Electrolyte Leakage Test Research Articles

Cold hardiness of rhododendron cultivars grown in different photoperiods and temperatures

Two rhododendron cultivars, ‘Pohjola's Daughter’ and ‘Helsinki University’, were grown at +15 and +24°C, each combined with a photoperiod of 14 h (short day, SD) or 20 h (long day, LD). After a 112‐day growing season, they were subjected to a hardening regime of fortnightly decreasing temperature (+9, +5, +1 and −2°C) and a 12‐h photoperiod, except that part of the plants grown in LD had LD also at +9 and +5°C. At −2°C, all plants were in darkness. Controlled freezing tests of the leaves were performed before each change in temperature. The injury was evaluated visually and by electrolyte leakage (EL) tests. The observations on the visual assessment were analysed with logit models, and the EL data with non‐linear sigmoid functions. The visually scored 50% damage (VD50) correlated better with the EL tests than 10 or 90% damage. Photoperiod and temperature during the growing season affected the cold hardiness of both cultivars, but they differed in their responses. ‘Pohjola's Daughter’ benefited from SD as well as from high temperature, while ‘Helsinki University’ attained better hardiness at a cool growing season temperature and was less sensitive to photoperiod.

Cold hardiness of diploid and corresponding autotetraploid rhododendrons

SummaryFreezing tolerance was studied in two diploid rhododendron cultivars, Rhododendron `PJM' and R. `Cunningham's White', and their tetraploid derivatives, R. `Northern Starburst' (NSB) and CW4. After the growing season and initial hardening at 15to 108C in a greenhouse, the acclimation regime in a phytotron comprised three consecutive weeks at 15, 11 and 228C. The hardiness was studied with controlled freezing tests before each decrease in temperature and at the end of the experiment. The injury on leaves and stem sections was visually assessed and the data analysed using logit models. Electrolyte leakage tests provided a comparison. Flower bud hardiness was studied by differential thermal analysis. Leaves of the diploid clones attained better cold hardiness than those of the tetraploid clones. At the end of the experiment, the LT50 of the `PJM' leaves was 247.18C and that of NSB 234.28C. The diploid `Cunningham's White' leaves hardened to 235.08C and the tetraploid ones to 222.78C. The LT50 of the stems of `PJM' and NSB was between 2338C and 2408C depending on test and date. There was no statistically significant difference in the stem hardiness between the ploidy levels. The mean hardiness of the `PJM' florets was 211.18C and of the NSB florets 28.18C. Since in other studies `PJM' florets have been much more cold tolerant, it seems that the conditions in the phytotron did not allow full acclimation.

Relating Electrolyte Leakage to Shelled Corn Storability

ABSTRACTCorn from three growing seasons was harvested, dried, and stored in small bins. Samples taken at harvest and after various periods of bin storage (up to 77 months) were evaluated by two primary tests: carbon dioxide evolution during accelerated storage at ≈20.5% moisture content and 26°C and electrolyte leakage from bulk (100 g) samples soaking in deionized water. The initial (t < 72 hr) slope of carbon dioxide evolution rate curves (SLOPE72) was used as a base measure of storability (i.e., potential for safe storage without significant mold invasion). In electrolyte leakage tests, both test temperature and initial sample moisture content influenced results. Additionally, water conductivity after 10 min was correlated (r = 0.79) with SLOPE72, implying that electrolyte leakage has the potential to provide rapid information regarding future storability.

