Effects of Temperature and dl-Strigol on Seed Conditioning and Germination of Witchweed (Striga asiatica)

Seed conditioning and germination in witchweed (Striga asiatica(L.) Kuntze) were temperature-dependent. With higher conditioningtemperatures, shorter conditioning time was required for germinationwith terminal dl-strigol (strigol) treatment at 30 °C. Maximumgermination (80–100%) was obtained by conditioning inwater at 20, 25, 30 and 35 °C for 14, 7, 5 and 3 d, respectively,and terminally treating with 10^–6 M strigol at 30 °C.Seeds conditioned in 10^–8 M strigol instead of water germinatedmuch less with the same terminal strigol treatment. Generally,conditioning was slower when seeds were conditioned in strigolrather than water. The reduction in germination rate by pretreatmentin strigol or pretreatment at low temperatures could be overcomeby increasing the terminal strigol concentration in the germinationtest. Conditioned seeds did not germinate at 10 and 15 °Cwith a terminal 10^–6 M strigol treatment but yielded closeto maximum germination at 25, 30 and 35 °C with the sameterminal strigol treatment. To obtain maximum germination, boththe minimum conditioning temperature and the minimum germinationtemperature for conditioned seeds were 20 °C. Factors suchas conditioning time, and strigol concentration and temperatureduring conditioning and/or germination determine whether seedsremain in the conditioning phase or shift to a germination phase. dl-Strigol, germination stimulation, parasitic plants, seed conditioning, seed germination, Striga asiatica, temperature, weed control     

Effect of Chlorflurenol on Sex Expression, Fruit Set and Yield in Abelmoschus esculentus (L. ) Moench

Plants of Abelmoschus esculentus were given a single foliarspray of chlorflurenol at 1, 10, 100, and1000 parts 10^–6by a hand atomizer. Chlorflurenol increased the number of flowersat all the concentrations used except 1000 parts 10^–6where a drastic reduction was noticed. Various stages of suppressionin the growth and reduction in number of stamens were seen inflowers of treated plants. Formation of stamenless flowers,i.e. pistillate flowers, was a striking influence of chlorflurenol.Chlorflurenol also increased fruit set, and therefore yield,up to 100 parts 10^–6 but drastically reduced both at 1000parts 10^–6. Parthenocarpic fruit set was induced by chlorflurenolonly at 100 and 1000 parts 10^–6.     

Inhibition of Pinus radiata Primary Needle Epicuticular Wax Biosynthesis by Trichloroacetate

High concentrations (1000 parts 10^–6) of trichloroacetate(TCA) inhibit germination of Pinus radiata seed. Seedlings growingin the presence of lower concentrations (100 parts 10^–6)take up TCA where it becomes concentrated in cotyledons anddeveloping primary needles. TCA inhibits biosynthesis of nonacosan-10-oland long chain diol constituents of the primary needle epicuticularwax concomitant with a reduction in appearance of tubular waxexcept around stomatal pores. Epicuticular wax from TCA-treatedplants consists mainly of alkyl esters, and is amorphous. Itis suggested that P. radiata stomatal subsidiary cells possesstubular epicuticular wax chemically distinct from that of epidermalcells.     

Ethylene, Nitrate and Nitrite Interactions in the Promotion of Dark Germination of Common Purslane Seeds

Ethylene (10 µ1^–1) caused about one-third of highlydark-dormant seeds of common purslane (Portulaca oleracea L.)to germinate in the dark. Attempts were made to increase germinationin the dark with nitrate and ethylene combinations. When applieddirectly to the seeds, KNO₃ did not stimulate germination andKNO₃ plus ethylene did not increase germination above that ofethylene alone. Pre-incubation of seeds in KNO₃ for 4 to 7 dbefore the ethylene applications significantly increased germination.The effects of the KNO₃ pre-incubation were additive at eachof four ethylene concentrations (0.1–100 µ11^–1).Potassium nitrate was effective only when ethylene followedthe KNO₃ pre-incubation period. Potassium nitrite stimulatedabout 25 per cent of the seeds to germinate without a pre-incubationperiod and without ethylene. Also, ethylene plus KNO₂ enhancedgermination above that achieved by either stimulus alone. Silvernitrate did not block the ethylene promotion of germination,but reversed the typical ethylene inhibition of seedling growthfollowing germination. The results support the views that nitrateexerted its effect via conversion to nitrite within the seedand that the rate of nitrate conversion may be a limiting factorin the dark germination of common purslane seeds. Ethylene mayfacilitate nitrite activity by increasing seed sensitivity tothe stimulus. Common purslane, Portulaca oleracea L., ethylene, nitrate, nitrite, germination, dormancy     

