Bryan D. McKersie's research while affiliated with University of Guelph and other places

Publications (107)

Article
A physical barrier exists in Vitis vinifera L. (wine-quality grapevines) between the canes that freeze at subzero temperatures and the buds that supercool, thereby avoiding ice formation in these delicate organs. Our objective was to characterize the ice nucleation barrier by observing grape buds at different stages of acclimation, by treating them...
Article
A mutant was isolated from irradiated seed of alfalfa, Medicago sativa L. cv. Excalibur. The mutant plant, Ex-139, displayed symptoms of premature senescence in the leaf palisade mesophyll. The leaves emerged as a normal phenotype, but light microscopy revealed that they rapidly began to accumulate starch in plastids of some cells in the palisade m...
Article
The physical and chemical properties of microsomal membranes and cellular antioxidant systems were investigated in imbibed soybean (Glycine max L. Merr. cv. Maple Arrow) seeds following aging for 5 years at room temperature. The loss of germination capacity in aged seeds was associated with increased solute leakage during imbibition and with a loss...
Article
Plant heat shock transcription factors (HSFs) regulate transcription of heat shock (HS) genes. In Arabidopsis thaliana, 21 HSFs have been classified into groups A-C. Members of class A act as typical transcriptional activators, whereas B HSFs function as coactivators or repressors depending on promoter context. The function of class C HSFs is still...
Article
The symptoms of injury in microsomal membranes isolated from crowns of seedlings of Triticum aestivum, L. cultivar Fredrick after a lethal freeze-thaw stress included an increased lipid phase transition temperature, loss of lipid phosphate (lipid-P), and increased free fatty acid levels. However, minimal changes in fatty acid saturation were observ...
Article
Full-text available
Expression of individual superoxide dismutase (SOD) transgenes improves environmental stress tolerance and biomass production in alfalfa (Medicago sativa L.). The objective of this study was to test the hypothesis that synergy exists between transgenic SOD stress‐tolerance mechanisms, specifically that the simultaneous expression of two SOD transge...
Article
Expression of individual superoxide dismutase (SOD) transgenes improves environmental stress tolerance and biomass production in alfalfa ( Medicago sativa L.). The objective of this study was to test the hypothesis that synergy exists between transgenic SOD stress‐tolerance mechanisms, specifically that the simultaneous expression of two SOD transg...
Article
Full-text available
To determine whether overexpression of Fe-superoxide (SOD) dismutase would increase superoxide-scavenging capacity and thereby improve the winter survival of transgenic alfalfa (Medicago sativa L.) plants, two genotypes were transformed with the vector pEXSOD10, which contains a cDNA for Arabidopsis Fe-SOD with a chloroplast transit peptide and cau...
Article
To determine whether overexpression of Fe-superoxide (SOD) dismutase would increase superoxide-scavenging capacity and thereby improve the winter survival of transgenic alfalfa (Medicago sativa L.) plants, two genotypes were transformed with the vector pEXSOD10, which contains a cDNA for Arabidopsis Fe-SOD with a chloroplast transit peptide and cau...
Article
In grapevines, buds and canes have different strategies of freezing tolerance - buds avoid freezing by supercooling, whereas canes tolerate extracellular freezing. To further understand the relationship between freezing tolerance and carbohydrate composition of these tissues in Vitis vinifera, analyses were made of starch, glucose, fructose, sucros...
Article
To test the hypothesis that enhanced tolerance of oxidative stress would improve winter survival, two clones of alfalfa (Medicago sativa) were transformed with a Mn-superoxide dismutase (Mn-SOD) targeted to the mitochondria or to the chloroplast. Although Mn-SOD activity increased in most primary transgenic plants, both cytosolic and chloroplastic...
Chapter
Full-text available
Condensed tannins (proanthocyanidins) are plant phenolic polymers with protein-binding, carbohydrate-binding, and antioxidant properties. Dietary condensed tannins deter some insects from feeding on crops, disrupt insect digestion and growth,1 and deter larger browsing and foraging animals.2 As well, the very high levels of condensed tannins found...
