Electrical Conductivity Of Medium Research Articles

Reducing Time and Expense to Recycle Perlite for Repeat Use in Greenhouse Tomato Operations

Planting greenhouse tomatoes (Solanum lycopersicum) in the same perlite more than once without reconditioning to restore medium loose structure, desalination to remove excess salt, and disinfection to guard against pest contamination is risky, and replacing the perlite to produce every new crop is costly. Reconditioning and treating perlite with hot water at a minimum cost provides a favorable solution for both problems and saves natural resources. A study was conducted in a 30 × 96-ft greenhouse in Spring 2007, 2008, and 2009 (January–July) to evaluate three methods for perlite recycling cost, desalination efficiency, and effects on tomato yield at three or four fruit per cluster. Each recycling method consisted of two components: the reconditioning action and the hot water treatment. The three recycling methods included no stir/sift then disinfect, stir then disinfect, and sift then disinfect. Perlite recycled with the no stir/sift then disinfect method was not reconditioned before the hot water treatment. Instead, it was agitated with a nozzle mounted on a pressure washer wand during the hot water treatment. Perlite recycled with the stir then disinfect method was reconditioned first with an auger mounted on an electric drill and then treated with hot water. Perlite recycled with the sift then disinfect method was reconditioned first by sifting the perlite with a homemade apparatus and was then treated with hot water. Recycling perlite with the no stir/sift then disinfect method reduced labor input by 49% and 81% compared with the stir then disinfect and the sift then disinfect methods, respectively. The no stir/sift then disinfect method reduced recycling cost by 22% and 50% compared with the other two methods, respectively. Perlite that was not reconditioned (no stir/sift) had higher nitrate-nitrogen (NO3-N) before hot water treatment than the stirred perlite and equal NO3-N to the sifted perlite. Hot water treatment significantly reduced medium electrical conductivity, NO3-N, potassium, and sodium. Tomatoes grown in perlite recycled with any of the three methods produced similar marketable and cull yields and fruit weight. Pruning fruit to three per cluster increased marketable yield, fruit weight, and reduced cull yield. There was no significant recycling method × cluster pruning interaction for yield components, indicating that all recycling methods had similar effects on tomato yield at three or four fruit per cluster. We conclude that the no stir/sift then disinfect method is less time consuming, more economical, and has no negative impact on yield. Tomatoes grown with three fruit per cluster in perlite recycled with any of the three methods produced greater marketable yield, less cull yield, and heavier fruit than tomatoes grown with four fruit per cluster.

Influence of irrigation method and container type on northern red oak seedling growth and media electrical conductivity

Container production of hardwood seedlings has not been extensively practiced. Efficient nursery production of hardwood seedlings in containers can be limited by formation of a broad foliar canopy, which limits irrigation uniformity. This study was established to investigate suitability of subirrigation, a method of irrigating seedlings from the container base that relies on rise of water through capillary action, for production of broad-leaved hardwood seedlings. Northern red oak ( Quercus rubra L. [Fagaceae]) seeds were sown into 4 container types, and seedlings were grown in a controlled greenhouse environment under either traditional overhead irrigation or subirrigation. Media electrical conductivity (EC) was measured at container depths of 1, 5, and 10 cm (0.4, 2, and 4 in) after 57 d. Subirrigated seedlings had significantly higher EC at each depth compared with overhead irrigated seedlings, with a trend of decreasing EC with increasing measurement depth. A significant container type x irrigation method interaction suggested potential for toxic EC levels in some subirrigated containers, which can be alleviated by periodic leaching using clear water to dissipate salts from the top 1 cm (0.4 in). At the end of the growing period, seedling height and root-collar diameter were not influenced by irrigation method or container type, indicating that subirrigation is suitable for hardwood seedling production.

