ABA and Low Temperature Induce Freezing Tolerance via Distinct Regulatory Pathways in Wheat

The role of ABA in the induction of freezing tolerance was investigatedin two wheat (T. aestivum L.) cultivars, Glenlea (spring var)and Fredrick (winter var). Exogenous application of ABA (5x10^–5M for 5 days at 24°C) increased the freezing tolerance ofintact plants by only 3°C (LT₅₀) in both cultivars. Maximalfreezing tolerance (LT₅₀ of –9°C for Glenlea and –17°Cfor Fredrick) could only be obtained with a low temperaturetreatment (6/2°C; day/night) for 40 days. These resultsshow that exogenously applied ABA cannot substitute for lowtemperature requirementto induce freezing tolerance in intactwheat plants. Furthermore, there was no increase in the endogenousABA level of wheat plants during low temperature acclimation,suggesting the absence of an essential role for ABA in the developmentof freezing tolerance in intact plants. On the other hand, ABAapplication (5x10^–5 M for 5 days at 24°C) to embryogenicwheat calli resulted in an increase of freezing tolerance similarto that achieved by low temperature. However, as in intact plants,there was no increase in the endogenous ABA level during lowtemperature acclimation of calli. These results indicate thatthe induction of freezing tolerance by low temperature is notassociated with an increase in ABA content. Using an antibodyspecific to a protein family associated with the developmentof freezing tolerance, we demonstrated that the induction offreezing tolerance by ABA in embryogenic wheat calli was correlatedwith the accumulation of a new 32 kDa protein. This proteinis specifically induced by ABA but shares a common antigenicitywith those induced by low temperature. These results suggestthat ABA induces freezing tolerance in wheat calli via a regulatorymechanism different from that of low temperature. (Received June 15, 1993; Accepted September 16, 1993)     

Effect of Temperature, Light, Nutrients and Dehardening on Abscisic Acid Induced Cold Hardiness in Bromus inermis Leyss Suspension Cultured Cells

The effects of culture conditions on abscisic acid (ABA)-inducedfreezing tolerance were determined in smooth bromegrass Bromusinermis Leyss cv. Manchar) cell suspension cultures. Bromegrasscultures initiated with 2 g fr wt of cells achieved maximumfreezing tolerances (greater than –32?C) at 25 to 30?Cin the presence of 75 to 100 µM ABA. High levels of freezingtolerance induced by ABA were correlated with high growth ratesat 25 and 30?C. In control cells, incubation at 10?C inducedoptimum levels of hardiness with minimal growth. Prolonged exposure(6 weeks) of cells to 3?C, with or without ABA, increased freezingtolerance only by several degrees. Exogenous ABA concentrationsgreater than 100 µM were not inhibitory to growth. Repeatedexposure to ABA, however, retarded growth and made the cellstolerant to temperatures below –40?C. Removal of ABA fromthe medium resulted in dehardening of the cells both at 25 and3?C. Nitrogen had a marginal effect on ABA-induced hardeningat 25?C, but inhibited age-dependent hardening of control cellcultures. Light had no effect on the freezing tolerance of culturedcells. Addition of 10% sucrose, 30 min prior to freezing, tobromegrass cells treated with ABA for 4 days increased freezingtolerance more than 15?C. These observations are discussed inrelation to the contrasting behaviour of the low temperatureand photoperiod dependent cold acclimation of plants (Received July 14, 1989; Accepted October 23, 1989)     

Induction of freezing tolerance in potato (Solanum commersonü) suspension cultured cells

The induction of freezing tolerance by abscisic acid (ABA) or cold treatment in suspension cultured cells of Solanum commersonii was studied. Both ABA (50–100 μ M ) at 23°C and low temperature (4°C) increased freezing tolerance in cultured Solanum commersonii cells from a LT₅₀ (freezing temperature at which 50% cells were killed) of —5°C (control) to —11.5°C in 2 days. Cold-induced freezing tolerance reached its maximum at 2 days and remained constant throughout the cold acclimation period of 11 days. The freezing tolerance induced by ABA, however, showed a rapid decline 2 to 5 days after initiation of ABA treatments. Addition of ABA (100 μ M ) to the culture medium at the inception of low temperature treatment did not enhance freezing tolerance of the cells beyond the level attainable by either treatment singly. Poly(A⁺)-RNA was isolated from the respective treatments, translated in a rabbit reticulocyte lysate cell free system, and the translation products were resolved by two dimensional polyacrylamide gel electrophoresis (ID-PAGE). Analysis of the in vitro translated products revealed changes in the abundance of approximately 26 products (encoding for polypeptides with M, of 14 to 69 kDa and pl of 4.90 to 6.60) in ABA-treated cells 12 h after treatment, and 20 (encoding for polypeptides with M_r of 12 to 69 kDa, with pl of 4.80 to 6.42) in cells exposed to 4°C for 12 h. There were only 5 novel translation products observed when the ABA-treated cells reached the highest level of freezing tolerance (2 days after the initiation of ABA treatment). Changes in translatable RNA populations during the induction of freezing tolerance in cells treated with either ABA or low temperature are discussed.     