Article
Summary The effects of callus inoculation concentration and culture duration on somatic embryogenesis of orchardgrass,Dactylis glomerata L., were evaluated in suspension cultures of an embryogenic genotype Embryogen-P. Somatic embryo formation was induced in liquid SH medium containing 30 μM dicamba (SH-30 and 1.5% casein hydrolysate; embryo develo...
Article
A mutant phenotype isolated from alfalfa (Medicago sativa L) cv. Excalibur appeared to have dramatic changes in source-sink relations and the partitioning of carbohydrates. Leaves emerged normally, but starch accumulated in the chloroplasts of the palisade mesophyll cells with maturity. Subsequently, the cells of the palisade layer lost chlorophyll...
Article
Winterhardiness is a composite of tolerances to freezing, desiccation, ice-encasement, flooding and diseases. From one point of view, winterhardiness may not be easily manipulated by genetic engineering technology because many different genes are involved in the tolerance of these diverse stresses. However, these various stresses have similarities....
Chapter
Winterhardiness is a complex trait involving tolerances to freezing, water deprivation, ice-encasement (severe anoxia), flooding (milder anoxia) and disease. The combination and severity of these stresses that crops must tolerate varies from environment to environment and from year to year. Different crops, even in the same environment, experience...
Article
Among the forage legumes somatic embryogenesis has been most studied in alfalfa (Medicago sativa L.) reflecting inherent breeding problems and the high demand for seeds of this species. Current methods of somatic embryogenesis are reviewed with emphasis on each of the 3 stages involved: the acquisition of competence, the induction of somatic embryo...
Article
Full-text available
Transgenic alfalfa (Medicago sativa) expressing Mn-superoxide dismutase cDNA tended to have reduced injury from water-deficit stress as determined by chlorophyll fluorescence, electrolyte leakage, and regrowth from crowns. A 3-year field trial indicated that yield and survival of transgenic plants were significantly improved, supporting the hypothe...
Article
Winter cereal production in many areas of eastern Canada is limited by a lack of consistent winter survival. A cold acclimated crown freezing test has been adopted to circumvent high variability associated with field tests. Relationships between field survival and crown freezing tolerance (LT50, lethal temperature for 50% of seedlings) of artificia...
Article
At the time of protrusion, radicles of lettuce seeds became susceptible to desiccation damage. Concomitant with radicle elongation, both the reducing sugar content and the amount of lipid-aldehydes increased. The role of the hydroxy- and lipid-aldehydes in browning reactions that occurred during desiccation and re-imbibition was analysed. It was co...
Article
The vigor of seedlings from desiccated somatic embryos of Medicago sativa is less than in seeds and this limits the utilization of synthetic seeds for the establishment of plants in the field or greenhouse. To determine whether low seedling vigor was caused by a lack of protein or carbohydrate reserves, the desiccated somatic embryos were imbibed o...
Article
Soluble carbohydrates were identified and quantified during development, maturation and desiccation of somatic embryos of alfalfa (Medicago sativa L.) and compared to soluble carbohydrates in leaflets and mature seeds, to relate changes in soluble carbohydrates to maturation events. Somatic embryos have elevated levels of sucrose. However, in contr...
Article
The damage caused by active oxygen generated by paraquat was investigated in two wheat cultivars, Triticum aestivum L. Frederick and Glenlea, which differed in their sensitivity to heat and chilling stress. Application of paraquat induced photoinhibition and loss of fresh mass, protein, and membrane integrity in the leaves. The photosynthetic pigme...
Article
Desiccated somatic embryos lack the vigor that is accociated with seeds, and this reduces the feasibility of using artificial seeds as a means of plant propagation. Although desiccated somatic embryos of alfalfa (Medicago sativa L.) are characterized by faster imbibition than in seeds, radicle and shoot emergence are slower. To determine the physio...
