Distinction between the Responses of Developing Maize Kernels to Fluridone and Desiccation in Relation to Germinability, alpha-Amylase Activity, and Abscisic Acid Content

Developing kernels of the maize (Zea mays) hybrid W64A x W182E germinated precociously following fluridone treatment. Likewise, following premature drying, the kernels germinated upon subsequent rehydration. Tolerance of the aleurone layer to premature desiccation considerably preceded that of the embryo. The increase in α-amylase activity following premature drying was substantial and was equal to, or exceeded, the increase which occurred following normal maturation drying. In contrast, there was only a small increase in enzyme activity, regardless of the concentration of the supplied gibberellic acid, following fluridone treatment. Both fluridone and drying cause a decrease in abscisic acid content within the developing kernels. While this decline in growth regulator may permit kernels to germinate, alone this is not sufficient to permit an increase in α-amylase activity. Thus drying is necessary to sensitize the aleurone layer to gibberellin, and thereby elicit enzyme synthesis. For this tissue to achieve its full potential to produce α-amylase, it must not only be free of the inhibitory effects of abscisic acid, but it must also be competent to respond to gibberellin.     

The Role of Maturation Drying in the Transition from Seed Development to Germination: VII. EFFECTS OF PARTIAL AND COMPLETE DESICCATION ON ABSCISIC ACID LEVELS AND SENSITIVITY IN RICINUS COMMUNIS L. SEEDS

During mid-development (25–40 d after pollination: DAP)of the castor bean seed the amount of abscisic acid (ABA) increasesin both the endosperm and the embryo, declining substantiallythereafter until there is little present in the mature dry (60DAP) seed. Premature desiccation of the seed at 35 DAP alsoleads to a major decline in ABA within the embryo and endosperm.Partial water loss from the seed at 35 DAP which, like naturaland premature desiccation, leads to subsequent germination uponreturn of the seed to full hydration, causes a much smallerdecline in ABA levels. In contrast, ABA declines substantiallyin the non-dried (hydrated) control at 35 DAP, but the seedsdo not germinate. Hence, a clear negative correlation betweenABA content and germinability is not observed. Both drying,whether natural or imposed prematurely, and partial drying decreasethe sensitivity of the isolated embryo to exogenous ABA by about10-fold. The protein synthetic response of the castor bean embryo exposedto 0.1 mol m^–3 ABA following premature desiccation exhibitssome similarity to the response of the non-dried developingembryo—in both cases the synthesis of some developmentalproteins is enhanced by ABA, and germination is suppressed.Germination of mature seeds is also suppressed by 0.1 mol m^–3ABA, but the same developmental proteins are not synthesized.In the cotyledons of prematurely-desiccated seed, some proteinsare hydrolysed upon imbibition in 0.1 mol m^–3 ABA, a phenomenonthat occurs also in the cotyledons of similarly treated matureembryos, but not in developing non-dried embryos. Hence theembryo exhibits an ‘intermediate’ response uponrehydration in 0.1 mol m^–3 ABA following premature desiccation;viz. some of the responses are developmental and some germinative.Following natural or imposed drying, the isolated embryo becomesrelatively insensitive to 0.01 mol m^–3 ABA: germinationis elicited and post-germinative reserve breakdown occurs inthe radicle and cotyledons. The reduced sensitivity of the embryoto ABA as a consequence of desiccation may be an important factorin eliciting the switch to germination and growth within thewhole seed. Key words: Abscisic acid, desiccation, astor bean endosperm, seed development, germination, protein synthesis, isolated embryos, hormone sensitivity     

The Role of Maturation Drying in the Transition from Seed Development to Germination: IV. PROTEIN SYNTHESIS AND ENZYME ACTIVITY CHANGES WITHIN THE COTYLEDONS OF RICINUS COMMUNIS L. SEEDS

