Showing papers on "Germination published in 1974"

Promotion of seed germination by nitrate, nitrite, hydroxylamine, and ammonium salts.

Abstract: Action and uptake of azides, nitrates, nitrites, hydroxylamines, and ammonium salts were measured on germination of Amaranthus albus, Lactuca sativa, Phleum pratense, Barbarea vulgaris, B verna , and Setaria glauca seeds Nitrate and nitrite reductase activities were measured in vivo for each of these kinds of seeds Activities were measured in vitro for catalase, peroxidase, glycolate oxidase, and pyridine nucleotide quinone reductase on extracts of A albus and L sativa seeds before and after germination The enzymic activities measured and the responsiveness of the haemproteins to inhibition by the several compounds indicate that nitrites, azides, and hydroxylamines promote seed germination by inhibition of H 2 O 2 decomposition by catalase Ammonium salts showed pronounced promotive activity only for B verna and B vulgaris seeds, for which they served as metabolic substrates The promotion of germination is thought to depend on coupling of peroxidase action to NADPH oxidation, which can regulate the pentose pathway of d-glucose 6-phosphate use Pyridine nucleotide quinone reductase is the possible coupling enzyme This enzyme and others required for the action are present in the seeds before imbibition of water

Seed aging: chromosome stability and extended viability of seeds stored fully imbided.

Abstract: Increase in moisture content of seeds of Lactuca sativa L. and Fraxinus americana L. in air-dry storage caused a rapid decline in longevity and an increase in the rate of accumulation of chromosome aberrations. Storage of seeds fully imbibed but unable to germinate allowed a high germination capacity to be maintained for long periods, together with a very low incidence of chromosome aberrations. Seedlings grown from dry-stored seeds showed an increase in morphological abnormalities with length of storage, whereas seedlings from imbibed-stored seeds appeared normal. It is suggested that in dry tissues, enzyme-controlled turnover and repair may be temporarily suspended, and that this may be an important factor in the loss of seed viability in storage. The effect of increasing seed longevity by lowering the moisture content of dry-stored seeds is discussed in relation to this hypothesis. The relevance of the proposal is also discussed in relation to ecological studies.

Effects of gazelles and seed beetles (bruchidae) on germination and establishment of acacia species

Abstract: The germination potential of Acacia species in the Negev and Sinai is greatly affected by populations of gazelles and by several species of seed beetles (bruchids). Most of the seeds produced are eaten by gazelles or damaged by bruchids. In seeds with intact embryo (not damaged by bruchids or by the teeth of gazelles), germination was improved by passage through the digestive tract of the mammals. The role of bruchid infestation and gazelle feeding in this improved germination is discussed. The interactions between acacias, bruchids and gazelles are conducive to the development of characters with a high adaptive value to extreme desert conditions.

Factors Affecting Seed Germination in Three Annual Species from an Arid Region of Western Australia

Abstract: Since arid regions are usually zones in which rain falls in sporadic heavy showers, plant growth is limited to the periods of high soil moisture content following these showers (e.g. see Koller 1969). Annual plants must complete their life cycle during these periods, so that mechanisms which ensure the successful germination and establishment of annuals during favourable moisture conditions are important in the survival of the annual community. In the arid Murchison Region of Western Australia (annual rainfall <200 mm), the bimodal pattern of annual rainfall leads to the development of both summer and winter annual floras (Mott 1972a, 1973). In these communities seed is evident on the soil surface throughout the year, and germination takes place on the soil/air interface (Mott 1973). The three species dominating the annual floras are the summer grass Aristida contorta F. Muell., and the two winter composites Helipterum craspedioides W.V. Fitzg. and Helichrysum cassinianum Gaud. Both Aristida contorta and Helipterum craspedioides have an obligate requirement for light at germination (Mott 1972a). Little viable seed of these species remains after any rainfall sufficient to result in germination (Mott 1973), and so the factors controlling germination are critical to the survival of the annual communities in this area. Even in moist environments the conditions for germination are more severe on the surface than for buried seed (Meeklah 1958; Evans, Eckert & Kay 1967). This can be explained by the rapid fluctuations in moisture and humidity in the micro-environment at the soil/air interface, which result in unfavourable conditions for germination (Miller & Perry 1968; Dowling, Clements & McWilliam 1971). The possibility of litter modifying soil surface conditions has also been investigated by these workers and it appears that litter cover favours seedling establishment by increasing the humidity in the microenvironment surrounding the seed. The importance of seed surface characteristics in modifying the seed/soil interface has been emphasized by Sedgley (1963) and Harper & Benton (1966). These workers showed that germination was enhanced when a greater area was in contact with the substrate, and that mucilaginous seeds showed the greatest germination under high moisture tensions. Other studies have shown that artificial water absorbent coatings increase germination of pasture plants when humidity in the micro-environment is high, due to more efficient

The Metabolism of Hormones during Seed Germination and Dormancy: IV. The Metabolism of (S)-2-C-Abscisic Acid in Ash Seed.

