Helena Maria Carmignani Pescarin Chamma

Viabilidade das sementes de braquiária pelo teste de tetrazólio

The objective of this research was to determine the conditions to evaluate the viability of Brachiaria brizantha seeds by the tetrazolium test. Using eight seed lots, preconditioning periods and temperatures (2, 4 and 6 hours at 35oC and 40oC; 6 and 16 hours at 30oC, between paper) and staining periods and temperatures (1, 2 and 4 hours at 35oC, 40oC and 45oC; 6 hours at 30oC, bisected seed through the embryo, immersed in an aqueous solution of 0.075% tetrazolium chloride) were tested. The tetrazolium test was performed classifying the seeds in two categories: viable and non- viable. Seed water content (oven method, 105±3oC/24h) and germination (TP, 20-35oC, count at 7, 14 and 21 days) were determined. The experimental design was a randomized block with four replications for each seed lot. The multiple mean comparison within treatments was performed using Tukeys test at a 0.05 error level. It was concluded that the tetrazolium test constitutes an efficient option for estimating the viability of Brachiaria brizantha seeds. The most adequate condition would be that resulting from a combination of six hours of preconditioning at 30oC (seed water content was 25%) followed by a two hours of staining at 40oC.

Sementes de ipê-branco (Tabebuia roseo-alba (Ridl.) Sand. - Bignoniaceae): temperatura e substrato para o teste de germinação

The research evaluated the temperature and substrate for the germination test of ipe-branco (Tabebuia roseo-alba (Ridl.) Sand.) seeds. The effects on germination of 11 temperatures intervals between 15.0°C and 35.0°C were evaluated in a thermo-gradient table with a daily 8-hour photoperiod . The substrates paper (on top of paper and between papers) and vermiculite (in vermiculite) were analyzed in chambers with daily 8-hour photoperiod at 30°C and 35°C. The seeds and seedlings were evaluated daily, by the criteria indicated in the Brazilian Rules for Seed Testing, and the percentage and germination speed were determined. The most favorable condition for the germination test for Tabebuia roseo-alba seeds was 30°C using paper as substrate.

Testes de envelhecimento acelerado e de deterioração controlada para avaliação do vigor de sementes de soja

Seed vigor testing is an important component for the seed industry quality control. This study was conducted to compare different procedures of the accelerated aging and the controlled deterioration tests to evaluate soybean [Glycine max (L.) Merrill] seed vigor. Two soybean cultivars, BR-37 and Embrapa 48, each represented by different seed lots were used. All lots were submitted to two procedures of placing seed samples on the accelerated aging tray: 1. the addition of a monolayer of seeds or 2. the use of a standard weight (42.5 g) of seeds. The study also examined the possibility of using a saturated NaCl solution in substitution to water in comparison to the standard accelerated aging test (48 and 72 h at 41°C, followed by germination during four days). Controlled deterioration test was conducted using seeds with water content raised to 15.5%, placed in laminated aluminum bags and maintained in water-bath at 40°C for 48h followed by a germination test. Information provided by the accelerated aging test was not influenced significantly by the procedure used to place seed samples on the tray, both in the standard test and in the salt accelerated aging test. This procedure and also the controlled deterioration test may be considered as efficient alternatives for the assessment of soybean seed vigor allowing for results as consistent as those provided by the standard accelerated aging test.

Teste de germinação de sementes de sansão-do-campo (mimosa caesalpiniaefolia benth. - Fabaceae-mimosoideae)

This research was carried out to study procedures for the germination test in sansao-do-campo seeds (Mimosa caesalpiniaefolia Benth.). The first study was done on a thermo-gradient table with temperature varying from 15°C to 35°C and daily 8-hour photoperiod. The best temperature from the first study (30°C and 35°C) was then evaluated in two substrata (paper - on top of paper and paper rolls, and vermiculite - between vermiculite). Evaluations were performed daily, according to the criteria established in the Brazilian Rules for Seed Testing, and the percentage and germination speed were determined. The best temperature was 30°C distributing the seeds using paper or vermiculite.

Teste de tetrazólio para as sementes de milho: períodos de hidratação e de coloração das sementes

The objective of this research was to determine the conditions to evaluate the viability of corn seeds by tetrazolium test. Using three seed lots, cultivar D657, preconditioning periods and temperatures (4, 6, 12 and 16 hours at 25 and 30oC and 4, 6 and 8 hours at 35 and 40oC) and staining periods and temperatures (seeds moistened during 4h at 25, 30, 35 and 40oC and staining during 1, 2 and 3 hours at 40oC in a solution of 0,075% tetrazolium chloride) were tested. Seed water content (oven method, 105±3oC/24h) and germination (TP, 25oC, count at 4 and 7 days) were determined. The tetrazolium test was performed classifying the seeds in two categories: viable and non- viable. The experimental design was a randomized block with two replications for each seed lot. The multiple mean comparison within treatments was performed using Tukeys test at a 0,05 error level. It was concluded that tetrazolium test constitutes an efficient option for estimate the viability of corn seeds. The most adequate condition would be that resulting from a combination of four hours of preconditioning at 35 or 40oC (seed water contents reached values from 19,5 and 21,3%, respectively) followed by 1, 2 and 3 hours of staining at 40oC.

