Stratified Seeds Research Articles

Germination control of stratified sugar maple seeds

A method for the control of germination of stratified sugar maple seeds based on the water content of the seeds prior to stratification has been developed and is described.

Electrophoretic investigation of phenol oxidases in stratified apple seeds

The substrate specificity of apple seeds phenol oxidases was investigated in polyacrylamide gel electropherograms. The nonspecifico-diphenol oxidases were distinguished as well as fractions showing the specificity for some structural elements of substrate molecule. The role of particular oxidases in phloridzin transformations in apple seed was discussed.

The effect of stratification on [formula omitted] protein synthesis in seeds of [formula omitted

Incorporation of 14C-phenylalanine in in vitro systems from sugar pine ( Pinus lambertiana ) seeds was studied. Embryo ribosomes from both dry and stratified seeds supported incorporation (431 and 326 pmoles, respectively, of phenylalanine per mg ribosome) when combined with an embryo pH 5 fraction from stratified seeds. Female gametophyte ribosomes from dry seeds were active (302 pmoles phenylalanine incorporated per mg ribosome) but lost 61 percent of their capacity to support protein synthesis after 35 hours' stratification. The pH 5 fraction from embryos increased in capacity to support incorporation as stratification progressed up to 60 days (398 pmoles phenylalanine per mg ribosome when ribosomes were from 90-day stratified embryos) while the pH 5 fraction from female gametophytes was never active.

Changes in Endogenous Growth Kegulators in Loblolly Pine Seeds During the Process of Stratification and Germination

AbstractThe seeds of loblolly pine (Pirns taeda L.) were cold‐stratified for 0, 14, 28, 42, and 56 days. Endogenous growth regulators were extracted from these seeds, and also from the germinating and the 28‐day warm stratified seeds. Partially purified extracts were separated on chromatographic paper. The chromatograms were cut into 10 equal segments, and these were tested for biological activity using three different btoassays.The results indicated that the unstratified seeds and those stratified up to a period of 28 days contained very little or no growth promoter (GA‐like substances), and a relatively high concentration of an inhibitor (presumably abscisic acid), Following 42‐day stratification, the promoter concentration gradually increased while the inhibitor level fell almost to zero. A high level of promoter but no inhibitor was detected in germinating seeds.No auxin‐like activity was noted in the unstratified seeds. This activity slowly increased up to a period of 28 days and remained at this level for the subsequent stratification periods. However, the activity greatly increased in the germinating seeds.Very little changes in the levels of growth regulators were noted in warm‐stratified seeds as compared to the unstrati‐fied controls.

A Photoperiod Response in Germination of Western Hemlock Seeds

Unstratified and stratified seeds of western hemlock (Tsugaheterophylla) germinated fastest under 4-h photoperiods and slowest under 24-h photoperiods at 20 °C. No differences were found between total darkness and an 8-h photoperiod. Stratification tended to reduce the degree of response to photoperiod. Several indices of germination rate and capacity were compared.

Peach Seed Dormancy in Relation to Endogenous Inhibitors and Applied Growth Substances1

Abstract An inhibitor was present in both seed coat and embryo of a high and a low chilling cv. of unstratified peach seeds and its concn decreased as stratification proceeded, Embryonic tissue retained more of the inhibitor than the seed coat. As the concn of inhibitor decreased, seed germination increased. The inhibitor was tentatively identified as abscisic acid (ABA) by chromatography. A bound inhibitor was also present in the seed parts of both cvs., and its concn increased in the embryo as stratification proceeded. More ABA and bound inhibitor were present in the high-chilling cv. than in the low-chilling counterpart, indicating that they may be related as factors which cause a cv. to require long periods of chilling. Application of ABA reduced germination percentage on stratified seeds without seed coats. Application of gibberellic acid (GA) and N-benzyladenine (BA) combined had a synergistic effect in promoting germination of dormant seeds.

Germination Promotion of Loblolly Pine and Baldcypress Seeds by Stratification and Chemical Treatments

AbstractThe effects of 4 chemicals on the germination promotion of stratified and unstratified seeds of loblolly pine (Pinus taeda) and baldcypress (Taxodium distichum) were studied. The chemicals used were gibberellic acid, kinetin, potassium nitrate and thiourea, each at 3 different concentrations.Stratification promoted the germination of both seed species. Certain concentrations of gibberellic acid, potassium nitrate and thiourea improved the germination of unstratified loblolly pine and baldcypress seeds while kinetin had no stimulatory effect.All 4 chemicals at specific concentrations promoted the germination of loblolly pine seeds stratified for a short period of time. Considering both speed and completeness of germination, best results were obtained when 21‐day stratified seeds were treated with either gibberellic acid (100 mg/1) or kinetin (10 mg/1). In baldcypress, on the other hand, none of these chemicals had any stimulatory effect on the germination of stratified seeds. Germination of both species of seeds was either partially or completely inhibited by the highest concentration of thiourea (30,000 mg/1) used.

