Resposta à qualidade de luz como estratégia para estabelecimento de Bidens gardneri
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Data
2012-12-01
Autores
Rondon, Josimara Nolasco
Takaki, Massanori [UNESP]
Zaidan, Lilian Beatriz Penteado
Título da Revista
ISSN da Revista
Título de Volume
Editor
Sociedade de Investigações Florestais
Resumo
O objetivo deste trabalho foi verificar o envolvimento do fitocromo na germinação de aquênios do Bidens gardneri Baker., conhecido como picão preto. Os aquênios foram separados em curtos, médios e longos. Dois experimentos utilizaram apenas aquênios médios devido às diferenças quanto à resposta de germinação na ausência de luz, quando foram armazenados artificialmente no solo de cerrado, em um estudo anterior. A resposta dos aquênios curtos, médios e longos ao aumento da fluência de luz branca foi verificada sob um gradiente de luz branca entre 0 e 46,44 mmol m-2 s-1 de fluência. A reversão do fitocromo vermelho extremo (Fve) em fitocromo vermelho (Fv) no escuro em aquênios médios recém coletados e os armazenados por 14 meses a 4 ºC, que foram embebidos em água por 24 horas e incubados a 35 °C durante 24, 48 e 72 horas no escuro e a germinação foi a 25 ºC no escuro e observada após 15 e 30 dias. Por ultimo, foi construído um gradiente de fotoequilíbrio para cada tamanho e idade de aquênio em placas de petri umedecidos com água destilada, na qual a germinação foi observada a cada dois dias. em irradiâncias de 0 a 46,44 mmol m-2 s-1, a germinabilidade dos aquênios longos e médios aumentou com a irradiância, porém os aquênios curtos sempre tiveram baixa germinabilidade. Aquênios médios armazenados, pré-embebidos por 24h e incubados no escuro por 24 h, 48 h e 72 h a 35 ºC mantiveram resposta fotoblástica quando a germinação foi observada a cada dois dias e após 15 e 30 dias, portanto não apresentaram reversão de Fve para Fv no escuro. No entanto, aquênios médios recém coletados e submetidos aos mesmos tratamentos tiveram o Fve removido quando incubados por 48 e 72 horas. Estes aquênios mostraram a resposta de fluência muito baixa de luz, quando a germinação foi observada a cada dois dias, sob luz verde. Os resultados indicam que heteroblastismo pode conferir à espécie estratégias diferentes de invasão e sobrevivência no cerrado: em locais com baixa disponibilidade de luz poderá ocorrer a germinação dos aquênios longos, ainda na estação chuvosa, (fevereiro). Enquanto os aquênios curtos podem permanecer armazenados no solo, vindo a germinar apenas no final da estação seca (em setembro). Portanto, o aquênio curto persiste no banco de sementes no solo por sete meses e é o que possibilita o estabelecimento de Bidens gardneri em campos de cerrado e pastagens.
The objective of this study was to investigate the involvement of phytochrome on the germination of achenes of Bidens gardneri Baker., known as black tick. The seeds were separated into short, medium and long sizes. Two experiments used only achenes medium due to differences in the response of germination in the dark, when they were artificially stored in Cerrado soil, in a previous study. The response of achenes short, medium and long to increase flow of white light was observed under a white light gradient from 0 to 46.44 µmol m-2 s-1 creep. The reversal of phytochrome far red (Pfr) in phytochrome red (Pr) in the dark, achenes medium newly collected and stored for 14 months at 4 °C, which were imbibed in water for 24 hours and incubated at 35 °C for 24, 48 and 72 hours in the dark and germination was 25 ° C in the dark and observed after 15 and 30 days. Finally, a gradient was constructed photoequilibrium for each size and age of achene in petri dishes moistened with distilled water, and the germination was observed every two days. In irradiances from 0 to 46.44 µmol m-2 s-1, germinability of achenes long and medium sizes increased with irradiance, but the seeds had low germination always short. Achenes medium stored imbibed for 24 h and incubated in the dark for 24 h, 48 h and 72 h at 35 °C remained response photoblastic when germination was observed every two days and after 15 and 30 days therefore showed no reversion Pfr for Pr in the dark. However, achenes medium newly collected and subjected to the same treatments were removed when the Pfr incubated for 48 and 72 hours. These achenes showed response very low fluence of light, when germination was observed every two days under green light. The results indicated that heteroblastism can check to the species different strategies of invasion and survival in the savanna: in places with low light availability may occur germination of achenes long, even in the rainy season (February). While short achenes can remain stored in the soil to germinate only come at the end of the dry season (in September). So, the short achene persists in the soil seed bank for seven months and is what allows the establishment of Bidens gardneri at the fields and savannah grasslands.
The objective of this study was to investigate the involvement of phytochrome on the germination of achenes of Bidens gardneri Baker., known as black tick. The seeds were separated into short, medium and long sizes. Two experiments used only achenes medium due to differences in the response of germination in the dark, when they were artificially stored in Cerrado soil, in a previous study. The response of achenes short, medium and long to increase flow of white light was observed under a white light gradient from 0 to 46.44 µmol m-2 s-1 creep. The reversal of phytochrome far red (Pfr) in phytochrome red (Pr) in the dark, achenes medium newly collected and stored for 14 months at 4 °C, which were imbibed in water for 24 hours and incubated at 35 °C for 24, 48 and 72 hours in the dark and germination was 25 ° C in the dark and observed after 15 and 30 days. Finally, a gradient was constructed photoequilibrium for each size and age of achene in petri dishes moistened with distilled water, and the germination was observed every two days. In irradiances from 0 to 46.44 µmol m-2 s-1, germinability of achenes long and medium sizes increased with irradiance, but the seeds had low germination always short. Achenes medium stored imbibed for 24 h and incubated in the dark for 24 h, 48 h and 72 h at 35 °C remained response photoblastic when germination was observed every two days and after 15 and 30 days therefore showed no reversion Pfr for Pr in the dark. However, achenes medium newly collected and subjected to the same treatments were removed when the Pfr incubated for 48 and 72 hours. These achenes showed response very low fluence of light, when germination was observed every two days under green light. The results indicated that heteroblastism can check to the species different strategies of invasion and survival in the savanna: in places with low light availability may occur germination of achenes long, even in the rainy season (February). While short achenes can remain stored in the soil to germinate only come at the end of the dry season (in September). So, the short achene persists in the soil seed bank for seven months and is what allows the establishment of Bidens gardneri at the fields and savannah grasslands.
Descrição
Palavras-chave
Luz vemelha extrema, fitocromos, Heteroblastismo, Irradiância, Far red light, phytochromes, heteroblastism, irradiance
Como citar
Revista Árvore. Sociedade de Investigações Florestais, v. 36, n. 6, p. 1145-1154, 2012.