Abstract: Embryos from dormant and stratified Fraxinus americana seed were incubated with (S)-2-(14)C-abscisic acid (ABA) under a variety of conditions. Both dormant and stratified embryos rapidly metabolize abscisic acid to phaseic acid, dihydrophaseic acid, and an unidentified polar metabolite apparently derived from dihydrophaseic acid. Although the stratified embryos may have an increased capacity to metabolize abscisic acid, our calculations suggest that such an increased capacity would probably not be physiologically significant.Dormant intact seeds also metabolize (S)-2-(14)C-abscisic acid during stratification at 5 C or incubation at 25 C. The metabolites appear to be similar to those observed in excised embryos although by 12 days of stratification a fourth metabolite is observed. More than 90% of the (14)C-abscisic acid was metabolized after 26 days of stratification at 5 C or after 12 days of incubation at 25 C. Stratification at 5 C leads to the breaking of dormancy while incubation at 25 C does not.

Effects of Fluctuating Temperatures on Germination

Abstract: Germination responses to alternating daily cycles involving transfers between different temperatures over the range 0 to c. 40 °C were investigated in four species : Lycopus europaeus LClarkia unguiculata Lindl., Apium graveolens L. cv. Giant Red, and Suene dioica (L.) Clairv. Comparisons of the germination of these species revealed distinctive differences which could be related to particular features of the geographical regions or ecological habitats in which they occur naturally. The effects of fluctuating as opposed to constant temperatures varied from one species to another. L. europaeus depended almost absolutely on fluctuating temperatures for germina tion. Germination of S. dioica was greatly increased by fluctuating temperatures. Moderate increases occurred over a restricted temperature range in A. graveolens cv. Giant Red and C. unguiculata was affected in only minor ways. These results are discussed in relation to previous attempts to explain the mechanisms responsible for the frequently beneficial effects of fluctuating temperatures on germination.

Promoting Effect of Fusicoccin on Seed Germination

Abstract: The effects of fusicoccin on the germination of dormant, light-requiring or abscisic acid-inhibited seeds has been investigated. (1) Fusicoccin (10−6M) induces germination in dormant wheat seeds (Triticum durum cv. Cappelli; 1972 crop) and stimulates it in seeds already relieved from dormancy (1971 crop), with an effect similar to that of gibberellic acid. (2) Fusicoccin (1.5 × 10−6M) is more active than the two phytohormones gibberellic acid and benzyladenine and than white light in stimulating light-requiring lettuce seeds (Lactuca sativa cv. Grand Rapids) to germinate. Germination of radish seeds (Raphanus sativus) is also accelerated by fusicoccin, while benzyladenine and gibberellic acid are less active in this material. (3) Fusicoccin (1.5 × 10−5M) removes almost completely the inhibitory effect of abscisic acid on germination of radish and lettuce seeds, whereas benzyladenine (10−4M) and gibberellic acid (3 × 10−4M) remove the inhibition only partially. The possible relationship between these results and previous information on growth by cell enlargement is discussed in terms of the mechanism of action of fusicoccin as compared with natural hormones.

The effect of salinity and temperature on seed germination and growth of Hordeum jubatum

Abstract: Studies on the germination of Hordeum jubatum seeds indicate that they were highly tolerant of salinities up to 1.0%, with little reduction in germination. Each increase in salt concentration did, ...

Diterpenes from Nicotiana glutinosa and their Effect on Fungal Growth

Abstract: SUMMARY: The diterpenes sclareol and 13-epi-sclareol were isolated as a eutectic mixture from leaves of Nicotiana glutinosa. These compounds were probably present in liquid droplets which occurred on the leaf surface. These diterpenes did not prevent germination of fungal spores but markedly inhibited the radial extension of colonies growing on agar. This inhibition is shown to be due to an effect on the morphology of the fungi in which the degree of hyphal branching is increased. The possibility that sclareol/13-epi-sclareol influence the growth-regulatory processes of fungal hyphae and the potential of these compounds to affect growth of fungi on the surface of leaves of N. glutinosa is discussed.

