André Delly Veiga

Effects of different drying rates on the physiological quality of Coffea canephora Pierre seeds

Desiccation tolerance in seeds depends on the species, development stage and drying conditions, especially the water removal rate. Coffea seeds are considered of intermediate performance, because they tolerate relative dehydration compared to orthodox seeds and are sensitive to low temperatures. The objective of this study was to verify the effect of different drying rates on the viability and storability of Coffea canephora seeds. A complete randomized experimental design was used, in a factorial 3 x 5 x 2 design, with three drying rates (fast, intermediate and slow), five final mean water contents after drying (51, 42, 33, 22 and 15 %) and two storage temperatures (10 and 20°C). The germination and seed vigor assessments, using radicle protrusion, cotyledon leaf opening, seedling emergence and emergence speed index, were performed shortly after drying and after two and four months storage. It was observed that with reduction in the water content there was reduction in the germination values and seed vigor, for all the drying rates. The greatest reductions in physiological quality occurred when the seeds were dried quickly and the best results were obtained at the intermediate drying rate. There was an effect of drying rate and storage temperature on the physiological quality of the seeds, and lower germination and vigor values were observed in seeds with lower water content stored at 20°C. C. canephora seeds were tolerant to desiccation down to 15 % water content and can be stored for four months at 10°C. A temperature of 20oC can be used to store C. canephora seeds, as long as the water content is not reduced to values below 22 % water content.

Influência do potássio e da calagem na composição química, qualidade fisiológica e na atividade enzimática de sementes de soja

A composicao quimica das sementes pode ser influenciada por fatores geneticos, ambientais e pela disponibilidade de nutrientes no solo durante a producao e, como consequencia, terem o seu vigor afetado. O potassio pode influenciar a atividade de varias enzimas presentes nas plantas, necessarias em varias reacoes envolvidas na utilizacao de energia, sintese de amido, metabolismo do nitrogenio e respiracao. Avaliou-se o efeito da adubacao potassica e da calagem na composicao quimica, qualidade fisiologica e na atividade de enzimas de sementes de soja. A pesquisa foi desenvolvida nos laboratorios de analises e biotecnologia de sementes do Departamento de Agricultura e no Laboratorio de Producao Vegetal do Departamento de Ciencias dos Alimentos da Universidade Federal de Lavras (UFLA). Em sementes de soja do cultivar Msoy 8001, produzidas sob 2 niveis de saturacao por base (48% e 85%) e quatro doses de K2O por hectare (0, 50, 100 e 200 kg), foram avaliados teores de oleo e proteina, germinacao, envelhecimento acelerado e atividade das enzimas envolvidas nos processos de germinacao e deterioracao de sementes. A adubacao potassica nao afeta a germinacao e o vigor das sementes, enquanto a elevacao da saturacao por base, proporciona maior vigor de sementes de soja. Ha aumento no teor de oleo e reducao no teor de proteina em sementes de soja a medida que a dose de K2O e aumentada. Ocorre aumento de teor de proteinas em sementes de soja, produzidas sob maiores niveis de saturacao por base. A atividade das enzimas piruvato quinase, esterase e alcool desidrogenase em sementes de soja e afetada pela concentracao de potassio e saturacao por base no solo.

Armazenabilidade de sementes de cafeeiro colhidas em diferentes estádios de maturação e submetidas a diferentes métodos de secagem

The harvesting time and drying methods may influence the quality of coffee seeds during storage. This work was conducted with the objective of understand the effects of maturation stages and drying methods on the physiological quality and storability of coffee seeds. The experiments were performed at the Seed Analysis and Electrophoresis Laboratory of the Department of Agricultural of UFLA. The fruits of the cultivar Rubi were harvested, depulped and the mucilages removed by fermentation and the seeds washed and let on paper for removal of the water. The seeds were submitted to conventional drying (under shade) and drying in stationary drier at temperature of 35oC. As a control, seeds with no drying were analyzed. The evaluations were done soon after the drying treatments and after four and eight months of storage. The seeds were stored at 10oC in air-tight plastic packages. The germination test, radicle protrusion, seedling dry matter, emergence index speed, electric conductivity, electrophoresis analyses of heat-resistant proteins and quantification of endo-â-mannanase activity were the parameter evaluated. The design was completely randomized with 2 (maturation stages) x 3 (dryings) x 3 (storage time) factorial scheme with four replications. Seeds harvested in the cherry stage have greater storage potential than in the green-yellow stage. Reduced germination and vigor occur in the coffee seeds harvested in the green yellow stage, when submitted to fast drying. The presence or intensity heat-resistant protein bands is associated with seed drying. Greater activity of endo-s-mananase enzyme occurs in seeds harvested in the cherry stage than in the green yellow stage. Increase of the activity of endo-s-mananase enzyme occurs during storage.

