Seed Dormancy in Red Rice (<i>Oryza sativa</i>) I. Effect of Temperature on Dry-Afterripening

Cohn, Marc Alan; Hughes, Jack

doi:10.1017/s0043174500039898

Cited by 63 publications

(57 citation statements)

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“…Both the hull and pericarp have a role in maintenance ofprimary dormancy in red rice. However, isolated embryos from freshly harvested seeds germinate readily (1). Primary dormancy ofdehulled red rice is broken by exogenously applied cytokinins, but there is no effect on intact seeds (2).…”

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confidence: 99%

Seed Dormancy in Red Rice

Cohn¹,

Butera²,

Hughes³

1983

Plant Physiol.

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Sodium nitrite at 10 millimolar breaks dormancy of dehulled red rice (Oryza satira). While germination is light independent, low pH conditions (pH 3) are required for mimum response. Water and buffer controls at pH 3 remain dormant. The response to nitrite occurs at 25 and 30°C but is reduced at 20°C, although nondormant seeds germinate readily at this temperature. The contact time for response to nitrite is less than 2 h at the start of imbibition. Seeds imbibed first in water show reduced germination when subsequently transferred to nitrite. Dehulled seeds show little or no response to nitrate and ammonium ions.Intact seeds remain dormant in the presence of nitrite or nitrate unless partilly dry-afterripened. The pH dependence of nitrite sensitivity is reduced in intact, afterripening seeds. In highly dormant seeds, vacuum infiltration experiments suggest that the hull restricts uptake of nitrite.Red rice, an annual species, is a problem weed in rice production. Seeds of red rice shatter at maturity and can remain dormant in soil (4). The conditions that promote and break dormancy in this species are not well understood. Previously, it has been shown that freshly harvested seeds dry-afterripen at ambient temperatures. Both the hull and pericarp have a role in maintenance ofprimary dormancy in red rice. However, isolated embryos from freshly harvested seeds germinate readily (1). Primary dormancy ofdehulled red rice is broken by exogenously applied cytokinins, but there is no effect on intact seeds (2).Although there are many reports concerning the response of dormant seeds to nitrate, nitrite, and ammonium ions (e.g. 5, 11, and references therein), no information is available for red rice. As part of a comprehensive study of primary dormancy in red rice, the effects of these inorganic nitrogen compounds have been evaluated. MATERIALS AND METHODSMature, strawhulled red rice (Oryza sativa) was obtained from fields at the Rice Experiment Station, Crowley, LA, in 1979LA, in , 1980LA, in , and 1981 2 To whom correspondence should be addressed.sealed glass jars at -15°C. Seed moisture during frozen storage was 12%. Unless otherwise specified, seeds from the 1980 harvest were used, and germination tests were performed at 30°C for 7 d in dark incubators. Nine-cm-diameter glass Petri dishes containing one sheet of Whatman No. 3 filter paper and 10 ml of test solution were the standard germination system. A double layer oftissue paper was used to cover the seeds to insure uniform hydration. When required, intact seeds were dehulled by hand just prior to treatments. Five replicates of 30 seeds were used for each treatment. Experiments were repeated at least three times. Chemicals used were reagent grade and stored at room temperature. Test solutions were freshly prepared for each experiment. Dilute HCI or NaOH were used to adjust the pH of solutions.Procedures for experiments regarding the effects of light, dryafterripening, and vacuum infiltration were those employed previously (2). Effects of Light. Dehulle...

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Seed Dormancy in Red Rice

Cohn¹,

Butera²,

Hughes³

1983

Plant Physiol.

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“…Neste caso, os embriões, quando isolados das sementes, prontamente germinam (COHN & BUTERA, 1982). A outra categoria de dormência se deve à incapacidade do embrião germinar por si, a qual vai sendo reduzida com o aumento da idade pós-colheita (DORE, 1955;KETRING & MORGAN, 1970;COHN & HUGHES, 1981;SUZUKI, 1981;de KLERK, 1987;NORTON,1987;VIEIRA & BARROS, 1994).…”

Section: Barreira Física Ou Dormência Do Embrião ?unclassified

“…A duração da dormência em Oryza sativa é bastante variável, são encontrados biotipos que germinam prontamente após a colheita (SIKDER, 1967), outros onde a dormência dura de uma semana a quatro meses (DORE, 1955;MENEZES et al, 1995), ou até mais de onze meses (COHN & HUGHES, 1981). Há relatos de sementes que se mantiveram dormentes no solo por mais de doze anos (GROSS & BROWN, 1939), porém, nestes casos, é possível ter sido utilizada metodologia inadequada para avaliação da idade pós-colheita das sementes.…”

Section: Duração Da Dormência X Condições Pós-colheitaunclassified

“…A temperatura é um dos principais fatores envolvidos. Segundo COHN & HUGHES (1981), a manutenção de sementes com 11 a 12% de umidade a 30 o C reduziu a dormência a quatro semanas, a 20 o C para seis semanas, enquanto a 5 o C a dormência manteve-se até onze meses de idade pós-colheita, e a -15 o C não foi observado alívio da dormência mesmo após um ano. Os autores consideraram que a dormência se devia à presença de glumas e glumelas (pálea e lema), no entanto a retirada destas reduziu a dormência em apenas uma ou duas semanas em relação às sementes com cascas, porém sementes mantidas a -15 o C, quando sofriam algum dano no pericarpo, prontamente germinavam.…”

Section: Duração Da Dormência X Condições Pós-colheitaunclassified

“…Segundo COHN & HUGHES (1981), cariopses que sofriam dano no pericarpo germinavam prontamente. Várias hipóteses podem ser sugeridas, o pericarpo poderia estar restringindo a entrada ou saída de substâncias, (dormência devido às estruturas envoltórias); o dano causado aos tecidos pode causar síntese de substâncias que respondem ao estresse, as quais podem atuar na superação da dormência, (devido ao embrião em si e não às estruturas envoltórias).…”

Section: Relação Das Estruturas Envoltórias Com a Dormênciaunclassified

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