Effect of Auxin and Gibberellin on Conidial Germination in Neurospora crassa II. "Conidial Density Effect" and Auxin

Conidial germination in liquid shake culture of Neurospora crassawas affected by the number of conidia in the medium (conidialdensity effect) with the optimum density being around 2?10⁶conidia/ml. The conidial density effect at 2?10⁴ and 2?10⁵ conidia/mlwas eliminated by the addition of auxin, IAA or 2,4-D with theoptimum concentrations of IAA and 2,4-D being around 10^–6M. IAA and 2,4-D had no effect on the effect at 2?10⁷ conidia/ml.An active substance(s) for conidial germination which was relatedto the conidial density effect was detected in the cell-freefiltrate of the germination medium, and was found to be non-dialyzableand thermolabile. At the early stage of germination, the concentrationof active substance(s) in the medium increased in proportionto the conidial density and reached a supraoptimum amount forgermination at 2?10⁷ conidia/ml. IAA (10^–6M) enhancedthe concentration. Endogenous auxin concentrations in filtratesof the germination media containing 2?10⁵, 2?10⁶ and 2?10⁷ conidia/mlwere 5.8?10^–12, 4.6?10^–11 and 1.7?10^–10M IAAequivalent, respectively. The conclusion reached was that auxinmay control conidial germination with mediation by the activesubstance(s). (Received June 8, 1982; Accepted September 27, 1982)     

Effect of Spermidine and Methylglyoxal-bis (Guanyl-hydrazone) (MGBG) on In Vitro Pollen Germination and Tube Growth in Catharanthus roseus

Incorporation of polyamine-spermidine into the nutrient mediumat 10^–6 and 10^–5 M concentrations stimulates pollen-tubegrowth in vitro in Catharanthus roseus L. G. Don. MGBG, an inhibitorof spermidine biosynthesis, at 0.5 x 10^–3 and 1 x 10^–3M concentrations reduced the percentage of germination as wellas tube growth and at a concentration of 1.5 x 10^–3 Mgermination was totally inhibited. Pollen grains incubated inthe medium containing 1.5 x 10^–3 M MGBG, when transferredto a fresh medium with 10^–5 M spermidine, resulted in80% germination recovery, along with considerable tube growth.Experiments with actinomycin-D indicate that stimulation ofpollen-tube growth by spermidine may involve de novo synthesisof protein. Catharanthus roseus, pollen germination, tube growth, spermidine, MGBG, inhibition, actinomycin-D     

Organogenesis in the Cultured Female Gametophyte of Ephedra foliata

The female gametophyte of Ephedra foliata was used as an explantfor the production of haploids as it is composed of haploidcells, all of the same genotype. The regeneration of roots wasdependent upon the presence of NAA, while BAP had a modifyingeffect. At lower concentrations (0.05 parts 10^–6 and 3.5parts 10^–6) BAP enhanced the root promotion of NAA (0.05–4.0parts 10^–6). At higher concentrations of BAP (1–6parts 10^–6), roots and shoot buds were formed. Kinetinat 4.0 parts 10–6 with 0.5 parts 10–6 2, 4-D wasoptimal for shoot bud production in explants at the archegonialstage and 2, 4-D at 2.0 parts 10–6 with 0.5 parts 10–6kinetin was optimal for root formation. Cells of the callusand root tip had the haploid number of chromosomes, n = 7. Meristemoidswere located on the surface or embedded in the callus tissue.The deep seated meristemoids organized only root primordia,but the peripheral ones gave rise to root as well as shoot budprimordia. Initially, there was no vascular connection betweenthe shoot-bud and the callus. This was established later. Key words: Ephedra, Female gametophyte, Haploid, Tissue culture     

Response of Seed Germination in Three Genera of Compositae to White Light of Varying Photon Flux Density and Photoperiod