Comparison of surface and bulk doping levels in chemical polypyrroles of low, medium and high conductivity

AbstractChemical polypyrroles (PPys) of low (σ < 75 S/cm), medium (75 < σ < 200 S/cm) and high electrical conductivity (σ > 200 S/cm) having chloride dopants have been investigated by XPS, chloride ion‐selective electrode (ISE) measurements and high‐resolution termogravimetric analysis (TGA). The average surface doping level in these PPys was 0.28 ± 0.03 as determined from deconvoluted XPS N 1s, Cl 2p and C 1s spectra by using the well‐established N+/N and Cl−/N atomic ratios as well as a new ratio denoted as Cα*/CαTotal. This new ratio provides an estimation of the relative amount of α‐C atoms in charged pyrrole units per total α‐C atoms. The average bulk doping level in these materials was 0.31 ± 0.02 from direct chloride ISE measurements. High‐resolution TGA was employed for the first time in the determination of the amount of hydrogen chloride evolved from the PPy samples during degradation at high temperatures. The resulting average bulk doping level by TGA was 0.30 ± 0.04 for these PPys, in very good agreement with the ISE results. Since surface and bulk doping levels are almost identical for the PPys of low, medium and high conductivity, the differences in conductivity between samples have been attributed to differences in conjugation length among them. For PPy of high conductivity (σ = 288 S/cm), a conjugation length 2.6 times higher than that of PPy of low conductivity (σ = 29 S/cm) has been calculated. Copyright © 2006 John Wiley & Sons, Ltd.

Structure–conductivity relationships in chemical polypyrroles of low, medium and high conductivity

Chemically synthesized polypyrroles of low ( σ < 75 S/cm), medium (75 < σ < 200 S/cm) and high ( σ > 200 S/cm) electrical conductivity ( σ) with the same dopant and degree of doping have been investigated by means of Wide Angle X-ray Scattering (WAXS), 13C Cross Polarized Magic Angle Spinning Nuclear Magnetic Resonance ( 13C CP/MAS NMR) spectroscopy and Fourier Transform Infrared (FTIR) Spectroscopy to establish structure–conductivity relationships useful for industrial applications. A similar amorphous structure was found by WAXS even for the higher conducting PPy ( σ = 288 S/cm). WAXS spectra for polypyrroles of medium and high conductivity showed a weak peak at 2 θ = 10–11° due to improved order of the counterions in these materials. The effect of the counterion size in the asymmetry of the PPy main WAXS peak was elucidated by performing ion exchange of the Cl − dopant with counterions of larger size such as BF 4 − and ClO 4 −. From 13C CP/MAS NMR measurements predominantly α–α′ bonding was found in these materials. The main 13C CP/MAS NMR resonance peak of PPy located at 126–128 ppm was broadened upon increasing conductivity. Interestingly, a linear relationship was observed between the half-width at half-height (HWHH) of the 13C CP/MAS NMR peak and conductivity where a doubling of the polypyrrole conductivity leads to an increase of HWHH by 6–7 ppm. FTIR data of these materials were analysed in the framework of the Baughman–Shacklette theory describing the dependence of conductivity on conjugation length. By comparison of model predictions and experimental results, the PPy samples were found to be in the regime of long conjugation lengths, L ≫ K 2/ k B T, where K 2 is a parameter related to the energy change on going from j − 1 to j charges on a conjugated segment of conjugation length L, k B the Boltzman constant and T is the absolute temperature.

In Situ Probes for Measurement of Electrical Conductivity of Soilless Substrates: Effects of Temperature and Substrate Moisture Content

Growing medium electrical conductivity (EC) is used in laboratory analysis and greenhouse production as a measure of the nutrient content of the growing medium. Fast, accurate ways to measure growing medium EC will make it easier to determine EC and maintain it within a suitable range for a particular crop. Several probes have been developed that can be inserted directly into the growing medium of container-grown crops for measurement of EC. We tested the sensitivity of four in situ EC probes (Field Scout, HI 76305, WET sensor, and SigmaProbe) at a range of temperatures, substrate volumetric water contents (VWC), and fertilizer concentrations. The HI 76305 probe was highly sensitive to temperature, while the WET sensor was temperature-sensitive at high ECs above its normal operating range. The probes responded differently to increasing VWC. The SigmaProbe and WET sensor measure the EC of the pore water specifically and show a decrease in EC with increasing water content, as the fertilizer ions in the pore water become more diluted as VWC increases. EC readings of the HI 76305 and Field Scout probes, which measure the EC of the bulk substrate (growing medium, water, and air combined) increased with increasing water content as the added water helps conduct the current of these meters. At a VWC above 35%, there was little effect of VWC on EC readings of all probes. The EC measured with the various in situ probes differed slightly among the probes but was highly and positively correlated with all three of the standard solution extraction methods [pour-through, 1:2 dilution, and saturated media extract (SME)] over the range of fertilizer concentrations at a given temperature and VWC. These results make it possible to convert substrate EC guidelines that have been established for any of the three standard methods for use with the in situ probes, though our results indicate the substrate VWC must be above 35% for the interpretation to be valid. The in situ probes are a viable alternative for measurements of substrate EC and eliminate the step of substrate solution extraction, thus simplifying data collection.

