Abscisic acid-induced growth inhibition of sweet potato (Ipomoea batatas L.) in vitro

The inhibitory effects of abscisic acid (ABA) on in vitro growth and development of axillary buds from nodal segments of sweet potato (Ipomoea batatas L.) was investigated. ABA at concentrations of 0.01, 0.1, 1.0 or 10.0 mg 1^-1 inhibited axillary bud and root development and subsequent plantlet growth. ABA at 10 mg 1^-1 completely inhibited axillary shoot development but did not affect the viability of cv. Jewel explants over a culture period of 365 days. Transfer of nodal segments cultured for 90, 180 or 365 days from basal medium containing 10 mg 1^-1 ABA to growth regulator-free media resulted in rapid and normal plantlet development. Gibberellic acid at 0.1, 1.0 or 10.0 mg 1^-1 in the presence of ABA at 0.1, 1.0 or 10.0 mg 1^-1 did not counteract the ABA-induced growth inhibition. Although ABA totally inhibited the growth of 6 sweet potato plant introductions at a concentration of 10.0 mg 1^-1, the efficacy of ABA as a suppressant of shoot growth varied with genotype.Abbreviations ABA abscisic acid - GA gibberellic acid - cDNA complementary DNA - PI plant introduction - SE standard error     

Cytokinin Reversal of Abscisic Acid Inhibition of Growth and α-Amylase Synthesis in Barley Seed

The effect of cytokinin, kinetin, on abscisic acid (dormin) inhibition of α-amylase synthesis and growth in intact barley seed was investigated. Abscisic acid at 5 × 10^?5M nearly completely inhibited growth response and α-amylase synthesis in barley seed. Kinetin reversed to a large extent abscisic acid inhibition of α-aniylase synthesis and coleoptile growth. The response curves of α-amylase synthesis and coleoptile growth in presence of a fixed amount of abscisic acid (6 × l0^?6M) and increasing concentrations of kinetin (from 5 × l0^?7M to 5 × 10^?5 M) showed remarkable similarity. Kinetin and abscisic acid caused synergistic inhibition of root growth. Gibberellic acid was far less effective than kinetin in reversing abscisic acid inhibition of α-amylase synthesis and coleoptile growth. A combination of kinetin and gibberellic acid caused nearly complete reversal of abscisic acid inhibition of α-amylase synthesis but not the abscisic acid inhibition of growth. The results suggest that factors controlling α-amylase synthesis may not have a dominant role in all growth responses of the seed. Kinetin possibly acts by removing the abscisic acid inhibition of enzyme specific sites thereby allowing gibberellic acid to function to produce α-amylase.     

Stimulation of Growth and Nucleic Acid Biosynthesis at Low Concentration of Abscisic Acid in Tissue Culture of Spinacia oleracea

The effect of abscisic acid on growth, ultrastructure and nucleic acid biosynthesis was studied in tissue culture of spinach (Spinacia oleracea L.). Low concentration (0.01 mg l^?1) of abscisic acid increased fresh and dry weight of calluses, whereas 1.0 mg l^?1 was inhibitory. The stimulating effect was observed only in the presence of a relatively high concentration of kinetin (1 mg l^?1). The inhibitory effect was partly overcome by the same kinetin concentration. The low concentration of abscisic acid probably accelerated the induction of callus growth after subculture and stimulated cell division in the exponential phase of growth. Electron microscopy showed the presence of numerous polysomes and rough endoplasmic reticulum in callus cells grown at the stimulating abscisic acid concentration. Control cells and cells at the inhibitory concentration had slightly hyaline cytoplasm and were more vacuolated. Incubation of callus tissue with ³²P in the presence of stimulating concentration of abscisic acid showed a significant increase in the rate of biosynthesis of all nucleic acid classes after 8 h, whereas inhibitory concentration produced a decrease in ³²P incorporation. However, when the tissue was grown in the presence of abscisic acid for 20 days, both concentrations decreased the rate of nucleic acid biosynthesis, as compared to the controls.     

