W.R. da Silva

Efeito da disponibilidade hídrica do substrato, DA QUALIDADE FISIOLÓGICA E do teor de água inicial das sementes de soja no PROCESSO de germinação

With the main purpose of studying the relations among water availability, moisture content, and seed physiological quality on the germination process, seeds from three soybean [Glycine max (L.) Merrill] lots of the cv. IAC-15 with different levels of physiological quality, were used. Moistening of the seeds was accomplished to reach three moisture levels: 90, 110 and 130g of water.kg-1 fresh weight. The seeds of each lot, with 90, 110 e 130g of water.kg-1 were placed under different water potentials to germinate in soil and paper towel substrates. Moistening of paper towels was done with polyethylene glycol solutions, with water potencials of -0.04, -0.10, -0.20 e -0.40 MPa. Soil moistening was based on a water retention curve, adding a corresponding volume of water to reach the same water potencials as above. Speed and percentage of seedling emergence from soil were evaluated; radicel protrusion at three days after instalation, abnormal seedling and germination percentages at the seven days after seeding were determined from the paper towel sustrate. The data analysis and the results led to the following conclusions: There is a relationship between physiological quality and moisture level of seeds during the germination; the water potencials of -0,20 e -0,40 MPa considerably reduce the germination; the water potencial of -0,40 MPa decreases the seedling emergence of soybean.

COMPORTAMENTO DAS SEMENTES DE SOJA DURANTE A FASE INICIAL DO PROCESSO DE GERMINAÇÃO

With the main purpose of studying the performance of soybean seeds during the early stage of the germination process, seeds from three soybean [Glycine max (L.) Merrill] lots of cv. IAC-15 with different levels of physiological quality were used.Three moisture levels: 90, 110 and 130g of water.kg-1 fresh weight, were obtained artificially in air 20oC and 100% relative humidity. The rate of water uptake for each lot was measured. The imbibition damage after different periods of time was also evaluated. Seeds were placed between layers of paper towels, moistened with different polyethylene glycol solutions (PEG 6000), simulating water potentials of -0.04, -0.10, -0.20 e -0.40 MPa. The analysis and the interpretation of the results led to the following conclusions: The low water availability decreases the water uptake rate, and the increase in the water content of the seeds resulted in a reduced imbibition damage, at lowest water availability of the substrate.

Avaliação da embebição e do desenvolvimento inicial das estruturas embrionárias de sementes de milho submetidas a diferentes potenciais hídricos

Empregando substratos com potenciais hidricos variaveis entre 0 e -12atm, o presente trabalho objetivou avaliar o comportamento das sementes de milho postas a germinar. As situacoes de deficiencia hidrica foram diretamente comparadas a testemunha (plena disponibilidade de agua), usando sementes com e sem tratamento fungicida. A analise e a interpretacao dos resultados permitiram concluir que a absorcao de agua, a emergencia e o desenvolvimento inicial das estruturas embrionarias sao interdependentes e reagem no mesmo sentido ao deficit hidrico; para esses casos, a reducao do potencial hidrico promove dificuldades na evolucao dos processos. Paralelamente, a presenca de tratamento fungicida pode nao influenciar, quantitativamente, os fenomenos envolvidos no inicio da germinacao.

Processing effects on the quality of corn seed infected by Fusarium moniliforme sheld

Com o objetivo de avaliar os efeitos do beneficiamento na qualidade de lotes com sementes de milho infectadas com Fusarium moniliforme Sheld, sementes foram submetidas a classificacao por peneiras, originando 4 fracoes (24/64; 22/64; 20/64; 18/64 de polegada) e a separacao por peso atraves da acao da mesa gravitational, originando tres fracoes que foram individualmente submetidas ao mesmo equipamento gerando, cada uma, mais tres fracoes. Todas as fracoes foram avaliadas quanto a germinacao, ao vigor, a densidade, ao peso de mil sementes e a sanidade. A classificacao por largura nao e eficaz para separar as sementes infectadas; no entanto, o aumento da largura das sementes e acompanhado pela elevacao dos valores da germinacao e do vigor.