Changes in the Translatable RNA Population during Abscisic Acid Induce Freezing Tolerance in Bromegrass Suspension Culture

Abscisic acid (ABA) has been shown to increase freezing toleranceof bromegrass (Bromus in-ermis Leyss cv. Manchar) cell suspensioncultures from a LT₅₀ (the temperature at which 50% cells werekilled) of –7 to – 30?C in 5 days at 23?C. Our objectivewas to study the qualitative changes in the translatable RNApopulation during ABA induced frost tolernace. In vitro translationproducts of poly(A)⁺ RNA isolated from bromegrass cells withor without 75 µM ABA treatment for various periods oftime were separated by 2D-PAGE and visualized by fluorography.SDS soluble proteins from the same treatments were also separatedby 20-PAGE. After 5 days treatment, at least 22 new or increasedabundance SDS soluble polypeptides were observed. From fluorographs,29 novel or increased abundance in vitro translation productscould be detected. The pattern of changes between ABA inducedSDS-soluble proteins and translation products from the 2D gelswere similar. A time course study (0–7 days) showed that17 of the 29 translation products were detected after 1 dayABA treatment, and at least 14 were present after 1 h. Coldtreatment (+4?C) induced fewer changes in the pool of translatableRNA than with ABA treatment. Three translation products inducedby cold appear to be similar to 3 of the ABA induced translationproducts. The majority of the ABA inducible translatable RNAsappeared at 10 µM or higher which coincides with the inductionof freezing tolerance. Many of these ABA inducible RNAs persisted7 days after ABA was removed from the media and correspondinglythe LT₅₀ (–17?C) was still well above the control level(–17?C). The results suggest that ABA alters the poolof translatable RNAs during induction of freezing tolerancein bromegrass suspension culture cells. ¹Oregon Agricultural Experiment Station Technical Paper No.9256. (Received August 3, 1990; Accepted October 18, 1990)     

The Expression of an Abscisic Acid-Responsive Glycine-Rich Protein Coincides with the Level of Seed Dormancy in Fagus sylvatica

By differential screening of a cDNA library constructed frompoly (A⁺) RNA of ABA-treated seeds of Fagus sylvatica L., wehave isolated an ABA-responsive clone that is present in dormantseeds and under conditions that maintain dormancy, but it tendsto disappear under conditions breaking seed dormancy. A searchof the sequence data bases showed that the clone codes for aGlycine-Rich Protein and has sequence similarity to RNA-bindingproteins. The clone, which exibits the characteristics of lea-genes,is up-regulated by ABA and down-regulated by GA3. Paclobutrazolabolishes the effect of GA³, which is restored upon additionof GA3. The possible relationship of this Glycine-Rich Proteinto seed dormancy in F. sylvatica is discussed. (Received May 23, 1997; Accepted September 22, 1997)     

Developmental control of xylem hydraulic resistances and vulnerability to embolism in Fraxinus excelsior L.: impacts on water relations