The influence of the photoperiodic regime and red-far red light treatments of Portulaca oleracea L. plants on the germinability of their seeds.

Abstract: Plants of Portulaca oleracea L. were grown in a temperature controlled greenhouse. In one experiment plants received 8 hrs of daylight and during the following 16 hrs (“dark period”) they either were grown in darkness or received white, red and far red light of low intensity for various times preceeding the dark period or in the middle or the end of the dark period. In other experiments the plants were grown in photoperiods of 8, 11, 13, 15, 16 hrs and in continuous light. The effect of these treatments on number of leaves until the appearance of the first flower bud and the germination of the seeds collected from these plants were studied. P. oleracea was found to be a photoperiodic facultative or quantitative short day plant. The photoperiodic treatments of the mother plants affect the germinability of their seeds, dependent on the last 8 days of seed maturation on the mother plants. The shorter the daylength the faster the germination. Red or far-red treatments of the mother plant also affect the germinability. But in no case is there dark germination even after 8 days of seed maturation under continuous red light. These results suggest that the influence of the light treatments of the mother plants on the germination of its seeds is not mediated via phytochrome but rather through some other pathway.

Actions of Gibberellic Acid and Phytochrome on the Germination of Grand Rapids Lettuce Seeds

Abstract: Red light and gibberellic acid were about equally effective in promoting germination of Grand Rapids lettuce (Lactuca sativa L.) seeds. With initial far red light treatment more than 80% remained dormant in subsequent dark storage. After 2 days of dark storage, red light effectively promoted germination, while gibberellic acid action was weak. With between 2 and 10 days of dark storage, gibberellic acid had little effect, while promotion by red light decreased slowly and finally disappeared. After 10 days of dark storage, both gibberellic acid and red light were required for germination. The dark storage treatment interferes with phytochrome-independent germination processes and cannot be overcome by added gibberellic acid. However, storage may also decrease the effectiveness of endogenous gibberellins. Phytochrome-dependent germination seems to require only low levels of endogenous gibberellin activity or the addition of gibberellic acid. Gibberellins and red light appear to act on germination by regulation of sequential sites of a branched-looped pathway.

New germination inhibitor from Aegilops ovata L.

Abstract: IT has been previously reported1 that the dispersal units of Aegilops ovata L. contain a germination inhibitor. Leachates of the hulls inhibited the germination of Lactuca achenes. This inhibition was considerably stronger in light than in darkness, an unusual feature, since all germination inhibitors already described inhibit the germination of Lactuca achenes in darkness more than in light. We therefore felt it essential to isolate and characterise this specific inhibitor present in Aegilops ovata.

The Effects of SO2 on in vitro Forest Tree Pollen Germination and Tube Elongation

Abstract: The effects of SO₂ on in vitro pollen germination and tube elongation were examined for Populus deltoides (Bartr.), Pinus resinosa (Ait.), Pinus nigra (Arnold), and Picea pungens (Engelm.). Comparisons were made between pollen fumigated in a dry condition and then placed on the germinating media, and moist pollen fumigated while on the germinating media. Moist P. deltoides pollen germination was significantly reduced at SO₂ concentrations of 0.75 ppm and above. Populus deltoides pollen tube elongation was more sensitive to SO₂ exposure and highly significant decreases in tube length occurred at 0.30 ppm for 4 hours. Tube elongation decreased linearly with increases in SO₂ concentration. Frequent bursting of pollen tubes occurred at SO₂ concentrations greater than or equal to 0.3 ppm for 4 hours. Exposure to SO₂ caused similar effects on pollen germination and tube elongation for Pinus resinosa, Pinus nigra, and Picea pungens. Moist pollen was far more sensitive than dry pollen to SO₂ exposure. A 4-hour exposure to 1.4 ppm SO₂ severely restricted moist pollen germination and tube elongation of the three conifer species. However, a similar exposure to 10 ppm SO₂ had no effect on dry pollen of the three species. Absorption of SO₂ resulted in an acidification of the germination media. Germination trials on acidified media indicated that the resultant acidification could account for much of the reduced germination and tube elongation in P. deltoides but could not adequately explain the reduced conifer pollen germination and tube elongation.