Drying of immature seeds of Ricinus communis L. cv. Hale (castorbean) during the desiccation-tolerant phase of development causesthem to germinate upon subsequent rehydration. This desiccation-inducedswitch from development to germination is also mirrored by achange in the pattern of soluble and insoluble protein synthesiswithin the cotyledons of the castor bean. Following rehydrationof seeds prematurely dried at 40 d after pollination (DAP),cotyledonary proteins characteristic of development (e.g. storageproteins) are no longer synthesized; hydrolytic processes resultingin their degradation commence (after 12 h) in a manner similarto that observed following imbibition of the mature seed. Apattern of protein synthesis recognizable as germination/growth-associatedoccurs; premature drying has elicited a redirection in metabolismfrom a developmental to a germinative mode. Desiccation is alsorequired for the induction (within cotyledons of 35 DAP seeds)of enzymes involved in protein reserve breakdown (leucyl ß-naphthylamidase;LeuNAase) and lipid utilization (isocitrate lyase; ICL), anevent intimately associated with the post-germinative (growth)phase of seedling development. Thus, at a desiccation-tolerantstage of development, premature drying results in the suppressionof the developmental metabolic programme and a permanent switching-onof the germination/growth metabolic programme. Key words: Desiccation, metabolism, seed development, seed germination, castor bean, cotyledons     

The Role of Maturation Drying in the Transition from Seed Development to Germination: II. POST-GERMINATIVE ENZYME PRODUCTION AND SOLUBLE PROTEIN SYNTHETIC PATTERN CHANGES WITHIN THE ENDOSPERM OF Ricinus communis L. SEEDS

Kermode, A. R. and Bewley, J. D. 1985. The role of maturationdrying in the transition from seed development to germination.II. Post–germinative enzyme production and soluble proteinsynthetic pattern changes within the endosperm of Ricinus communisL. seeds.—J. exp. Bot. 36: 1916–1927. Immature seedsof Ricinus communis L. cv. Hale (castor bean) removed from thecapsule at 30 or 40 d after pollination (DAP) do not germinateunless first subjected to a desiccation treatment. This changefrom development to germination elicited by premature desiccationis also mirrored by a change, upon subsequent rehydration, inthe pattern of soluble protein synthesis within the endospermstorage tissue. Following rehydration of prematurely dried 30or 40 DAP seeds, soluble proteins characteristic of developmentcease to be synthesized after 5 h of imbibition, and those uniquelyassociated with germination and growth are then produced. Apattern of soluble storage protein breakdown comparable to thatfound in endosperms from mature seeds following imbibition isalso observed. In contrast, hydration of 40 DAP seeds immediatelyfollowing detachment from the mother plant results in a continuationof the developmental pattern of protein synthesis. Prematuredesiccation at 40 DAP elicits the production within the endospermof enzymes involved in protein reserve breakdown (leucyl ß–naphthylamidase;LeuNAase) and lipid utilization (isocitrate lyase; ICL) to levelscomparable to those observed in mature–hydrated endosperms.It is proposed that drying plays a role in redirecting metabolismfrom a developmental to a germinative mode; it also appearsto be a prerequisite for the induction of hydrolytic enzymesessential to the post–germinative (growth) phase of seedlingdevelopment. Key words: Desiccation-tolerance, germinability, seed development, castor bean     

Desiccation of Axes of Phaseolus vulgaris during Development of a Switch from a Development Pattern of Protein Synthesis to a Germination Pattern

Immature seeds of Phaseolus vulgaris removed from the pod at 32 days of development do not germinate unless first subjected to a desiccation treatment. This change from development to germination caused by premature drying is mirrored in the pattern of protein synthesis by the axes. Rehydrated axes from 32-day-developed seeds cease to synthesize proteins that are uniquely associated with development, but instead synthesize some proteins that are similar to those made in the germinating axes from mature dry seeds. Desiccation of 22-day-developed seeds does not lead to their germination, nor does it cause a switch from a developmental to a germination mode of protein synthesis by the axes. It is proposed that desiccation plays a role in permanently suppressing developmental protein synthesis and in inducing germination protein synthesis.     

The Role of Maturation Drying in the Transition from Seed Development to Germination: V. RESPONSES OF THE IMMATURE CASTOR BEAN EMBRYO TO ISOLATION FROM THE WHOLE SEED: A COMPARISON WITH PREMATURE DESICCATION

