Nature of Seed Dormancy in
            <i>Phacelia tanacetifolia</i>

Chen, Shepley S. C.; Thimann, Kenneth V.

doi:10.1126/science.153.3743.1537

Cited by 57 publications

(27 citation statements)

References 2 publications

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“…Previous works in this laboratory show that increasing the osmolarity of the germination medium depresses cell enlargement and the development of oxidative metabolism in the embryo (Lado 1964), and that continuous water uptake during the early phase of germination is required for active protein synthesis (Sturani et al 1968, Hsiao 1970. The data of Ikuma and Thimann (1963) and Chen and Thimann (1966) also support the possibility that an increased capacity of the cell for water uptake might be a crucial factor in both germination and interruption of dormancy.…”

Section: Discussionsupporting

confidence: 52%

Acidification of the Medium Associated with Normal and Fusicoccin‐Induced Seed Germination

Lado¹,

Rasi‐Caldogno²,

Colombo³

1975

Physiologia Plantarum

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Fusicoccin, a toxin stimulating cell enlargement and inducing proton extrusion in various plant tissues, has been shown to replace kinetin, gibberellic acid and red light in breaking seed dormancy. It also removes the inhibitory effect of abscisic acid. The present data also show that the stimulating effect of fucicoccin on embryo growth of decoated radish (Raphanus sativus L.) and maize (Zea mays) seeds and on the development of maize embryos is accompanied by an early, significant acidification of the medium. Acidification of the medium is also observed when fusicoccin reverses the abscisic acid‐induced inhibition of germination. These results support the hypothesis that the mode of action of fusicoccin in promoting germination involves, as in stimulation of cell enlargement, the activation at the cell membrane level of proton extrusion processes. The physiological significance of fusicoccin‐induced release of protons at the onset of germination is discussed in comparison with the results concerning the mechanism of action of fusicoccin on cell enlargement in other plant materials.

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Section: Discussionsupporting

confidence: 52%

Acidification of the Medium Associated with Normal and Fusicoccin‐Induced Seed Germination

Lado¹,

Rasi‐Caldogno²,

Colombo³

1975

Physiologia Plantarum

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“…A previous report inferred that the inhibiting effect of light on germination of phacelia seeds can be overcome by removing the tip of the endosperm; however, immersion in solutions of high osmotic pressure such as 0.3 m mannitol in the presence of 2% sucrose reinstates the light sensitivity and inhibition of germination by high temperature behaves similarly [8]. Removal of that part of the covering structures of the seeds allows full germination in light [46] suggesting that seed coat and its components play important roles in releasing light dormancy in phacelia seed.…”

Section: Discussionmentioning

confidence: 99%

“…There are, however, several conflicts and contradictory reports related to optimal germination parameters for phacelia seeds. For instance, although the optimum soil temperature for germination was previously reported between 10 and 20°C [7, 8], a more recent report indicated that the highest germination percentages might be obtained at the low temperatures of 3 and 5°C [6]. Reports also indicate that the inhibitory effect of light exposure decreased when seeds were treated with gibberellic acid (GA 3 ) or potassium nitrate (KNO 3 ) and germinated at temperatures below 8°C [6], even though other reports did not recommend any treatment to enhance the germination of phacelia seeds [2].…”

Section: Introductionmentioning

confidence: 99%

Reversal of the inhibitory effect of light and high temperature on germination of Phacelia tanacetifolia seeds by melatonin

