Tathiana Elisa Masetto

DESICCATION TOLERANCE AND DNA INTEGRITY IN Eugenia pleurantha O. Berg. (MYRTACEAE) SEEDS 1

The aim of this study was to assess the desiccation tolerance and DNA integrity in Eugenia pleurantha seeds dehydrated to different moisture contents (MCs). Seeds extracted from mature fruits were submmited to drying in silica gel and evaluated at every five percentual points of decrease from the initial MC (35.5%, fresh weight basis). The effects of dehydration on seeds were verified through germination tests and DNA integrity assessment. Undried seeds achieved 87% germination, value reduced to 36% after being dried to 9.8% MC. When dried slightly more, to 7.4% MC, seeds were no longer able to germinate, suggesting an intermediate behavior in relation to desiccation tolerance. It was observed DNA degradation in seeds with 7.4% MC, which might have contributed to the loss of seed germination.

Avaliação da qualidade de sementes de Eugenia pleurantha (Myrtaceae) pelo teste de raios X

The X ray test is a useful tool to evaluate seed physical quality, thatt can be affected by the occurrence of empty seeds and the presence of insects and physical alterations. The objective of this study was also to investigate the efficiency of the X ray test in the evaluation of internal damage in seeds of Eugenia pleurantha, as well as to examine the consequence of this damage in the germination. Seeds of Eugenia pleurantha were placed in supports and exposed to several radiation intensities (35, 45, 50 and 60 Kvp) for 45 and 60 seconds to determine the X ray pattern. According to the anatomy visualized in the X rays, the seeds were classified as full seeds and infested seeds. The seeds were submitted to the germination test with sand as substratum placed at 30°C under continuous light. The 50 Kvp radiation intensity and a 60 second exposure to the X rays allowed clear visualization of the internal damage caused by the presence of insects in the seeds. The internal damage caused by insects prevented Eugenia pleurantha seed germination.

Avaliação da qualidade de sementes de cedro (Cedrela fissilis - meliaceae) pelo teste de raios X

O teste de raios X tem se demonstrado uma tecnica muito eficiente no controle de qualidade de sementes de especies florestais, caracterizando fases do desenvolvimento, danos causados por secagem, beneficiamento e predacao, entre outros. Objetivouse com este trabalho avaliar a qualidade fisica de sementes de cedro (Cedrela fissilis) pelo teste de raios X. Para isso, apos o beneficiamento, as sementes de cedro foram expostas as seguintes condicoes de intensidade de radiacao e tempos (25 Kv durante 60/30 segundos e 30 Kv durante 40 segundos) para determinar o padrao de raios X. De acordo com a anatomia visualizada pela imagem radiografica, as sementes foram classificadas em Sementes Cheias, Sementes Com Danos, Sementes Mal Formadas e Sementes Vazias. Em seguida, foi realizado o teste de germinacao em BOD, utilizando-se substrato de papel umedecido dentro de caixas para germinacao, sob 25oC e luz branca constante. Ao final de 20 dias, foram registrados os numeros de plântulas normais, anormais e sementes mortas. Pelos resultados obtidos, a intensidade de radiacao de 25 Kv durante 60 segundos permitiu melhor visualizacao das caracteristicas internas e os danos observados pela imagem radiografica afetaram a germinacao das sementes, reduzindo a qualidade do lote.

Condicionamento fisiológico e níveis de sombreamento em sementes de barbatimão (Stryphnodendron polyphyllum (Mart.) e S. adstringens (Mart.) Coville)

The technical difficulty to obtain seedlings due to seed dormancy is an obstacle in the production of native species in the recovery of Brazilian Savannah degraded areas programs. Thus, the objective of the present study was to evaluate the effect of physiological conditioning and shading on seed quality of two species of barbatimao (Stryphnodendron polyphyllum and Strypnhodendron adstringens). Seeds were soaked in seven conditions: 1) PEG -1.0 MPA; 2) PEG -1.0 MPA+ KNO3 -1.0 MPA; 3) PEG -0.5 MPA; 4) PEG -0.5 MPA + KNO3 -0.5 MPA; 5) KNO3 -1.0 MPA; 6) distillate water and 7) without soaking (control). During the treatments, the seeds remained incubated in BOD 20/30 oC for 24 h, then they were sown in cell trays containing Plantmax®, and maintained under four shading levels (full sun, 30%, 50% and 70%) with four repetitions of 20 seeds. After the evaluation of the emergency percentage, the seedlings were transplanted and kept under the same shade levels. The physiological conditioning on water of both species seeds, followed by sowing under 50 to 70% shade, are effective for faster and high emergency, greater height and dry mass of seedlings. S. polyphyllum seeds can be conditioned with PEG -1.0 MPa and PEG - 0.5 MPa if sown under 30% shade. However, seeds from S. polyphyllum and S. adstringens species should not be sown at full sun.

CONDICIONAMENTO OSMÓTICO DE SEMENTES DE Sesbania virgata (CAV.) PERS (FABACEAE)

Conduziu-se este trabalho, com o objetivo de avaliar o efeito do condicionamento osmotico sobre a germinacao e o vigor de sementes de Sesbania virgata. Foram utilizadas sementes escarificadas em acido sulfurico concentrado durante 40 minutos e, posteriormente, embebidas em solucoes de PEG 8000 com os potenciais osmoticos de 0,0; -0,2; -0,4; -0,6 e -0,8 MPa durante 12, 24 e 48 horas. Apos o condicionamento, as sementes foram submetidas a secagem em silica gel ate que fosse atingido o grau de umidade inicial das sementes e, posteriormente, foram envelhecidas artificialmente (40 oC/48 h/100% UR). Os efeitos do condicionamento e do envelhecimento foram avaliados por meio do teste de germinacao, primeira contagem e indice de velocidade de germinacao. O osmocondicionamento das sementes beneficiou a germinacao e o vigor das sementes de Sesbânia, submetidas ou nao ao envelhecimento acelerado. O periodo de 24 horas de condicionamento favoreceu o desempenho das sementes osmocondicionadas.