Kennode, A. R, and Bewley, J. D. 1988. The role of maturationdrying in the transition from seed development to germination.V. Responses of the immature castor bean embryo to isolationfrom the whole seed; a comparison with premature desiccation.—J.exp. Bot. 39: 487–497. Desiccation is an absolute requirement for germination and post-germinativegrowth of whole seeds of the castor bean, whether desiccationis imposed prematurely during development, at 35 d after pollination(DAP) or occurs naturally during late maturation (50–60DAP). Desiccation also plays a direct role in the inductionof post-germinative enzyme synthesis in the cotyledons of embryosin the intact seed; this event is not simply due to the presenceof a growing axis. Isolation of embryos from the developingcastor bean seed at 35 DAP results in both germination and growth,despite the absence of a desiccation event. We have comparedthe metabolic consequences of premature drying of whole seeds(35 DAP) and isolation of the developing 35 DAP embryos. Inboth cases, hydrolytic events involved in the mobilization ofstored protein reserves proceed in a similar manner and mirrorthose events occurring within germinated mature seeds. Thereare differences, however, for post-germinative enzyme (LeuNAaseand isocitrate lyase) production occurs to a lesser extent innon-dried isolated embryos than in those from prematurely dried(35 DAP) whole seeds, or from mature dry (whole) seeds. Desiccationof the 35 DAP whole seed does not alter the subsequent responseof the embryo upon isolation. Thus, while drying does not affectthe metabolism of isolated embryos, it has a profound effecton that of embryos within the intact seed. Tissues surroundingthe embryo in the developing intact seed (viz. the endosperm)maintain its metabolism in a developmental mode and inhibitgermination. This effect of the surrounding tissues can onlybe overcome by drying or by their removal. Key words: Metabolism, isolation, desiccation, embryo, endosperm, castor bean, development, germination     

Onset of desiccation tolerance during development of the barley embryo

We have investigated events which take place in the developing barley (Hordeum vulgare L.) embryo during its acquisition of desiccation tolerance. Excised embryos are capable of precocious germination as early as 8 d after pollination (DAP). At this age, however, they are not capable of resisting a desiccation treatment which induces a loss of 96–98% of their initial water content. At 16 DAP the embryos germinate despite the drastic drying treatment. The pattern of in-vivo and in-vitro proteins synthesized by the developing embryos from 12 DAP (desiccation-intolerant) and 16 DAP (desiccation-tolerant) were compared. A set of 25–30 proteins was identified which is denovo synthesized or enhanced during the developmental period leading to desiccation tolerance. Abscisic acid (ABA; 100 M) applied in vitro for 5 d to 12-DAP embryos induces desiccation tolerance and represses a subset of polypeptides preferentially associated with 16-DAP embryos. During in vitro culture of barley embryos ABA stimulates the appearance of a set of proteins and prevents the precocious germination allowing embryogenesis to continue in vitro. It also suppresses a set of germination-related proteins which appear 4 h after the incubation of the dissected embryo on a germination medium without ABA. Almost all mRNAs remain functional for translation when isolated embryos are dried at the desiccation-intolerant and tolerant stages of embryo development.Abbreviations ABA abscisic acid - DAP days after pollination - GM germination medium - poly(A)RNA polyadenylated RNA - SDS sodium dodecyl sulfate     

Seed development and vivipary in Zea mays L.

Seed development was investigated in kernels of developing wild-type and viviparous (vp-1) Zea mays L. Embryos and endosperm of wild-type kernels began to dehydrate at approx. 35 d after pollination (DAP); viviparous embryos did not desiccate but accumulated fresh weight via coleoptile growth in the caryopses. Concentrations of endogenous abscisic acid (ABA) in the embryo were relatively high early in development, being approx. 150 ng·g^-1 fresh weight at 20 DAP. The ABA content declined thereafter, falling to approx. 50 ng·g^-1 at 30 DAP. Endosperm ABA content was always low, being less than 20 ng·g^-1. There were no differences between wild-type and vp-1 tissues. Immature kernels did not germinate when removed from the ear until late in development. The ability to germinate was correlated with decreasing moisture content in the endosperm at the time of removal; premature drying of immature kernels resulted in greatly increased germination following imbibition. Excised embryos germinated precociously when removed from the endosperm as early as 25 DAP. Such germination could be prevented by treatment with 10^-5 M ABA or by lowering the solute potential (_s) of the medium with 0.3 M mannitol. Treatment of excised embryos with ABA led to internal ABA concentrations comparable to those in embryos in which germination was inhibited in situ. Mannitol treatment did not have this effect, although water-deficit stress of excised embryos resulted in substantial ABA production. Germinated vp-1 embryos were less sensitive to growth inhibition by ABA or mannitol than germinating wild-type embryos. The vp-1 seedlings were not wilty and their transpiration rates were reduced in response to ABA or water shortage.Abbreviations and symbols ABA abscisic acid - DAP days after pollination - FW fresh weight - vp-1 viviparous genotype - _s solute potential     