Article
Free fatty acids accumulate in plant membranes after exposure of plants to environmental stress, such as freezing and desiccation. Fatty acid accumulation has been linked to various biophysical changes and to the occurrence of lipid peroxidation, but the relationships appear complex and inconsistent. The interactions between oxygen free radicals, f...
Chapter
Since the beginning of agriculture plants have been propagated whenever possible by seeds as a convenient means of multiplication, storage, and distribution. At the end of every harvest, the highest quality portion of the seed crop is set aside for the next year’s planting. In many respects, seeds are an ideal propagation system because they (1) co...
Article
The low vigor of seedlings from dry somatic embryos of alfalfa (Medicago sativa L.) limits the establishment of plants from artificial seeds. slow growth and development may be associated with low storage protein deposition in the somatic embryo. The nutritional regulation of storage protein accumulation by nitrogen and sulfur nutrients was investi...
Article
Compared to seeds, somatic embryos accumulated relatively low levels and different types of storage carbohydrates. The regulation of starch accumulation was studied to determine its effects on desiccation tolerance and vigor of dry somatic embryos. Somatic embryos of Medicago sativa are routinely matured through three phases: 7 days of development;...
Article
Injury from freezing stress may be caused by degradative reactions initiated by activated oxygen. The relationship between tolerance of freezing and oxidative stresses was investigated in winter-cereal seedlings during cold acclimation. Freezing tolerance was evaluated as an LT50 (lethal temperature causing 50% mortality) based on regrowth from cro...
Article
Three methods of increasing the productivity of somatic embryogenesis in Medicago sativa L. were investigated. In the basic procedure, somatic embryos were initiated from young petioles and carried through several phases: callus formation, suspension culture, selection of the embryogenic fraction by sieving, development, maturation, desiccation and...
Chapter
Crop plants require a free exchange of atmospheric gases for photosynthesis and respiration. Like animals, plants can be easily suffocated if this gas exchange is impeded. The most common impediment to gas diffusion is water that saturates the root environment in poorly drained soils or that accumulates above soil capacity as a result of the overfl...
Chapter
Heat stress in plants in general, and especially in cultivated agricultural or horticultural species, is a complicated issue since it often occurs simultaneously with drought stress. For this reason, it is sometimes difficult to distinguish between the two and extensive research theoretical and applied, has taken this stress bull by its two horns,...
Chapter
The concept of optimal growth temperatures is a fundamental principle in biology. Since living organisms cannot control environmental temperature, they have evolved two major strategies for surviving extreme temperatures — they either avoid the stress, or tolerate it. The avoidance mechanism is most obvious in warm blooded animals that maintain the...
Book
1. The overall implications of biological stress.- 2. Oxidative stress.- 3. Salt stress.- 4. Chilling stress.- 5. Freezing stress.- 6. Desiccation.- 7. Water and drought stress.- 8. Heat stress.- 9. Anaerobic stress - flooding and ice-encasement.- 10. Environmental pollution stress.- Epilogue.
Chapter
One of the paradoxes of life on this planet is that the molecule that sustains aerobic life, oxygen, is not only fundamentally essential for energy metabolism and respiration, but it has been implicated in many diseases and degenerative conditions (Marx 1985). A common element in such diverse human disorders as aging, arthritis, cancer, ALS (Lou Ge...
Article
Full-text available
Activated oxygen or oxygen free radicals have been implicated in a number of physiological disorders in plants including freezing injury. Superoxide dismutase (SOD) catalyzes the dismutation of superoxide into O2 and H2O2 and thereby reduces the titer of activated oxygen molecules in the cell. To further examine the relationship between oxidative a...
Chapter
Water stress in mesophytic (non drought tolerant), as opposed to xerophytic (drought tolerant) cultivated species is probably the most common type of plant stress and in many regions is the bottleneck of agricultural development. Based on data collected from various geobotanical regions, Hurvitz (1958) has categorized drought tolerance of cultivate...
Chapter
Increasing salinity of irrigation water, in combination with progressive salinization of agricultural soils is inhibiting agricultural productivity in many semi-arid and arid regions of the world. However, the problem also exists in lands, intended for agricultural use, recently reclaimed from the sea as in the case of the polders in the Netherland...