The freezing tolerance of many plants, such as pea (Pisum sativum),is increased by exposure to low temperature or abscisic acidtreatment, although the physiological basis of this phenomenonis poorly understood. The freezing tolerance of pea shoot tips,root tips, and epicotyl tissue was tested after cold acclimationat 2C, dehydration/rehydration, applications of 10^–4M abscisic acid (ABA), and deacclimation at 25C. Tests wereconducted using the cultivar ‘Alaska’, an ABA-deficientmutant ‘wil’, and its ‘wildtype’. Freezinginjury was determined graphically as the temperature that caused50% injury (T₅₀) from electrical conductivity. Endogenous ABAwas measured using an indirect enzyme-linked immunosorbant assay,and novel proteins were detected using 2-dimensional polyacrylamidegel electrophoresis. The maximum decrease in T₅₀ for root tissuewas 1C for all genotypes, regardless of treatment. For ‘Alaska’shoot tips and epicotyl tissue, exogenous ABA increased thefreezing tolerance by –1.5 to –4.0C, while coldtreatment increased the freezing tolerance by –7.5 to–14.8C. Cold treatment increased the freezing toleranceof shoot tips by –9 and –15C for ‘wil’and ‘wild-type’, respectively. Cold acclimationincreased endogenous ABA concentrations in ‘Alaska’shoot tips and epicotyls 3- to 4-fold. Immunogold labeling increasednoticeably in the nucleus and cytoplasm of the epicotyl after7 d at 2C and was greatest after 30 d at the time of maximumfreezing tolerance and soluble ABA concentration. Cold treatmentinduced the production of seven, three, and two proteins inshoot, epicotyl, and root tissue of ‘Alaska’, respectively.In ‘Alaska’ shoot tissue, five out of seven novelproteins accumulated in response to both ABA and cold treatment.However, only a 24 kDa protein was produced in ‘wil’and ‘wild-type’ shoot and epicotyl tissues aftercold treatment. Abscisic acid and cold treatment additivelyincreased the freezing tolerance of pea epicotyl and shoot tissuesthrough apparently independent mechanisms that both resultedin the production of a 24 kDa protein. Key words: Pisum sativum, cold acclimation, immuno-localization     

Freezing tolerance, protein composition, and abscisic acid localization and content of pea epicotyl, shoot, and root tissue 3

The freezing tolerance of many plants, such as pea (Pisum sativum),is increased by exposure to low temperature or abscisic acidtreatment, although the physiological basis of this phenomenonis poorly understood. The freezing tolerance of pea shoot tips,root tips, and epicotyl tissue was tested after cold acclimationat 2C, dehydration/rehydration, applications of 10^–4M abscisic acid (ABA), and deacclimation at 25C. Tests wereconducted using the cultivar ‘Alaska’, an ABA-deficientmutant ‘wil’, and its ‘wildtype’. Freezinginjury was determined graphically as the temperature that caused50% injury (T₅₀) from electrical conductivity. Endogenous ABAwas measured using an indirect enzyme-linked immunosorbant assay,and novel proteins were detected using 2-dimensional polyacrylamidegel electrophoresis. The maximum decrease in T₅₀ for root tissuewas 1C for all genotypes, regardless of treatment. For ‘Alaska’shoot tips and epicotyl tissue, exogenous ABA increased thefreezing tolerance by –1.5 to –4.0C, while coldtreatment increased the freezing tolerance by –7.5 to–14.8C. Cold treatment increased the freezing toleranceof shoot tips by –9 and –15C for ‘wil’and ‘wild-type’, respectively. Cold acclimationincreased endogenous ABA concentrations in ‘Alaska’shoot tips and epicotyls 3- to 4-fold. Immunogold labeling increasednoticeably in the nucleus and cytoplasm of the epicotyl after7 d at 2C and was greatest after 30 d at the time of maximumfreezing tolerance and soluble ABA concentration. Cold treatmentinduced the production of seven, three, and two proteins inshoot, epicotyl, and root tissue of ‘Alaska’, respectively.In ‘Alaska’ shoot tissue, five out of seven novelproteins accumulated in response to both ABA and cold treatment.However, only a 24 kDa protein was produced in ‘wil’and ‘wild-type’ shoot and epicotyl tissues aftercold treatment. Abscisic acid and cold treatment additivelyincreased the freezing tolerance of pea epicotyl and shoot tissuesthrough apparently independent mechanisms that both resultedin the production of a 24 kDa protein. Key words: Pisum sativum, cold acclimation, immuno-localization     

Rapid degradation of starch in chloroplasts and concomitant accumulation of soluble sugars associated with ABA-induced freezing tolerance in the moss Physcomitrella patens

