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Seeds of A. nudicaulis and S. floribundus were collected in a restinga located at Presidente Kennedy (ES, Brazil). This sandy community is characterized by the presence of patches of vegetation interspersed by open areas with a sparse plant covering. In order to evaluate the capacity of A. nudicaulis and S. floribundus to recruit individuals from seeds in the distinct microclimates generated by this heterogeneous plant covering, experiments were conducted in laboratory to test the effects of light and temperature on the germination for both species. Seeds of A. nudicaulis were unable to germinate in darkness but they achieved high germinability (&#8805;90%) from 15 to 40°C under red light. Seeds of S. floribundus germinated in darkness only at 40ºC (22.5%), whereas the germinability was high (&#8805;90%) from 15 to 30ºC under light. For both species, the germination rate was highest at 25ºC. For these bromeliads, alternating temperature (20/30ºC) promoted high germinability (&#8805;92.5%) only under red light. The seeds at 20/30°C in darkness were later transferred to light and a high germinability (>89%) was achieved for both species. No seed germinated at alternating temperatures of 20/50ºC and they were dead after 720h of incubation. The seeds showed to be photoblastic and did not tolerate high temperatures. The results suggest that under natural conditions the germination of seeds of A. nudicaulis and S. floribundus is restricted to microclimates where light and moderate temperatures are present. The microsites generated by the plant covering seem to provide these requirements. Sementes de A. nudicaulis e S. floribundus foram coletadas em uma restinga em Presidente Kennedy (ES). Esta comunidade arenosa caracteriza-se pela presença de moitas de vegetação separadas por areia nua ou com rala cobertura vegetal. Para examinar a capacidade das sementes em germinar nas distintas situações microclimáticas presentes neste ambiente, foram conduzidos, em laboratório, experimentos de germinação sob diferentes condições de temperatura e luminosidade. Sementes de A. nudicaulis não germinaram no escuro, mas sob luz vermelha atingiram alta germinabilidade (&#8805;90%) entre 15 e 40°C. Sementes de S. floribundus germinaram no escuro apenas a 40ºC (22,5%), enquanto na luz, a germinabilidade foi acima de 90% entre 15 e 30ºC. Para ambas as espécies a velocidade de germinação foi máxima a 25ºC. Para as duas bromélias, temperaturas alternantes (20/30ºC) resultaram em alta germinabilidade (&#8805;92,5%) apenas na luz. Sementes mantidas a 20/30°C no escuro foram posteriormente transferidas para luz, resultando numa alta germinabilidade (>89%) para ambas as espécies. Nenhuma semente germinou a 20/50ºC, perdendo a viabilidade após 720h de incubação. As sementes mostraram-se fotoblásticas positivas e não toleraram altas temperaturas. Em condições naturais, a germinação de A. nudicaulis e S. floribundus parece ser dependente da presença de luz e de cobertura vegetal, sendo limitada em condições de soterramento e em sítios que apresentam temperaturas do solo elevadas

acta botanica brasílica/acta botânica brasílica

Light and temperature requirements for germination of seeds of Aechmea nudicaulis (l.) Griesebach and Streptocalyx floribundus (Martius ex Shultes f.) Mez (Bromeliaceae)