Various photon doses (net number of photons per unit area perday), provided by varying both photon flux density and photoperiod,were applied to imbibing seeds of seven lots of four speciesof Compositae in various germination test regimes. In all fourspecies germination was dependent upon photon dose, the productof photon flux density and daily duration of exposure. The responsewas quantified by linear relations between the probit of percentagegermination and the logarithm of photon dose. In general, photonflux density and photoperiod only influenced the stimulationof germination by the low energy reaction indirectly (as factorsof daily photon dose), whereas there was a tendency for photoperiodto have a direct influence on the inhibition of germinationby the high irradiance reaction. Reducing the germination testtemperature from 25?C to 20?C and 15?C not only increased thedark germination of L. sativa L., but also broadened the photondose range at which full germination occurred by reducing theminimum value necessary for the germination of the most dormantseeds, and increasing the maximum value which failed to inhibitthe germination of any seeds. Differences between L. sativaand L. serriola L. in the response of germination to white lightwere only quantitative, rather than qualitative. The singlemost promotory dose for all four species was 3 ? 10^–3mol m^–2 d^–1, although the inhibitory action of dosesup to 10– mol m– d– was generally only slight. Key words: Light, seed germination, seed dormancy, Compositae     

Promotion by gibberellin of lettuce seed germiation as a function of presoaking period

Germination of lettuce seeds (Lactuca sativa L. cv. Grand Rapids)was examined in the presence of various doses (10^–5.0–10^–3.0M) of gibberellic acid applied at various times (hour 0–8)of soaking. Germination promotion by gibberellic acid was greateras the dose of gibberellic acid was increased and attenuatedwith the length of the presoaking period. As an exception, ca.95% germination was always evoked by the largest dose (10^–3M) of gibberellic acid given at any time of soaking. The dose-responsecurve obtained for each presoaking period had a distinct sigmoidalprofile. Synergistic and photoreversible promotion by red light of thegibberellin-induced germination was also investigated. Far-redlight pulse given 6 hr after the red pulse was still effectivein removing the red light action. Application of enzyme kineticsto the gibberellin action and also to the synergism betweengibberellin and red light was suggested. ¹National Institute for Basic Biology, Myodaiji, Okazaki 444,Japan. (Received December 18, 1979; )     

Quantal Response of Seed Germination in Seven Genera of Cruciferae to White Light of Varying Photon Flux Density and Photoperiod

The response of the germination of seeds of Barbarea vema (Mill.)Aschers, Brassica chinensis L., Brassica juncea (L.) Czern.& Coss., Brassica oleracea L. var. gongylodes L., Camelinasaliva (L.) Crantz, Eruca saliva Mill., Lepidium sativum L.,Nasturtium officinale R. Br., and Rorippa palustris (L.) Besserto white fluorescent light of different photon flux densitiesapplied for different daily durations in a diurnal alternatingtemperature regime of 20 °C/30 °C (16 h/8 h) was quantifiedby linear relations between probit percentage germination andthe logarithm of photon dose, the product of photon flux densityand duration. The low energy reaction, in which increasing dosepromotes germination, was detected in all the seed populationsbut in Barbarea vema and Brassica Juncea the lowest photon doseapplied (10^–5–2 and 10^{–5 7} mol m^–2 d^–1,respectively) was sufficient to saturate the response. Comparisons,where possible, between photoperiods demonstrated reciprocity,i.e. germination was proportional to photon dose irrespectiveof photoperiod, for the low energy reaction in Brassica oleracea(1 min d^–1 to 1 h d^–1), Camelina saliva (1 min d^–1to 8 h d^–1), Eruca saliva (1 min d^–1 to 24 h d^–1),Lepidium sativum (I min d^–1 to 8 h d^–1) and Rorippapalustris (1 min d^–1 to 8 h d^–1), but not in Brassicachinensis and Nasturtium officinale. The high irradiance reaction,in which increasing dose inhibits germination, was detectedin Barbarea vema, Brassica chinensis, Brassica juncea, Brassicaoleracea, and Camelina saliva. The minimum dose at which inhibitionwas detected was lO^–0–3 mol m^–2 d^–1.These results are discussed in the context of devising optimallight regimes for laboratory tests intended to maximize germination The response of germination to photon dose was also quantifiedwith 3 x 10^–4 M GA₂, co-applied (Brassica chinensis, Camelinasaliva, and Lepidium sativum) and with 2 x 10^–2 M potassiumnitrate co-applied (Brassica chinensis). In the latter casepotassium nitrate had no effect in the dark and inhibited germinationin the light, but GA₂, promoted germination substantially inall three species. Variation amongst seeds in the minimum photondose required to stimulate germination was not affected by co-applicationof GA₂, in Brassica chinensis and Camelina saliva, whereas seedsof Lepidium salivum showed a narrower distribution of sensitivitiesto the low energy reaction in the presence of GA₂ Barbarea vema (Mill.) Aschers, Brassica chinensis L., Brassica juncea (L.) Czern. & Coss., Brassica oleracea L. var. gongylodes L., Camelina saliva (L.) Crantz, Eruca saliva Mill., Lepidium satiaum L., Nasturtium officinale R. Br., Rorippa palustris (L.) Besser, Cruciferae, light, gibberellic acid, seed germination, seed dormancy     

