Rapporti Fra Endosperma ed Embrione Nella Germinazione di Pinus Pinea L.: Nota i: Effetti del Grado di Maturità del Seme

Abstract

Endosperm embryo interrelationships during germination of PINUS PINEA L. 1rst note. — Seeds and excised embryos have been cultured in vitro in the dark. Experiments with ripe seeds and embryos have been paralleled with exper. with unripe ones (6 months before natural seed dispersal). The results are as follows:

Both ripe and unripe seeds germinate in the dark into green seedlings.

In both types of seedlings the rootlet is the only part which rapidly increases in length, actually growing, but the growth speed of the root is greater in ripe seeds than in the unripe ones.

Both ripe and unripe excised embryos grow slowly, with greenles cotyledons and dwarf roots, showing a very slight geotropic curve.

The root stops growing more sharply in ripe embryos than in unripe ones.

The hypothesis is raised that the rootlet reaches its full growing power, under the endosperm control, and that this control encreases more and more, as the seed approaches its full maturity.     

Nuove Prospettive Nello Studio dei Fattori che Controllano la Germinazione Dei Semi

Abstract

New perspectives in the study of factors which control seed germination. — Seedlings of Triticum durum, cv. « Cappelli », coming from unirradiated embryos grafted on to irradiated endosperms (EM(u)/EN(i) of presoaked seeds (in distilled water for 24 h. at 20[ddot]C.) (treatment: X-rays, doses, 2,4,6,8,10 and 20 Kr), grow more than seedlings of control EM(u)/EN(u) (dose 0) (fig. 1). To have this reaction, it is necessary that the used seeds be after-ripe; at the various stages of seed ripening, be ginning from the milk stage, the phenomenon is not present.

On this basis, the author has thought that a natural inhibitor occurs in the after-ripe endosperm of « Cappelli », which is neutralized or destroyed by X-rays.

As an experimental demonstration, some trials have been made of growing wheat seedlings in Petri dish, on moistened (distilled water) filter paper, together with excised embryos or isolated endosperms (fig. 2): the after-ripe endosperm is able to depress the seedling growth (fig. 3). In the same experimental conditions, X-rays, dose 6 Kr, neutralize the inhibition effect given by the endosperm. (fig. 4).

A completely different situation occurs in wheat seed, during its ripening: endosperm is inactive, embryo produces inhibition effects on the seedling growth, which, also in this case, are reduced by X-rays.

These phenomena, put in relation with dormancy in Triticum durum, cv. « Cappelli », which is a relative dormancy, having its maximum at the milk stage, have led the author to the general conclusion that, during dormancy, a germination inhibitor occurs in the embryo of wheat seed; when dormancy is finished, the inhibitor appears in the endosperm, in a situation which becomes stable and definitive.     

Primi Processi di Germinazione in Pinus Pinea L. var. Fragilis Du Hamel

Abstract

Early stages of germination in PINUS PINEA L. var. FRAGILIS Du Hamel. — The main stages of the hydration process preceeding germination and accompaning root elongation have been observed in Pinus pinea L. seeds, by means of vital colours (Congo red, neutral red, acid fuchsine).

The results are as follows:

a) water penetrates easily through the outer shell of the seed reaching its deepest layer which is less permeable to water. Two or three days were required in our experience for water could overcome this barrier.

b) The inner shell (known as « soft shell ») is almost water-proof and seems to draw water towards the micropilar pole of the seed, so that the first region of the seed which sucks up water is the micropile.

c) Through the micropile water enters the seed and imbibes the column, the pericolumn and the endosperm cells.

The endosperm swells with water until the seed shell blows up, because of the inside pressure. At this time water freely penetrates the seed everywhere.

In natural conditions we may infer that the first tissues which take contact with the soil water are the column and pericolumn. As a certain amount of time is required for penetration of water as far as the column (two or three days in experience conditions) germination starts only after a given amount of water is available in the soil for a certain period of time.

When seed hydration is performed the embryo root starts elongating and gets out of the seed.

The behaviour of the column, the pericolumn and the root cap during the early stages of germination are dexcribed.     