The Effect of Photosynthetic Enhancement on Photorespiration in Sinapis alba

High external concentrations of potassium were found to promote light-induced growth of cucumber cotyledons similarly to the effects previously observed for the growth induced by cytokinins. At 40 mM KCl, the response to white light was 3.6 times greater than in the absence of KCl. The promotive effect of calcium on the growth induced by cytokinin was not observed for light. In 40 mM KCl and 10 mM CaCl₂, the responses to light and cytokinin were similar and additive. Both near-red and far-red light induced growth at low intensities. The response to white light at low intensities was sharply increased with higher intensity up to 24 μE m^-2 s^-1 and only slightly increased above that level. Abscisic acid was found to inhibit strongly the responses to light and cytokinin. The inhibition was greater in the presence of KCl than in its absence and thus abscisic acid appeared to inhibit primarily by its interference with potassium uptake. Kinetic analysis found the light response promoted by potassium to be inhibited competitively by abscisic acid, with the light response having a K_m of 34 mM KCl and a V_max of 115 mg/cotyledon × 4 days. The inhibition of the cytokinin response by abscisic acid was noncompetitive in relation to potassium, having a K_m of 1 mM KCl and a V_max of 50 mg/cotyledon × 4 days. It is suggested that cytokinin, light and abscisic acid have primary properties affecting membrane permeability and that their interaction with potassium is an explanation of many similarities between light and cytokinin responses and their inhibition by abscisic acid.     

Studies on the role of abscisic acid in the initiation of bud dormancy in Alnus glutinosa and Betula pubescens

Summary The effects of leaf-applied (+-)-abscisic acid on the growth and dormancy of Betula pubescens Ehrh. and Alnus glutinosa Gaertn. growing under long days provide no evidence that leaf-applied abscisic acid induces or promotes the formation of resting buds in these species. Radiotracer studies show that a small percentage of the radioactivity applied as [2-¹⁴C]abscisic acid to the leaves accumulates in the apical region of the shoot. Of the radioactivity that was recovered from this region after 8 days, less than 10% was chromatographically similar to [2-¹⁴C]abscisic acid. The significance of these results with respect to the role of abscisic acid in regulating the induction of bud dormancy is discussed.Abbreviation ABA abscisic acid     

Enhancement of paclitaxel production by abscisic acid in cell suspension cultures of Taxus chinensis

Addition of 5 mg abscisic acid l^–1 after 12 days' growth of Taxus chinensis suspension culture gave the greatest paclitaxel accumulation at 11 mg l^–1, which was almost 5 times that of the control culture. The highest paclitaxel production, 18 mg l^–1, was obtained using 5 mg abscisic acid l^–1 and 20 mg methyl jasmonate l^–1.     

Callus and Cell Suspension Cultures of Carnation

Callus cultures of carnation, Dianthus caryophyllus L. ev. G. J. Sim, were grown on a synthetic medium of half strength Murashige and Skoog salts, 3 % sucrose, 100 mg/l of myo-inositol, 0.5 mg/l each of thiamin, HCl, pyridoxin, HCl and nicotinic acid and 10 g/l agar. Optimal concentrations of growth regulators were observed to be 3 × 10^?6M indoleacetic acid (JAA) combined with 3 × 10^?6M benzylaminopurin (BAP) or 10^?6M 2,4-dichlorophenoxy acetic acid (2,4-D) alone. IAA + BAP caused a 100 fold increase in fresh weight over 4 weeks at 25°C. Addition of casein hydrolysate increased growth further. Cell suspension cultures worked best in media containing 2,4-D in which they had a doubling time of about 2 days. Filtered suspensions were successfully plated on agar in petri dishes, but division was never observed in single cells. The cultures initiated roots at higher concentrations of IAA or NAA, but all attempts to induce formation of shoots or em-bryoids gave negative results.     

Post-harvest age-induced seed dormancy of Acer ginnala and its alleviation by growth regulator and low temperature treatments

One-month-old fruits of Acer ginnala with winged pericarp attached gave 44% germination and this was not increased by cold treatment at 4°C for 0, 10, 20, or 30 days, gibberellic acid treatment at 0, 1, 10, 100 or 1000 mg litre^-1, or ethephon treatment at 0, 2, 20, 200 or 2000 mg litre^-1. After 6 months of storage at 20–25 °C, germination of untreated fruits fell to 5% but could be restored to that of 1-month-old fruits by incubation at 4 °C for 30 days. After 9 months storage, no germination occurred in untreated fruits. Cold treatment (30 days at 4 °C partially restored germination (26%). Treatment with either gibberellic acid (1000 mg litre^-1) and 30 days at 4 °C (40%) or ethephon (100 mg litre^-] and 30 days at 4 °C improved germination (69%). The combination of all three treatments, i.e. 100 mg litre^-1 gibberellic acid, 100 mg litre^-1 ethephon and 30 days at 4 °C, optimised germination (86%). Thus, dormancy of A. ginnala developed during storage but could be reversed by a combination of treatment with low temperature and growth regulators. The highest germination (86%) was achieved after low temperature and growth regulator treatment of stored fruit.     