Armazenamento e qualidade de sementes de tomate enriquecidas com micronutrientes e reguladores de crescimento

O estudo foi desenvolvido na Universidade Federal de Lavras, em Lavras, MG, com o objetivo de avaliar o efeito da aplicacao de micronutrientes e reguladores de crescimento na germinacao, no vigor, na atividade de algumas enzimas e no teor de proteinas totais em sementes de tomate, durante o armazenamento. As sementes foram tratadas com os produtos Starter®, Cellerate® e Stimulate® nas dosagens correspondentes a 0%, 50%, 100%, 150% e 200% da dose recomendada pelo fabricante, utilizando a tecnica de peliculizacao. As avaliacoes foram realizadas aos zero, 6 e 12 meses de armazenamento, pelos seguintes parâmetros: porcentagem de germinacao, porcentagem e indice de velocidade de emergencia, atividade das enzimas endo-â-mananase e esterase, teor de proteinas totais e sanidade. Foi utilizado o delineamento inteiramente casualizado, em esquema fatorial 3 x 5 x 3 ( 3 produtos x 5 doses x 3 epocas de armazenamento), com quatro repeticoes de 50 sementes por tratamento. Concluiu-se que a combinacao dos reguladores de crescimento contidos no produto Stimulate® promove aumento na velocidade de emergencia das plântulas de tomate quando aplicados na dose recomendada e na pre-semeadura; a atividade da enzima esterase aumenta com o periodo de armazenamento das sementes de tomate, indicando aumento no processo de deterioracao; o revestimento enriquecido com os micronutrientes e reguladores de crescimento contidos nos produtos Starter®, Cellerate® e Stimulate® e o armazenamento interferem na atividade da enzima endo-â-mananase em sementes de tomate; ha um aumento no teor de proteinas totais em sementes de tomate com o aumento do periodo de armazenamento.

Inibição do desenvolvimento in vitro de embriões de Coffea por cafeína exógena

Caffeine, the alkaloid known as 1,3,7 - trimetilxantina, is found in quiescent coffee seeds, amounting to a total of 1.1 to 1.7% in Coffea arabica L. and 2 to 3% in Coffea canephora Pierre, mostly localized in theo endosperm, in the free cytoplasm of cells or complexed with chlorogenic acids. With the physiological function in plants not yet completely understood, caffeine causes an allelophatic effect, either inhibiting germination of a number of species or as an anti-herbivore or a natural pesticide agent. The slow germination of coffee seeds has not yet been elucidated and several causes are pointed to, such as the presence of the endocarp, low water and O2 uptake and presence of natural inhibitors and hormonal balance. Although suggested, studies on coffee seed inhibition by the action of endogenous or exogenous caffeine are scarce. Thus, the present study was designed to investigate the effect of exogenous caffeine on both germination and embryo development of Coffea arabica L. and Coffea canephora Pierre. The experiment was conducted by utilizing seeds from red ripe berries of the cultivars Rubi and Apoata IAC-2258. After disinfecting the berries for 30 minutes by soaking in sodium hypochlorite (2% a.i.) and washing three times in distilled water and autoclaved, the embryos were removed and inoculated in a aseptic manner, in Petrri dishes with 50% MS medium with the addition of sucrose and supplemented with different of concentrations of caffeine (0.00; 0.05; 0.10; 0.15; 0.20; 0.25; 0.30 and 0.40%). The embryos were maintained in a growth room at 27±20oC and photon flow density of 13µmol.m-2.s-1 for 23 days, when shoot length, root length and seedling fresh mass were evaluated. Five days after cultivation, the percentage of radicle emission and that of cotyledons were evaluated, calculating the embryos with open cotyledons and with expanded radicles. A complete randomized experimental design was used six replications per treatment, each replicate consisting of five embryos. It follows that germination and in vitro development of embryos of Coffea arabica L. and of Coffea canephora Pierre are affected by exogenous caffeine. The detrimental effect of exogenous caffeine on Coffea embryos is greater on the radicles than on the cotyledons. Coffea arabica L. embryos are more sensitive to the negative effects of exogenous caffeine than embryos of Coffea canephora Pierre. Caffeine can contribute to the slow seed germination and slow coffee seedling development.