The physiological basis of seed dormancy in <i>Avena fatua</i> III. Action of nitrogenous compounds

Adkins, S. W.; Simpson, G. M.; Naylor, J. M.

doi:10.1111/j.1399-3054.1984.tb04569.x

Cited by 56 publications

(37 citation statements)

References 23 publications

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“…Increased sensitivity of intact seeds to dormancy-breaking chemicals was observed during afterripening which confirmed similar trends reported previously (1,2,5,6,9). In addition, the pH-dependence for activity in red rice was shown to diminish as afterripening proceeded.…”

Section: Discussionsupporting

confidence: 78%

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Seed Dormancy in Red Rice

Cohn

Hughes²

1986

Plant Physiol.

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The activity of NaN3 (0.5 millimolar), hydroxylamine-HCI (10-18 millimolar), and potassium cyanide (1 millimolar) as dormancy-breaking agents of dehulled red rice (Oryza sativa) is pH-dependent such that medium pH values favoring formation of the uncharged chemical species resulted in the highest germination percentages. There was no promotive effect of pH itself in the range of 3 to 10. The minimum contact times for maximum response (.:90% germination) to NaN3, KCN, and NH2OH-HCI are 8 hours at pH 4, 24 hours at pH 8, and 72 hours at pH 6 or 7, respectively, for exposure commencing at the start of imbibition. Dehulled seeds, imbibed first in water, show only slightly reduced germination when subsequently transferred to solutions of dormancybreaking chemicals.Intact seeds remain dormant in the presence of NaN3, KCN, or NH2-OH-HCI unless partially dry-afterripened. The pH dependence of these chemicals is reduced in intact, afterripening seeds.Azide, cyanide, and hydroxylamine are known dormancybreaking agents of seeds (2,3,7,8,10,11,(20)(21)(22)(23). In most cases, only partial germination of a highly viable seed population was observed after chemical treatment. However, in other studies, maximum dormancy-breaking activity of gibberellic acid (17), nitrite (5), and NO2 (6) was obtained with the incubation medium pH adjusted so that the undissociated form of each chemical was the most prevalent in solution. Considering the importance of solution pH for penetration and/or activity of weak acids and bases in a wide variety of situations (13)(14)(15)(16)19), it has been suggested that the incubation medium pH should be controlled when studying dissociable, dormancy-breaking chemicals (5).Another common problem is the lack of reproducibility of germination percentages between seed lots of different ages after chemical treatment. Very short periods of dry-afterripening have been shown to increase the sensitivity of red rice to nitrate, nitrite, and nitrogen dioxide (5, 6). Furthermore, in red rice, afterripening diminished the pH dependency necessary for nitrite activity (5). Afterripening-enhanced sensitivity to ethylene (1), nitrite, hydroxylamine (2), azide and cyanide (9) has been reported in other species as well.It is also fairly well established that extended imbibition of dormant seeds in water results in a loss of sensitivity to subsequently applied dormancy-breaking chemicals (8,12,18 loss of sensitivity to chemicals applied to red rice under these circumstances has been observed for kinetin and nitrite (4, 5).It was of interest to extend our recent observations concerning the effects of afterripening, H20 incubation, and incubation medium pH (5, 6) to other dormancy-breaking chemicals, particularly those with neutral and basic pKa values. In this report, we describe the response of intact and dehulled red rice to azide, cyanide, and hydroxylamine.MATERIALS AND METHODS Mature, strawhulled red rice (Oryza sativa) was obtained from fields adjacent to the Rice Experiment Station, Crowley, LA in 1982. H...

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Section: Discussionsupporting

confidence: 78%

“…Azide, cyanide, and hydroxylamine are known dormancybreaking agents of seeds (2,3,7,8,10,11,(20)(21)(22)(23). In most cases, only partial germination of a highly viable seed population was observed after chemical treatment.…”

Section: Introductionmentioning

confidence: 99%

Seed Dormancy in Red Rice

Cohn

Hughes²

1986

Plant Physiol.

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“…Nitrates and nitrites may promote germination by acting as electron acceptors, thus increasing respiration (Adkins et al 1984). The hypothesis is consistent with the increase in respiration rate which precedes nitrate-induced germination but is not supported by evidence that KNO 3 can promote germination without being metabolically reduced (Hilhorst 1990).…”

Section: Discussionsupporting

confidence: 55%

The roles of inorganic nitrogen salts in maintaining phytochrome- and gibberellin A3-mediated germination control in skotodormant lettuce seeds

