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PubMed1967

Effects of metabolic poisons on rice: the comparative sensitivity of aerobic and anaerobic modes of germination.

Rice germinates equally well when incubated in air and in nitrogen. It was therefore chosen for a comparative study of the effect of oxygen status in a single organism upon the activity of conventional metabolic poisons. Inhibitor activity was based upon the concentration required for 50% inhibition of germination. The inhibitors were: AgNO(3), HgCl(2), phenylmercuric acetate, iodoacetamide, KCN, NaN(3), NaF, fluoroacetate, 2,4-dinitrophenol, Na(2)HAsO(4) and CO. Only 5 inhibitors out of 11 differed significantly in their effects on aerobic and anaerobic germination. These included phenylmercuric acetate (N(2)), sodium fluoroacetate (air), NaN(3) (air), and 2,4-dinitrophenol (N(2)). CO activity was manifest only in air and it was photo-reversible. The effects of CO, NaN(3), and fluoroacetate were consistent with their conventional role in aerobic metabolism. The failure of KCN to discriminate was attributed to its relative non-specificity. 2,4-Dinitrophenol behaved anomalously, requiring a 20-fold lower concentration for inhibition under nitrogen than under air. Among sulfhydryl poisons, only phenylmercuric acetate differentiated between germination in air and nitrogen and was nearly 8 times more active under nitrogen. Uptake measurements using phenylmercuric acetate and arsenate showed both compounds to be in greater concentration under aerobic conditions, thereby rendering unlikely any explanation based upon greater permeability under nitrogen. In addition to other anomalies, the fact that NaN(3), fluoroacetate and CO inhibited anaerobic germination at any concentration requires explanation. It was concluded that the general significance and utility of metabolic inhibitor studies in vivo required further evaluation.

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PubMed1969

A Study of the Aminoacyl-sRNA Synthetases of Phaseolus vulgaris in Relation to Germination.

Optimum conditions for the extraction and assay by ATP-pyrophosphate exchange of the aminoacyl-sRNA synthetases of the various tissues of french bean (Phaseolus vulgaris) seeds and seedlings are described. Extracts of plumules, after passage through Sephadex G-25, were assayed for synthetase activity using an amino acid mixture as substrate, when a 30 to 100-fold stimulation of exchange above the endogenous level was obtained. This marked enhancement of exchange by added amino acids is largely attributed to the use of dilute extracts.The total synthetase activity of the cotyledons was studied in relation to germination. Synthetase activity was highest in the dry cotyledon; activity decreased in proportion to the loss of protein during germination, i.e. the specific activity of the synthetases remained constant for at least the first 6 days of germination. With a few minor exceptions, the specific activity of the individual synthetases remained constant during germination.The absolute activity of the synthetases of the plumule and radicle increased exponentially during germination. The specific activity of the synthetases in both tissues increased approximately 2-fold during the first 2 to 3 days of germination, then gradually decreased. However the asparaginyl-, valyl-, and histidinyl-sRNA synthetases in the plumule did not conform with this general pattern.

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PubMed1970

Influence of Water Activity, Temperature, and Their Interaction on Germination of Verticillium albo-atrum Conidia.

Conidia were germinated at three temperatures in media in which available water, expressed as water activity, was controlled at three levels. Rate of germination in the basal medium (0.9964 water activity) was most rapid at 25 C and was inhibited at 15 and 30 C. Lowering the water activity at a particular temperature decreased rates of germination. However, at a low water activity (0.9778) germination rate was greater at 30 C than at 25 C. Thus, the effect of temperature on germination appears to be dependent on the water activity of the medium.

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PubMed1971

Enhancement of germination rate of aged seeds by ethylene.

Naturally and artificially aged seeds of rape, Brassica napus L., produced less ethylene than freshly harvested seed during the early stage of germination. With freshly harvested seeds one peak of ethylene production was observed during germination, which coincided with the emergence and elongation of root and cotyledon, accompanied by splitting of the seed coat. Application of exogenous ethylene was effective in accelerating germination in aged seeds but did not significantly improve the percentage of germination. Ethylene as a hormone was considered to serve as a stimulator of germination and growth. One of the factors causing seed aging might be the degeneration of an ethylene-producing system in the seed. Exogenous ethylene may be effective only for the seeds in which the ethylene-producing system is weakened but the following responding systems are still functional.