Le Basi Anatomiche Dei Rapporti Nutritivi Tra Pianta Madre,Seme Ed Embrione

Abstract

The anatomical basis of the nutritive relationships between mother plant, seed, and embryo. — The morphology and anatomy of the fruits and seeds of the Angiosperms show a great variety of structures and adaptments, even within the same family, and one must be cautious in drawing generalized conclusions.

If we first examine the ovary we see that the single carpel receives three vascular traces from which the three main bundles originate, a dorsal and two ventral ones, all more or less reduced. Except in the case of laminar placentation the ovule traces are connected to the ventral vascular system, but often the entire vascular system of the ovary is anastomosed and therefore reticular. However especially when the placentae are at the centre or at the basis of the ovary, it is possible to detect a tendency towards a separation between the vascular system of the ovarian wall and that of the placentae.

The ovular bundle runs through the funicle reaching the chalaza, where it can either end or continue towards the micropyle with a single bundle or with a few branches or even forming a complete reticular envelope surrounding the ovule. The ovular vascular bundles are normally found in the outer integument.

The ovule is made of an inner part (nucellus), and an outer one (integuments). The integuments play a very important role in the processes of seed maturation, dormancy, and germination. They are isolated from the interior of the seed by a cuticle which is a common production of the inner integumentary epidermis, and of the nucellus. The cuticle is not present in the chalaza and can be dissolved in the micropylar region: through these two apertures nutrients can penetrate into the seed or haustoria can grow out of it. During the course of maturation these openings become closed by various means, often through the formation of a new cuticle or of a suberised chalazal plate.

The nutrients which pass through the chalaza penetrate into the nucellus where in some cases one can find some structures which facilitate the communications between the chalaza and embryo sac. The endosperm feeds at the expense of the nucellus but often it can establish a direct contact with the chalaza or the integuments or even the placentae. This occurs often thanks to haustoria.

The embryo is normally surrounded at first by a more or less liquid endosperm: in a second stage the endosperm becomes cellular and the embryo grows at its expense through the digestive activity of the cotyledonar epidermis.

From an anatomo-physiological point of view the following points seem of particular interest:

(I) The endosperm and the embryo show a remarkable autonomy in respect of the mother plant: from an anatomical point of view this is shown by the isolation of the endosperm and embryo by means of a cuticular covering or substitutive structures and by the interposition of nutritive tissues between the vascular system of the mother plant and the endosperm.

(II) Given the importance of the inner cuticle its presence and its constitution should be ascertained in the various species having also in mind the properties of selective permeability shown by the testa.

(III) Two nutritive mechanisms exist: translocation of nutrients via the vascular system and the nutritive tissues, and digestion of surrounding cells. In the digestive phenomena it is important to explain the mechanisms by which only the right cells are digested and not the others.

(IV) The embryo very frequently is immersed at first in a more or less liquid endosperm and is later surrounded by a compact tissue; the nutritive mechanisms are probably different in the two cases.

(V) Two endospermic zones are often distinguishable: one having an haustorial or at least a digestive or elaborative function, and being typically non cellular; another zone, typically cellular, forms a tissue which is sooner or later absorbed by the embryo. The cellularization of this zone seems to coincide with the establishment of polarity and with the beginning of maximum growth of the embryo.

(VI) The relationships between the inner seed and the integuments is complex and there is a correlation between the histoanatomical and biochemical changes of these two parts during seed development. The modifications undergone by the integuments are important steps also towards the preparation of the seed to the processes of dispersal, dormancy, and germination.     