In vitro Propagation of Red Cabbage (Brassica oleracea L. var. capitata)

By manipulation of various growth regulators and physical conditions,plants have been regenerated from excised roots, stem segments,cotyledons, leaves, and callus cultures of red cabbage (Brassicaoleracea var. capitata) grown under in vitro conditions. Shootbuds were induced on isolated root segments (1 cm long) culturedon Murashige and Skoog's medium and the frequency of bud formationwas greatly enhanced by the addition of kinetin (0.5 part 10^–6).Callus obtained from the seeds, cotyledons, and hypocotyl segmentscultured on a medium fortified with 2,4-D (1 part 10^–6),kinetin (0.1 part 10^–6), and coconut milk (10%, v/v) hasbeen repeatedly subcultured. The callus is slow growing, andon transference to a kinetin (2 parts 10^–6) and IAA (2parts 10^–6) medium underwent morphogenesis to give riseto plants. The significance of the propagation of red cabbageby in vitro culture is pointed out.     

Dehydration of germinating perennial ryegrass seeds can alter rate of subsequent radicle emergence

Perennial ryegrass (Lolium perenne L.) seeds (caryopses) germinateat or near the soil surface, where water potential can fluctuatewidely. This study examined germination of ‘Del Ray’perennial ryegrass seeds when imbibition was interrupted bydehydration prior to radicle emergence. Seeds were hydratedfor 0 to 40 h (26C), dehydrated at atmospheric water potentialsof –4, –40, –100 and/or –150 MPa for4–168 h, then rehydrated. Germination (radicle elongation 1 mm), seedling growth, solute leakage, and endogenous abscisicacid (ABA) levels were measured. Treatment differences in finalgermination percentage, seedling growth, and solute leakagewere generally not significant. However, the onset of radicleemergence was delayed and the rate of germination slowed whendehydration at –150 MPa was initiated after 36 or 40 hhydration. Slowed germination rates were not observed when dehydrationwas initiated before 36 h, when dehydration occurred at –4MPa, or when dehydration at –150 MPa was preceded by dehydrationat –4 MPa for 24 h. Exogenous abscisic acid (ABA) concentrationsabove 10^–6 M inhibited germination. However, endogenouswhole seed ABA levels declined during imbibition due to leaching,and did not increase during dehydration treatments that delayedgermination. These results illustrate that rate of late-occurringdehydration treatments is critical in determining subsequentgermination response. We propose that seed response to late-occurringdehydration may be of ecological significance in timing radicleemergence to coincide with adequate soil moisture for seedlingestablishment. Key words: Abscisic acid, seed germination, timing     

Light Actions in the Germination of Cocklebur Seeds: IV. DISAPPEARANCE OF RED LIGHT-REQUIREMENT FOR THE GERMINATION OF UPPER SEEDS SUBJECT TO ANOXIA, CHILLING, CYANIDE OR AZIDEPRETREATMENT

Esashi, Y., Fuwa, Nn Kojima, K. and Hase, S. 1986. Light actionsin the germination of cocklebur seeds. IV. Disappearance ofred light-requirement for the germination of upper seeds subjectto anoxia, chilling, cyanide or azide pretreatmenL—J.exp. Bot. 37: 1652–1662. The effects on the germination of positively photoblastic uppercocklebur (X anthium pennsylvanicum Wallr.) seeds by pretreatingwith anoxia, chilling, cyanide or azide, which stimulates theirdark germination, were examined in relation to light actions.Prior to experiments, seeds were pre-soaked at 23 °C inthe dark for 1 or 2 weeks to remove the pre-existing Pfr. Whenthe prctreatment conditions were suboptimal for germinationinduction, the stimulating effects of the pretreatments on germinationduring a subsequent dark period at 23 °C were manifest onlywhen seeds were irradiated with red light before or after thepretreatment Red light promotion was reversed by blue or far-redlight treatment. However, both prc-chilling for 6 d at 8 °Cand prctreatment with 1· 5 mol m ^{– 3} NaN³ for 2d could induce full germination without red light exposure.On the other hand, both pre-exposure to anoxia for 8 d and pretreatmentwith 30 mol m^–3 KCN could induce the dark germinationonly when germination occurred at 33 °C which is known toaugment the ratio of an alternative respiration flux to a cytochromeone. Moreover, the dark germination in response to these inductionswere strongly inhibited by the inhibitors of alternative respiration,propyl gallate and benzohydroxamic acid, applied during a subsequentdark period. It was thus suggested that Pfr has some relationto the operation of two respiration systems of cocklebur seeds,but it is not indispensable to germination of this positivelyphotoblastic seed. Key words: Anoxia, azide, blue light, chilling cyanide, dark germination, far-red light, red light, seed germination, X anthium pennsylvanicum     