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PubMed1971

Evidence for osmotic regulation of hydrolytic enzyme production in germinating barley seeds.

alpha-Amylase levels in intact seeds of barley (Hordeum vulgare L. cv. Himalaya) reach a maximum at 3 to 4 days of germination while gibberellin levels continue to increase beyond 6 days of germination. In contrast to its effect on half seeds, gibberellic acid does not increase the total amount of alpha-amylase produced in germinating seeds. The inability of gibberellic acid to stimulate alpha-amylase production is not related to its availability; rather, evidence suggests that a factor(s) in whole seeds prevents further enhancement of alpha-amylase formation and accumulation. Hydrolysis products accumulate in the subaleurone space of the endosperm of germinating seeds up to concentrations of 570 milliosmolar. Chromatography of these hydrolysis products indicate the presence of maltose and glucose. Calculations based on reducing sugar determinations show that glucose accounts for as much as 57% of the solutes present in the endosperm fluid. Both maltose and glucose in the range of 0.2 to 0.4 M effectively inhibit the production of alpha-amylase by isolated barley aleurone layers. This inhibition is quantitatively similar to that brought about by solutions of polyethylene glycol and mannitol. On the basis of these data we propose that hydrolysis products which accumulate in the starchy endosperm of germinating seeds function to regulate the production of hydrolytic enzymes by the aleurone layer.

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PubMed1972

Pollen germination and tube growth: dependent on carbon dioxide and independent of ethylene.

The influence of ethylene and CO(2) on pollen germination and tube growth was investigated employing ventilated culture systems. Ethylene had no effect on pollen germinability or tube growth. Germinating pollen did not produce a detectable amount of ethylene (less than 0.1 nl/g.hr). Supplementing the cultures with CO(2) caused a marked increase in germination and tube growth. The half-maximal response for germination was less than 0.5%. CO(2) levels ranging from 1.08 to 2.22% were found in the internal cavity of lily styles. CO(2) derived from stylar metabolism may, therefore, modulate pollen tube growth thus integrating the events leading to fertilization.

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PubMed1972

Isolation of Plastids from Sunflower Cotyledons during Germination.

Plastids from cotyledons of sunflower (Helianthus annus L.) seedlings, germinated in the dark or in the light, were isolated by isopycnic sucrose density gradient centrifugation. At all stages of development the whole plastids contained triose phosphate isomerase, NADPH-glyoxylate reductase, and l-dihydroxyphenylalanine oxidase, which were used as marker enzymes. At the beginning of germination the isopycnic density of whole plastids (proplastids) was about 1.22 g cm(-3). During development of proplastids into etioplasts in the dark, their isopycnic density increased to 1.26 g cm(-3). During exposure of germinating seedlings to white light for 2 days, the isopycnic density of whole plastids decreased from 1.26 to 1.22 g cm(-3). These changes in isopycnic density of plastids on sucrose density gradients are consistent with changes in the plastid ultrastructure caused by the protein-rich prolamellar body or by the lipid-rich thylakoids. Broken plastids (thylakoids), determined by the main peak of chlorophyll, increased in isopycnic density from less than 1.14 to about 1.17 g cm(-3) during illumination. During germination no major changes occurred in the isopycnic density of mitochondria. Microbodies had an isopycnic density of 1.24 g cm(-3) in very early stages of germination, and their density increased to 1.265 g cm(-3), when glyoxysomal enzymes reached maximum development.

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PubMed1972

Antagonistic effects of high and low temperature pretreatments on the germination and pregermination ethylene synthesis of lettuce seeds.

Red light-induced germination of Grand Rapids lettuce seeds (Lactuca sativa L.) incubated at 20 C was inhibited if the seeds were first imbibed at 30 C for 36 hours. This effect was counteracted by exogenous ethylene and associated with a reduction in the rate at which the seeds produced ethylene throughout the pregermination period. A chilling treatment reversed the effect of a prior imbibition at 30 C on both germination and ethylene production. The possibility that the pretreatments influence germination through their effects on ethylene production is discussed.Other evidence presented indicates that the inability of seeds to germinate at supraoptimal temperature is not due either to a rapid loss of far red-absorbing phytochrome or to an inadequate capacity for ethylene synthesis. It was also shown that a chilling treatment potentiated germination at high temperature without affecting the ethylene synthetic capacity of the seeds.

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PubMed1973

Promotion of seed germination by cyanide.

Potassium cyanide at 3 mum to 10 mm promotes germination of Amaranthus albus, Lactuca sativa, and Lepidium virginicum seeds. l-Cysteine hydrogen sulfide lyase, which catalyzes the reaction of HCN with l-cysteine to form beta-l cyanoalanine, is active in the seeds. beta-l-Cyanoalanine is the most effective of the 23 alpha-amino acids tested for promoting germination of A. albus seeds. Aspartate, which is produced by enzymatic hydrolysis of asparagine formed by hydrolysis from beta-cyanoalanine, is the second most effective of the 23 amino acids. Uptake of aspartate-4-(14)C is much lower than of cyanide.Radioactive tracer in K(14)CN shows uptake of about 1.5 mumoles of HCN per gram of A. albus and L. sativa seeds after 20 hours of imbibition. Extracts of the seeds gave high (14)C activity in beta-cyanoalanine, asparagine, and aspartate. The acid-hydrolyzed protein extract gave high activity only in aspartate. Tests were negative for free cyanide in the seed. Respiration of the seed is inhibited more than 75% by KCN and by KN(3) at 10 mm. Azide at greater than 1.0 mm inhibits the promotion of germination by cyanides. Neither 0.1 mm KCN nor KN(3) inhibit O(2) consumption, whereas lower concentrations promote germination. It is concluded that the high rate of utilization of cyanide in the reaction to form beta-l-cyanoalanine and the subsequent incorporation into protein limit any inhibition of oxygen consumption. The promotion of seed germination is substrate-limited by asparagine-aspartate, which is required for protein synthesis.