Immunolocalization of endo-β-mannanases in Phacelia tanacetifolia seeds during early phases of germination

ABSTRACT

Endosperm weakening is a key event for completion of seed germination in plants such as tomato and tobacco. Weakening is related to the action of endo-β-mannanases able to hydrolyse the mannose polymers typically stored in the wall of the endosperm cells. In this study, we determined the presence and the localisation of endo-β-mannanases in Phacelia tanacetifolia seeds during the early phases of germination. In endosperm cells of dry seeds, and of seeds incubated in the light for 16 h, a similar distribution of endo-β-mannanases, mainly localised in protein bodies, was revealed by immunolocalization. In contrast, under conditions of permissive germination (seeds incubated for 16 h in the dark), these enzymes appeared localised near the cell walls, and were no longer detectable in protein bodies. Western blot analyses showed the presence of three isoforms of endo-β-mannanases in the endosperm and one isoform in the embryo. All these isoforms had similar molecular weights (approx 38 kDa). A possible role of endo-β-mannanases during early phases of germination is suggested.     

Effects of ethylene and some other environmental factors on different stages of germination in red root pigweed (Amaranthus retroflexus L.) seeds*

Abstract. Ethylene was found to promote two distinct processes during germination of redroot pigweed (Amarantus retroflexus L.) seeds: embryo expansion that splits the seed coat (incomplete germination), and radicle penetration through the more elastic endosperm (complete germination). The two events can be separated in time by subjecting seeds to low water potential or low CO₂ levels, which arrest germination of some seeds at the incomplete stage. Ethylene applications to incompletely germinated seeds promote complete germination, with a response threshold near 0.02 cm³ m^?3 and saturation near 0.5 cm³ m^?3. Higher ethylene concentrations (0.5 to 50 cm³ m^?3) given during the first day of seed imbibition also increase the percentage of seeds which initiate embryo expansion and split the seed coat. Light and elevated CO₂ also promote radicle penetration of the endosperm in seeds incubated under water stress. The results support the view that the germination pause at the incomplete stage is an adaptation to environmental stresses that can be overcome with exogenous ethylene or certain other stimuli.     

Aspetti Enzimatici Della Maturazione e Germinazione dei Semi di Ricino

Abstract

Enzyme levels during ripening and germination of castor bean seeds. — During the development of the endosperm of castor bean seeds two distinct phases can be recognized: pre-maturation and germination. The former is characterized, metabolically, by the rapid conversion of carbohydrates into lipids, and storage proteins. The latter is characterized by the reconversion of these storage materials into sugars. Both these processes are dependent upon the activity of the glycolytic pathway; for this reason the behaviour of some enzymes of this pathway and, in general, of the carbohydrate metabolism have been studied during the two phases. The changes (during the evolution of the seeds) of the following enzymes have been studied:

Gl-6-P-dehydrogenase, 6-P-gluconate dehydrogenase, P-glucomutase, Hexokinase Hexoseisomerase, Aldolase, alcaline and acid Phosphatase, Pyrophosphatase and ATP-ase.

All these activities have been measured in the 20.000 × g supernatant fraction of cell homogenates.

The results show that all the enzymes activities measured increase rapidly during the period of accumulation of storage materials. In the following period all of these activities decrease until the stage of ripeness of the seed. During the first few days of germination the activities increase again rapidly. A particular behaviour is the one of Fr-1-6-P-phosphatase (the enzyme cleaving the phosphate bond in C ¹ position). This enzyme reaches during germination a level much higher than the maximal observed during the ripening process. This might be an important fact correlated with the inversion of the glycolytic reactions during germination.     

Changes in low-molecular-weight thiol-disulphide redox couples are part of bread wheat seed germination and early seedling growth