Tiryaki

Keleş

2012

Journal of Pineal Research

132

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Possible role of melatonin in the germination of negatively photoblastic and thermosensitive seeds of Phacelia tanacetifolia Benth was studied. Final germination percentage (FGP) was determined in the presence or absence of light at various temperatures, ranging from 0 to 40°C. The highest FGP was determined as 48.7% and 92% at temperature of 15°C in the presence and absence of light, respectively. Seeds were primed with 1% KNO(3) containing various concentrations (0.3, 1, 6, 12, 30, 60, or 90 μM) of melatonin for 2 days at 15°C in darkness. Primed seeds were germinated at an inhibitory temperature of 30°C, and results were compared to those occurring at the optimum temperature of 15°C under both light and no light conditions. Melatonin incorporated into priming medium significantly reversed the inhibitory effects of light and high temperature. Germination was elevated from 2.5% to 52% of FGP for seeds primed in the presence of 6 μM melatonin in darkness at 30°C, while 1 μM melatonin had the highest FGP (21.0%) in the presence of light at 30°C. The highest FGP (47.5%) was obtained from seeds primed in the presence of 0.3 μM melatonin under the light condition at 15°C, while untreated seeds had 1.5% of FGP. The fastest seed germination was determined from seeds primed in the presence of 0.3 μM melatonin (G(50) = 0.56 days) at 15°C in darkness. The possible roles of melatonin in promoting germination parameters of photo- and thermosensitive seed germination are discussed.

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“…49,1972 bee plant) seeds is inhibited by light. It should be mentioned that in dicotyledonous seeds such as P. tanacetifolia, GA3 does not appear to enhance amylase synthesis, while it stimulates germination (4). In Grand Rapids lettuce, the germination of which is also promoted by GA, fat is the major stored food, and no amylase is synthesized during germination (unpublished).…”

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confidence: 99%

Does Gibberellic Acid Stimulate Seed Germination via Amylase Synthesis?

Chen¹,

Chang²

1972

Plant Physiol.

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Gibbereilic acid is known to break dormancy of several types of seeds: (a) light-promoted seeds, such as Grand Rapids lettuce seed (Lactuca sativa L. var. Grand Rapids); (b) lightinhibited seeds, such as the seed of the honey-bee plant (Phacelia tanacetifolia Benth; (c) seeds requiring stratification (storage at low temperatures in a moist condition), such as the hazel nut (Corylus avellana L.); (d) seeds requiring after-ripening (storage at room temperature in dry condition), such as the wild oat (Avena fatua L.).Recent findings indicate that when dormant hazel nut seeds are soaked at 5 C for 28 days, which is a natural means of breaking dormancy, the gibberellin-synthesizing mechanism is activated and that actual synthesis of gibberellins takes place when the seeds are transferred to a suitably higher temperature. Accumulation of GA results in germination (10).It has also been suggested that in the phytochrome-controlled germination of Grand Rapids lettuce seeds, the role of Pfr is to activate GA biosynthesis (8).One biochemical reaction known to be enhanced by GA is the synthesis of hydrolases (especially a-amylase) in the endosperm of cereal grains, such as barley (2,9,13). Since starch is a major food reserve in the cereal grains, its breakdown is generally assumed to be an essential process of germination. Many writers have implied that GA stimulates seed germination via amylase synthesis (1,7,12).Drennan and Berrie (5) compared the time course of amylase development in dormant and nondormant wild oats (Avena spp.). Their results indicated that both types of seeds contained traces of amylases. When dormant seeds were soaked, there was neither germination nor a change in the level of amylases. When nondormant seeds were soaked (in water), they germinated in 4 days and from the 6th day, amylase activity increased. Thus, they concluded that buildup of amylases is a postgermination phenomenon, and a lack of amylase synthesis must be eliminated as a possible cause of dormancy.We have investigated the time course relationship of GAinduced germination and amylase development in an attempt to find out if GA-induced germination is mediated by amylase production.

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Nature of Seed Dormancy in Phacelia tanacetifolia

Cited by 57 publications

References 2 publications

Acidification of the Medium Associated with Normal and Fusicoccin‐Induced Seed Germination

Acidification of the Medium Associated with Normal and Fusicoccin‐Induced Seed Germination

Reversal of the inhibitory effect of light and high temperature on germination of Phacelia tanacetifolia seeds by melatonin

Does Gibberellic Acid Stimulate Seed Germination via Amylase Synthesis?

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