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PubMed1975

Inhibition of Prechill-induced Dark Germination in Sorghum halepense (L.) Pers. Seeds by Phytochrome Transformations.

A 10 C dark prechilling of johnsongrass [Sorghum halepense (L.) Pers.] seeds, when terminated by a 2-hr, 40 C temperature shift, potentiates about 40% germination at 20 C in darkness. Irradiation of the seeds before, during, and at the end of prechilling with far red light reduces the subsequent germination, although red irradiation after the far red can overcome some of the inhibition. However, either brief red or far red irradiation given immediately after the temperature shift inhibits subsequent germination by one-third to one-half. The results suggest that the far red-absorbing form of phytochrome is a factor in the prechill-induced dark germination and that phytochrome participates in the inhibition of germination by irradiations immediately after the temperature shift.

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PubMed1975

Regulation of Alcohol Dehydrogenases in Maize Scutellum during Germination.

The pattern of change in the activity of alcohol dehydrogenase in maize (Zea mays L.) scutellum during seed germination is not altered by 10 mug/ml cycloheximide or 50 mug/ml actinomycin D. The enzyme does not become density labeled when maize seeds are germinated in the presence of D(2)O and (15)NH(4)Cl, indicating that no new alcohol dehydrogenase molecules are synthesized after the onset of germination. However, the activity of an endogenous inhibitor for alcohol dehydrogenase is increased after germination. The increase of this inhibitor is concomitant with the decline of alcohol dehydrogenase activity, indicating that the activity of alcohol dehydrogenase during seed germination is controlled by the level of the inhibitor.

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PubMed1975

Transcription of Ribosomal and Messenger RNAs in Early Wheat Embryo Germination.

Germinating wheat embryos (Triticum aestivum L). synthesize both ribosomal and messenger RNA at the earliest times after the onset of germination. The rates of synthesis of these two RNAs are determined at various stages in germination by an analysis of newly synthesized radioactive RNA on oligo(dT)-cellulose. The rate of messenger RNA synthesis is essentially constant throughout 18 hours of germination, while that of ribosomal RNA synthesis increases steadily, particularly after the onset of cell expansion (6 hours), reaching at 16 to 18 hours, a rate of synthesis between 5- and 20-fold greater than that observed at the earliest stages. The net effect is a relative decrease in the fraction of transcribed high molecular weight RNA that is mRNA. Throughout the first 7 hours of germination, mRNA is 25 to 30% of the transcribed fraction, whereas by 16 to 18 hours it has declined to a level of 4 to 8%.

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PubMed1975

Temperature regulation of germination in crimson clover seeds.

Seeds of Dixie crimson clover (Trifolium incarnatum cv. Dixie) completed germination in 36 hours at 20 C. At 10 C germination was delayed by 24 hours. At 30 C only 20% germinated and the rest remained viable for a long time but not germinable. Different patterns of adenylate energy state and zymograms of acid phosphatase and esterase were observed from seeds grown under the three temperatures for 24 hours. Varied specific activities of protease, alpha-amylase, ATPase, RNase, acid phosphatase, glutamine synthetase, and fumarase were also found. Protein-synthesizing ability was proportional to temperature. These data indicate that temperature regulates seed germination at multiple sites.

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PubMed1976

Inhibition of cottonseed germination with abscisic Acid and its reversal.

Germination of cottonseed (Gossypium hirsutum L.) was inhibited by abscisic acid. Inhibition was greater when seeds were soaked in abscisic acid for 5 hours and dried prior to germination than when abscisic acid was applied in the germination medium. (2-Chloroethyl)phosphonic acid, gibberellic acid, and kinetin partially overcame the inhibitory action of abscisic acid. Combinations of (2-chloroethyl)phosphonic acid with gibberellic acid or kinetin were more effective than the individual substances. Germination also was partially restored by removal of seed coats. Fusicoccin completely restored germination of abscisic acidtreated seeds.

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PubMed1977

Developmental Biochemistry of Cottonseed Embryogenesis and Germination: VIII. Free Amino Acid Pool Composition during Cotyledon Development.