Tamanho da semente e o teste de envelhecimento acelerado para soja

A pesquisa teve como objetivo avaliar a possivel relacao entre efeitos da utilizacao de sementes de soja com diferentes tamanhos nos resultados do teste de envelhecimento acelerado. Foram analisados lotes dos cultivares BR-37 e Embrapa 48 (sementes nao classificadas e de tres tamanhos, classificadas em peneiras de crivos oblongos). Para cada lote e peneira, foram distribuidas tres subamostras de 42,5 g de sementes, em camadas simples ou pre-pesadas (42,5 g) na superficie da tela metalica de cada compartimento individual (caixa plastica), utilizado como câmara interna para a conducao do teste. Cada caixa plastica recebeu 40 mL de agua (constituindo ambiente com 100% U.R. do ar) ou 40 mL de solucao saturada de cloreto de sodio (ambiente com 76% U.R.). Estudaram-se os periodos de 48 e 72 horas de envelhecimento das sementes, em BOD, a 41°C. O teste de germinacao subsequente foi avaliado no quarto dia apos a semeadura. A distribuicao de amostras com massa uniforme nao elimina os efeitos do tamanho das sementes. Desta maneira, o teste de envelhecimento acelerado, em sementes de soja, fornece informacoes mais consistentes quando as amostras comparadas sao constituidas por sementes de tamanho semelhante. O uso de solucao salina torna o teste menos severo, mas nao reduz sua eficiencia.

Relações entre momento de colheita, composição química e potencial de armazenamento de sementes de soja

Soybeans IAC-8 were harvested in the growth stages R7 and R8 commercial harvesting time and at two other subsequent times to compare their physiological and technological characteristics. Seeds were stored at two moisture levels, 12% and 15%, for 6 months. Germination and vigor (acelerated aging, electrical conductivity), oil and free fatty acids, peroxide and iodine values were evaluated periodically. As expected, the time of harvesting and seed moisture content affected seed performance, while oil content did not correlate to physiological quality as did acidity, peroxide value and iodine number.

Genetic variation of germination cold tolerance in Japanese rice germplasm

Low temperatures at the initial stages of rice development prevent fast germination and seedling establishment and may cause significant productivity losses. In order to develop rice cultivars exhibiting cold tolerance, it is necessary to investigate genetic resources, providing basic knowledge to allow the introduction of genes involved in low temperature germination ability from accessions into elite cultivars. Japanese rice accessions were evaluated at the germination under two conditions: 13°C for 28 days (cold stress) and 28°C for seven days (optimal temperature). The traits studied were coleoptile and radicle length under optimal temperature, coleoptile and radicle length under cold and percentage of the reduction in coleptile and radicle length due to low temperature. Among the accessions studied, genetic variation for traits related to germination under low temperatures was observed and accessions exhibiting adequate performance for all investigated traits were identified. The use of multivariate analysis allowed the identification of the genotypes displaying cold tolerance by smaller reductions in coleoptile and radicle lenght in the presence of cold and high vigour, by higher coleoptile and radicle growth under cold.

Germinação de sementes de Panicum maximum Jacq. pré-tratadas com ácido sulfúrico

O presente trabalho foi realizado com o objetivo de avaliar o efeito da aplicacao do pre-tratamento com acido sulfurico sobre a germinacao de sementes de Panicum maximum Jacq., em condicoes de laboratorio. Sementes recem colhidas dos capins Coloniao, Tobiata, Centenario, Centauro e Tanzânia 1, nao tratadas e pre-tratadas (escarificadas), foram submetidas a ensaios de germinacao, a partir de agosto de 1991 ate abril de 1993, em intervalos de aproximadamente 4 meses entre cada epoca. Os dados colhidos, apos analise estatistica, permitiram elaborar a seguinte conclusao: o pre-tratamento com acido sulfurico nao contribuiu para melhorar a porcentagem de germinacao das sementes testadas, desde o inicio ate o final do periodo de armazenagem.

Efeito da luz e de diferentes temperaturas na germinação de sementes de Heliocarpus popayanensis L

n Heliocarpus popayanensis is a pioneer tree species used in Brazil mainly for forest restoration. The aim of this research was to evaluate the effect of light and temperature on the germination of H. popayanensis seeds. Seeds were put to germinate inside transparent and black plastic boxes and incubated in chambers at 25∞C for light evaluation on germination. For temperature evaluation, nine intervals of constant temperatures between 15∞C and 35∞C and two alternate temperatures (15-35∞C and 20-30∞C) were analyzed in thermo- gradient table. For both experiments, seeds were distributed on the top of two blotter paper sheets and the daily photoperiod was eight hours of light. Germination was evaluated from primary root protrusion and formation of normal seedlings, and three lots of seeds were studied. The results showed that H. popayanensis seeds are non-photoblastic, the optimum temperature interval is between 28.1∞C and 30.2∞C, temperatures around 35∞C stimulated seed impermeability overcome, and the primary root protrusion was not efficient to determine the optimum germination temperature, since the formation of normal seedlings is more indicated for this determination.