The tripeptide antioxidant glutathione (γ-l-glutamyl-l-cysteinyl-glycine; GSH) essentially contributes to thiol-disulphide conversions, which are involved in the control of seed development, germination, and seedling establishment. However, the relative contribution of GSH metabolism in different seed structures is not fully understood. We studied the GSH/glutathione disulphide (GSSG) redox couple and associated low-molecular-weight (LMW) thiols and disulphides related to GSH metabolism in bread wheat (Triticum aestivum L.) seeds, focussing on redox changes in the embryo and endosperm during germination. In dry seeds, GSH was the predominant LMW thiol and, 15?h after the onset of imbibition, embryos of non-germinated seeds contained 12 times more LMW thiols than the endosperm. In germinated seeds, the embryo contained 17 and 11 times more LMW thiols than the endosperm after 15 and 48?h, respectively. This resulted in the embryo having significantly more reducing half-cell reduction potentials of GSH/GSSG and cysteine (Cys)/cystine (CySS) redox couples (E_GSSG/2GSH and E_CySS/2Cys, respectively). Upon seed germination and early seedling growth, Cys and CySS concentrations significantly increased in both embryo and endosperm, progressively contributing to the cellular LMW thiol-disulphide redox environment (E_{thiol-disulphide}). The changes in E_CySS/2Cys could be related to the mobilisation of storage proteins in the endosperm during early seedling growth. We suggest that E_GSSG/2GSH and E_CySS/2Cys can be used as markers of the physiological and developmental stage of embryo and endosperm. We also present a model of interaction between LMW thiols and disulphides with hydrogen peroxide (H₂O₂) in redox regulation of bread wheat germination and early seedling growth.     

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.     

Ricerche Sulla Flora e Vegetazione dei Fontanili Dell'Agro Milanese

Abstract

Nucleic Acids in Ripening of Castor Bean Endosperm. - I. Quantitative and Qualitative Changes of total RNA. — The ripe Castor Bean seed endosperm (Ricinus Communis var. Sanguinea) has a very low level of nucleic acids and particularly of ribosomal RNA. However, they rapidly increase during the germination of the seed (S. Cocucci et al., Acc. Naz. Lincei, 38, 545, 1965).

The behaviour of the nucleic acids, obtained by phenol extraction from Castor Bean seed endosperm at different ripening stages, is the following:

1. From the moment when the developing seed has reached the maximal fresh weight to the moment of its complete ripening, the RNA content decreases from about 700 μg per seed to about 200 μg.

2. During the same period the DNA level (about 13–15 μg per seed) remains nearly costant.

3. Fractionation by sucrose density gradient of the phenol extracted RNA (H. L. Sanger and C. A. Knight, Biochem. Biophys. Reserch Commun., 13, 445, 1963) shows that during the ripening of the seed the high molecular weight RNA decreases much more than the low molecular weight RNA.

4. Radioactive phosphate injected in the seeds is incorporated in the RNA at all the stages. Fractionation by sucrose density giadient shows that the phosphate is essentially incorporated in low molecular weight RNA and there is pratically no labelling of the heavier RNA after quite a long period (2 hr.).

These data suggest that the decrease of the RNA during the ripening of the seed can be due to a fall in the ability to synthesize high molecular RNA.     

Ulteriori ricerche sulla germinazione di Cercis siliquastrum L. Azione dell'acido gibberellico e ruolo dell'endosperma nel fenomeno della dormienza

Abstract

Further research on the germination of Cercis siliquastrum L. Effect of gibberellic acid (GA₃) and role of endosperm in dormancy.—In order to locate the causes of the dormancy in Cercis siliquastrum L., researches have been carried out also on non-scarified seeds without integument, as well as on isolated embryos.

We have noted that gibberellic acid can substitute the cold treatment to interrupt the dormancy and we have also investigated the optimal concentrations.

The results we have obtained do not show the inhibition to be located in the integument and point out a determinant role of the endosperm.

Histological investigations are being carried out to study better the possible occurrence of a mechanical restraint imposed by the albumen on the non-dormant embryo.     

Osservazioni Sull'Assunzione Dell'Acqua Durante le Prime Fasi Di Germinazione Di Semi Di Pinus Pinea L

Abstract

Water assumption during the early germination stages in «Pinus pinea» L. seeds. – Germination of «Pinus pinea» L. seeds in several conditions has been studied. The main results attained are the following: 1) The micropyle appears to be the only water way into the seed, to start root growth. When this route is prevented and water is absorbed only by the seed surface, the embryo grows into a big cotyledon-hypocotyl complex, where the radicle is still blocked in the embryonic stage; 2) The micropyle appears to be involved also in gas exchange processes during germination.     