The structure and hardening status of Scots pine needles at different potassium availability levels

Scots pine (Pinus sylvestris L.) seedlings were exposed to three levels of potassium (low, medium and high) and their needle morphology, the cellular structure of the mesophyll and transfusion parenchyma, and the hardening status of the mesophyll cells were examined by light and transmission electron microscopy. The higher the potassium level the greater was the growth of the needles. The area of the mesophyll tissue increased slightly and those of the phloem, xylem and resin ducts decreased in the needles of the seedlings grown at the high K level. Cellular studies revealed that swelling of the chloroplast thylakoids, accumulation of starch in the chloroplasts, translucency of the cytoplasm and plasmolysis in the mesophyll cells were related to a low K level. The hardening status of the mesophyll cells was enhanced after 5 weeks of hardening treatment at high K as seen in changes in chloroplast shape and position and the structure of the endoplasmic reticulum, but the pines showed no major differences in the hardening status of their mesophyll cells between K levels at the end of the experiment, after 9 weeks of hardening. Frost resistance, as shown by the electrolyte leakage test, was nevertheless highest at low K, being related to the increase in the concentration of polyamine putrescine at this potassium level.

Effects of an abscisic acid pretreatment on membrane leakage and lipid composition of Vigna unguiculata leaf discs subjected to osmotic stress

In leaf discs of Vigna unguiculata cv. EPACE-1 subjected to osmotic stress (PEG MW 8000, −1.3 MPa) a significant decrease in membrane integrity occurred, as evaluated by electrolyte efflux. This effect was significantly reduced when discs were treated with ABA (0.1 mM in Tris buffer) prior to PEG treatment. In PEG-treated discs, membrane lipids were drastically degraded, particularly the galactolipids. The percentage of linolenic acid in MGDG also decreased significantly. An ABA pretreatment of discs before osmotic stress significantly decreased galactolipid degradation and preserved their linolenic acid content. We concluded that ABA had a protective effect on membranes against osmotic stress, as attested by electrolyte leakage test and polar lipid analysis. Some possible roles for exogenous ABA in the acquisition of such an enhanced capacity to maintain membrane integrity under dehydration conditions are suggested.

Frost hardiness of Philadelphus and Hydrangea clones during ecodormancy

The frost hardiness of clones of two ornamental shrubs, hydrangea (Hydrangea paniculata Sieb. ‘Grandiflora') and mock orange (Philadelphus lewisii Pursh. var. lewisii ’Waterton'), was measured after completion of endodormancy. In addition to actual hardiness, minimum and potential hardiness were examined with the aid of four artificial hardening and dehardening treatments. Logit models were used for determining the lethal temperature. Artificial dehardening at 12°C (3 or 7 days) diminished the hardiness of Philadelphus from ‐38 to ‐22°C and that of Hydrangea from ‐37 to 26 ‐ ‐28°C. Hardening at ‐ 15°C (3 or 7 days) had no effect on hardiness. Visual assessment of injuries revealed no differences between clones of different origin, whereas electrolyte leakage tests indicated slight interclonal variation, especially after dehardening treatments.

Heat tolerance in food legumes as evaluated by cell membrane thermostability and chlorophyll fluorescence techniques

The genotypic variation for heat tolerance in chickpea, groundnut, pigeonpea, and soya bean was evaluated by testing membrane stability and photosystem (PSII) function in leaves at high temperatures. The legumes could be ranked from heat-tolerant to sensitive in the order: groundnut, soya bean, pigeonpea and chickpea. The damage to cell membranes (as reflected by an increased leakage of electrolytes) and PS II (as reflected by a decrease in the ratio of variable to maximum fluorescence) was less, and recovery from heat stress was faster in groundnut than in other crops. Prior exposure of plants to 35°C for 24h led to a reduced leakage of electrolytes at high temperatures in all crops but the differences among legumes were consistent. Substantial genotypic variation for heat tolerance was found in all legumes. Membrane injury was negatively associated with specific leaf weight in groundnut (r=−0.69**) and soya bean (r=−0.56**) but not in the pulses. Electrolyte leakage and fluorescence ratio were negatively correlated in all legumes. The potential use of electrolyte leakage and fluorescence tests as screening procedures for breeding heat-tolerant legumes is discussed.