Soya Bean Seed Growth and Maturation In vitro without Pods

Immature Glycine max (L.) Merrill seeds, initially between 50and 450 mg f. wt, were grown and matured successfully in vitro.Excised seeds were floated in a liquid medium containing 5 percent sucrose, minerals and glutamine in flasks incubated at25 °C under 300 to 350 µE m^–2 s^–1 fluorescentlight. During 16 to 21 d in culture, seeds grew to a matured. wt of 100 to 600 mg per seed at an average rate of 5 to 25mg d. wt per seed d^–1 depending on initial size. Growthrates were maximal during the first 8 to 10 d in vitro but declinedwith loss of green colour in the cotyledons. Seed coats rupturedwith rapid cotyledon expansion during the first 2 d in culture.Embryos were tolerant to desiccation and 80 to 90 per cent germinatedif removed from culture before complete loss of green colour.The growth of excised seeds in vitro exceeded the growth ofseeds in detached pods, but when windows were cut in pods topermit direct exposure of seeds to the medium, seed growth wascomparable. Glycine max (L.) Merrill, soya bean, seed culture, seed growth, seed maturation, germination     

Ribulose-1,5-Diphosphate Carboxylase Protein during Flag Leaf Senescence

Ribulose-l,5-diphosphate (RuDP) carboxylase protein and activitywere determined in relation to net photosynthetic rate duringthe senescence of intact flag leaves of wheat on the plant.Initially the decrease in RuDP carboxylase activity was greaterthan the decline in net photosynthesis. The major decrease inRuDP carboxylase activity over this period resulted from a decreasein enzyme specific activity from 11 to 2 µmol CO₂ fixedh^–1 mg^–1 protein. Loss of RuDP carboxylase proteindid not occur until late in senescence by which time chlorophyllconcentration had decreased by more than 50%. Treatment of flagleaves at weekly intervals with either 1000 parts 10^–62-chloro-ethyltrimethylammonium chloride or 100 parts 10^–6gibberellic acid with 1 part 10^–6 kinetin did not significantlyaffect net photosynthetic rate, RuDP carboxylase protein oractivity during senescence.     

The Effect of Salinity on Germination and Its Correlation with K+, Na+, Cl- Accumulation in Germinating Seeds of Triticum aestivum L. cv. Akbar

NaCl salinity stress consistantly decreased the rate of germinationof wheat. GA alone or in combination with kinetin alleviatedthe inhibitory effect of salinity on germination. However, kinetinfurther decreased the rate of germination under NaCl salinitystress. NaCl salinity increased accumulation of Na⁺ and Cl^–while it decreased K⁺ accumulation in germinating seeds. GAcaused an increase in K⁺ accumulation and a decrease in Cl^–accumulation in the germinating seeds while kinetin increasedCl^– accumulation in salinity stressed plants. The co-relationbetween the effect of salinity on germination and that on accumulationof ions is discussed. (Received February 12, 1992; Accepted August 4, 1992)     

Stomatal Responses to Applied ABA and CO2 in Epidermis Detached from Well-Watered and Water-Stressed Plants of Commelina communis L.

Epidermal strips from either well-watered or water-stressedplants of Commelina communis L. were subjected to a range ofABA concentrations (10^–6–10^–3 mol m^–3)in the presence (330 parts 10^–6 in air) or virtual absence(3 parts 10–6 in air) of CO₂. The stomatal response toCO₂ was greater in epidermis from water-stressed plants, althoughthere was a distinct CO₂ response in epidermis from well-wateredplants. Additions of ABA via the incubation medium had littleeffect on the relative CO₂ response. Stomata responded to ABAboth in the presence and virtual absence of CO₂, but the relativeresponse to ABA was greatest in the high CO₂ treatment. Whenwell-watered plants were sprayed with a 10^–1 mol m^–3ABA solution 1 d prior to use, the stomatal response of detachedepidermis to both CO₂ and ABA was very similar to that of epidermisdetached from water-stressed leaves. It is hypothesized thata prolonged exposure to ABA is necessary before there is anymodification of the CO₂ response of stomata.     