Germination Promotion of Loblolly Pine and Baldcypress Seeds by Stratification and Chemical Treatments

The effects of 4 chemicals on the germination promotion of stratified and unstratified seeds of loblolly pine (Pinus taeda) and baldcypress (Taxodium distichum) were studied. The chemicals used were gibberellic acid, kinetin, potassium nitrate and thiourea, each at 3 different concentrations. Stratification promoted the germination of both seed species. Certain concentrations of gibberellic acid, potassium nitrate and thiourea improved the germination of unstratified loblolly pine and baldcypress seeds while kinetin had no stimulatory effect. All 4 chemicals at specific concentrations promoted the germination of loblolly pine seeds stratified for a short period of time. Considering both speed and completeness of germination, best results were obtained when 21-day stratified seeds were treated with either gibberellic acid (100 mg/1) or kinetin (10 mg/1). In baldcypress, on the other hand, none of these chemicals had any stimulatory effect on the germination of stratified seeds. Germination of both species of seeds was either partially or completely inhibited by the highest concentration of thiourea (30,000 mg/1) used.

Seedcoat Influences Dormancy of Loblolly Pine Seeds

The rate and percent of dark germination were low in untreated Pinustaeda L. seeds. Both increased with seedcoat clipping or removal, but not to the level of stratified seeds. Coats did not reduce the rate of initial water inhibition but did limit total uptake prior to germination, probably by restricting swelling of the megagametophyte and embryo. Respiration followed the pattern of water absorption in decoated seeds. However, it was at a common low level in stratified, clipped, and unstratified seeds until germination began, and there seemed to be no causal relation between respiration and coat permeability. Dormancy is likely to be the result of mechanical constraint by the seedcoat.

Effects of Some Endogenous and Exogenous Growth Regulators on Plum Seed Dormancy1

Abstract Radicle growth of stratified Italian plum seeds (Prunus domestica cv. Italian) was inhibited when treated with extracts of unstratified plum seeds. An inhibitor was identified by gas-liquid chromatography as abscisic acid (ABA). Analyses of stratified seeds showed that gibberellin-like substances increased and ABA decreased during a 90-day period. Intact unstratified seeds did not germinate when treated with gibberellic acid (GA) and N-6-benzyladenine (N-6-BA), however, these materials did promote germination of unstratified seeds with testas removed.

Germination of Cyperus inflexus Muhl.

Seeds (achenes) of the annual sedge Cyperus inflexus Muhl. (Cyperaceae) were dormant at maturity. Dormancy was overcome by stratification, scarification, and soaking of the seeds in solutions of certain N-compounds. In all cases light was found to be necessary for germination, and none of the treatments used in this study substituted for the light requirement. Stratified seeds germinated better at daily alternating temperatures (28-18 C) than at constant temperatures (28 or 18 C). Nonstratified seeds that were mechanically scarified at the embryo end or acid scarified gave good germination at 28 and 28-18 C. Chemicals that caused 75% or more of the seeds to germinate included thiourea, potassium nitrite, and hydroxylamine. The germination requirements of C. inflexus are considered in relation to its ecological life history and to its cedar glade habitat.

Effect of Stratification and Gibberellin on Seed Germination in Ginkgo biloba

WEST, W. CHARLES, FRANCESCA J. FRATTARELLI, ancd KAREN J. RusSIN (The City College, New York, N.Y. 10031). Effect of stratification ancd gibberellin on seed germinationi in Ginkgo biloba. Bull. Toirey Bot. Club 97: 380-384. 1970.-The effects of stratification ancd exogenous gibberellic acid on seed germination in Ginkgo biloba were followed for a 12-week period. Most nonstratified seeds either remain dormant or decompose during this period, while nearly 100% of stratified seeds germinate within 7-10 weeks. Reilloval of the hard portion of the seed coat produces oiily a slight enhancement in germination of noiistratified seeds. Exogenous application of gibberellic acid to nonstratified seeds enhaniees ger mination to a level that approaches that of stratified seeds. Barley endosperm bioassay data of ethyl acetate extractable gibberellins froim Ginkgo embryos indicate that stratified embryos contain approximately 100 times more GA, equivalents thani nionstratified embryos. It is coneluded that stratificationi anid gibberellin metabolism are related in the germination of Ginkgo seeds, anid that exogenious GA3 will largely substitute for stratification in lionstratified seeds to promote germ-iinationi.