Phytochrome and Seed Germination: VI. Phytochrome and Temperature Interaction in the Control of Cucumber Seed Germination.

Abstract: Phytochrome control of cucumber seed germination is temperature-dependent. A prolonged exposure to radiation from broad spectrum far red sources (Pfr/P = 0.05 to 0.07) prevents germination at temperatures below 20 C. Above 20 C there is no inhibition and it appears as if there is an escape from phytochrome control. However, radiation from a monochromatic, narrow band 730 nanometer source (Pfr/P < 0.02) inhibits germination at temperatures above 20 C. This result supports the idea that, even at high temperatures, Pfr is responsible for the activation of germination. After 4 days of exposure to far red, a short red irradiation is quite effective in promoting germination if temperatures during the dark incubation periods are maintained below 20 C; red becomes effective at temperatures above 20 C. Promotion of germination will take place at a temperature of 25 C or higher without red irradiation. Again, we have an apparent escape from phytochrome control at high temperatures. However, if higher temperatures are used for only short periods, 2 to 6 hours, in combination with short red irradiation, one can demonstrate that activation of germination at high temperatures is still dependent on phytochrome. Phytochrome is probably destroyed during prolonged exposure to far red. Thus, the subsequent short red irradiation establishes levels of Pfr which may not be sufficient to promote germination at low temperatures but are probably adequate at high temperatures.

Mechanisms Controlling Dormancy in the Arid Zone Grass Aristida contorta. I. Physiology and Mechanisms of Dormancy

Abstract: Two dormancy mechanisms are evident in young A. contorta grain. One is an after-ripening requirement of the embryo, and can be satisfied by storage at ambient temperatures; the second is associated with the hull and requires prolonged periods of high temperatures before germination can take place. The dormancy imposed by the hull is not controlled by a leachable inhibitor, but germination can be stimulated by oxidizing agents or by the removal of small sections of the hull directly over the embryo. The oxygen uptake of dormant grain is very low, but non-dormant grain, or dormant grain with the hull removed, shows a much higher uptake. The possibility remains that there is a mechanical restriction of gas exchange by the hull, the hull of non-dormant grain being more permeable than that of dormant grain.

Effects of dolomitic limestone, gypsum, and potassium on yield and seed quality of peanuts

Abstract: The interactive effects of dolomitic limestone, gypsum, and potassium on yield and seed quality of a Virginia-type peanut was investigated. Responses were assessed in field experiments using a split-plot design with varying rates and combinations of dolomitic limestone and gypsum as the main plots. Two rates of potassium applied at planting were used as the split plots. Treatment effects were measured by changes in soil mineral composition, mineral content of the plant and fruit, yield, seed maturity, and seed quality. Applications of dolomitic limestone increased soil pH and soil calcium levels, but did not improve seed quality or increase yields or kernel content of the fruits. Applications of gypsum improved seed germination, seedling survival, seedling vigor, and root growth. Dark plumule abnormality was reduced by addition of gypsum. Soil pH was reduced and chemical composition of peanut leaves, hulls, and seed was influenced more by gypsum than by either dolomitic limestone or potassium. Po...

Lettuce seed germination and cytokinins: their entry and formation.

Abstract: Cytokinins overcome the inhibitory effect of abscisic acid on the germination of isolated embryos of Grand Rapids lettuce. We have used this fact to assess the content of cytokinins in embryos removed from intact seeds which have been supplied with these growth substances i.e. to determine hormonal uptake. The method has also been used to examine the hypothesis that phytochrome and gibberellin lead to increases in active cytokinin levels in seeds. Appreciable amounts of cytokinins enter intact seeds yet seem unable to promote germination. On the other hand, little or no cytokinin-like activity seems to result from light or gibberellin treatments. We conclude that there are unresolved difficulties inherent in the “cytokinin hypothesis” of phytochrome and gibberellin action.

Growth of Bacillus subtilis and Spore Germination in Soil Observed by a Fluorescent-antibody Technique

Abstract: Vegetative bacteria of Bacillus subtilis placed in contact with an acid forest soil initially declined in number but grew after the development of fungal hyphae. Growth did not occur in sterile soil, nor in alkaline forest soil unless fungal growth was stimulated. Spores of B. subtilis would not germinate in the same acid forest soil unless fungal growth took place, and hardly germinated at all in the alkaline soil. Roots of seedlings of Pinus sylvestris inhibited both vegetative growth and spore germination. These results are consistent with the observed distribution of vegetative bacteria and spores of B. subtilis in forest soils.