Pecan Cold Hardiness Determined by Differential Thermal Analysis

Our objectives were to 1) Determine acclimation and deacclimation patterns of buds and stems of four pecan cultivars in Mississippi and 2) to determine the relationship between cold hardiness, based on DTA, and tissue injury, based or viability tests. Stem critical temperatures for September showed that `Hughes' was slower in acclimating than `Jackson'. Maximum hardiness for all cultivars occurred in January, except for `Desirable', which reached maximum hardiness in December but started deacclimating in January. Deacclimation for the remaining cultivars started in February. Bud critical temperatures for September and October also show that `Hughes' was slower in acclimating compared to the remaining cultivars. Maximum bud hardiness for `Desirable' occurred in December, with the remaining cultivars reaching maximum hardiness in January. Bud deacclimation for all cultivars occurred in March. The LD50 for the tetrazolium and electrolyte leakage tests occurred at about –32 and –30C, respectively. In buds, LT50 for the tetrazolium test was –18C. The LT50 electrolyte leakage and browning test was –20C.

PECAN COLD HARDINESS DETERMINED BY DIFFERENTIAL THERMAL ANALYSIS

Stem critical temperatures for September showed that `Hughes' was later in acclimating than `Jackson'. Maximum hardiness for all cultivars occurred in January and deacclimation in February. Bud critical temperatures for September and October also showed that `Hughes' acclimated later than the other cultivars. Maximum hardiness for buds occurred in January and deacclimation in March. In December, the LT50 for the tetrazolium test, the electrolyte leakage test, and the tissue browning test were –18, –20, and –20C, respectively, as shown by differential thermal analysis of `Desirable'.

COLD HARDINESS OF RABBITEYE BLUEBERRY

Cold acclimation of `Tifblue' rabbiteye blueberry was determined using differential thermal analysis (DTA). Electrolyte leakage and tissue browning test results were correlated with DTA. DTA showed that three exotherms occurred: exotherm 1 (ET) associated with extracellular freezing, exotherm 2 (CT) associated with tissue injury, and exotherm 3 (LTE) not associated with tissue injury. Maximum hardiness (–20C) occurred in January. The LT50 measured by electrolyte leakage and tissue browning was about –17C and –15C, respectively. Acclimation began in November and deacclimation in mid-Feb. 1994.

Comparison of Seed-quality Indices Resulting from Single-seed Electroconductivity Measurements

Five seed-quality indices based on individual seed electrolyte leakage tests were evaluated. Zea mays L. seeds were soaked for 6 hours, and individual seed leachate conductivity values were obtained. A total of 100 cells were scanned, one seed per cell, at 5-minute intervals for the first 30 minutes, followed by 15-minute intervals for the remaining 330 minutes. Seeds were allowed to dry for 5 to 7 days at room temperature and then were tested for germinability at 25C for 7 days. Radicle lengths were measured after 72 hours. The Richards function was fitted to cumulative frequency distributions of μAmps to obtain internal slope (IS), mean μAmp, and median μAmp values for each scan. Initial leach rate (ILR) was estimated after fitting hyperbolic functions to μAmp vs. soak time data. Average leach rate (ALR) was also derived from fitting the Richards function to μAmp vs. soak time data. Linear regression of seed quality on IS, mean, and median μAmp values after 5 hours of imbibition yielded r2 values of 0.91, 0.81, and 0.86 for predicting viability and 0.56, 0.46, 0.52 for predicting radicle length. Thus, IS was the best seed quality predictor, followed closely by median and mean μAmp values. ILR and ALR were not correlated with seed quality.

299 ELECTROLYTE LEAKAGE FROM INDIVIDUAL MAIZE AND WHEAT SEEDS TO PREDICT GERMINATION PERCENTAGE AND RADICLE LENGTH

Multiple electroconductivity readings (μAmps) of leachates from individual seeds during the first 6 hr of imbibition was examined as a possible predictor of seed quality. Readings from each sample of 100 seeds were formed into frequency distributions and the mean, median. and internal slope were calculated using an automated computer retrieval system. Internal slope is a non-central tendency measure based on the slope of a line tangent to the inflection point of the S-shaped cumulative frequency distribution (CFD) of μAmps. Radicle lengths (3 days) and germination (7 days) percentages were regressed on each of the two measures of central tendency and also the CFD shape indicator, internal slope. None of the three predictors were satisfactory for estimating seed vigor (root lengths) of maize (Zea mays L.) or wheat (Triticum aestivum L.) or germination of wheat seed lots. Internal slope was useful in estimating viability of artificially aged maize seeds (r2= 0.91), which compared favorably with our previous results using naturally aged red clover (Trifolium pratense L.) seed lots. Overall the seed quality of the unaged wheat lots was fairly high and the electrolyte leakage test was not sensitive enough to detect differences within these lots.

