrier.

Exposure of human sperm to low-calcium medium enhances fertilizing ability.

This investigation was conducted to evaluate whether exposure of human sperm to low calcium enhances the fertilizing ability. When sperm from normal semen samples were preincubated in low-calcium mBWW medium for 1 h, the percentages of live acrosome-reacted sperm after 4 and 6 h of culture were significantly higher than control (5.0 +/- 0.5 vs. 3.2 +/- 0.3% and 6.0 +/- 0.5 vs. 4.2 +/- 0.3%, p < .05). The penetration rate (%P) and fertility index (FI) in zona-free hamster egg sperm penetration assay significantly increased, compared to control (%P: 66.4 +/- 9.0 vs. 42.7 +/- 8.1%; FI: 1.69 +/- 0.19 vs. 1.34 +/- 0.11; p < .01). When low-calcium treatment was used for human in vitro fertilization and embryo transfer (IVF-ET) for male infertility, the fertilization and pregnancy rates were significantly higher than those in control. The results indicate that preincubation of human sperm in low-calcium medium enhances their fertilizing ability. This method is a simple and useful for preparing sperm from subfertile men for human IVF-ET.

Stimulation of radial expansion in arabidopsis roots by inhibitors of actomyosin and vesicle secretion but not by various inhibitors of metabolism.

Plant morphogenesis depends on accurate control over growth anisotropy. To learn to what extent the control of growth anisotropy depends on cellular metabolism, we surveyed the response of growing roots to a range of inhibitors. Seedlings of Arabidopsis thaliana L. (Heynh), 7-8 d old, were transplanted onto plates containing an inhibitor, and elongation and radial expansion of roots were measured over the subsequent 2-d period. Fourteen inhibitors of diverse metabolic processes inhibited root elongation but failed to stimulate radial expansion. These inhibitors were aluminum sulfate, aphidicolin (DNA synthesis), caffeine (cell-plate formation), cisplatin (DNA synthesis), cycloheximide (protein synthesis), 3,4-dehydro-L-proline (proline hydroxylation), 6-dimethylaminopurine (protein kinases), dinitrophenol (mitochondrial ATP synthesis), galactose (UDP-glucose formation), Lovastatin, formerly mevinolin (isoprenoid formation), methionine sulfoximine (glutamine synthetase), methotrexate (folate metabolism), XRD-489 (synthesis of branched-chain amino acids), and high or low calcium treatments. These results show that various types of metabolic disruption, although inhibitory to elongation, do not reduce the high degree of anisotropic growth of the root. However, five chemicals did stimulate radial expansion; namely, the detergent, digitonin; two inhibitors of vesicle secretion, monensin and brefeldin A; and two inhibitors of actomyosin, cytochalasin B and butanedione monoxime. The maximum radial expansion induced by these compounds (except butanedione monoxime) was greater than that caused by ethylene, and the morphology of treated roots did not resemble that of roots treated with ethylene. These results indicate that vesicle secretion and actomyosin play a role in controlling anisotropic expansion.

Calcium plays a central role in phase shifting the ocular circadian pacemaker of Aplysia.

The eye of the marine mollusk Aplysia californica contains an oscillator that drives a circadian rhythm of spontaneous compound action potentials in the optic nerve. Both light and serotonin are known to influence the phase of this ocular rhythm. The aim of the present study was to evaluate the role of extracellular calcium in both light and serotonin-mediated phase shifts. Low calcium treatments were found to cause phase shifts which resembled those produced by the transmitter serotonin. However, unlike serotonin, low calcium neither increased ocular cAMP levels nor could these phase shifts be prevented by increasing extracellular potassium concentration. Low calcium-induced phase shifts were prevented by the simultaneous application of the translational inhibitor anisomycin and low calcium treatment resulted in changes in [35S]methionine incorporation into several proteins as measured by a two-dimensional electrophoresis gel analysis. Finally, light treatments failed to produce phase shifts in the presence of low calcium or the calcium channel antagonist nickel chloride. These results are consistent with a model in which serotonin phase shifts the ocular pacemaker by decreasing a transmembrane calcium flux through membrane hyperpolarization while light-induced phase shifts are mediated by an increase in calcium flux.