Development and storage-protein synthesis in Brassica napus L. embryos in vivo and in vitro

Immature embryos of Brassica napus were cultured in vitro with and without various concentrations of germination inhibitors, and the progress of embryogeny was monitored by comparing accumulation of storage proteins in culture with the normal accumulation in seeds. The two major B. napus storage proteins (12S and 1.7S) were purified from seed extracts and analyzed by rocket immunoelectrophoresis (12S protein) or by sodium lauryl sulfate polyacrylamide gel electrophoresis (1.7S protein). During embryo development within seeds both the 12S and 1.7S proteins were first detected when the cotyledons were well developed (embryo dry weight, 0.4 mg), and each storage protein accumulated at an average rate of 26 g d^-1 during maximum deposition. Accumulation of the 1.7S protein stopped when the water content of the embryo began to decline (embryo DW, 2.7 mg), but accumulation of the 12S protein continued until seed maturity (embryo DW, 3.6 mg). At the end of embryo development the 12S and the 1.7S proteins comprised approx. 60 and 20% of the total salt-soluble protein, respectively. When embryos were removed from seeds at day 27, just as storage protein was starting to accumulate, and placed in culture on a basal medium, they precociously germinated within 3d, and incorporation of amino acids into the 12S storage protein dropped from 3% of total incorporation to less than 1%. If 10^-6 M abscisic acid (ABA) was included in the medium, amino-acid incorporation into the 12S protein increased from 3% of total incorporation when embryos were placed into culture to 18%, 5d later, and the accumulation rate (27.1±2.6 g embryo^-1 d^-1) matched the maximum rate observed in the seed. High osmotica, such as 0.29 M sucrose or mannitol, added to the basal medium, also inhibited precocious germination, but there was a lag period before 12S-protein synthesis rates equaled the rates on ABA media. These results indicate that some factor in the seed environment is necessary for storage-protein synthesis to proceed, and that ABA is a possible candidate.Abbreviations ABA abscisic acid - PAGE polyacrylamide gel electrophoresis - PMSF phenylmethylsulfonylfluoride - SDS sodium lauryl sulfate     

The effect of plant growth regulators on growth, morphology and condensed tannin accumulation in transformed root cultures of Lotus corniculatus

This study concerns the effects of four different classes of plant growth regulators on root morphology, patterns of growth and condensed tannin accumulation in transgenic root cultures of Lotus corniculatus L. (Bird's-foot trefoil). Growth of transformed roots in 2,4-dichlorophenoxyacetic acid (2,4-D) resulted in decreased tannin levels relative to controls at concentrations of 10^-6 M and above, while gibberellic acid (GA₃) inhibited tannin accumulation at concentrations of 10^-7 M and above. Benzyladenine (BA) had little effect at low concentrations (10^-7 M and below) but resulted in an increase in tannin levels at 10^-6 M. Abscisic acid had little effect on levels of condensed tannins at any of the concentrations used. Experiments involving growth regulator addition and medium transfer demonstrated that 2,4-D inhibition of tannin accumulation could be reversed by GA₃ and BA, while GA₃ downregulation could only be reversed by the addition of 2,4-D. Although 2,4-D inhibited tannin accumulation, addition of 2,4-D to root cultures grown for 14 or 28 days in the absence of plant growth regulators stimulated both growth and tannin biosynthesis. Characteristic alterations in root morphologies accompanied growth regulator-mediated modulation of tannin biosynthesis. Growth in 2,4-D resulted in partially de-differentiated root cultures while growth in GA₃ produced roots with an elongated phenotype. Restoration of tannin biosynthesis in 2,4-D-treated roots was accompanied by root re-differentiation and the production of new lateral roots.Abbreviations ABA abscisic acid - BA benzyladenine - 2,4-d 2,4-dichlorophenoxyacetic acid - GA₃ gibberellic acid 3 - FW fresh weight     

The influence of hexavalent chromium salt on the population growth,cell morphology,and physiological parameters of the benthic microalga <Emphasis Type="Italic">Attheya ussurensis</Emphasis> Stonik,Orlova, Crawford, 2006 (BACILLARIOPHYTA) in culture