Growth of Barberry Liners in Media Amended with Noncomposted Recycled Waste

One-year-old `Royal Burgundy' barberry (Berberis thunbergii var. atropurpurea) liners were potted in 1-gal (3.8-L) containers. Container media consisted of noncomposted recycled waste mixed at rates of 0% (control), 25%, 50%, 75%, and 100% by volume with a (by volume) 3 pine bark: 2 peat: 1 sand media. Treatments were replicated eight times. Three grams (0.1 oz) of Osmocote 13-10-13 (13N-4.37P-10.8K) with micronutrients were topdressed on all containers. Media electrical conductivity (EC) and pH readings were recorded every fifteen days over the course of 5 months. Dry shoot, root, and total weights were recorded at the end of the project and a foliar analysis was performed for nutrient and metal content. Results indicate a general trend of higher EC with greater volumes of recycled waste. EC levels for the control and 25% treatment were within recommendations for the optimal plant growth of plants for the duration of the study. All treatments had an acceptable pH level for plant growth. Nitrogen levels were below the recommended foliar analysis sufficiency range. Levels of phosphorus and potassium were above or within the recommended foliar analysis sufficiency range. Metals were below or within recommended ranges for all treatments. Total dry weights revealed no statistical difference between the control, 25%, 50%, and 75% treatments. This study indicates that 25% noncomposted recycled waste could be used in container media for production of `Royal Burgundy' barberry.

Use of Precharged Zeolite to Provide Aluminum During Blue Hydrangea Production

Aluminum (Al) drenches are repeatedly applied during blue hydrangea (Hydrangea macrophylla Thunb.) production because Al is required for blue sepal coloration, but soilless root media do not retain Al. The ability of clinoptilolitic zeolite to retain and release Al, and its evaluation as the sole source of Al during blue hydrangea production, was evaluated in laboratory and greenhouse experiments. Adsorption and desorption isotherms indicated that Al is adsorbed and released by this zeolite. Clinoptilolite was precharged with Al and combined at 10–40% with a peat and perlite mix to evaluate its use as a sole source of Al during the production of mini‐pot blue hydrangea “Kuhnert.” Root medium Al, pH, and electrical conductivity (EC) were measured during production. Sepal color and growth measurements, and foliar and sepal analyses were conducted at the end of the production cycle. Aluminum from zeolite was released rapidly during the vegetative stage of production. Dry mass of plants grown with 10 and 20% zeolite was similar to the commercial control. Blue sepals were produced in the 10–40% zeolite treatments, however, growth was significantly reduced from the 30 and 40% zeolite treatments. Aluminum‐charged zeolite up to 20% of the root medium may be used as a sole source of Al during forcing and may simplify blue hydrangea production; however, its use affects phosphorus (P), potassium (K), pH, and EC management.

Effect of activated charcoal and 6-benzyladenine on in vitro nitrogen uptake by Lagerstroemia indica.

A sterile hydroponic culture system suitable for studying nitrogen (N) uptake ofLagerstroemia indica L.in vitro was developed. Four different treatments were assayed: with and without activated charcoal (AC and NAC, respectively), with and without 50 μM of 6-benzyladenine (+BA and −BA, respectively). Medium pH, electrical conductivity (EC), NO3 − and NH4 + concentrations were measured weekly. At the end of the culture, propagules were sampled and SPAD indices, and shoot and root fresh weights were determined. Explants grown in media with activated charcoal were able to take up both NO3 − and NH4 +, although NH4 + uptake was lower. Subsequently the pH of the media was maintained between 5.5–6.0. In treatments with no addition of activated charcoal, NH4 + uptake was preferential and the pH dropped to 3.1. Explants in these conditions were unable to raise the pH by taking up NO3 −, especially when root morphogenesis was inhibited by addition of BA. Supply of this PGR produced root growth inhibition, which was almost complete in the treatment without activated charcoal. This component significantly reduced the inhibitory effect of 50 μM BA on root growth.