Effetto di Inibitori Della Sintesi Proteica Sull'aumento di Attività Enzimatiche e sul Risveglio del Metabolismo Nell'Endosperma di Semi di Ricino in Germinazione

Abstract

Effects of inhibitors of protein synthesis on the development of metabolic activity in the endosperm during the germination of castor bean seeds. — The effect of chloramphenicol, streptomycin and actinomycin-C on the increase of the activities of glyceroaldehyde-phosphate dehydrogenase, aldolase, glucose-6-phosphate dehydrogenase, fructose 1–6 diphosphate-1-phosphatase, phosphomonoesterase, in the endosperm of germinating castor bean seeds was investigated.

In all cases, the protein synthesis inhibitors depressed the activation of the enzymes tested: in particular, actinomycin (50 μg/ml) completely suppressed the increase of the activities.

The development of the rate of oxygen uptake and the conversion of fats to sugars was strongly affected by the inhibitors.

These data suggest that the increase of the activities of several enzymes in the germinating endosperm is dependent on enzyme synthesis rather than on the conversion from the inactive to the active form of the enzymes.     

Effects of APETALA2 on embryo, endosperm, and seed coat development determine seed size in Arabidopsis

Arabidopsis APETALA2 (AP2) controls seed mass maternally, with ap2 mutants producing larger seeds than wild type. Here, we show that AP2 influences development of the three major seed compartments: embryo, endosperm, and seed coat. AP2 appears to have a significant effect on endosperm development. ap2 mutant seeds undergo an extended period of rapid endosperm growth early in development relative to wild type. This early expanded growth period in ap2 seeds is associated with delayed endosperm cellularization and overgrowth of the endosperm central vacuole. The subsequent period of moderate endosperm growth is also extended in ap2 seeds largely due to persistent cell divisions at the endosperm periphery. The effect of AP2 on endosperm development is mediated by different mechanisms than parent-of-origin effects on seed size observed in interploidy crosses. Seed coat development is affected; integument cells of ap2 mutants are more elongated than wild type. We conclude that endosperm overgrowth and/or integument cell elongation create a larger postfertilization embryo sac into which the ap2 embryo can grow. Morphological development of the embryo is initially delayed in ap2 compared with wild-type seeds, but ap2 embryos become larger than wild type after the bent-cotyledon stage of development. ap2 embryos are able to fill the enlarged postfertilization embryo sac, because they undergo extended periods of cell proliferation and seed filling. We discuss potential mechanisms by which maternally acting AP2 influences development of the zygotic embryo and endosperm to repress seed size.     

Alcuni Aspetti Citologici Dell'Endosperma di Phaseolus Coccineus L.

Abstract

Some cytological aspects of Phaseolus coccineus L. endosperm. — Cytological observations were made on the endosperm of Phaseolus coccineus, in a limited stage of development of the seed, using different dyes and labelling with ³H-thymidine and ³H-uridine. The results seem to indicate that, contrary to suspensor cells, in the endosperm of Phaseolus, at least in the considered stage, extra DNA synthesis is not present. Chromosomes in these nuclei, however, undergo several endoreduplication cycles. Nucleoli may be either one or more in a cell, and show a characteristic structure. They are often eccentric in the nucleus and extrusions of nucleolar content in the nucleoplasm or cytoplasm are seen. An apparent alternate activity of RNA synthesis in the nucleoli of the suspensor and in those of endosperm cells is discussed.     

A threatened alpine species,Fritillaria tubiformis subsp. moggridgei: Seed morphology and temperature regulation of embryo growth

Abstract

Alpine plants have evolved to fit their life cycle into the short vegetative season of mountain habitats. Fritillaria tubiformis Gren. & Godr. subsp. moggridgei (Boiss. & Reuter ex Planch.) Rix (Liliaceae) is an endemic alpine geophyte, bearing seeds with underdeveloped embryos. Seeds are dispersed in August and embryos complete their development by spring when seeds germinate. In order to optimize seed banking procedures and to develop a proper germination protocol for plant regeneration, we studied embryo morphogenesis and analyzed how this process is influenced by temperature. Radicle protrusion occurred after an incubation of 5 months at 4°C. Under these conditions, underdeveloped embryos reached maturity and acquired a well-defined shoot apex. At the time of dispersal, abundant storage compounds were present in seeds. Lipids and lipid/proteins were uniformly distributed within the embryo and the endosperm, respectively. At late stages of embryo development, starch granules were localized at the cotyledonary tip and were also detected around the shoot meristem. Results suggested that F. tubiformis embryos resumed growth over a large range of temperatures, but were only able to complete development at low temperatures after which they were able to germinate by spring.     