In Situ Abscisic Acid Synthesis : A Requirement for Induction of Embryo Dormancy in Helianthus annuus

When applied to young nondormant embryos of sunflower (Hellanthus annus) (7-10 day[s] after pollination [DAP]), abscisic acid (ABA) inhibited germination as long as it was present. However, whatever the dose used and the duration of its application, ABA was unable to induce dormancy because after transfer of treated embryos to control (without ABA) medium, germination occurred. Thereafter, exogenous ABA became effective and allowed the dormancy to develop in 13 and 17 DAP embryos, i.e. in embryos which after isolation were still able to germinate in high percentage. After embryo dormancy was well established (21 DAP), application of fluridone allowed the germination to occur very quickly on control medium. Isolated dormant axes were also induced to germinate by an application of fluridone. Radioimmunological analysis showed that 24 hours after these treatments, endogenous ABA levels were drastically reduced in the axes. When these fluridone-treated embryos were cultured on ABA medium, germination was again inhibited as long as exogenous ABA was present but germination occurred as soon as embryos were transferred to control medium. Such behavior suggested that in situ ABA synthesis is necessary to impose and maintain the embryo dormancy.     

Significance of the zygotic seed coat on quiescence and desiccation tolerance of Medicago sativa L. somatic embryos

Summary The influence of the zygotic seed coat on precocious germination and desiccation tolerance of somatic embryos has been studied using alfalfa (Medicago sativa L.). When cultured in contact with somatic embryos, seed coats at certain developmental stages inhibited precocious germination and induced desiccation tolerance in the somatic embryos. Germination of somatic embryos was inhibited by seed coats at the age of 16–26 days after pollination (DAP) and desiccation tolerance was induced after 20–26 DAP. Both phenomena were related to the synthesis of abscisic acid in the seed coat. The absence of a quiescent phase and desiccation tolerance in alfalfa somatic embryos may be related to the lack of developmental control by the seed coat.Abbreviations ABA Abscisic acid - DAP Days after pollination     

Abscisic acid and osmoticum prevent germination of developing alfalfa embryos,but only osmoticum maintains the synthesis of developmental proteins

Developing seeds of alfalfa (Medicago sativa L.) acquire the ability to germinate during the latter stages of development, the maturation drying phase. Isolated embryos placed on Murashige and Skoog medium germinate well during early and late development, but poorly during mid-development; however, when placed on water they germinate well only during the latter stage of development. Germination of isolated embryos is very slow and poor when they are incubated in the presence of surrounding seed structures (the endosperm or seed coat) taken from the mid-development stages. This inhibitory effect is also achieved by incubating embryos in 10^?5 M abscisic acid (ABA). Endogenous ABA attains a high level during mid-development, especially in the endosperm. Seeds developing in pods treated with fluridone (1-methyl-3-phenyl-5[3-(trifluoromethyl)-phenyl]-4(1H)-pyridinone) contain low levels of ABA during mid-development, and the endosperm and seed coat only weakly inhibit the germination of isolated embryos. However, intact seeds from fluridone-treated pods do not germinate viviparously, which is indicative that ABA alone is not responsible for maintaining seeds in a developing state. Application of osmoticum (e.g. 0.35 M sucrose) to isolated developing embryos prevents their germination. Also, in the developing seed in situ the osmotic potential is high. Thus internal levels of osmoticum may play a role in preventing germination of the embryo and maintaining development. Abscisic acid and osmoticum impart distinctly different metabolic responses on developing embryos, as demonstrated by their protein-synthetic capacity. Only in the presence of osmoticum do embryos synthesize proteins which are distinctly recognizable as those synthesized by developing embryos in situ, i.e. when inside the pod. Abscisic acid induces the synthesis of a few unique proteins, but these arise even in mature embryos treated with ABA. Thus while both osmoticum and ABA prevent precocious germination, their effects on the synthetic capacity of the developing embryo are quite distinct. Since seeds with low endogenous ABA do not germinate, osmotic regulation may be the more important of these two factors in controlling seed development.     

