Germinação de sementes de espécies de Melastomataceae de Cerrado sob condições controladas de luz e temperatura

Abstract

-(Germination of seeds of Melastomataceae species from the Cerrado under controlled light and temperature). The aim of this study was to investigate the germination of seeds of Miconia albicans, M. langosdorffii, M. rubiginosa, M. stenostachya, Schizocetron elegans and Tibouchina gracilis that occur in Cerrado areas. The seeds were exposed daily to light during 0, 10 min, 15 min, 30 min, 60 min, 90 min, 180 min, 360 min, 720 min and 1.440 min at 25 ºC. Com relação à temperatura, a germinação das sementes ocorreu preferencialmente entre 20 e 30 ºC e na temperatura alternada. Germinação na luz e na faixa de temperatura entre 20 ºC e 30 ºC são características que contribuem para o sucesso do estabelecimento das Melastomataceae de regiões de cerrado. Ali, elas permanecem por longos períodos no banco de sementes do solo e podem germinar quando recebem luz, mesmo por períodos curtos, apesar das variações diurnas de temperatura.

Seed germination in Cerrado species

“…Seeds of all species belonging to the Melastomataceae that had been investigated by Carreira and Zaidan (2007) are positively photoblastic and no germination in darkness was registered. Nevertheless, Ranieri et al (2003) and Silveira et al (2004) observed some germination in the dark.…”

“…Another effect of alternate temperatures is to substitute the positive effects of light on the germination of photoblastic seeds, as seen in B. gaardneri, although this effect was not observed in seeds of some species of Xyris (Abreu and Garcia, 2005) and of some Melastomataceae, as seen in S. elegans and T. gracilis (Carreira and Zaidan, 2007). The period of storage, both in the soil and in refrigerator at 4°C, affected the photoblastism of the seeds of Psychotria barbiflora DC.…”

“…Oliveira (1998) observed that fire may interfere on the structure and the composition of species in a community through its effects on sexual reproduction. Nevertheless, few studies have been conducted using high temperatures (Gorla and Perez, 1997;Carreira and Zaidan, 2007), Andira humilis Mart. ex Benth (Periotto et al, 2004), S. lycocarpum (Oliveira et al, 2004, Aires et al, 2005 were considered to have allelopathic effects.…”

“…ex Benth (Periotto et al, 2004), S. lycocarpum (Oliveira et al, 2004, Aires et al, 2005 were considered to have allelopathic effects. From these, only the seeds of M. albicans were experimentally tested and showed to be affected by their own extracts (Carreira and Zaidan, 2007). These authors mentioned that field observations point to the hypothesis of an allelopathic effect on other plant species, considering that plants of the same species form homogenous groups and could inhibit the germination of certain seeds and the establishment of others.…”

Seed germination and dormancy of Miconia chartacea (Melastomataceae) in response to light, temperature and plant hormones.

“…son pequeñas (< 1 mg), presentan relación embrión: semilla cercana a uno, cotiledones foliáceos y carecen de endospermo (Baumgratz, 1985;Forbis, Floyd, & de Queiroz, 2002;Carreira & Zaidan, 2007). Además, presentan fotoblastismo positivo y su germinación es estimulada por el aumento de calidad y cantidad de luz, con umbrales altos de fotoperiodo (1 a 8 h), irradiancia (> 25 μmol / m 2 .s) y razón R / RL (> 0.54 fotoequilibrio del fitocromo) (Carreira & Zaidan, 2007;Godoi, Grandis, & Takaki, 2009;Silveira et al, 2013). Además, las especies de Miconia difieren en los requerimientos luminosos (Carreira & Zaidan, 2007), pudiéndose presentar partición de nicho regulada por la respuesta a la luz.…”