Capacity for biocompatibility assessment in tissue culture and hydroponic systems

In vitro and hydroponic intercropping systems were compared to examine the biocompatibility responses between ‘Fiona F1’ tomato (Lycopersicon esculentum Mill.) and ‘Spunta’ potato (Solanum tuberosum). The biological response of monocultures (with four plantlets per vessel) of each species (including change in medium electrical conductivity (EC), osmotic potential (OS), and tissue mineral element content) were directly compared to intercropped cultures of the following tomato:potato; 1:1, 2:1, 3:1, 1:2, 1:3, and 2:2 plantlets per vessel. The in vitro intercropping systems were performed using a Murashige and Skoog (MS) shoot proliferation medium (5.0 μM BA and 0.5 μM IBA). The parallel hydroponic intercropping system was performed using a Hoagland's solution. Monoculture of both species grows better in both systems than intercropped species. In the intercropped vessels, tissue mineral content decreased, medium pH became more acidic, OS decreased and EC increased as compared to monocultures in parallel vessels. A lettuce seedling bioassay did not indicate evidence of allelopathic compound accumulation in either hydroponic or in vitro intercropped systems.

Stability of chemical parameters of tissue culture medium (pH, osmolarity, electrical conductivity) as a function of time of growth

Changes in medium pH, osmolarity (OS), and electrical conductivity (EC) were studied as a function of time in Murashige and Skoog (MS) liquid proliferation and rooting medium. Microshoots of wild pear (Pyrus syriaca), bitter almond, and ‘Spunta’ potato were targeted. Results indicated an acidic drift in pH in the different species on both proliferation and rooting medium. The EC was increased significantly with time whereas solution OS was decreased. Different species caused different effects on EC or OS depending on growth medium. The decline in OS in the proliferation medium was higher when pear and almond were grown, while on rooting medium the decline was sharper with potato and almond. The EC of proliferation medium was increased more when almond was grown; while on the rooting medium all species had similar effects. Under these saline conditions, low nutrient elements availability, poor plant growth, and nutrient element imbalance are expected. This study illustrates that the change in the chemical parameters of the culture medium could lead to undesirable effects on plant growth and nutrient element availability. Therefore, it is recommended to monitor the change in these parameters of the medium over the incubation time.

Effects of Fertilizer Concentration and Minimum-leach Drip Irrigation on the Growth of New Guinea Impatiens

New Guinea impatiens `Barbados' (Impatiens ×hawkeri) were fertilized with solutions containing N at 6, 12, or 18 mmol·L-1 delivered from a drip irrigation system with either minimum leaching or standard leaching (0.3 to 0.4 leaching fraction). Irrigation was monitored and controlled by computers using microtensiometers placed in representative pots of each treatment. In two separate experiments, growth index, fresh mass, and dry mass were dependent upon both fertilizer concentration and irrigation treatment. Maximum growth overall was achieved at 12 mmol·L-1 N regardless of irrigation treatment; however, standard-leached plants receiving N at both 6 and 18 mmol·L-1 produced larger plants than did similarly fertilized minimum-leached plants. Leaf scorch, spotting, or marginal necrosis did not occur in any of the treatments. Leaf N, P, and K concentrations were highest in plants treated with N at 18 mmol·L-1, but Ca, Mg, and several micronutrients were highest in plants at 6 mmol·L-1 N. At the end of the cropping period for both experiments, growing medium electrical conductivity (EC) in the uppermost one-third layer of the pot was two to four times as high as that in the bottom two-thirds (root zone) layer. Root-zone EC ranged from 0.6 to 4.0 dS·m-1 and increased as fertilizer concentration increased. Standard leaching had little effect in reducing root-zone EC except in plants fertilized with N at 18 mmol·L-1. All plants continued to perform well and flower after 4 weeks in a simulated interior environment. Minimum-leach drip irrigation used ≈35% less solution than did standard irrigation with leaching, and eliminated N runoff.