Abscisic acid (ABA) has been postulated to play a role in the development of freezing tolerance during the cold acclimation process in higher plants, but its role in cold tolerance in tower land plants has not been elucidated. The moss Physcomitrella patens rapidly developed freezing tolerance when its protonemata were grown in a medium containing ABA, with dramatic changes in the LT50 value from -2 degrees C to over -10 degrees C. We examined physiological and morphological alterations in protonema cells caused by ABA treatment to elucidate early cellular events responsible for rapid enhancement of freezing tolerance. Microscopic observations revealed that ABA treatment for 1 day resulted in a dramatic alteration in the appearance of intracellular organelles. ABA-treated cells had slender chloroplasts, with a reduced amount of starch grains, in comparison with those of non-treated cells. The ABA-treated cells also had several segmented vacuoles while many of non-treated cells had one central vacuole. When frozen to -4 degrees C, freezing injury-associated ultrastructural changes such as formation of aparticulate domains and fracture-jump lesions were frequently observed in the plasma membrane of non-treated protonema cells but not in that of ABA-treated cells. The ABA treatment increased the osmotic concentration of the protonema cells, in correlation with accumulation of free soluble sugars. These results suggest that ABA-induced accumulation of soluble sugars, associated with morphological changes in organelles, mitigated freezing-induced structural damage in the plasma membrane, eventually leading to enhancement of freezing tolerance in the protonema cells.     

Effect of Plant Growth Regulators on Flower-Opening of Pharbitis nil

Flower buds of Pharbitis nil (due to open the next morning)cut from plants in the field before noon open very slowly bothin darkness and at a low temperature (20°C), unlike thebuds cut in the evening. On cool cloudy days, even the budscut in the evening open very slowly. Addition of sucrose, mineralnutrients or plant growth regulators other than ABA to the waterin which the cut buds were placed did not promote flower-openingunder such conditions, but addition of ABA (10–100 µM)greatly promoted it. IAA (100 µM) given alone or in combinationwith ABA suppressed floweropening completely. Mature flowerbuds placed in an ABA solution opened even under continuouslight at 25°C just as those kept in darkness without ABA;flower-opening occurred about 12 h after the application ofABA. ABA given to the buds in darkness at 25°C and thatgiven in continuous light at 20°C also advanced the timeof flower-opening. The action mechanism of ABA is discussed. ¹ This paper is dedicated to the memory of Dr. Joji Ashida,the first president of the Japanese Society of Plant Physiologist. (Received October 28, 1982; Accepted January 7, 1983)     

The Influence of Season and Phenology on Freezing Tolerance in Silene acaulis L., a Subarctic and Arctic Cushion Plant of Circumpolar Distribution

Changes in the freezing tolerance for Silene acaulis L., a subarcticand arctic species of circumpolar distribution, were examinedto understand the extent of cold hardening and dehardening thatoccurs seasonally and with changes in plant phenology. Shootsof whole plants collected on a mountain ridge near Tromsø,Norway (69° N, 700 m above sea level) were frozen undercontrolled conditions at cooling rates of 3 to 4°C h^-1.The extent of freezing-induced injury was examined both by chlorophyllfluorescence and by visual inspection with a microscope. A freezingtolerance level of -30°C was observed in mid-winter, basedon a 50% lethal point for freezing injury. Loss of cold hardinesswas substantial in mid-summer, with freezing tolerance of -8·5to -9°C observed in mid-July. Plants still covered by snowin mid-July had a freezing tolerance of -12·5 to -13°C.The maintenance of a basic level of freezing tolerance throughoutthe summer may be adaptive in the northern latitude-regionsbecause of the occurrence of episodic frosts during the growingseason.Copyright 1993, 1999 Academic Press Silene acaulis L., Caryophyllaceae, freezing tolerance, chlorophyll fluorescence, cushion plant     

Microelectrophoretic and 9-Aminoacridine Fluorescence Study of the Surface Electrical Properties of Suspension Cultured Catharanthus roseus Cells and Isolated Protoplasts: Effects of Abscisic Acid Treatment

The effects of abscisic acid (ABA) treatments on the surfaceelectrical properties of cells and isolated protoplasts fromCatharanthus roseus cell suspension cultures were studied byelectrophoretic mobility and 9-aminoacridine (9AA) fluorescencemeasurements. The surface charge densities of the cells andprotoplasts estimated from electrokinetic data were –0.064Cm^–2and –0.048 C m^–2 respectively. These values wereclose to that estimated by 9AA fluorescence technique i.e.,–0.053 Cm^–2 for the cells and –0.041 Cm^–2for the isolated protoplasts accordingly. The net negative surfacecharge density decreased after application of 10 µM and50 µM ABA in both cells and protoplats, the more pronouncedeffect being observed at 10 µM ABA. When 100 µMABA was supplemented to the cell suspension culture the oppositeeffect was observed. The average charge density increased to–0.074 C m^–2 for the cells, and to –0.055C m^–2 for protoplasts, as revealed from the 9AA measurements.The results are discussed in terms of specific concentrationdependent ABA-induced alterations of the electrostatic propertiesof cell and protoplast membranes. (Received December 12, 1994; Accepted April 3, 1995)     

