Seed germination in Cerrado species

Abstract

The aim of this review is to comment on the available data about germination of seeds from herb, shrub and tree species of the Cerrado after the publication of the review written by Felippe and Silva in 1984. Studies on seed germination of herbaceous species focused mainly on the responses of seeds to light, different ranges of temperature and storage in the soil. The majority of seeds from herb species germinate between 20°C and 30°C, and are photoblastic. Alternate temperatures favored germination in some seeds, but changed light sensitivity of the achenes of Bidens gardneri. Seeds of most of the shrub species of Melastomataceae are positive photoblastic; among the Velloziaceae, germination in the dark was observed in some species. Other shrub species show dormancy caused by impermeability of the seed tegument, as described for seeds of some species of Bauhinia. Their dormancy is broken by chemical scarification using sulphuric acid. Seeds of Heteropterys pteropetala are sensitive to very high temperatures, similar to those registered during burnings. Some species were considered to have allelopathic effects and could inhibit the germination of seeds of other species and the establishment of plantlets. Seeds of most tree species do not require light to germinate and the focus of the studies were on methods of dormancy breaking. Sulphuric acid and incisions in the tegument proved to be the most efficient methods to break dormancy. In general, the studies are limited to three major aspects: responses to light, effects of different temperatures and dormancy breaking. More studies are necessary to understand the physiological and biochemical aspects of reserve compounds and their mobilization during germination, as well as the effects of fire in these seeds. Key words: dormancy, photoblastism, soil seed bank, temperature Germinação de sementes de espécies de Cerrado: O objetivo desta revisão é comentar dados disponíveis sobre a germinação de sementes de espécies herbáceas, arbustivas e arbóreas do Cerrado, desde a publicação da revisão feita por Felippe e Silva na década de 1980. Estudos de germinação de sementes de espécies herbáceas do Cerrado enfatizam as respostas das sementes à luz, temperatura e armazenamento no solo. A maioria dessas sementes germina entre 20ºC e 30ºC e são fotoblásticas. Temperaturas alternadas nem sempre favoreceram a germinação das sementes, no entanto, alteraram a sensibilidade à luz em aquênios de Bidens gardneri. A maioria das sementes das espécies arbustivas de Melastomataceae estudadas apresentaram fotoblastismo positivo; entre as Velloziaceae, foi observada germinação no escuro em algumas espécies. Sementes de algumas espécies arbustivas possuem dormência causada pela impermeabilidade do tegumento, quebrada com imersão em ácido sulfúrico, como no gênero Bauhinia. Sementes de Heteropterys pteropetala são sensíveis a temperaturas altas, similares àquelas registradas durante as queimadas. Plantas de algumas espécies têm efeitos alelopáticos e podem inibir a germinação de sementes de o...

Seed germination performances of Styrax species help understand their distribution in Cerrado areas in Brazil

“…We observed that S. pohlii pulp provided conditions for fungal infection, leading to 100% seed mortality. In addition, fleshy drupes of S. pohlii fruits are described as an important diet for birds in forest remnants (Zaca et al, 2006). As S. pohlii seeds exhibit thin seed coat and fast imbibition (Kissmann et al, 2012), as well as high %G after pulp removal, as evidenced by the present study, it seems reasonable to suggest that seeds of this species is zoochorically dispersed.…”

“…We did not test alternate temperatures (e.g. diurnal/nocturnal), but all these observations suggest possible effects of thermal amplitude occurring in soil seed banks, which could break any seed dormancy, as generally suggested by Zaidan and Carreira (2008). Moreover, in the present study, around 50% of S. ferrugineus seeds remained viable, as evidenced by the tetrazolium test, reiterating that these seeds show some type of dormancy.…”

“…Many germination results obtained under laboratory conditions have been reported (Zaidan and Carreira, 2008) for species of the Brazilian savanna (Cerrado), which is a biodiversity hot spot in South America (Klink and Machado, 2005). However, few results, if any, possess relationships with data obtained in the field.…”

“…On the other hand, rapid germination may not be considered advantageous in unpredictable habitats, such as the savannas. Seeds of savanna species commonly exhibit dormancy, preventing these seeds from germinating under unfavorable conditions (Zaidan and Carreira, 2008).…”

EFEITO DE ALTAS TEMPERATURAS NA GERMINAÇÃO DE SEMENTES DE Plathymenia reticulata Benth. E Dalbergia miscolobium Benth.

“…Características como alta suberização do tronco e dos galhos, que permitem certo grau de isolamento térmico (COUTINHO, 1990;GUEDES, 1993), a capacidade de rebrotar (COUTINHO, 1990) e a capacidade dos frutos de isolarem suas sementes do calor (CIRNE; MIRANDA, 2008) indicam a adaptação da vegetação do Cerrado ao fogo. Embora existam diversos trabalhos sobre a relação entre o fogo e a vegetação do Cerrado (SATO et al, 2010;MUNHOZ;AMARAL, 2010), o efeito das altas temperaturas na germinação de sementes é pouco estudado, e os trabalhos apresentam resultados contrastantes (ZAIDAN;CARREIRA, 2008;ANDRADE;MIRANDA, 2010). Para gramíneas, Overbeck et al (2006) apresentaram dois padrões diferentes: Andropogon lateralis e Shizachyrium microstachium não têm a germinação alterada quando as sementes são expostas até 110 °C por 2 min, enquanto Leptochoryphium lanatum e Elionurus muticus apresentam redução na germinação a partir da exposição a 70 °C, por 2 min.…”