The presence of hexavalent chromium salt in culture medium negatively affected the growth dynamics and physiological parameters of the benthic microalga Attheya ussurensis. After 1 day of exposure to toxicant at concentrations of 2, 4, 7, and 10 mg/l, the cell counts were 10, 7.9, 5.6, and 4.3 × 10³ cells/ml, respectively (versus 13 × 10³ cells/ml in the control). A tendency towards a decrease in cell number remained until the end of the experiments; after 7 days of exposure the cell counts were 133, 102, 11, and 7.5 × 10³ cells/ml (versus 204 × 10³ cells/ml in the control). With increase in potassium bichromate concentration in the culture medium, there was an increase in the ratio of cell height to width and a change in the form of the cell to horseshoe shaped. The contents of chlorophyll a in microalgal cells after 1 day of exposure to 2, 4, 7, and 10 mg/l were 40, 37, 34, and 30 μg/l, respectively (45 μg/l in the control). After 7 days, at chromium salt concentrations of 2 and 4 mg/l, the chlorophyll a content was higher (670 and 647 μg/l) than in the control (605 μg/l); at 7 and 10 mg/l, it significantly decreased to 87 and 65 μg/l, respectively. The contents of carotinoids in microalgal cells after 7 days of exposure to 2 and 4 mg/l were comparable to the control values, while at 7 and 10 mg/l they decreased sharply. The amount of phaeophytin (as a percentage of total chlorophyll a content) increased with increasing potassium bichromate concentration.     

Effects of gibberellin GA7 on kinetics of growth and tropane alkaloid accumulation in hairy roots of Brugmansia candida

Summary Brugmansia candida, an indigenous South American plant, produces the tropane alkaloids scopolamine and hyoscyamine, which are widely employed in medicine as anticholinergic agents. In this research, hairy roots of Brugmansia candida, obtained through infection with Agrobacterium rhizogenes LBA 9402, were employed to produce these tropane alkaloids in vitro. The effects of different concentrations of GA₇ on kinetics of growth and alkaloid accumulation on two different hairy root clones of B. candida were analyzed, and the influence of GA₇ on the number of new branches and rates of elongation was also studied. On clone 7A, GA₇ at concentrations of 10⁻⁴, 10⁻¹, and 1 mg/l increased the exponential growth rate. Levels of 10⁻¹ and 10⁻⁴ mg/l GA₇ elevated the scopolamine/hyoscyamine (S/H) ratios in the early phases of growth, but the sum of scopolamine plus hyoscyamine per flask (S + H) decreased during that period. When 1 mg/l GA₇ was used, the highest S/H ratios were observed in late exponential/early stationary phases, but the highest S + H totals were obtained in mid-exponential phase. GA₇ at levels of 10⁻¹ and, especially, 1 mg/l exerted a positive effect on formation, emergence, and rate of elongation of lateral roots (clone 7A). On clone 7B, levels of 10⁻¹ and 1 mg/l GA₇ did not alter significantly the exponential growth rate. GA₇ in concentrations of 10⁻¹ mg/l induced increases in both S/H ratio and S + H totals in late phases of growth.     

Growth promotion of <Emphasis Type="Italic">Xanthium italicum</Emphasis> by application of rhizobacterial isolates of <Emphasis Type="Italic">Bacillus aryabhattai</Emphasis> in microcosm soil

This study was conducted using rhizobacteria, which are able to exert beneficial effects upon plant growth in the infertile soil collected from barren lakeside areas. Four strains of plant growth promoting bacteria were isolated from the rhizosphere of a common wild plant, Erigeron canadensis. Isolated strains LS9, LS11, LS12, and LS15 were identified as Bacillus aryabhattai by 16S rDNA sequence analysis. B. aryabhattai LS9, LS11, LS12, and LS15 could solubilize 577.9, 676.8, 623.6, and 581.3 mg/L of 0.5% insoluble calcium phosphate within 2 days of incubation. Production of indole acetic acid, a typical growth promoting phytohormone auxin, by strain LS15 was 471.3 mg/L in 2 days with the addition of auxin precursor L-tryptophan. All the strains also produced other phytohormones such as indole butyric acid, gibberellins, and abscisic acid, and strain LS15 showed the highest production rate of gibberellin (GA₃), 119.0 μg/mg protein. Isolated bacteria were used in a microcosm test for growth of wild plant Xanthium italicum, which can be utilized as a pioneer plant in barren lands. Seed germination was facilitated, and the lengths of roots, and shoots and the dry weights of germinated seedlings after 16 days were higher than those of the uninoculated control plants. Root lengths of seedlings of X. italicum increased by 121.1% in LS11-treated samples after 16 days. This plant growth-promoting capability of B. aryabhattai strains may be utilized as an environmentally friendly means of revegetating barren lands, especially sensitive areas such as lakeside lands.     