Effects of osmotic shock and calcium on growth and solute composition of Phaseolus vulgaris plants

Identification of the primary response to salinity is of great importance in order to develop salt tolerant species. In this work the effect of a NaCl osmotic shock on leaf elongation of Phaseolus vulgaris L. cv. Contender has been studied. After establishing an osmotic shock by adding NaCl to the root medium, three consecutive events could be distinguished. First, there was a sudden interruption of leaf growth, followed by a period of retardation of growth, and then by a restoration of growth to reach the steady‐state growth rate. High calcium (5 mM) in the growth medium diminished the initial loss of water in the roots and kept the water content higher upon restoration of leaf growth, as compared to low calcium levels (0.5 mM). During the low calcium treatment, leaf malate started to increase already 3 h after the start of the osmotic treatment, showing a maximum concentration at around 9 h, then decreasing and approaching the value of control plants. At high calcium, malate concentration remained unchanged with time. Plants grown in the presence of low calcium showed an increase in the concentration of total amino acids upon NaCl shock. It is estimated that organic metabolites, if confined to the cell cytoplasm, contribute significantly to the osmotic adjustment, together with inorganic ions. Our results support the hypothesis that water shortage in the roots is responsible for the initial inhibition of leaf elongation. The beneficial effect of calcium on restoration of growth after the NaCl shock is a consequence of short‐term, energetically expensive osmotic adjustment, in which mainly organic metabolites are involved. Under steady state conditions, high calcium treatment results in a faster growth rate than low calcium. In a process of osmotic adjustment, in which inorganic ions are principally involved, this is the result of a decrease in leaf Na+ concentration in expanding leaves, together with an increase in K+ and Ca2+.

1046 EFFECT OF POSTHARVEST CALCIUM TREATMENT OF APPLES ON POLYGALACTURONASE PRODUCED BY BOTRYTIS CINEREA.

Decay caused by Botrytis cinerea is significantly reduced by increasing the calcium concentration of apple fruit tissue. Electron microscope studies have revealed that cracks in the epicuticular wax may be an important pathway by which calcium penetrates into the fruit and increases the calcium concentration. In fruit inoculated with B. cinerea, the decay induced compositional changes in the cell walls of high-calcium fruit were smaller than those observed in the low calcium treatment. The effect of calcium in reducing decay is associated with maintaining cell wall structure by delaying chemical changes in cell wall composition. B. cinerea produced five polygalacturonase isozymes in vitro but only one in vivo. Among the cations studied-m was the most potent inhibitor of polygalacturonase activity in in vitro studies. Its mode of inhibition appears to involve the alteration of substrate availability for hydrolysis, rather than any direct effect on the active sites of the enzyme.

The role of extracellular calcium in generating and in phase-shifting the Bulla ocular circadian rhythm.

Since extracellular calcium is known to be involved in the entrainment of the circadian pacemaker in the retina of Bulla gouldiana, we have assessed the requirement for extracellular calcium in the generation of the circadian rhythm. To enable us to assay the state of the pacemaker during low-calcium treatment, which often obscures rhythmicity, long-duration pulses of low-calcium artificial seawater (no added calcium, 10 mM EGTA, calculated calcium concentration = 4.5 x 10(-10) M) were applied, and the phase of the subsequent rhythm was measured. Pulse treatments started at zeitgeber time (ZT) 6, and durations ranged from 4 to 72 hr. Although no phase shifts followed pulses ending before the next projected dawn (ZT 24), phase delays of up to 4 hr followed pulses ending after projected dawn, and delays of up to 8 hr followed pulses spanning two dawns. Some activity records exhibited unequivocal circadian rhythmicity during the long low-calcium treatments, with phases and periods similar to untreated control eye records; this finding suggests that the phase delays observed following long low-calcium pulses are attributable to the pulsatile nature of the treatment. These data suggest that extracellular calcium is not an essential requirement for the pacemaker in generating the circadian rhythm.