Recycled Waste Paper as a Non-chemical Alternative for Weed Control in Container Production

Abstract Studies were conducted to evaluate recycled waste paper mulch as a means of controlling weeds in the production of container-grown crops. Two forms of recycled waste paper products were evaluated—pelletized and crumbled. Both were tested at two depths, 12.5 mm (0.5 in) and 25 mm (1 in). A fabric disk and a fabric disk treated with Spin Out were also evaluated. With both the recycled waste paper mulch treatments and the fabric disk treatments, spurge seed were sown either under or on top of the treatment. Recycled waste paper pellets applied to a depth of 25 mm (1 in) suppressed spurge germination, regardless of whether spurge seed were sown on top of the mulch or under the mulch. Recycled crumble provided poor spurge control at both depths, and there was increased spurge growth when spurge were sown on top of the mulch compared to when the seed were sown under the crumble mulch. Pellets at the 25 mm (1 in) depth, provided weed control equal to that of Rout (oxyfluorfen + oryzalin) herbicide. Results from the fabric disks showed limited spurge control was obtained with any treatment. Fabric disks allowed weed growth around the container circumference and in the area where the disk fits around the plant. Both cultivars of azaleas grown with recycled waste paper mulch were generally similar in size to non-treated control plants and Rout treated plants at 240 DAT (days after treatment). At 550 DAT plant growth was similar among all treatments except ‘Fashion’ azalea had smaller growth indices when grown with pellets compared to those grown with crumble. Container medium solution pH and electrical conductivity (soluble salts) were within the recommended range for acceptable plant growth. Research suggests that pellets applied at 25 mm (1 in) should provide effective non-chemical weed control resulting in less herbicide use and/or fewer hours of labor for weeding.

Irrigation Systems Alter Distribution of Roots, Soluble Salts, Nitrogen, and pH in the Root Medium

Pelargonium hortorum Bailey `Pinto Red' plants were grown with 220 mg·L−1 N (20N-4.4P-16.6K) using hand (HD), microtube (MT), ebb-and-flow (EF), and capillary mat (CM) irrigation systems. At harvest, root balls were sliced into three equal regions: top, middle, and bottom. A negative correlation existed between root medium electrical conductivity (EC) and N concentration to root number such that the best root growth was obtained with low medium EC and N concentrations. EF root numbers were greatest in the middle region. The two subirrigation systems (EF and CM) had higher average root numbers than the two surface-irrigation systems (HD and MT). For all irrigation systems, root numbers were lowest in the top region. In general, less difference in medium soluble salt and N concentrations existed between regions for surface-irrigated than for subirrigated root balls. Soluble salt concentration was lowest in the bottom and middle regions of EF and the bottom region of MT and CM. For subirrigation, the highest medium soluble salt and N concentration was in the top region. For all systems, pH was lowest in the bottom region. Plant growth for all irrigation systems was similar. EF and MT systems required the least water and EF resulted in the least runoff volume.

Pretransplant Watermelon Nutrition with Various Nitrate: Ammonium Ratios and Supplemental Calcium

Watermelon [Citrullus lanatus (Thunb.) Matsum. and Nakai `Crimson Sweet'] was seeded in a commercial peat medium in multicell containers. Five NO3: NH4 ratios and five levels of supplemental Ca were combined factorially in a 100N-31P-265K mg·liter-1 pretransplant nutrition regime. The medium was amended with CaCO3 in 1989; the medium was not amended in 1990. Dry-matter accumulation had decreased with increasing NH4-N 3 weeks after seeding both years. In 1989, increasing NH4-N also had decreased seedling growth by the last sampling date due to decreased NH+4 uptake. Shoot N concentration was higher in 1990 than 1989, but N uptake was similar. On the first sampling date in both years, increasing the Ca concentration decreased seedling growth and increased medium electrical conductivity (EC). In 1990, increasing the Ca concentration raised shoot N concentration but did not increase seedling growth or N uptake. Either N form at 100 mg N/liter and Ca at 4 to 8 mmol·liter-1 were optimal for watermelon transplant production, but Ca at &gt;8 mmol·liter-1 suppressed transplant growth.