Effect of hormones on nucleolar growth and vacuolation in elongating cotton fibers

A rather precise combination of the three phytohormones, gibberellic acid, auxin, and abscisic acid, is necessary for the considerable growth of fiber nucleoli in Gossypium hirsutum L. for about 8 days after anthesis and for nucleolar vacuolation in the second half of that period. Nucleolar growth and vacuolation must occur in a precise sequence for the fiber to reach a good final length. Nucleolar vacuolation indicates simultaneous output and neosynthesis of nucleolar material.Abbreviations ABA abscisic acid - 2,4-D 2,4-dichlorophenoxyacetic acid - FAA 5% acetic acid glacial, 5% formaldehyde (35%), 90% ethanol (50%) - Fl fiber length - Fl_x fiber length at day x post anthesis - GA₃ gibberellic acid - IAA indole-3-acetic acid - NPS nonpollinated, grown in situ - Nu nucleolus - NuS size of the nucleolus - PS normal pollination, grown in situ - PV pollinated, grown in vitro - Vac F vacuolation frequency     

Effects of Abscisic Acid, Salicylic Acid and Trans-cinnamic Acid on Phosphate Uptake, ATP-level and Oxygen Evolution in Scenedesmus

The effects of abscisic acid, salicylic acid and trans-cinnamic acid were tested on the light-induced phosphorylating reactions and oxygen evolution of the unicellular green alga Scenedesmus. It was found that abscisic acid and cinnamic acid had practically no influence on the total inorganic phosphate uptake, while salicylic acid in the concentration range of 10^-6 to 10^-3M gave a small decrease in the total inorganic phosphate uptake. The ATP level in the cells is in most cases increased when these three acids are given to the algae. The oxygen output is not significantly changed by abscisic acid or salicylic acid. Trans- cinnamic acid inhibits the oxygen evolution at concentrations of 10^-4–10^-3M None of the substances investigated caused such effects on photophosphorylation and oxygen evolution in Scenedesmus as those caused by the inhibitor β-complex from potatoes according to earlier reports. It is suggested that these effects are due to other components in the inhibitor β-complex.     

Radioimmunoassay for the determination of free and conjugated abscisic acid

The characterization and application of a radioimmunoassay specific for free and conjugated abscisic acid (ABA) is reported. The antibodies produced against a bovine serum albumin-(±)-ABA conjugate have a high affinity for ABA (K_a=1.3x10⁹l mol^-1). Trans, trans-ABA and related compounds, such as xanthoxin, phaseic acid, dihydrophaseic acid, vomifoliol or violaxanthin do not interfere with the assay. The detection limit of this method is 0.25x10^-12 mol ABA, the measuring range extends to 20x10^-12 mol, and average recoveries are 103%. Because of the high specificity of this immunoassay, no extract purification steps are required prior to analysis. Several hundred plants can be analyzed per day in a semi-automatic assay performance. ABA has been detected in all higher plant families examined, but was absent in the blue-green alga, Spirulina platensis, the liverwort Marchantia polymorpha, and two species of fungi.Abbreviations ABA abscisic acid - BHT 2.6-di-t-butyl-4-methyl phenol - TLC thin-layer chromatography - HSA human serum albumin Part 7 in the Series: Use of Immunoassay in Plant Science     

Somatic embryogenesis and plant regeneration from immature embryos of western larch

Somatic embryogenesis was initiated from immature embryos of western larch (Larix occidentalis Nutt.) on media containing 2,4-dichlorophenoxyacetic acid and N6- benzyladenine. The effects of explant type and ammonium nitrate and glutamine concentrations on initiation were tested. Although 21–93% of explants rendered cultures in various experiments, only 3% yielded sustainable embryogenic lines. Excised embryos at the early cotyledonary stage were optimal for initiation. Maturation of somatic embryos was promoted by abscisic acid. Response to abscisic acid concentrations and duration of exposure to abscisic acid varied with genotype. Maximal results were obtained with 0.025 M abscisic acid for 1 to 2 weeks followed by individual culture on medium without growth regulators. Mature somatic embryos developed into shoots with roots. Plantlets have been established in peat.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - BA N⁶-benzyladenine - IBA indole-3-butyric acid - ABA abscisic acid     

