Superação de dormência na qualidade de sementes e mudas: influência na produção de Senna multijuga (L. C. Rich.) Irwin & Barneby Overcoming of dormancy in the quality of seeds and seedlings: influence in the production of Senna multijuga (L.C. Rich.) Irwin & barneby

O objetivo deste trabalho foi determinar a qualidade fisiológica e sanitária de sementes de Senna multijuga(L. C. Rich.) Irwin & Barneby relacionada aos métodos de superação de dormência e à interferência na produção de mudas. As sementes foram submetidas aos seguintes métodos: imersão em água fervente, as sementes foram imersas em água, com temperatura de 100°C, até esfriar, por 24 horas; escarificação ácida, onde as sementes foram imersas em ácido sulfúrico (H2SO4) a 90%, por 10 e 20 minutos, e testemunha (sem tratamento). Foram realizados os testes de sanidade, germinação, tetrazólio e avaliação da qualidade das mudas. O delineamento experimental foi inteiramente casualizado. Para a avaliação da germinação foi utilizado um esquema fatorial (4 X 2), com quatro métodos de superação de dormência X dois fotoperíodos, para os substratos rolo-de-papel e vermiculita. A escarificação ácida constituiu-se no método mais eficiente para a superação da dormência das sementes de Senna multijuga. Penicillium sp. e Aspergillus sp. tiveram sua incidência aumentada quando o tegumento foi danificado pela escarificação ácida por 20 minutos. O controle de Fusarium spp. aumentou gradativamente com o aumento do tempo de exposição ao ácido sulfúrico.<br>The objective of this work was to determine the physiological and sanitary quality of Senna multijugaseeds related to the methods of dormancy overcoming and the influence on the seedlings quality. The seeds had been submitted to the following methods :immersion in water fervent, the seeds had been immersed in water, at 100°C, until cooling for 24 hours; acid escarification, where the seeds had been immersed in sulfuric acid (H2SO4) 90%, for 10 and 20 minutes, and control (without treatment). The tests of sanity, germination and tetrazolium had been carried through, and were evaluated the quality of the seedlings. For the germination of the evaluation an factorial project was used (4 X 2), with four methods of dormancy X two light periods, for substrate paper and vermiculite. The acid scarification consisted in the method most efficient for the dormancy of Senna multijugaseeds. Penicillium sp. and Aspergillus sp. they had for its increased incidence when the seed coast was damaged by the acid scarification for 20 minutes. The control of Fusarium spp. increases gradual with the increase of the time of sulfuric acid exposition

Cytogenetic analysis of wheat seeds submitted to artificial aging stress

Several studies have been developed to understand the physiology of seed deterioration, however, the initial steps of the deterioration process are not completely clear. Seed vigor and viability losses are also associated with genetic material damage. This study was carried out to detect cytogenetic and physiological alterations occurring during the deterioration process of wheat seeds, due to artificial aging stress. Two cultivars, Ônix and Fundacep Campo Real, were submitted to six different treatments: control (T1), 24 (T2), 48 (T3), 72 (T4), 96 (T5) and 120 (T6) hours under artificial aging conditions: 42 °C and 100% relative humidity. Germination and vigor tests (First Count of Germination, Electrical Conductivity, Seedling Emergence in the Field and Emergence Speed Index) were performed. Cytogenetic evaluations were performed through smear technique for root tips, stained with 2% acetic orcein. Total number of cells under division and mitotic index (MI) were determined. According to results, vigor and mitotic index were affected due to deterioration process induced by artificial aging stress. A reduced number of dividing cells were observed in seeds submitted to prolonged period of aging. Chromosomal abnormalities in mitotic cells of aged seeds were detected with the occurrence of micronuclei, chromosome breaks and bridges

Envelhecimento acelerado em sementes de trigo Accelerated aging in wheat seeds

O presente trabalho teve o objetivo de estudar procedimentos de condução do teste de envelhecimento acelerado para determinar o potencial fisiológico de sementes de trigo. Utilizaram-se quatro cultivares: 'Pampeano', 'Safira', 'Ônix' e 'Jaspe'. Foram realizadas determinações de teor de água e avaliações de germinação, emergência, índice de velocidade de emergência e teste de envelhecimento acelerado. O teste de envelhecimento acelerado foi conduzido de três formas: teste tradicional (água), teste com solução saturada de NaCl (11g de NaCl por 100mL de água) e teste com solução supersaturada de NaCl (40g de NaCl por 100mL de água), nos períodos de 48, 72 e 96h de permanência na câmara de envelhecimento a 42&deg;C. O teste de envelhecimento acelerado com solução saturada de NaCl, no período de 96h, foi o mais adequado para avaliar o potencial fisiológico das sementes de trigo, em alto, médio e baixo vigor.<br>This research aimed to study procedures for conducting the accelerated aging test to determine the physiological potential of wheat seeds. The experiment was conducted with four varieties: 'Pampeano', 'Sapphire', Onyx' and 'Jasper'. Tests were performed with water content, germination, seedling emergence, speed of emergence and accelerated aging. The accelerated aging test was conducted in three stages: traditional (water), test using saturated NaCl solution (11g of NaCl per 100mL of water) and with the use of supersaturated solution of NaCl (40g of NaCl per 100mL of water), each for 48, 72 and 96h at 42&deg;C. The accelerated aging test with saturated solution of NaCl, within 96h was suitable to evaluate the physiological potential of seeds of wheat in high, medium and low vigor