Growth of New Guinea Impatiens Inhibited by High Growth-medium Electrical Conductivity

To test the effects of fertilizer concentration and growth medium electrical conductivity (EC) on the growth of New Guinea impatiens (Impatiens sp. hybrids or I. platypetala Lindl.), plants of `Selenia' were grown 70 days in a commercial soilless medium and irrigated with solutions of 20N-4.3P-16.6K at concentrations of 0.5, 1.0, 1.5, or 2.0 g·liter-1. In a fifth treatment (“delay”), no fertilizer was applied for the first 14 days after planting, then 0.5 g·liter-1 was applied for the next 14 days, followed by 1.0 g·liter-1 until the end of the experiment. Measurements of shoot dry weight and growth medium EC were made at 14-day intervals. Differences in dry weight between fertilizer treatments became significant (P = 0.0001) 42 days after planting. Over the 70-day experiment, plants grew most with 0.5 g·liter-1 and delay treatments. High fertilizer concentrations (1.5 and 2.0 g·liter-1) caused the most growth suppression and resulted in increasing growth medium EC with time. An EC of ≈1.5 dS·m-1 or higher was associated with suppressed growth beginning 42 days after planting. A mild chlorosis developed on the leaves of some plants at the two highest fertilizer concentrations.

Medium Nutrient Extraction with the Pour-through and Saturated Medium Extract Procedures for Poinsettia

The relationship between medium nutrient levels extracted with the pour-through (PT) and the saturated medium extract (SME) procedures was investigated. These procedures were used as indicators of plant nutrient uptake and growth of poinsettia, Euphorbia pulcherrima Wind. ex. Klotzch. The medium nutrient levels and electrical conductivity associated with optimal plant growth were about two times greater for PT than for SME. The pH values were similar for both procedures. Regression analysis of the relationship between applied and extracted nutrient levels gave higher R2 values for the SME, although the relationship for PT was acceptable. Both procedures provided an acceptable and similar correlation between the level of NO3-N extracted and the level of N absorbed by the plants. The results demonstrate the utility of both PT and SME as indicators of the nutritional status of a greenhouse medium.

Salt Tolerance ofEchinochloa crusgalli

Salt tolerance ofEchinochloa crusgalli was studied using gravel culture with root medium electrical conductivity between 3 to 25 dS m-1. Salinity depressed germination and shoot yield. A 50 % reduction in shoot yield occurred at 15.9 dS m-1. The plant was able to maintain its tissue water content and K concentration in the tissue water while Na, Ca and Cl increased and Mg decreased with increasing root zone salinity.

Occurrence of periodic regimes in steady supersonic mid flows due to loss of electrical conductivity of medium

A study is made of the features of supersonic magnetohydrodynamic (MHD) flows due to the vanishing of the electrical conductivity of the gas as a result of its cooling. The study is based on the example of the exhausting from an expanding nozzle of gas into which a magnetic field (Rem ≫ 1) perpendicular to the plane of the flow is initially frozen. It is demonstrated analytically on the basis of a qualitative model [1] and by numerical experiment that besides the steady flow there is also a periodic regime in which a layer of heated gas of electric arc type periodically separates from the conducting region in the upper part of the nozzle. A gas-dynamic flow zone with homogeneous magnetic field different from that at the exit from the nozzle forms between this layer and the conducting gas in the initial section. After the layer has left the nozzle, the process is repeated. It is established that the occurrence of such layers is due to the development of overheating instability in the regions with low electrical conductivity, in which the temperature is approximately constant due to the competition of the processes of Joule heating and cooling as a result of expansion. The periodic regimes occur for magnetic fields at the exit from the nozzle both greater and smaller than the initial field when the above-mentioned Isothermal zones exist in the steady flow. The formation of periodic regimes in steady MHD flows in a Laval nozzle when the conductivity of the gas grows from a small quantity at the entrance due to Joule heating has been observed in numerical experiments [2, 3]. It appears that the oscillations which occur here are due to the boundary condition. The occurrence of narrow highly-conductive layers of plasma due to an initial perturbation of the temperature in the nonconducting gas has previously been observed in numerical studies of one-dimensional flows in a pulsed accelerator [4–6].

The relation between the electrical conductivity of the external medium and the rate of cell-division in sea-urchin eggs

Dilution of sea water with isotonic sugar solution leaves the rate of cleavage of Arbacia eggs almost unchanged until the proportion of sea water is decreased to 20 or 25 volumes per cent. From this point cleavage becomes progressively slower with further dilution. Many eggs fail to cleave at dilutions of 5 to 6 volumes per cent. No cleavage occurs in 2 volumes per cent sea water or in pure sugar solution. Eggs returned from these media to sea water resume cleavage and development. There is thus no relation between the rate of cleavage and the electrical conductivity of the medium, except possibly within the range of dilutions from 20 to 5 volumes per cent sea water. In this range cleavage rate decreases as conductivity decreases, but the relation is not a linear one.