Chapter
In a strictly biological-biochemical context the terms “stress” and its concomitant GAS (general adaptation syndrome) were originally coined over a half a century ago by the Canadian endocrinologist Hans Selye (1907–1982) in a brief, 72-lined article — “A syndrome produced by diverse nocuous agents” published in the 4th of July issue of “Nature” in...
Chapter
The study of environmental stress physiology has captured the interest of plant scientists for over a century — for good reason. The study of environmental stress affords an opportunity for us to study fundamental physiological processes, such as photosynthesis, growth, and reproduction, by perturbing the normal response of the plant through the im...
Chapter
Plants are polluted, prevent pollution and pollute. This statement summarizes modes of interaction of plants with environmental stress, but the focus of this chapter will be on the effects of environmental pollution on plants. This type of pollution can be grouped into two categories: xenobiotic and biotic pollution.
Chapter
The winterhardiness of perennial and winter annual crops has been a major preoccupation with agronomists in northern latitudes for over a century, because over-wintering crops have inherent advantages. For example, winter cereal crops compared to their spring counterparts have 15–25% higher yields, provide ground cover over winter and reduce erosio...
Chapter
Tolerance of desiccation is relatively rare in plants but is obvious in seeds and pollen. Desiccation is considered by some to be a necessary prerequisite for the completion of the life cycle in species producing seeds that are “orthodox” with regard to their ability to withstand storage at low moisture. Other species do not exhibit maturation dryi...
Article
Somatic embryogenesis in alfalfa (Medicago sativa L.) was induced in petiole derived cultures in the presence of 1 mg/1 2,4-dichlorophenoxyacetic acid (2,4-D) and 0.2 mg/1 kinetin and embryo elongation occurred when the embryogenic calli were transferred to hormone-free medium. A number of supplements to the induction medium, which in other systems...
Article
The vigor of seedlings from dry somatic embryos of alfalfa (Medicago sativa L.) is considerably less than the vigor of those from truw seeds, hypothetically as the result of low levels of storage proteins, an inhibitory effects of the ABA in the maturation medium, or injury from the desiccation process. In an attempt to increase vigor, three differ...
Article
The low vigour of seedlings grown from somatic embryos limits their use as artificial seeds. It was postulated that seedlings vigour could be enhanced by improving the nutrition of the somatic embryo during maturation, and thereby increasing deposition of storage carbohydrates and proteins. The maturation of alfalfa (Medicago sativa L.) somatic emb...
Article
Full-text available
Desiccation tolerance is one of the most fundamental properties of seeds. It is acquired late in seed development and is considered necessary for the completion of the plant's life cycle, as an adaptive strategy to enable seed survival during storage or environmental stress, and to ensure better dissemination of the species. The role of water statu...
Article
The role of lipid and water soluble antioxidants in providing tolerance to chilling stress in tomato leaves was investigated using two species, Lycopersicon esculentum and L. hirsutum, which differed in their sensitivity to chilling. The levels of a-tocopherol, ascorbate and glutathione, and their reduced/oxidized ratios in non-chilled leaves were...
Article
For successful application of artificial seed technology to alfalfa (Medicago sativa L.), parental plants must possess the necessary genes for somatic embryogenesis and produce progeny having high commercial value. A backcross procedure was initiated to transfer the ability to form somatic embryos from genotype A70-34, a selection from the cultivar...
Article
The vigor of seedlings from dry somatic embryos is considerably less than the vigor of seedlings from seeds, perhaps due to the low levels of storage proteins and low levels or different species of carbohydrates deposited in the dry somatic embryos. The effects of sucrose, abscisic acid and glutamine applied during maturation on the accumulation of...
Article
Somatic embryo quality is an important aspect of artificial or synthetic seed production and is dependent on proper morphological development and deposition of sufficient storage reserves to support early growth of the seedling. The abilities of a somatic embryo to survive desiccation and to establish a rapidly growing seedling were used as estimat...