Comportamento Alla Germinazione e Mutabilità Cromosomica Spontanea in Triticum Durum Desf. Durante I Primi Due Anni di Vita del Seme

Abstract

Germination and spontaneous chromosome mutations in Triticum durum Desf. during the first two years of storage of the seed. — Spontaneous chromosome aberrations were recently observed in the meristem of radicles of seedlings raised from seeds (caryopses) of Triticum durum cv. Cappelli erop 1966. Germination and frequency of chromosomal aberrations, starting from the ripening of the caryopses to the end of the second year of their storage at room temperature were investigated. Cytological analysis and germination tests were accomplished at monthly intervals. It was shown that: 1) soon after ripening, the germination process was very slow, but chromosomal damage was high; 2) at the end of the dormancy period the percentage of aberrant anaphases and of chromatid breaks fell to a «minimum». This low chromosomal damage lasted for almost the whole of the two years of storage; 3) the nuclear damage was esclusively of chromatide type. This result and fact that the cytological damage is decreasing with time, are interpreted as evidence that the mutagenic agent(s) responsible is (are) more active during the germination period than during the quiescence of the embryo.     

SEED DORMANCY AND GERMINATION IN MELAMPYRUM LINEARE

Immature seeds of Melampyrum lineare Desr. have very high germination percentages and dormancy is induced in a variable fraction of the seed crop during ripening. Correlated with this is the endogenous gibberellin-like activity which is found in considerable amounts in immature seeds, less in batches of ripe seeds, and is not detectable in batches containing only dormant seeds. For germination dormant seeds require activation followed by cold storage. In the laboratory activation is produced by allowing moist, dormant seeds to respire freely for several weeks at 20 C, or by treatment with exogenous GA₃. Dormancy appears to be most directly related to inability of the embryo to hydrolyze the thickened, mannan-containing endosperm cell walls. Embryos excised from dormant seed can be grown on agar enriched with whole macerated dormant seeds or with the ethanol-extractable materials from these (mostly sucrose and a glycoside). However, dormant seed material does not support growth when extracted to remove benzene- and ethanol-soluble materials.     

The Mechanism of Low Temperature Dormancy in Mature Seeds of Syringa Species

The mechanism of seed dormancy at low temperatures (15-9°C) was investigated in the seeds of Syringa josikaea, S. reflexa and S. vulgaris. Low temperature dormancy in Syringa species was mainly imposed by endosperm embedding the radicle. Different degrees of embryo dormancy may occur in S. reflexa seeds. In most cases the low temperature dormancy was broken completely by removing the endosperm around the radicle. The endosperm did not seem to contain significant quantities of germination inhibitors, and the results indicate that it prevents germination mainly due to its mechanical resistance. The mechanical resistance of endosperm did not change during chilling or during induction of dormancy by high temperature incubation. The strength of the endosperm decreased rapidly in non-dormant seeds before visible germination. Similar changes were not observed in dormant seeds. Generally, the strength of the endosperm was lower in the non- (or less) dormant species S. josikaea and S. vulgaris than in the more dormant S. reflexa seeds. The growth potential of the embryos, measured as their ability to germinate in osmotic solutions (mannitol or polyethylen glycol 4000), was increased by chilling and by GA₃-treatment. The growth potential of untreated S. josikaea and S. vulgaris embryos was generally higher than that of S. reflexa embryos. Acid ethyl acetate fractions of methanol extracts from embryos of all three species contained substances with GA³-like activity in the lettuce hypocotyl test. The activity was found at Rf 0.9–1.0 on paper chromatograms run in distilled water. No significant changes in the activity were detected during chilling or prior to visible germination.