Isolation of cDNA for a Plasma Membrane H+-ATPase from Guard Cells of Vicia faba L.

cDNA encoding the plasma membrane H⁺-ATPase of guard cells ofVicia faba L. was isolated. The clone encoded a 105-kDa polypeptide(956 amino acids) that was 79–85% identical in terms ofamino acid sequence to other plant H⁺-ATPases. High levels ofmRNA explain the high H⁺-ATPase activity of these plasma membranes. (Received December 24, 1994; Accepted April 12, 1995)     

Characterization of an abscisic acid carrier in suspension-cultured barley cells

The uptake of [³H]-abscisic acid in barley (Hordeum vulgareL. cv. Heartland) cell cultures was found to be mediated throughboth non-saturable and saturable components. The kinetic parametersof the saturable component, determined at pH 4.5 and 21 °C,showed a K_m for natural or (+ )-ABA of 1.3±0.7µMand an apparent V_mex of 7.0 ± 2.8 nmol g^–1 cellsh^–1. The carrier showed a strong preference for the naturalenantiomer of ABA as compared to the unnatural one. Other substancestested, e.g. amino acids, organic acids, and other growth regulators,did not appear to interfere with the carrier-mediated uptakeof ABA. At low external concentrations of ABA (below 2.0 µM),the saturable component was greater than the diffusion component.Similarly, between pH 4.0 and 6.0, the saturable uptake wasresponsible for more than 50% of the total uptake. The carriermay be important in vivo for mediating uptake when endogenouslevels of ABA are low (c. 1 µM). The carrier specificity was evident in inhibition experimentsdone with ABA analogues. Our data showed that the carrier couldaccommodate small modifications in the ABA structure. Four analogueswere able to compete efficiently with ( + )-ABA for the bindingsite of the carrier. Three of these competitors were of the(+)-series. Only one ( –)-analogue, (–)-ABA, wasable to inhibit markedly the saturable uptake of ( + )-ABA.The induction of the ABA-respons-ive gene WCS120 (Houde et al.,1992) presented stricter requirements for the ABA molecule thanthe carrier, although with a similar preference for the ( +)-analogues. Besides ( + )-ABA itself, only two of the analoguestested, both ( + )-series, were able to induce the WCS120 geneafter a 24 h incubation period. The absence of correlation betweenthe activity of the analogues as ABA inhibitors in the carriersystem, and their capacity to induce the WCS120 gene tend tosuggest that the carrier is not directly involved in the signaltransduction pathway leading to the induction of this specificgene. Key words: Abscisic acid, barley, gene induction, Hordeum vulgare, uptake carrier     

Inhibition of Light-Stimulated Leaf Expansion by Abscisic Acid

Abscisic acid (ABA) applied to intact bean (Phaseolus vulgaris)leaves or to isolated leaf discs inhibits light-stimulated cellenlargement This effect may be obtained with 10^–4 molm^–3 ABA, but is more significant at higher concentrations.The inhibition of disc expansion by ABA is greater for discsprovided with an external supply of sucrose than for discs providedwith KC1, and may be completely overcome by increasing the KC1concentration externally to 50 mol m^–3. Decreased growthrate of ABA-treated tissue is not correlated with loss of solutesfrom growing cells, but is correlated with a decrease in cellwall extensibility. ABA does not prevent light-stimulated acidificationof the leaf surface, and stimulates the acidification of theexternal solution by leaf pieces. However, the capacity of thecell walls to undergo acid-induced wall loosening is diminishedby ABA-treatment. The possibility that ABA acts directly byinhibiting growth processes at the cellular level, or indirectlyby causing stomatal closure, is discussed. Key words: Phaseolus vulgaris, ABA, Inhibition, Leaf expansion     

Genetic Variability in Recovery Growth and Synthesis of Stress Proteins in Response to Polyethylene Glycol and Salt Stress in Finger Millet