Cell wall composition of calcium-treated apples inoculated with Botrytis cinerea

The role of calcium in maintaining cell wall integrity was investigated in cortical tissue of apple fruit. Carbohydrate, phenolic, protein and mineral element composition were determined in cell walls of high- and low-calcium content fruit inoculated with Botrytis cinerea. Cell walls in fungal-infected tissue of low-calcium fruit showed a decrease in non-cellulosic polysaccharides containing galacturonosyl, rhamnosyl, arabinosyl, xylosyl and galactosyl moieties and increases in cellulose, wall-bound phenolics, protein and mineral elements. In infected tissue of high-calcium fruit, the compositional changes in the cell wall were generally smaller compared with those observed in the low-calcium treatment. The results of this investigation indicate that the effect of calcium in reducing decay is associated with maintaining cell wall structure by delaying and/or modifying chemical changes in cell wall composition.

The Effect of Dialysate Calcium Levels on Blood Pressure During Hemodialysis

A controlled double-blind prospective study was undertaken of the effect of dialysate calcium levels on BP during hemodialysis. Twenty patients and 240 dialyses were studied using a protocol in which patients underwent alternate hemodialyses with dialysate calcium of 2.5 and 3.5 mEq/L. Dialysate composition was otherwise the same. Mean BPs during dialysis were significantly lower at 1.5, 2.5, and 3.5 hours of dialysis when the lower dialysate calcium was used (P = .007 to .02). However, the difference in BP between the high and low dialysate calcium treatments was clinically minor, with a maximum mean difference (at 1.5 hours) of 4.6 mm Hg. Subgroups of patients with frequent hypotension and low or normal serum calcium did not appear more sensitive to the hypotensive effect of low calcium dialysate. Dialysate calcium levels of 2.5 and 3.5 mEq/L thus differ in their effect on intradialytic BP in a statistically significant, but clinically minor, way. Low calcium dialysate thus may prove useful in the management of patients in whom large amounts of enteric calcium absorption are indicated or unavoidable.

A new method of recording moulting in the fowl

Abstract 1. The moult of the remiges is described and existing methods of recording are outlined. 2. A new method of scoring, adapted to poultry, includes three criteria: primary moult score, intensity of the remiges moult and actual intensity of the remiges moult. 3. Contour moulting is considered and existing methods of recording are discussed. 4. A new method for its scoring, consists of two criteria: body moult intensity and index of body plumage regeneration. 5. An approach to the description of total moult is elaborated, involving two further criteria: index of total plumage regeneration and total moult rate. 6. Application of these seven criteria provides a clear description of the different responses in the case of moulting induced by fasting and by low calcium diets: the response is immediate following fasting but is retarded by about 15 d and is highly variable after the low calcium treatment.

Effects of subsoil calcium on the root growth of some lucerne genotypes (Medicago sativa L.) in acidic soil profiles

The root growth of lucerne was examined in an acidic soil profile modified by varying additions of calcium carbonate to different layers of the subsoil. Root growth responded strongly to changes in the concentration of exchangeable soil calcium. Symptoms of thickening, distortion and poor lateral formation occurred under low calcium treatments. The results were in agreement with the interacting effects of calcium (at 0.5–5.0mM) and aluminium ions (at 0–20,µM) on lucerne in separate solution culture experiments. Differences in root penetration were observed between three lucerne clones selected from the cultivars Hunter River and Siro Peruvian. At the first harvest, the magnitude of these differences was increased by the addition of lime to the profiles. The three genotypes produced similar total dry weight yields, but differed in their distribution of growth between shoots and roots. This distribution was not affected by the addition of lime to the subsoil. However, the length of roots in the lower layer of the profile ( &gt; 60 cm depth) was more responsive to subsoil treatment than was total dry weight. At the final harvest, the shoot yields of two genotypes were affected by lime treatments, but that of the deepest-rooted genotype was not. The results suggest that improved genotypes could be selected from Australian lucernes for establishment in areas with acidic subsoils, but that selection on root penetration alone would not necessarily lead to increased shoot yields.