Regulation of Embryo Dormancy by Manipulation of Abscisic Acid in Kernels and Associated Cob Tissue of Zea mays L. Cultured in Vitro

Sectors of Zea mays cobs, with and without kernels were cultured in vitro in the presence and absence of fluridone. Cultured kernels, cob tissue, and embryos developed similarly to those grown in the field. Abscisic acid (ABA) levels in the embryos were evaluated by enzyme-linked immunosorbant assay. ABA levels in intact embryos cultured in the presence of fluridone were extremely low and indicate an inhibition of ABA synthesis. ABA levels in isolated cob tissue indicate that ABA can be produced by cob tissue. Sections containing kernels cultured in the presence of fluridone were transferred to medium containing fluridone and ABA. Dormancy was induced in more than 50% of the kernels transferred from 13 to 15 days after pollination, but all of the kernels transferred at 16 days after pollination or later were viviparous. ABA recovered from kernels that were placed in medium containing fluridone and ABA suggest that ABA can be transported through the cob tissue into developing embryos and that ABA is required for induction of dormancy in intact embryos.     

Abscisic acid biosynthesis during corn embryo development

In this study we examined the biosynthesis of abscisic acid (ABA) by developing corn (Zea mays L.) embryos. Three comparisons were made: ABA biosynthesis in embryos isolated from kernels grown in vitro with those grown in the field; the developmental profile of ABA content with that of biosynthesis; and ABA biosynthesis in corn embryos lacking carotenoid precursors with ABA biosynthesis in normal embryos. Embryos were harvested at various times during seed development and divided into two groups. Endogenous levels of ABA were measured in one group of embryos and ABA biosynthetic capacity was measured in the other group. The ABA biosynthetic capacity was measured with and without tetcyclacis (an inhibitor of ABA degradation) in embryos from both field-grown and in-vitro-grown corn kernels. Reduced-carotenoid (either fluridone-treated or genetically viviparous) embryos were also included in the study. Corn kernels developing under field and in-vitro conditions differed from each other in their responses to tetcyclacis and in their profiles of ABA biosynthesis during development. Therefore, in-vitro kernel culture may not be an appropriate substitute for field conditions for studies of embryo development. The developmental profiles of endogenous ABA content differed from those of ABA biosynthesis in isolated embryos of both in-vitro-and field-grown kernels. This indicated that ABA levels in the developing embryos were determined by import from the maternal tissues available to the embryos rather than by in-situ biosynthesis. In embryos with reduced levels of carotenoids, either fluridone-treated or genetically viviparous embryos, ABA biosynthesis was low or nonexistent. This result is expected for the presence of an indirect pathway of ABA biosynthesis and in the absence of ABA precursors.Abbreviations ABA abscisic acid - DAP days after pollination     

Regulation of Gene Expression in Developing Zea mays Embryos: Protein Synthesis during Embryogenesis and Early Germination of Maize

Polypeptides synthesized in dissected embryos of Zea mays at different stages of embryogenesis and early germination have been characterized by their migration in two-dimensional gel electrophoresis. This analysis has been carried out with in vivo labeled polypeptides from excised embryos and with proteins synthesized in vitro in the rabbit reticulocyte system directed by poly(A⁺) RNA isolated from the different developmental stages. We have identified three main sets of expressed polypeptides: (a) embryonic set: this group of polypeptides is synthesized in young and mature embryos but not in early germination; (b) maturation set: this group of polypeptides is not present in young embryos and appears during the maturation period. Some of these polypeptides are still present in early germination while others disappear from stored mRNAs in dry embryos. One particular group from this set can be induced prematurely in young embryos by incubation with abscisic acid; and (c) germination set: this group of polypeptides is not expressed in the maturation period and appears after brief imbibition of the dry embryos.     

成熟脱水对种子发育和萌发的作用

成熟脱水是正常性种子发育的末端事件。种子在成熟时胚的脱水耐性增加;当种子萌发时胚变得不耐脱水。当种子获得脱水耐性时,糖、蛋白质和抗氧化防御系统等保护性物质积累;当脱水耐性丧失时,这些物质被降解。成熟脱水是种子从发育过程向萌发过程转变的“开关”,它降低发育的蛋白质和ｍＲＮＡ的合成,终止发育事件和促进萌发事件。顽拗性种子不经历成熟脱水的发育阶段,对脱水高度敏感。     

Early Events in Maize Seed Development : 1-Methyl-3-phenyl-5-(3-[trifluoromethyl]phenyl)-4-(1H)-Pyridinone Induction of Vivipary

Preharvest sprouting or vivipary is induced in developing maize (Zea mays, inbred Tx 5855 and Va 35) seeds by fluridone, a pyridinone inhibitor of carotenoid biosynthesis. Fluridone has a maximal effect on vivipary at 11 days after pollination (DAP) and little effect at 13 DAP in the inbred maize line Tx 5855. Abscisic acid partially reversed the chemically induced vivipary. Though the precise mechanism of fluridone-induced vivipary is unknown, these results indicate that there are important developmental changes occurring at 11 DAP which reversibly commit the immature embryo to vivipary or dormancy.     