Marked differences were found among 28 finger millet genotypes(Eleusine coracana Gaertn.) in acquired tolerance to osmoticstress as assessed by the recovery of root growth from severestress [-1·2 MPa polyethylene glycol, (PEG) or 400 mMNaCl]. However, these differences in tolerance were observedonly when the seedlings were subjected to a preceding mild inductionstress (-0·6 MPa PEG or 200 mM NaCl). In two contrastinggenotypes, synthesis of stress-induced proteins was studied.Proteins with apparent molecular weight of 70-72, 52, 37, 34and 23 kDa were synthesized in the highly responsive genotype(GE 415) and poorly responsive (VL 481) genotype following amild induction stress (200 mM NaCl). However, GE-415 synthesizeda 54 kDa protein that was not observed in VL-481. Addition ofabscisic acid (ABA) to the induction medium containing 200 mMNaCl enhanced the acquired tolerance of finger millet seedlingsover those without ABA in association with the appearance ofseveral ABA-responsive proteins. GE-415 required much less ABAthan VL-481 to obtain the same response. With 10 µM ABA+ 200 mM, A NaCl induction stress, GE-415 had significantlyhigher endogenous ABA. In association with higher levels ofABA, GE-415 had greater recovery root growth following severestress from 600 mM NaCl. Pretreatment with 10 µM ABA +200 mM NaCl induced several proteins with apparent molecularweights of 70-72, 54, 45, 36, 29 and 21 kDa in both genotypes.Qualitatively, GE-415 synthesized a unique 23-24 kDa proteinand quantitatively there was significantly more of the 21 kDaprotein in GE-415 compared to VL-481. The results indicate thatthe synthesis of stress proteins is correlated with the observedvariation in acquired tolerance of the two genotypes.Copyright1995, 1999 Academic Press Eleusine coracana Gaertn., salinity, polyethylene glycol, stress proteins, ABA, ABA-responsive proteins, finger millet seedlings     

Rice Embryo Globulins: Amino-Terminal Amino Acid Sequences, cDNA Cloning and Expression

A globulin fraction prepared from rice embryos contained polypeptidesor polypeptide groups of 49 kDa (designated REG1), 46 kDa (designatedREG2), about 35 kDa, 32 kDa and 25 kDa. The amino-terminal sequencesof REG1 and the major polypeptide in the 35-kDa group were identical,suggesting that the REG1 polypeptide undergoes partial proteolyticprocessing that removes a carboxy-terminal region. A cDNA clone,designated pcREG2, encoding REG2 was isolated, and its nucleotidesequence was determined. The deduced amino acid sequence ofREG2 was found to be 68% identical to that of the maize GLB2globulin. Reg2 mRNA was present at high levels during embryodevelopment for up to 14 days after flowering (DAF). Lower levelswere found 20 DAF when the maturation of embryos was almostcompleted, and at the dry mature stage. Reg2 mRNA almost disappearedupon imbibition of isolated dry mature embryos but it was re-inducedat a low level by further treatment with ABA. The expressionof Reg2 was not induced by ABA in suspension-cultured cells,unlike that of Osem, one of the late embryogenesis abundantprotein (LEA) genes. (Received November 6, 1995; Accepted April 22, 1996)     

Early Developments in RNA, Protein, and Sugar Levels during Cold Stress in Winter Rye (Secale cereale) Leaves

Changes in freezing tolerance of winter rye (Secale cerealeL. cv. Voima) were determined for leaf tissues during a 1-weekcold stress, which was performed by transferring the 7-d-oldseedlings from a greenhouse (25°C, long day) to 3°Cand short day conditions. The development of cold hardeningwas shown by using an ion leakage test and by determining theamounts of carbohydrates, soluble proteins and RNA. The firstevidence of the development of freezing resistance was foundafter 1 d at low temperature, i.e. an LT₅₀ value increased from-5 to -7°C. Plants cold treated for 7 d reached an LT₅₀value of -9°C. This increase in freezing tolerance was foundto be associated with the increased levels of soluble carbohydrates,total RNA and soluble proteins. These metabolic changes indicatethe association with adjustment of growth and cell metabolismto low temperatures at the beginning of cold acclimation ofwinter rye.Copyright 1994, 1999 Academic Press Secale cereale L., winter rye, cold stress, proteins, RNA, sugars     

Successful long-term preservation of abscisic-acid-treated and desiccated carrot somatic embryos

We have previously reported that strong desiccation tolerance in carrot somatic embryos can be achieved by treatment with abscisic acid (ABA). In this study, we examined the possibility of long-term preservation of ABA-treated and desiccated somatic embryos. Somatic embryos that had been desiccated after treatment with ABA survived for at least 169 weeks at –25 °C. By contrast, somatic embryos that had not been desiccated after treatment with ABA survived for at least 24 weeks at +5 °C but died at –25 °C. Received: 11 July 1998 / Revision received: 20 October 1998 / Accepted: 20 November 1998