Atributos morfológicos de sementes de espécies de Cerrado relacionados ao fogo
Carregando...
Data
2022-03-30
Autores
Bailon, Ramon Monteiro
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
No Brasil há uma considerável área de ecossistemas propensos ao fogo que exibem uma vegetação lenhosa esparsa com predominância de espécies herbáceas. São pertencentes majoritariamente ao domínio Cerrado. Os vegetais presentes certamente passaram por um processo de seleção natural para conseguirem suportar uma condição tão adversa. A adaptação gira em torno de estratégias vegetativas, com órgãos resistentes, protegidos e podendo apresentar gemas, e estratégias reprodutivas, como a floração pós-fogo, deiscência de frutos em função das chamas e produção de sementes cuja germinação responde positivamente ao fogo e/ou à fumaça. Este trabalho avaliou a anatomia de sementes de 18 espécies do estrato rasteiro em três famílias (Melastomataceae, Velloziaceae e Xyridaceae). Espécies responsivas ou não aos tratamentos com choque térmico e fumaça. O objetivo foi avaliar, com microscopia ótica e eletrônica, atributos teciduais que podem nortear o tipo de resposta. O estudo morfológico mostrou que há características peculiares em relação à forma da semente e ornamentação do tegumento, mas não revelou grandes diferenças entre espécies responsivas ou não responsivas a fumaça. A histoquímica revelou para família Melastomataceae que não há amido como substância de reserva, ao contrário de Vellozia, onde o mesmo teste acusou grande quantidade de amido. Para lipídios o resultado variou entre as espécies. Para as espécies de Xyris foi identificado o amido, já os lipídios ficaram restritos a membrana das células embrionárias. Com relação às análises fisiológicas em Melastomataceae não foi possível quantificar amido extraído enfatizando o que foi amostrado nos testes histoquímicos. Já as espécies de Vellozia tiveram altos índices de amido nas análises fisiológicas corroborando com o que foi observado nos testes histoquímicos, com exceção de V. albiliflora que não apresentou amido nas análises fisiológicas, porém grãos de amido foram verificados nos testes histoquímicos. Aparentemente não foi observada correlação direta entre espécies que respondem positivamente à fumaça com a presença ou não de amido, uma vez que há espécies com tal tipo de reserva que apresentam resposta positiva na germinação quando tratadas com a fumaça. O mesmo pode ser aplicado para lipídios e proteínas.
In Brazil, there is a considerable area of fire-prone ecosystems that exhibit sparse woody vegetation with a predominance of herbaceous species. The present vegetables have certainly gone through a process of natural selection to be able to withstand such an adverse condition. Adaptation revolves around vegetative strategies, with resistant, protected organs that may have buds, and reproductive strategies, such as post-fire flowering, fruit dehiscence due to flames, and production of seeds whose germination responds positively to fire and/or the smoke. This work evaluated the seed anatomy of 18 species from the low stratum in three families (Melastomataceae, Velloziaceae and Xyridaceae) with responsive species or not to treatments with thermal shock and smoke. The objective was to evaluate, with optical and electronic microscopy, tissue attributes that can guide the type of response. The morphological study showed that there are particular characteristics about seed shape and seed coat ornamentation, but did not reveal major differences between responsive and non-responsive species. Histochemistry revealed for the Melastomataceae family that there is no starch as a reserve substance, unlike Vellozia, where the same test showed a large amount of starch. For lipids, the result varied between species. Starch was identified for Xyris species, whereas lipids were restricted to the membrane of the embryo's cells. Regarding the physiological analyzes in Melastomataceae, it was not possible to quantify extracted starch, emphasizing what was sampled in the histochemical tests. The species of Vellozia had high levels of starch in the physiological analyzes corroborating what was observed in the histochemical tests, except V. albiliflora which did not show starch in the physiological analyses, but starch grains were verified in the histochemical tests. No direct correlation was observed between species that respond positively to smoke with the presence or absence of starch, since there are species with this type of reserve that present a positive response in germination when treated with smoke. The same can be applied to lipids and proteins.
In Brazil, there is a considerable area of fire-prone ecosystems that exhibit sparse woody vegetation with a predominance of herbaceous species. The present vegetables have certainly gone through a process of natural selection to be able to withstand such an adverse condition. Adaptation revolves around vegetative strategies, with resistant, protected organs that may have buds, and reproductive strategies, such as post-fire flowering, fruit dehiscence due to flames, and production of seeds whose germination responds positively to fire and/or the smoke. This work evaluated the seed anatomy of 18 species from the low stratum in three families (Melastomataceae, Velloziaceae and Xyridaceae) with responsive species or not to treatments with thermal shock and smoke. The objective was to evaluate, with optical and electronic microscopy, tissue attributes that can guide the type of response. The morphological study showed that there are particular characteristics about seed shape and seed coat ornamentation, but did not reveal major differences between responsive and non-responsive species. Histochemistry revealed for the Melastomataceae family that there is no starch as a reserve substance, unlike Vellozia, where the same test showed a large amount of starch. For lipids, the result varied between species. Starch was identified for Xyris species, whereas lipids were restricted to the membrane of the embryo's cells. Regarding the physiological analyzes in Melastomataceae, it was not possible to quantify extracted starch, emphasizing what was sampled in the histochemical tests. The species of Vellozia had high levels of starch in the physiological analyzes corroborating what was observed in the histochemical tests, except V. albiliflora which did not show starch in the physiological analyses, but starch grains were verified in the histochemical tests. No direct correlation was observed between species that respond positively to smoke with the presence or absence of starch, since there are species with this type of reserve that present a positive response in germination when treated with smoke. The same can be applied to lipids and proteins.
Descrição
Palavras-chave
Semente, Anatomia, Histoquímica, Fumaça, Seed, Anatomy, Histochemistry, Smoke