Article
The role of ethylene in the growth of callus and somatic embryogenesis in Medicago sativa was examined. The application of 2,5-norbornadiene, a competitive inhibitor of ethylene action, during a 10 d induction period to medium containing 2,4-D and kinetin inhibited the growth of callus but did not affect somatic embryogenesis, nor did it affect eth...
Article
Somatic embryogenesis and plantlet formation have been achieved from cultured mature zygotic embryos of blue spruce (Picea pungens Engelman.). The effect of three basal media LP, LM, and BLG, all used at half-strength, was tested at the induction phase. LM medium induced somatic embryogenesis to a higher extent than LP whereas BLG did not produce a...
Article
The metabolic responses of an alfalfa (Medicago sativa clone RL34) cell suspension culture to anoxia stress were determined over a period of 72 h. Sealing a 6-day-old suspension in a test tube caused complete depletion of oxygen within 35 min and caused significant loss of viability. For example, the ability to form somatic embryos was reduced at 8...
Article
The use of dry microspore derived embryos as cloning materials greatly facilitates long term storage and transportability. The effects of heat and cold pretreatments on microspore-derived embryos of Brassica napus L. were investigated in an attempt to induce desiccation tolerance in these embryos before drying to about 12% moisture. Heat treatment...
Article
The feasibility of inserting DNA into dry plant cells during imbibition was investigated using dry embryos of alfalfa (Medicago sativa L.). Somatic embryos produced in vitro from cell culture, were induced to become desiccation tolerant and dried to approx. 10–15% moisture. In the dry state, the lipid bilayer of the plasmalemma is disorganized and...
Article
Full-text available
The mechanism of chilling resistance was investigated in 4-week-old plants of the chilling-sensitive cultivated tomato, Lycopersicon esculentum Mill. cv H722, and rooted cuttings of its chilling-resistant wild relative, L. hirsutum Humb. and Bonpl., which were chilled for 3 days at 2 degrees C with a 14-hour photoperiod and light intensity of 250 m...
Article
Degradation of cellular membranes is commonly observed following a lethal freeze-thaw stress to plant tissue. This study sought to determine the specific point during this freeze-thaw cycle when membrane degradation occurred in winter wheat (Triticum aestivum L.) crown and to determine if the process was similar in nonacclimated and acclimated crow...
Article
Full-text available
Microspore-derived embryos from Brassica napus L. were dried to less than 15% moisture and stored dry for a minimum of 7 days. Successful plant regeneration was observed when embryos at the cotyledonary stage of development were treated with 50 uM ABA for 7 days prior to desiccation. Solid agar or liquid medium gave similar results. The rate of dry...
Article
The vigor of seedlings from dry somatic embryos of Medicago sativa, line RL-34, is considerably less than the vigor of those from true seeds. Sucrose, maltose and ammonium levels in the development and maturation media were manipulated in an attempt to enhance this seedling vigor. Increasing the sucrose concentration in both media from 3 to 6% almo...
Article
Peroxidation of three membrane lipid preparations from plants was initiated using Fe-EDTA and ascorbate and quantified as the production of aldehydes and loss of esterified fatty acids. Using liposomes prepared from commercial soybean asolecithin, the degree of peroxidation was shown to be dependent on: the free radical dose, which was varied by th...
Article
The effects of sucrose concentration in the maturation medium in combination with a heat shock treatment at 36°C were investigated in an attempt to improve the vigor of seedlings grown from dry somatic embryos of alfalfa (Medicago sativa L.). Callus was formed from petiole expiants and dispersed in liquid suspension medium in the presence of 5 μM 2...
Article
The use of somatic embryos from cell culture systems in the clonal propagation of plants would be greatly facilitated if the somatic embryos could be dried and stored in a dormant state similar to true seeds. A cell culture system was developed for alfalfa (Medicago sativa L.) line RL34 which gave high yields of somatic embryos in an approximately...