THE NATURE OF SEED DORMANCY AND GERMINATION IN THE SALT MARSH GRASS DISTICHLIS SPICATA

Summary Distichlis spicata, a salt marsh grass, sets dormant seeds which exhibit a low‐temperature, after‐ripening requirement. In addition to stratification, localized scarification and nitrate are effective agents in breaking dormancy and promoting seed germination. The pericarp and/or testa are impermeable to organic plant‐growth regulators, but not to water or inorganic salts. Gibberellic acid and kinetin are ineffective in breaking dormancy and do not affect germination. Abscisic acid, however, effectively inhibits stratified and scarified seeds. Dormancy and germination appear to be hormonally controlled.It is suggested that the endogenous inhibitor constitutes a block to nitrate reductase activity in the endosperm. Presumably the inhibitor blocks specific DNA transcription sites in the aleurone cells, but can be overcome by after‐ripening (inhibitor decay), abrasion (inhibitor leaching) or nitrate induction.

Specific phloridzin glucosidases from seeds and leaves of apple tree

Five enzymatic fractions of β-glucosidase (EC 3.2.1.21) activity were found in stratified apple seeds. Differences in their substrate specificity towards some phenolic β-glucosides were stated. Some characteristics of the enzymes showing the highest and the lowest specificities towards phloridzin are reported. β-Glucosidases of apple tree seedlings were fractionated. In spite of the markedly pronounced specificity of leaves glucosidases towards phloridzin those enzymes were found to be different from the analogous enzymes from the apple seeds.

Sweetgum Seed Stratification Requirements Related to Winter Climate at Seed Source

Sweetgum Seed Stratification Requirements Related to Winter Climate at Seed Source

Change of Respiratory Pattern in Stratified Pine Seeds

Change of Respiratory Pattern in Stratified Pine Seeds

GROWTH INHIBITION PRODUCED BY LEAF EXTRACTS FROM SIZE-CONTROLLING APPLE ROOTSTOCKS

Dilute alkali extracts of leaves from size-controlling rootstocks inhibited the growth of stratified apple seeds. Correlation coefficients of −0.9140** and −0.7292* exist between the vigor of the rootstocks and the respective growth of apple and wheat seedlings in the leaf extracts. The crude extract was chromatographed in isopropanol:ammonia:water (10:1:1). Two zones of growth inhibition were detected using a watercress bioassay. These zones were at 0 to 0.1 and 0.4 to 0.5 Rf units. The amount of growth made by the watercress was in the same ratio as the known vigor of the rootstocks M.II, M.VII, and M.IX. Measurement of the rate of indoleacetic acid oxidation showed that the material at an Rf 0.4 to 0.6 affected IAA breakdown. The more dwarfing rootstocks stimulated the oxidation of IAA. The significance of the results are discussed in relation to the dwarfing of apple rootstocks.

