Utilização do teste de raios - x na avaliação dos efeitos da dessecação e infestação em diásporos de Canela-Batalha - Cryptocarya aschersoniana Mez (Lauraceae)

Abstract

RESUMO:No presente trabalho, objetivou-se avaliar os efeitos da dessecação e identificar lesões por predação por insetos, em diásporos de canela-batalha (Cryptocarya aschersoniana Mez.), utilizando-se testes de raios X. Os danos provocados pela dessecação foram dimensionados nas imagens e associados à formação de plântulas. Diásporos recém-beneficiados (45 % de umidade e 37 % de germinação) foram colocados para secar em sala climatizada (20 °C e 60 % UR), dentro de bandejas plásticas em camada única. Posteriormente, com o intuito de acelerar o processo de secagem, foram colocados em caixas de secagem com solução saturada de hidróxido de sódio (28 % UR) e amostrados com 45, 37, 35, 31 e 26 % de umidade. Para as radiografias, utilizou-se a intensidade de radiação de 40 kVp e tempo de exposição de 1,5 minutos. Posteriormente, as radiografias foram fotografadas e as imagens analisadas em computador, sendo medido o afastamento entre o endocarpo e a semente. As sementes foram classificadas em sementes intactas, sementes com afastamento parcial, sementes com afastamento total e sementes predadas. Os testes de germinação foram realizados sobre areia, em germinadores tipo Mangelsdorf a 25 °C e luz branca constante. Pelos resultados, observa-se que a germinação é comprometida quando o teor de água das sementes fica abaixo de 26 %. Nesse ponto, o afastamento entre o endocarpo e a semente é de 0,65 mm. Houve uma correlação positiva entre a viabilidade das sementes, avaliada pelo teste de germinação, e o afastamento entre o endocarpo e a semente observado nas radiografias. A análise radiográfica possibilita identificar danos provocados por predação após infestação por insetos.Palavras-chave: Análise radiográfica, sementes recalcitrantes, espécie florestal, predação de sementes. USE OF X-RAY ANALYSIS IN STUDIES OF THE EFFECTS OF DESICCATION ON DIASPORES OF CANELA-BATALHA (Cryptocarya aschersoniana Mez -LAURACEAE) ABSTRACT: This study evaluated the effect of desiccation, and identified injuries and predation by insects in diaspores of "canelabatalha" (Cryptocarya aschersoniana Mez.) by using X-rays. The damages caused by desiccation were measured in the images and related to the formation of seedlings. Right after fruit depulping, the diaspores (endocarp plus seed) (45 % moisture content -MC and 37 % germination) were dried in acclimatized room (20 °C and 60 % RH), inside of plastic trays in

Analysis of radiographic images and germination of Campomanesia pubescens (Mart. ex DC.) O.Berg (Myrtaceae Juss.) seeds under drying

“…When one of the internal seed structures was not complete, the chances of the formation of either low-vigor seedlings or no seedlings increases (Nunes et al, 2014). Muxfeldt et al (2012) also found a higher percentage of seeds with internal voids or malformations in desiccated seeds of Cryptocarpa aschersoniana Mez (Lauraceae); however, this characteristic did not result in reduced germination, as observed in this study. This can be explained by the deleterious effects that drying could have caused to the internal morphology of the seeds, which can also be seen in the different percentage of filled seeds among the various water contents (Table 1).…”

Seed survival of the tropical treeCryptocarya aschersoniana(Lauraceae): Consequences of habitat disturbance

“…Cryptocarya aschersoniana seeds are sensitive to desiccation Muxfeldt et al 2012); therefore, their water content must remain high after dispersal to ensure their viability, with the critical water content near 28%, and the lethal water content between 18.1% and 21.5% (Tonetti 2013). In this study, the seeds that were used to establish the seed banks had water contents above 43%.…”

“…(Lauraceae) is a tropical tree species, widely distributed across Brazil, where it is known as 'canela-batalha' (Lorenzi 1998;Moraes 2007). This species belongs to the climax ecological group (Davide et al 1995) and produces seeds sensitive to desiccation Muxfeldt et al 2012). It is considered an ecologically important species because its fruits are consumed by several species of animals, which also act as seed dispersers (Lorenzi 1998).…”

“…In the literature, there are few studies covering the seed biology of this species; one of these studies has classified their seeds as physiologically dormant (Carvalho 2006). Despite the presence of the pericarp, physical dormancy is discarded because the germination unit is water-permeable (Baskin & Baskin 2004;Muxfeldt et al 2012). Some studies have reported a delay in seed germination of primary (Hopkins & Graham 1987) and recalcitrant species (Msanga 1998) of tropical forests that usually have rapid germination (Garwood 1989).…”

Seed Quality Evaluation of Senegalia polyphylla (DC.) Britton & Rose

“…The growing demand for seeds of native forest species, through production and conservation programs, has generated the need to develop technologies for evaluating the quality of these seeds (Carvalho et al, 2009) to make sure that they will originate healthy plants, since obtaining and maintaining high physiological quality of a seed lot is a critical step in the production of seedlings (Muxfeldt et al, 2012).…”