Estudo comparativo entre o desenvolvimento de plântulas de milho após período de exposição a vários potenciais hídricos

Submetendo sementes de milho com e sem tratamento fungicida, a ambientes de germinacao variaveis quanto a disponibilidade de agua (0 a -12atm), o presente trabalho avaliou o desenvolvimento posterior das plântulas postas em ambientes sem limitacoes hidricas. Os resultados obtidos permitiram concluir que a ocorrencia de deficit hidrico, durante o inicio do processo de germinacao, promove reducoes posteriores no comprimento das estruturas embrionarias e, de forma mais acentuada, do epicotilo; apesar disso, esse efeito se atenua com o passar do tempo pela elevacao progressiva na velocidade de crescimento em ambientes que oferecem menores potenciais hidricos. Paralelamente, o tratamento fungicida das sementes pode nao trazer vantagens em ambientes hidricamente deficientes; esta afirmacao, contudo, considera o papel toalha como meio fornecedor de agua o que, em contrapartida, exige cautela na sua extrapolacao para as condicoes proporcionadas pelo solo.

CONTROLE DA HIDRATAÇÃO DAS SEMENTES E DESENVOLVIMENTO INICIAL DE PLÂNTULAS DO FEIJOEIRO

The present work has the objective of studying the interferences of water availability on the germination process of dry bean seeds. For this purpose substrates with several hydric potentials were obtained using aqueous solutions of polyethylene glycol (PEG 6000) to evaluate the water uptake by seeds and the initial development of the seedlings. It was concluded that the minimum seed moisture content required by seeds for the radicle protrusion, which is the visible indicator of the onset of germination, is between 48 and 50%. The decrease of the external hydric potential causes greater reduction in the initial development of the seedlings than on the normal process of radicle protrusion.

Performance evaluation of corn seeds submitted to a partial remotion of the endosperm and the pericarp

In order to verify the interference of the excision of corn seed parts on their biological performance, this research was carried out by removing nearly 0, 14, 28 and 37% in weight from the seed, without influencing the embryo. The evaluation which was carried out in laboratory (germination and vigor) and in the field (outgrowth and yield) allowed the following conclusions: - There is a biological possibility of excising corn seed parts (±14% in weight), in pre-sowing and with fungicidal treatment, in high physiological quality lots to be sowed in suitable areas for the species upgrowth; the remotion of corn seed parts leads to the reduction of its conservation potential.

Transmissibilidade do virus do mosaico comum da soja (VMCS) por intermédio das sementes de soja(Glycine max (L.) Merrill)

In view of the long-range dissemination of the virus SMV in Brazilian soybean fields, this research was conserned with the transmission of the pathogen by seeds that show seedcoat mottling. Seeds proceeding from contaminated fields were submitted to emergence tests and examination of infected seedlings. The results indicated that the pathogen is transmited through the seeds even when they do not show seedcoat mottling; although no particular effect was found on emergence percentage, the use of mottled seeds tends to increase the number of infected seelings.

Efeito de várias disponibilidades hídricas, atuando como pré-condicionamento fisiológico durante a germinação das sementes de milho, no desenvolvimento das plântulas

The present paper considers the possible effects of physiological pre-treatment during the beginning of corn seeds germination in environments variable as to water availability (0 to -12 atm ). Periods of defficiency followed by 5 days without hydric limitations were compared with a control that remained equally, without reservations as to the disposability of water during 5 days. Results indicated that hydric pre-treatment of seeds can, if property adapted in its details, provide some advantages in the development of the seedlings derived from them. Chemical fungicide treatment of the seeds, submmited to the hydric pre-treatment may not be beneficial to the seedlings; as indicated by, in some isolated cases, the production of abnormalities in the embryonic structures.