The composition of the free amino acid pool in embryonic cotton (Gossypium hirsutum) cotyledons is quite distinct from that of endosperm, and that of germinated, greened cotyledons is quite distinct from that of leaves. During germination (including the precocious germination of immature seeds), the pool expands considerably showing a pronounced accumulation of asparagine. The high level of asparagine found in seedling roots and in the cotyledon vascular exudate indicates that this is the major transported amino acid in germination. There is no pool expansion in the presence of abscisic acid. In the presence of actinomycin D, the pool expands, but an enormous accumulation of glutamine takes place. The composition of the pool at any stage is not related to the composition of the isoacceptor transfer RNA pool, nor to the composition of the storage protein. Anaerobiosis leads to an accumulation of aspartate, alanine, and glycine at the expense of asparagine; however, desiccation does not result in an accumulation of proline. Conspicuously high levels of arginine are maintained through embryogenesis and germination. The levels of individual amino acids are presented as nanomol per cotyledon pair and as per cent of total pool.

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PubMed1977

Changes of Template Activity and Proteins of Chromatin during Wheat Germination.

Relationships between changes in template activity and composition of chromatin during germination of wheat embyros (Triticum aestivum L.) were investigated. The template activity of chromatin was determined with exogenous DNA-dependent RNA polymerase II (EC 2.7.7.6) prepared from wheat embryos. It was essentially constant for 18 hours of germination, corresponding to 2.5% of that of a native calf thymus DNA. Thereafter, the activity increased 2-fold and 5-fold at 24 and 60 hours of germination, respectively.Chromatin-associated proteins were separated into at least 22 distinct bands by sodium dodecyl sulfate gel electrophoresis throughout 60 hours of germination. Significant changes were observed in two nonhistone proteins, approximate molecular weights 59,000 and 39,000: the amount of the former was constant up to 18 hours, reduced for the period from 18 to 60 hours, and that of the latter was decreased for the period from 18 to 60 hours of germination. No change was observed in the number of histone components by acid-urea gel electrophoresis.

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PubMed1977

Carbon Dioxide and Ethylene Control of Spore Germination in Onoclea sensibilis L.

Regulation of spore germination in the fern Onoclea sensibilis L. was investigated by applying CO(2) alone and in combination with ethylene. Sterile spores were sown aseptically on Knops solution in loosely capped culture tubes, enclosed individually in 2-liter chambers, and grown under continuous white light. When maintained in enclosed containers with the ethylene-absorbent mercuric perchlorate and with atmospheres enriched up to 2% CO(2) (v/v), spores germinated without any inhibition. Higher levels of applied CO(2) were progressively inhibitory. Inhibition by CO(2) was reversible. When CO(2) was permitted to escape and spores were exposed subsequently to ambient laboratory air, recovery from inhibition occurred within 48 hours. Also, inhibition by CO(2) was specific, since the same degree of inhibition resulted regardless of whether spores were treated with exogenous CO(2) for 48, 72, or 96 hours. The effect on germination of 1 mul/l added ethylene depended upon the amount of applied CO(2). When containers of KOH were enclosed and ambient CO(2) was absorbed, inhibition of germination by 1 mul/l exogenous ethylene was 90%. When CO(2) was applied in concentrations from 0.25 to 1.0% (v/v), CO(2) increasingly antagonized the inhibitory action of 1 mul/l added ethylene. Thus, photoinduced germination of spores was regulated by competitively interacting levels of CO(2) and ethylene.

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PubMed1978

Thermoperiodism in cocklebur seed germination.

Germination potential in nondormant, upper cocklebur (Xanthium pensylvanicum Wallr.) seeds, which were incapable of germinating under constant temperatures below 25 C in air, was increased by exposure to diurnally alternating temperatures. The cocklebur seeds failed to respond to the temperature fluctuations in the beginning of water imbibition, and their responsiveness appeared only after aerobic presoaking for a limited period or after anaerobic pretreatment for 1 to 3 days.Maximal germination was obtained after exposure to a thermoperiodic regime of 8 hours at 23 C and 16 hours at 8 C. A process occurring during the high temperature phase was aerobic and had to precede the inductive low temperature phase, its effect increasing with temperature. Critical minimum length of the inductive low temperature phase changed with the duration of a preceding anaerobiosis, for instance about 4 hours after 1 day anaerobiosis, but about 2 hours after 2 days. Percentage of subsequent germination was in proportion to the number of thermoperiodic cycles. A process of the inductive low temperature phase was not perturbed by inserting a brief higher temperature period into its phase; indeed, such insertion rather increased germination potential when performed in the earlier parts of the inductive low temperature phase. The effect of the low temperature survived for 13 to 17 hours during the higher temperature period.

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