Methanol Accumulation in Maturing Seeds

During in vitro growth and maturation of soybean seeds, cessationof embryo growth and dry weight accumulation occurred in thepresence of abundant C and N nutrients. Axis followed by cotyledontissues changed from green to yellow, and post-harvest germinationpotential declined if cultured after yellowing of axis tissues.A tissue specific accumulat;on of methanol occurred during thein vitro culture of immature seeds (i.e. initially 50 to 70mg fresh weight) to maturity in liquid medium. Methanol accumulatedto 3.0 g m^–3 or 50 µg seed^–1 in the medium,while methanol decreased from 37 to about 3.0 µg g^–1fresh weight in cotyledons. By contrast, axis tissues increased20-fold in methanol concentration to 90 µg g^–1 during20 d in culture. Ethanol was present only in trace amounts inaxis tissues and medium. Addition of exogenous methanol vapourto in situ grown seeds during precocious maturation decreasedsubsequent seedling vigour and germination with increasing levelsof exposure. Methanol accumulation in axis tissues during thegermination phase was not correlated with high temperature andtissue water content treatments which simulated pre-harvestdeterioration of seeds. However, the accumulation of methanolduring in vitro seed development and maturation in liquid culturemay contribute to reduced post-harvest germination performance. Key words: Soybean, Glycine max, seed maturation, in vitro, methanol     

Effect of some Flavonoids and Phenolic Acids on Seed Germination and Rooting

Nandakumar, L. and Rangaswamy, N. S. 1985. Effect of some flavonoidsand phenolic acids on seed germination and rooting.Mdash;J.cxp. Bot. 36: 1313–1319. Effects of isovitexin (isolated from leaves of Rhynchosia minima),leucocyanidin, gallic acid, and protocatechuic acid on seedgermination and subsequent seedling growth of a crucifer Brassicacampestris, and two legumes Lens esculenta and R. minima, aswell as effects of isovitexin on rooting of onion bulbs aredescribed. Neither of the flavonoids affected seed germinationin any of the three systems studied. However, both the flavonoidspromoted seedling growth in B. campestris and L. esculenta;the promotion of root growth was more marked. At 10^–5and 10^–7M, isovitexin also promoted rooting of onion bulbs.In the range of 2.27 ? 10^–4M to 3.28 ? 10^–3M, leucocyanidinpromoted growth of both root and shoot in L. esculenta, whereasin the range 3.28 ? 10^–3M to l.64?lO^–3M it suppressedseedling growth. In contrast to the flavonoids, the two phenolicacids tested inhibited seed germination at 10^–3M, andat lower concentrations they suppressed seedling growth. The promotive effects of the flavonoids isovitexin and leucocyanidin,especially on root growth, hold promise for the use of suchnaturally occurring plant substances in studies on the physiologyof plant growth and development. Key words: Flavonoids, phenolic acids, seed germination, rooting     

Cotyledonary mRNA Species and Germinability of Immature Vigna unguiculata Seeds

We have defined four stages in the development of cowpea seeds:I(9–11 days after flowering), II (13–15), HI (17–19)and IV (22–24). Poly A⁺ RNA fractions were prepared fromcotyledons of developing (stages I–IV) and germinating(0, 12, 24 and 48 h after imbibition) seeds. Poly A⁺ RNAs fromstages I–III exhibited high translation activities witha maximum at stage II, and the activity was markedly reducedat stage IV. In cotyledons of germinating seeds, the translationactivity was low until 12 h after the onset of imbibition butrose thereafter. Analysis of in vitro translation products withSDS-polyacrylamide gel electrophoresis and fluorography showedthat the abundant mRNA population underwent a distinct changebetween stages II and III of seed development. Since the mRNApopulation at stage III was very similar to that of stage IV(mature seeds), it appears that, as far as mRNA species areconcerned, the prerequisites for germination are fully availablein the developing seeds by stage III. This assumption was supportedby the fact that immature seeds at stage III exhibited highgermination rates and normal axial growth and produced -amylaseat levels similar to those produced by mature seeds. Severalpolypeptides which have been regarded as translation productsof stored mRNA (poly A⁺ RNA from dry seeds) were detected atearlier stages of germination. (Received September 29, 1988; Accepted January 25, 1989)