SEASONAL COLD-ACCLIMATION PATTERNS OF `AUTUMN JOY' AND `BRILLIANT' SEDUM

Electrolyte leakage and regrowth tests were performed in successive months from September to January to determine cold hardiness of container-grown Sedum spectabile Xtelephium L. `Autumn Joy' and Sedum spectabile Boreau. `Brilliant' plants exposed to natural temperature and photoperiod. Plant crowns were subjected to 0, -3, -6, -9, -12, -15, -18, -21, -24, or -27C in a programmable freezer. Regrowth tests were performed on whole crowns and electrolyte leakage determinations were made on excised tuberous root and crown tissues. Regrowth data indicate both cultivars had killing temperatures of -3C at the September test date, prior to the onset of cold-acclimation. By October, the killing temperature for `Autumn Joy' had dramatically decreased to -12C, with more gradual acclimation occurring thereafter. The killing temperature for `Brilliant' decreased from -3C in October to -18C in November. In this study, maximum hardiness was achieved on the January test date with killing temperatures of -24 and -21C for `Autumn Joy' and `Brilliant', respectively. Correlation coefficients suggest the electrolyte leakage procedure was able to reliably estimate `Autumn Joy' cold hardiness at each test date, but was less accurate for `Brilliant'. Regrowth tests are tedious and qualitative, but remain reliable predictors of plant viability. Electrolyte leakage tests were successful in estimating survival potential of plants exposed to freezing temperatures using either excised crown or tuberous root tissue.

EVALUATION OF ELECTROLYTE LEAKAGE FROM CRYOPRESERVED APPLE BUDS

Three years ago we established a long-term cryogenic storage project for apple germplasm and utilized grafting of buds obtained from stored dormant shoot sections as the major viability assay. Grafting, however, is time consuming and requires considerable skill. Electrolyte leakage and oxidative browning tests were used as alternative viability assays. Using leakage from individual buds in a multiwell analyzer, we examined modifications of the electrolyte leakage test and analyzed the kinetics of leakage in an attempt to determine whether the test can predict grafting success. The results suggest that more buds were viable than were estimated by the grafting test. In vitro culture is being examined to test this and to determine if practical recovery is feasible for diversity within the germplasm collection.

OPERATIONAL COLD HARDINESS TESTING AND DATA ANALYSIS METHODS

Cold hardiness testing is an important tool used at US Forest Service nurseries for evaluating the physiological quality of conifer stock. Three tests were compared. A whole-plant freeze test without root system insulation permitted evaluation of cold injury without complication by drought symptoms if plants were misted. A cutting freeze test underestimated expected field foliar injury due to high humidity used to maintain the cuttings. An electrolyte leakage test failed to detect economically important bud mortality when buds were less hardy than other tissues. Data from all three testing methods were analyzed with an original software package consisting of standardized input files and a step-by-step series of fortran programs and command files for use with commercially available non-linear modelling programs. Injury (y) versus temperature (x) data were modelled with the versatile, 4-parameter Weibull sigmoid model. Injury estimates at specific temperatures (Ix) or temperature estimates causing specific injury levels (LTy) were calculated with confidence and calibration intervals, respectively. The statistical significance of differences between Ix or LTy estimates was then determined.

Comparison of three cold hardiness tests for conifer seedlings.