Seeds of tomato (Lycopersicon esculentum Mill.) which develop in a fully hydrated environment in the fruit switch from a developmental to a germinative mode without a requirement for desiccation

Seed water content is high during early development of tomato seeds (10–30 d after pollination (DAP)), declines at 35 DAP, then increases slightly during fruit ripening (following 50 DAP). The seed does not undergo maturation drying. Protein content during seed development peaks at 35 DAP in the embryo, while in the endosperm it exhibits a triphasic accumulation pattern. Peaks in endosperm protein deposition correspond to changes in endosperm morphology (i.e. formation of the hard endosperm) and are largely the consequence of increases in storage proteins. Storage-protein deposition commences at 20 DAP in the embryo and endosperm; both tissues accumulate identical proteins. Embryo maturation is complete by 40 DAP, when maximum embryo protein content, size and seed dry weight are attained. Seeds are tolerant of premature drying (fast and slow drying) from 40 DAP.Thirty-and 35-DAP seeds when removed from the fruit tissue and imbibed on water, complete germination by 120 h after isolation. Only seeds which have developed to 35 DAP produce viable seedlings. The inability of isolated 30-DAP seed to form viable seedlings appears to be related to a lack of stored nutrients, since the germinability of excised embryos (20 DAP and onwards) placed on Murashige and Skoog (1962, Physiol. Plant. 15, 473–497) medium is high. The switch from a developmental to germinative mode in the excised 30- and 35-DAP imbibed seeds is reflected in the pattern of in-vivo protein synthesis. Developmental and germinative proteins are present in the embryo and endosperm of the 30- and 35-DAP seeds 12 h after their isolation from the fruit. The mature seed (60 DAP) exhibits germinative protein synthesis from the earliest time of imbibition. The fruit environment prevents precocious germination of developing seeds, since the switch from development to germination requires only their removal from the fruit tissue.Abbreviations DAP days after pollination - kDa kilodaltons - SP1-4 storage proteins 1–4 - SDS-PAGE sodium dodecyl sulphate-polyacrylamide gel electrophoresis - HASI hours after seed isolation - MS medium Murashige and Skoog (1962) medium This work is supported by National Science and Engineering Research Council of Canada grant A2210 to J.D.B.     

The role of abscisic acid in germination, storage protein synthesis and desiccation tolerance in alfalfa (Medicago sativa L.) seeds, as shown by inhibition of its synthesis by fluridone during development

Abscisic acid and osmoticum maintain maturation and proteinsynthesis of developing alfalfa embryos, individually and incombination. The in situ environment of developing alfalfa zygoticembryos is rich in ABA and low in osmotic potential. When ABAsynthesis was inhibited by treating the pods with fluridoneat an early stage of development, the seeds which subsequentlydeveloped contained low amounts of ABA, but had a similar osmoticpotential as untreated control seeds. The reduced ABA in seedsfrom fluridone-treated pods did not change the morphology exceptthe colour of seeds, nor did it induce viviparous germinationor affect storage protein synthesis. However, two nonstorageproteins which were synthesized in control seeds during earlyto mid-development were absent from fluridone-treated seeds.Control seeds containing these two proteins were desiccation-tolerant,whereas the fluridone-treated seeds which lacked them were desiccation-intolerant,at least until the deposition of storage proteins was nearlycomplete. Culture of isolated embryos on nutrient medium inducedgermination and curtailed storage protein synthesis in the embryos.Addition of either ABA or osmoticum to the nutrient medium preventedgermination and maintained storage protein synthesis. When fluridonewas added along with osmoticum, germination occurred, but storageprotein synthesis was maintained. Key words: Embryogenesis, Medicago sativa L., alfalfa, ABA, osmotic potential, fluridone, desiccation, storage protein synthesis