On Dormancy and Seed Germination in Hemerocallis

1. Seeds obtained from selfing Hemerocallis minor and from intercrossing hybrid Hemerocallis plants of complex origin were used in a series of experiments in 1953, 1954, and 1955 to determine the nature of seed dormancy in this genus. 2. Freshly harvested seeds germinate to a limited extent but only within a narrow temperature range. Minimum, optimum, and maximum temperatures for non-stratified seeds were found to be above 16⚬, 22⚬-25⚬, and below 33⚬ C., respectively. 3. Differential peeling experiments demonstrated that an endosperm membrane one cell thick, which covers the protruding tip of the hypocotyl, was responsible for delayed germination at 22⚬ C., while at 16⚬ C., in addition to the membrane, endosperm storage tissue restricts gaseous diffusion. Complete germination was brought about at 16⚬ C. either by removing a wedge of storage tissue to expose about one-fourth of the embryo axis or by completely excising the embryo, as compared with little or no germination of intact seeds. Sealing of the hypocotyl tip with petroleum jelly or lanolin, following removal of the diminutive endosperm membrane, greatly retarded germination. 4. Results from seeds planted in soil in greenhouse flats and stratified outdoors during the winter for various periods indicated that 1 or 2 months of stratification sufficed for the breaking of dormancy. Stratified seeds germinated over a greater temperature range than did non-treated seeds. 5. Controlled stratification experiments carried out in Petri dishes indicated that 0⚬-10⚬ C. was the general range for after-ripening, with the optimum being near the lower temperatures. Inconsistent results were obtained with stratification temperatures below freezing. As little as a day of stratification at the optimum temperature was sufficient to increase slightly the percentage of germination at 16⚬ C. incubation over that of the controls. Longer periods of stratification were necessary at the higher temperatures of the effective range to bring about corresponding increases of germination. After-ripened seeds germinate over a greater temperature range than do non-stratified seeds. Thus, conditioned seeds germinate readily at 10⚬ C. and even lower. After-ripened seeds likewise are able to germinate at a slightly higher temperature than do non-conditioned seeds, providing the inhibitory effect of the enveloping structures has been removed. 6. After-ripening occurred only at low temperatures and only when the seeds were moist. The optimum degree of moisture saturation seems to be a function of the stratification temperature. Thus, with stratification at 3.5⚬ C., seeds reacted similarly over a wide range of moisture content, but, when stratified at -4⚬ C., the degree of saturation appeared to determine the efficiency of stratification more critically. 7. Oxygen must be available to the seeds if effective after-ripening is to occur during stratification. 8. The after-ripening effect persists for as long as 1 month after stratification if the seeds are maintained in an air-dry condition. 9. Presence of an inhibitor substance could not be demonstrated in non-stratified seeds, nor could any evidence be found of a stimulatory substance in after-ripened seeds. 10. Possible interpretations of the results obtained are discussed in the light of other investigations in the field of seed dormancy.

Embryo Dormancy of Pinus jeffreyi Murr. Seed as Affected by Temperature, Water Uptake, Stratification, and Seed Coat.

Almost three hundred years ago the English siivi-. -culturist, John Evlyn (7), recognized the general problem of forest tree seed dormancy. He did not discuss dormancy as such, but he did report that fall or early winter sowing of acorns, beech-nuts, haws and holly berries was a better practice than spring sowing. He went on to state that seeds may be prepared for the Vernal by being barrell'd or potted up in moist sand or earth stratum during the winter at the expiration whereof you will find them sprouted and being committed to the earth as apt to take as if they had been sown with the most early ... and will not be much concern'd with the increasing heat of the season, as such as being crude, and unfermented are newly sown in the beginning of the Spring. Thus, here is perhaps the first published recommendation for artificial stratification of dormant tree seed. It is obvious he did not know why it was effective?as a matter of fact, we do not know why today, even though we have recognized some of the associated biochemical changes (6,8, 11, 12, 14). Since the turn of the century numerous studies on seed dormancy have been reported; see reviews by Miller (11), Baldwin (1), Crocker (4), and Crocker and Barton (5). Specific reference to pine seed indicates that the dormancy mechanism of that seed is not entirely clear. For example to overcome dormancy, at least five different pregermination treatments have been recommended. They are: soaking the seeds in sulfuric acid (17); soaking the seeds in water at room temperature (9) ; soaking the seeds in water at low temperature (15, 16); cold storage in wet sand or peat moss (2, 3, 13, 23) and removal of the seed coat and papery membrane (19). The most widely used method of increasing seed germination is the low-temperature moist storage treatment generally referred to as stratification. During this particular type of pretreatment chemical changes apparently take place in the seed, after which the seed germinates. For example, Eckerson (6) found during stratification of Crataegus mollis seeds that the fats decreased while there was a progressive increase in sugars, acidity, catalase activity, peroxidase activity, and water-holding capacity. Similar results are reported by Pack (14) for seeds of Juniperus virginiana, J, communia and J. prostrata. He found that fats and proteins decreased while sugars, amino acids, catalase activity, and respiration all increased during stratification. On the other hand Koblet (10) found little change in the character of the food reserve in Pinus strobus seeds during stratification. Only a slight increase in reducing sugars, amino acids, and soluble nitrogen was noted. From this he concluded that the low temperature treatment facilitated a faster mobilization of the reserves during germination and . that low temperatures could effectively stimulate the plasma or upset its equilibrium thereby giving an impulse to growth. The major change Mirov (12) found* in stratified Pinus lambertiana seeds was an increased saturation of the fats. His data also suggested a build-up of auxin in the endosperm during stratification ? a change which Haddock (8) subsequently was unable to detect.