Changes in steady state on introduction of a Lactobacillus contaminant to a continuous culture ethanol fermentation

Lactobacillus paracasei was introduced as a contaminant into a multistage continuous culture ethanol fermentation system at ratios of 1:100, 1:1, and 70:1 with Saccharomyces cerevisiae, but failed to overtake the yeast. None of the inoculation ratios allowed L. paracasei to affect S. cerevisiae in the first fermentor in the multistage system. S. cerevisiae remained constant at ∼3×10⁷ CFU/ml regardless of the bacterial inoculation level, and even at the 70:1 inoculation ratio, glucose, ethanol, and lactic acid concentrations did not change from the steady-state concentrations seen before bacterial inoculation. However, L. paracasei decreased steadily from its initial inoculation level of ∼2.2×10⁹ CFU/ml and stabilized at 3.7×10⁵ CFU/ml after 10 days of steady-state operation. Both organisms then persisted in the multistage system at an approximate L. paracasei/S. cerevisiae ratio of 1:100 which confirms that, in continuous fuel ethanol production, it would be difficult to eliminate this bacterium. Only when the pH was controlled at 6.0 in fermentor 1 (F1) were changes seen which would affect the multistage system. Ethanol concentration then decreased by 44% after 4 days of pH-controlled operation. This coincided with an increase in L. paracasei to >10¹⁰ CFU/ml, and a 4× increase in lactic acid concentration to 20 g/l. When the clarified contents from other fermentors (F2–F5) in the multistage system were used as growth media, L. paracasei was not able to grow in batch culture. This indicated that the first fermentor in the multistage system was the only fermentor capable of supporting the growth of L. paracasei under the described conditions. Journal of Industrial Microbiology & Biotechnology (2001) 27, 39–45. Received 26 February 2001/ Accepted in revised form 29 May 2001     

Geotropic curvature of decapitated Avena coleoptiles after application of tips of maize roots,tips of Avena coleoptiles,indoleacetic acid,or abscisic acid

Isolated Avena coleoptiles were decapitated at different distances from the tip and then placed horizontally, after which the geotropic curvature was measured. No geotropic curvature could be detected during the first 3 h. Later, upward curvature occurred which was found to depend inversely on the length of the decapitated tips. When the tips of maize roots or Avena coleoptiles were placed on the cut surface of decapitated Avena coleoptiles, the coleoptiles showed a significantly stronger upward curvature as compared to controls which had been provided with agar blocks on the cut surface. The same upward curvature was found with decapitated coleoptiles provided with agar blocks containing 10^-6 or 10^-7 M indoleacetic acid (IAA). After application of abscisic acid (ABA) at concentrations of 10^-6 and 10^-8 M to the decapitated coleoptiles, the curvature observed was not different from that of the controls; at higher concentrations of ABA the curvature was found to be lower than that of the controls. It is concluded that root tips secrete a substance which may replace the effect of IAA in coleoptiles. The results are discussed in view of the validity of the Cholodny-Went hypothesis for the geotropic reaction of roots.Abbreviations ABA abscisic acid - IAA 3-indoleacetic acid     

Induction of desiccation tolerance in microspore-derived embryos ofBrassica napus

Summary A method was developed to induce desiccation tolerance in microspore-derived embryos ofBrassica napus. Treatment of 14- to 20-day-old embryos with 1&#x00D7;10^&#x2212;4 M abscisic acid, in the light, induced tolerance to slow desiccation over a 6-day period. Under these conditions 88 to 100% of embryos of the five cultivars tested survived (as measured by moisture uptake, greening, and growth of the shoot and root meristem) after storage for 1 wk at tissue water content levels of less than 20%. The response was found to be dependent on the abscisic acid concentration in the culture medium and time of exposure of the embryos to the abscisic acid-containing medium, with exposure times of as little as 1 day having a beneficial effect. Exposure times to abscisic acid (ABA) of 5&#x2013;7 days resulted in the highest survival rates. Embryo age and size at the time of ABA exposure also affected the subsequent survival and development of embryos, with older and larger embryos exhibiting the best responses.