Article
Phosphinothricin is a non-selective herbicide which inhibits glutamine synthetase (EC 6.3.1.2) activity causing an overaccumulation of ammonia in higher plants. Alfalfa (Medicago sativa L) shoot tissue and petiole-derived callus exposed to phosphinothricin show 50 and 70% reductions, respectively, in glutamine synthetase activity with a concomitant...
Article
To develop cultivars with greater tolerance to environmental stresses, an accurate assessment and ranking of experimental strains for stress environments is essential. This study was conducted to compare the regression, genotype mean — CV grouping, and superiority measure approaches for rating 16 alfalfa (Medicago saliva L.) populations for perform...
Article
The chilling tolerance of commercial Lycopersicon esculentum cultivars (H2653, H722), Solanum lycopersicoides, an F 1 hybrid of S. lycopersicoides × Sub-Arctic Maxi, and 25 BC 2 F 2 lines of L. hirsutum × H722 (backcrossed twice to H722) was evaluated using a chlorophyll fluorescence assay. The ratio of the initial to the peak fluorescence (Fo : Fp...
Article
In order to select cultivars with improved tolerance to environmental stresses, the relationship among tolerance to environmental stresses needs to be determined. This study evaluated 16 populations of alfafla for their tolerance to freezing (−8 to −16 °C), low temperature flooding (21 and 28 d), and ice encasement (10 and 14 d). Stresses were appl...
Article
Desiccation tolerance was induced in alfalfa (Medicago sativa L.) somatic embryos by exogenous application of abscisic acid (ABA). Subsequently, embroys were dried to 10–15% moisture and stored for at least 3 weeks in the dry state. To estimate embryo survival, dried somatic embryos were imhibed on moist paper with no moist filter paper with no add...
Article
Alfalfa (Medicago sativa L.) is a cross-pollinated, autotetraploid crop, sold commercially as synthetic populations of plants. The production of hybrids offers the potential advantages of minimizing inbreeding depression, maximizing genetic heterozygosity, and providing a uniform, consistent phenotype, which potentially will lead to improvements in...
Article
Ice encasement induced both quantitative and qualitative alterations in membrane proteins isolated from crown tissue of winter wheat (Triticum aestivum L.) cv. Norstar. Compared with a non-iced control, microsomes isolated after 1 day of icing showed the loss of at least 10 distinct polypeptides ranging from 14 to 80 kD, and the appearance of three...
Article
Free fatty acids accumulate in the membranes of plant cells following several lethal environmental stresses, and their accumulation has been correlated with the appearance of gel phase domains, increased microviscosity, and enhanced leakage of cytoplasmic solutes. Saturated and unsaturated free fatty acids which accumulate as a result of phospholip...
Article
Previous studies have shown that liposomes composed of phospholipids with low phase-transition temperatures can be stabilized in the absence of water, provided that fusion is inhibited between the vesicles during drying, and that during rehydration the phospholipids do not pass through the gel to liquid crystalline phase transition. These condition...
Article
Five-week old tomato (Lycopersicon esculentum L. cv. UC-82) seedlings were chilled at 4°C for 4 days at a 16 h light and 8 dark cycle. The leaves of chilled plants showed a loss of turgor, chlorosis, increased solute leakage followed by leaf death. All these symptoms of chilling injury were prevented by a soil application of the triazole uniconazol...
Article
Full-text available
The physical properties and chemical composition of microsomal membranes were examined during a 7 day period of ice encasement in crown tissue of winter wheat (Triticum aestivum L. cv Norstar). Membrane damage, detected as an increase in microviscosity and electrolyte leakage, began between 1 and 3 days of icing, and was associated with a reduction...
Article
Full-text available
The functional and physical properties of cellular membranes isolated from Triticum aestivum, cvs Norstar and Fredrick, were altered coincident with changes in composition after a lethal ice-encasement stress and further during a 6 hour post-thaw period. Crowns encased in ice for a duration which inhibited regrowth, exhibited enhanced rates of elec...