Hsiao

1996

J Plant Growth Regul

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Skotodormant seeds of Lactuca sativa GrandRapids imbibed in darkness for 10 days (10-day DS) germinated poorly upon terminal treatment with red light (R) or gibberellin A 3 (GA3). Inorganic nitrogen salts in the imbibition solutions reduced seed skotodormancy. Ten-day DS seeds, imbibed in 25 mM salt solutions followed by terminal R, germinated 99% if imbibed in NHaNO 3, 70% if imbibed in KNO 3 or NHaC1, and 55% if imbibed in NaNO 3. Seeds imbibed in higher salt concentrations germinated fully upon terminal R treatment. Seeds imbibed in 25 mM NHaC1 or in 50 mM NHnNO 3 germinated completely upon GA 3 treatment. Osmotic effects of imbibition media accounted for only part of the effect, since seeds imbibed in 50 mM CaC12 or NaC1 germinated poorly following R or GA 3 treatment. Seeds imbibed in 500 mM polyethylene glycol (PEG) 1000 or mannitol solutions for 10 days still exhibited skotodormancy. Treatments of R or GA 3 did not stimulate germination in seeds imbibed in mannitol, but germination was complete if seeds were given 1-h acid immersion plus a water rinse before the terminal R or GA 3 treatment. Seeds imbibed in 50-500 ms PEG during 10-day DS germinated significantly better in response to terminal R. Terminal GA 3 significantly improved germination only in seeds imbibed at 500 mM PEG. Pfr appeared to function in mannitol-imbibed seed only after an acid treatment. Seed exposure to inorganic nitrogen salts during the 10-day DS maintained seed sensitivity to terminal R or GA 3 treatment. The depth of seed skotodormancy was related to the availability of inorganic nitrogen and also involved the levels of Pfr or endogenous GA 3.

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“…3; Table I). These data are consistent with previous work on other dormancy-breaking compounds that are weak acids (8-11, 13, 21, 28, 30, 31 Increased sensitivity of intact seeds to dormancy-breaking compounds was observed during afterripening (Table II) confirming previous reports (1,2,(9)(10)(11)15). These data suggested that increased hull permeability to applied chemicals may occur during dry-afterripening.…”

Section: Discussionsupporting

confidence: 83%

Seed Dormancy in Red Rice

Cohn¹,

Chiles²,

Hughes³

et al. 1987

Plant Physiol.

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The weak acid character of many previously identified, but otherwise chemically dissimilar, dormancy-breaking compounds may contribute to their physiological activity. To test this idea, short chain monocarboxylic acids of one to six carbons, for which no previous reports of such activity exist, were incubated with dormant, dehulled red rice (Oryza sativa) seeds. Greater than 90% germination was observed after 24 hours of imbibition with 19 millimolar formic, 53 millimolar acetic, 20 millimolar propionic, 28 millimolar butyric, 20 millimolar valeric, or 16 millimolar caproic acid followed by 7 to 14 days incubation on water at 30°C. Dormancy-breaking activity was pH-dependent. Incubation medium pH values that favored formation of the protonated species resulted in the highest germination percentages. There was no promotive effect of medium pH itself in the range of 3 to 7. In contrast, germination of intact seeds was less than 40% in the presence of 55 millimolar monocarboxylic acids at pH 3, unless seeds were partially dry-afterripened. The pHdependent activity of these acids was maintained during afterripening of intact seeds. The results are consistent with the idea that the dissociable proton of weak acids is responsible for their dormancy-breaking activity. Many other weak acids may break seed dormancy but have been overlooked due to the rigid pH dependence necessary for activity.The pH of the incubation medium modulates the dormancybreaking activity ofgibberellic acid (8,13,21, 28,30,31), nitrite (9, 10), azide, cyanide, and hydroxylamine (11 ent with the concept that dormancy-breaking activity is due to the neutral form of each substance rather than a general effect of the acidity of the incubation medium, is provided. MATERIALS AND METHODSMature, awnless, strawhulled red rice seeds (Oryza sativa) were obtained at the South Farm, Rice Research Station, Crowley, LA in 1985. Harvesting, processing, and storage procedures used were those previously described (9). Air-dried seeds were stored at -I 5°C until use.Germination tests were performed using the system described by Cohn and Hughes (11). Seeds were incubated in buffered aqueous solutions of formic (pK=3.75), acetic (pK=4.76), propionic (pK=4.87), butyric (pK=4.82), valeric (pK=4.82), or caproic (pK=4.83) acid for 24 h. Germination was scored during a subsequent 7-or 14-d incubation on water. The pH of each test solution was recorded after incubation to check for sufficient buffering capacity during imbibition. All incubations were performed at 30°C in darkness. Each treatment consisted of five replications, and experiments were repeated at least three times. All chemicals employed were reagent grade and stored at room temperature. Monocarboxylic acid solutions were buffered with 25 mm citrate-phosphate and prepared fresh daily. Dilute HCI or NaOH were used to adjust the pH of test solutions. When required, intact seeds were dehulled by hand just prior to treatments. For experiments investigating the effect ofdry-afterripening at 30°C upon chemi...

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The physiological basis of seed dormancy in Avena fatua III. Action of nitrogenous compounds

Cited by 56 publications

References 23 publications

Seed Dormancy in Red Rice

Seed Dormancy in Red Rice

The roles of inorganic nitrogen salts in maintaining phytochrome- and gibberellin A3-mediated germination control in skotodormant lettuce seeds

Seed Dormancy in Red Rice

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