The Adaptive Nature of Seed Germination in Nemophila Menziesii Aggr.

Abstract: Nemopitila mnenziesii aggr. includes three closely-related winter annual plants found in many communities in cismontane California and Oregon. The germination response is adapted to the Mediterranean climate that characterizes the region, i.e., wet winters and dry summers. The seeds germinate in late fall or early winter and are inhibited from germinating during late spring, summer, and early fall by high temperatures, long photoperiods, and low available moisture. Temperature and photoinhibition are proportional to the length of the inhibitory period and, in the case of photoinhibition, to light intensity. In combination these factors interact synergistically to inhibit the germination response. Seeds of all ages are able to germinate but germination of young seed is inhibited at temperatures that do not affect mature seed. Seed maturation is a function of high summer temperatures and aging. Popula- tions from more northern and/or higher-elevation communities require more water and lower temperatures to germinate than more southern and/or lower-elevation communities. These adaptations reflect the greater precipitation and cooler temperatures of the former sites as compared to the latter sites. The ecological parameters and germination responses change gradually both latitudinally and elevationally; hence the adaptations are ecoclinal in nature.

Differentiation in some populations of Eucalyptus viminalis Labill. In Relation to Factors Affecting Seedling Establishment

Abstract: Genetic variation was observed among a series of Eucalyptus viminalis populations whose habitats range from wet to dry climates and from relatively fertile to infertile soils.. In comparison with populations from low-rainfall areas, two high-rainfall populations showed rapid germination and fast early seedling growth, the latter being correlated with large seed weight. Older seedlings were capable of continuing fast growth in response to high nutrient levels, and the root/shoot ratios of 6-month-old seedlings were significantly lower than those of seedlings from low-rainfall areas. Populations from within the low-rainfall areas showed some differences in germination, root lengths and growth rates and these appear to be related to site fertility and soil water-holding capacity. Relatively slow growth, even in response to increased nutrient supply, was observed in a population naturally occurring on a granite soil of fair fertility but poor water-holding capacity. Low-rainfall populations also showed a greater lignotuber development than high-rainfall populations and the growth of the lignotuber was not markedly affected by nutrient supply.

Some eco-physiological aspects of seed dormancy in Geranium carolinianum L. from central tennessee.

Abstract: In central Tennessee Geranium carolinianum L. behaves as a winter annual. Seed germination occurs in autumn, and seed ripening and dispersal are completed in May. Freshly-matured seeds have hard coats and will not imbibe water unless scarified. Embryos of freshly-matured seeds are conditionally dormant; scarified seeds germinate better in darkness than in light at high temperatures. After a short after-ripening period the embryo is essentially nondormant, and scarified seeds germinate to high percentages over a wide range of temperatures in both light and darkness. About 50% of the nonscarified seeds become germinable after 4.5 months of dry-laboratory storage. In order for the seed coat to become permeable (without scarification), seeds must be kept either dry or alternately wet and dry at relatively high temperatures during the summer dormancy period. The ecological significance of seed dormancy in G. carolinianum in central Tennessee is that it allows this non-drought tolerant species to avoid droughts that frequently occur in its habitat between late spring and early autumn. Conditional dormancy of the embryo of freshly-matured seeds, hard seed coats and the inability of seeds (non-scarified but permeable) to germinate in summer at high summer temperatures all seem to play a role in delaying germination until autumn.

Effects of Osmotic Concentration and pH on Plant Growth

Abstract: Osmotic concentration and pH may inhibit the seed germination and radicle growth of lettuce. At 25 milliosmols, an aqueous solution of Hoagland, sodium chloride, and sucrose exhibits over 50% inhibition on the radicle growth of lettuce. However, mannitol solution reveals 50% inhibition only at concentration above 125 milliosmols. The pH range of from 4 to 8 has only slight significant effect on the radicle growth of lettuce. Interaction between pH and osmotic effects is not evident. Compared with aqueous plant extracts, the nutrient solutions give less inhibition. The results of this study can be use as an indication of a solution of which the cause of inhibition is due to one or both of the aforementioned effects, or due to a phytotoxic effect.