Article
Senaratna, T., McKersie, B. D. and Borochov, A. 1987. Desiccation and free radical mediated changes in plant membranes.—J. exp. Bot. 38: 2005‐2014. In vitro treatment of microsomal membranes from the axes of soybean (Glycine max (L.) Merr.) seeds with free radicals simulates the type of membrane injury observed following a lethal desiccation stress...
Article
Seven day old wheat plants (Triticum aestivum L.), cv. Fredrick, were exposed to an ozone atmosphere of 0.5 ppm for a period of 6 h. The leaves of the control plants showed typical symptoms of ozone injury, i.e. chlorosis, necrotic lesions, increased solute leakage and reduced Hill activity. These phytotoxic symptoms were prevented in the plants gr...
Article
Full-text available
A freeze-thaw cycle to -12 degrees C induced several physical and compositional changes in the microsomal membranes isolated from crown tissue of winter wheat (Triticum aestivum L. cv Frederick). Exposing 7-day-old, nonacclimated seedlings to a single freeze-thaw cycle prevented regrowth of the crown and resulted in increased membrane semipermeabil...
Article
Protein hydrolysis can be extensive during ensiling of alfalfa (Medicago sativa L.) herbage. Such hydrolysis lengthens the ensiling phase and reduces the quality of the resultant feed. The objectives of this study were: (1) to estimate the genetic variance and narrow-sense heritability (via a half-sib analysis) of proteolytic activity in an alfalfa...
Article
Full-text available
Membrane injury is an important factor contributing to cellular death following environmental stress. Recent evidence suggests that in plants, changes in membrane phase properties after exposure to a lethal environmental stress may be a result of lipid deesterification mediated by free radicals. To test this hypothesis, the effects of primary free...
Article
The effects of growth temperature (2 degrees C and 24 degrees C), abscisic acid (ABA) concentration, duration of exposure to ABA, and light were assessed for their ability to induce acclimation to freezing temperatures in callus cultures of Lotus corniculatus L. cv Leo, a perennial forage legume. The maximal expression of freezing tolerance was ach...
Article
The structural and compositional changes which occur in cellular membranes after freezing stress were examined in a microsomal membrane fraction from the crown tissue of 7-day-old, nonacclimated Triticum aestivum L. cv. Fredrick seedlings, which were frozen to a lethal temperature of −12 °C. The freezing treatment induced a lipid phase separation a...
Article
The axis of soybean seeds suffer dehydration injury if they are dried to 10% moisture at 36 hours of imbibition, but tolerate this stress if dried at 6 hours of imbibition. Deesterification of membrane phospholipids has been correlated with the increased permeability and increased lipid phase transition temperatures of membranes from dehydration in...
Article
Smooth microsomal membranes were isolated from axes of soybean (Glycine max L. Merr.) seeds at the dehydration-tolerant (6 hours of imbibition) and dehydration-susceptible (36 hours of imbibition) stages of development and were exposed to free radicals in vitro using xanthine-xanthine oxidase as a free radical source. Wide angle x-ray diffraction s...
Article
Axes of soybean seeds are tolerant to dehydration at 6 hours of imbibition, but susceptible to dehydration injury if dried at 36 hours of imbibition. Smooth microsomal membranes were isolated from axes imbibed for 6 hours (dehydration tolerant state) and 36 hours (dehydration susceptible state) before and after dehydration treatment. The phase prop...
Article
Soybean (Glycine max L. Merr) seeds lose their tolerance of dehydration between 6 and 36 hours of imbibition. Soybean axes and cotyledons were excised 6 hours (tolerant of dehydration) and 36 hours (susceptible) after commencing imbibition and subsequently dehydrated to 10% moisture. Kinetics of the efflux of potassium, phosphate, amino acid, sugar...
Article
The sensitivity of soybean (Glycine max L. Merr. cv Maple Arrow) seeds to dehydration changed during germination. Seeds were tolerant of dehydration to 10% moisture if dried at 6 hours of imbibition, but were susceptible to dehydration injury if dried at 36 hours of imbibition. Dehydration injury appeared as loss of germination, slower growth rates...