Greenhouse-cultured, container-grown ponderosa pine (Pinus ponderosa var. scopulorum Engelm.), interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco), and Engelmann spruce (Picea engelmannii (Parry) Engelm.) were cold acclimated and deacclimated in growth chambers over 19 weeks. Cold hardiness was measured weekly by a whole-plant freeze test and by two quick tissue tests: freeze-induced electrolyte leakage of needles, and differential thermal analysis of buds. The whole-plant freeze test provided results in 7 days, and indicated differences in cold hardiness among stems, buds, and needles. Although the whole-plant freeze test could accurately measure cold hardiness, it was not precise, and it required destructive sampling. Results from freeze-induced electrolyte leakage and differential thermal analysis were available in 2 days and 1 hour, respectively. The freeze-induced electrolyte leakage test was a precise, sensitive and objective predictor of changes or differences in tissue cold hardiness. To determine actual cold hardiness, results could be calibrated to the response of the same tissue in the whole-plant freeze test. The speed and objectivity of differential thermal analysis made this test useful for rapid, general assessment of cold hardiness status, but calibration was difficult, and precision varied.

Membrane Thermostability and Heat Tolerance of Spring Wheat

Spring wheat (Triticum aestivum L.) is a major crop of the northern Great Plains. High temperature stress during the grain‐fill period is a major constraint to increased productivity of spring wheat, particularly in the southern part of the region. The electrolyte leakage or membrane thermostability (MT) test was conducted at anthesis on flag leaves of eight field‐grown genotypes of spring wheat and the results related to the yield of those genotypes grown at three other field locations. Genotypes were derived from two crosses involving parents adapted and unadapted to the region or thermal aspects of the climate. The three field locations represented northern, central, and southern areas of the northern Great Plains with soil classifications of Aeric Calciaquoll, Aeric Calciaquoll, and Typic Haplustoll, respectively. Based on MT values, genotypes were grouped as heat‐tolerant (HT, n = 4) vs. heat‐sensitive (HS, n = 4). The HT and HS genotypes produced similar grain yields at the northern and central locations. However, the HT group of genotypes produced 21% more grain yield (4.28 Mg ha−1) than the HS group (3.55 Mg ha−1) at the southern site, which was considerably warmer during the grain‐fill period than the other two locations. Average temperatures during July were 19.5, 21.7, and 23.4 °C at the northern, central, and southern locations, respectively. Based on results of this study it seems that the MT test is a useful screening procedure for selecting HT genotypes of spring wheat.

Seed Hydration Treatments For Improved Sweet Corn Germination and Stand Establishment

Abstract This research examines the potential of seed hydration for improving sweet corn (Zea mays L.) seed performance, especially for plantings in cool (10°–15°C) soils. In addition to the effect of hydration treatments, the influence of seed quality and cultivar was evaluated using electrolyte leakage tests and seedling growth cold tests. Seed hydration treatments included seed hardening (a wetting/drying cycle), seed moisturizing (placing seed in moist vermiculite), and osmoconditioning, which were compared to a dry seed control. Hardening and moisturizing treatments improved early emergence by as much as 20%, while osmoconditioning significantly lowered field emergence. Seed moisturizing and hardening also improved uniformity of emergence, and reduced the number of days required to attain 50% or 75% emergence. Seed hydration treatments were effective with the three levels (high, medium, and low) of seed quality and the three cultivars (‘Jubilee’, ‘Midway’, and ‘Reward’) studied.

Prediction of Sweet Corn Field Emergence by Conductivity and Cold Tests

Abstract Field-emergence trials and laboratory seed-quality tests were conducted on 45 seed lots of 13 sweet corn (Zea mays L.) hybrids. Results from standard laboratory germination tests were not correlated with field emergence in 4 field trials. Cold tests conducted in sterile sand and on rolled towels were correlated highly with field emergence. Electrolyte leakage tests conducted on individual seeds with the ASA-610 Automatic Seed Analyzer were superior to bulk-seed measurements with a conductivity meter. By combining the seedling-growth cold test (total seedling dry weight) with the Automatic Seed Analyzer test, multiple correlation values with field emergence ranged from 0.70 to 0.80.