Influência das variacões estacionais e profundidade de sementes no solo na dormência e germinação em Rumex crispus L.

The effects of seasonality and burial depth of seeds in the soil on the dormancy and germination of Rumex crispus L.

Influência das variacões estacionais e profundidade de sementes no solo na dormência e germinação em Rumex crispus L.

The effects of seasonality and burial depth of seeds in the soil on the dormancy and germination of Rumex crispus L.

Ricardo Carmona

Eng. Agr., PhD, Prof. Adjunto, Dep. Eng.Agronômica, Universidade de Brasília, Caixa Postal 04508, CEP 70910-970, Brasília, DF

RESUMO

Sementes de Rumex cripus L. foram enterradas às profundidades de 1 e 10 cm no solo e coletadas a intervalos regulares durante dois anos. As sementes coletadas foram testadas a 10 e 20oC no escuro; a 5/25oC (16/8 horas) com 10mM de nitrato de potássio e luz; e num regime de temperatura alternadas correspondendo às mínimas e máximas médias do solo (MMTS), a profundidade de 1 cm durante 6 dias anteriores a cada coleta. Os tratamentos MMTS foram executados no escuro com 1 mM de nitrato de potássio ou uma mistura de estimulantes de germinação consistindo de nitrato de potássio, tiuréia, etefon, azida de sódio e peróxido de hidrogênio. A perda de viabilidade das sementes no solo durante o período estudado foi praticamente desprezível. As sementes mostraram ciclos de dormência ao longo do ano, quando as baixas temperaturas do solo superaram a dormência primária e paralelamente induziram dormência secundária, a qual por sua vez era superada pela elevação da temperatura. A dormência decresceu no segundo ano. O ambiente a 10 cm favoreceu a perda de dormência, entretanto o decréscimo de sementes devido à germinação in situ foi mais acentuado a 1cm de profundidade. A mistura química foi mais eficiente quando a dormência era mínima e as temperaturas do solo eram mais promotivas, o que correspondeu ao período quente do ano (da primavera ao outono). Discutem-se as implicações destes resultados na interpretação do comportamento ecológico da espécie e na adoção de práticas de manejo de bancos de sementes da invasora no solo.

Palavras-chave: controle, decréscimo, estimulantes, língua-de-vaca.

ABSTRACT

Rumex crispus L. seeds were buried at 1 and 10 cm depth in the soil and retrieved at regular intervals during two years. Retrieved seeds were tested at 10o and 20o in darkness; at 5/25oC (16/8 hours) with 10 mM potassium nitrate and light; and at an alternating temperature regime corresponding to the minimum and maximum soil temperatures (MMTS) at a depth of 1 cm during the six days prior to each retrieval. MMTS treatments were carried out in darkness with either 1 mM potassium nitrate or a cocktail of dormancy relieving chemicals consisting of potassium nitrate, thiourea, ethephon, sodium azide and hydrogen peroxide. There was no appreciable loss of seed viability in the soil during the study period. The seeds showed dormancy cycles in the soil throughout the year, where low soil temperatures relieved primary dormancy and induced secondary dormancy, which in turn was relieved by high temperatures. There was a year-to-year reduction in seed dormancy. The environment at 10 cm favoured loss of dormancy, however the depletion due to in situ germination was faster at 1 cm. The chemical mixture was more effective when dormancy was minimal and the soil temperatures were more promotive, which coincided to the warm period of the year (from spring to autumn). These results are discussed in terms of the interpretation of the ecological behaviour of this species in the field and the adoption of practices of management of seed banks in the soil.

Additional index words: control, depletion, dock, stimulants.

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LITERATURA CITADA

Recebido para publicação em 20/09/93 e na forma revisada em 24/11/93.

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Datas de Publicação

• Publicação nesta coleção
  16 Maio 2012
• Data do Fascículo
  1993

Histórico

• Aceito
  24 Nov 1993
• Recebido
  20 Set 1993