Leila Martins

Sulphuric acid scarification effects on Brachiaria brizantha, B. humidicola and Panicum maximum seed dormancy release

3 ABSTRACT - Most tropical forage grass species have dormant seeds, which reduce percentages in germination tests. The objective of this study was to evaluate H 2 SO 4 scarification effects on seed dormancy releasing, through germination time (T 50 ) and variability among germination test replicates, in 630, 94 and 82 seed samples of B. brizantha, B. humidicola and P. maximum, respectively, tested at the Central Seed Testing Laboratory, Campinas, Brazil, from 1991 to 1999. Germination tests used two 4 x 100 replicates of intact and scarified seeds (15-, 10-, 5-minute treatments, respectively). Mean germination time (T 50 ) and variability among germination replicates were also analysed. Statistical analysis was performed by t-test paired samples for means. Scarification promoted general decreases in T 50 , while variability among germination test replicates was reduced in B. brizantha. Scarification increase germination in B. brizantha and P. maximum, but is deleterious in B. humidicola.

Germinação de sementes e desenvolvimento inicial de plântulas de achachairu

The achachairu (Garcinia sp), a fruit widely grown in Bolivia, has been commercialized in Brazil for many years. The fruit is globular-oblong shaped, with a white succulent pulp, mucilaginous texture and a well balanced sweet-acid flavor (oBrix 15; pH 4.1). Due to the increasing interest in its cultivation in Brazil, this work was carried out aiming to study the seeds germination and seedling development throughout the first 12 months after seed emergence. The seeds, after being extracted from full ripe fruits were placed in a B.O.D. type chamber, under the following temperatures: 25, 30, 20-30 oC, as well as under room temperature (25±2 oC). The best result was given by the steady temperature of 30oC, with a germination of 92% and a germination speed index (GSI) of 0,255. At room temperature, seeds germination was low (30%), with a GSI of 0,015. Seedling development at greenhouse conditions was very slow mainly throughout the first weeks post emergence. The first pair of leaves appeared 25 days after seedling emergence, when seedlings averaged 8cm. From the eighth month on, many lateral branches were burst out, from the seedling medial portion towards the apical one.

Preservation of Tabebuia chrysotricha seeds as a function of seed water content and storage temperature

O ipe-amarelo (Tabebuia chrysotricha (Mart. ex A. DC.) Standl.) e uma especie arborea de alto valor ecologico, economico e paisagistico. Suas sementes apresentam variacao significativa na qualidade durante o armazenamento, o que representa dificuldades no desenvolvimento de tecnicas de propagacao. O objetivo desta pesquisa foi estudar o comportamento fisiologico das sementes de ipe-amarelo durante o armazenamento atraves de variacoes no teor de agua das sementes e na temperatura do ambiente. Frutos colhidos manualmente de plantas matrizes foram colocados para secagem e posterior extracao das sementes. Primeiramente, foi determinado o teor de agua inicial do lote e, paralelamente, obtida a porcao com o maior teor de agua a ser estudado (21,1%). Em seguida, as sementes remanescentes foram submetidas a secagem, em secador com circulacao forcada de ar a 28 ± 2oC, por diferentes periodos, obtendo-se teores de agua de 15,9, 13,6, 11,9 e 8,5%. As porcoes correspondentes aos diferentes teores de agua foram armazenadas a -12, 10 e 20oC. No inicio e a cada 30 dias ate 270 dias de armazenamento, as sementes foram submetidas as avaliacoes de teor de agua, germinacao, emergencia, velocidade de emergencia e comprimento da parte aerea. O mais alto e o mais baixo teor de agua estudado (21,1% e 8,5%) sao prejudiciais a qualidade fisiologica das sementes mesmo a temperatura extremamente baixa (-12oC) de armazenamento. A conservacao das sementes de ipe-amarelo (Tabebuia chrysotricha) e favorecida quando armazenadas com teor de agua em torno de 11,9% nas temperaturas de 10 e -12oC.

Efeitos imediatos e latentes de tratamentos térmico e químico em sementes de Brachiaria brizantha cultivar Marandu

The objective of this research was to study the effects of thermal and chemical treatments on Brachiaria brizantha cv. Marandu seeds, particularly in relation to dormancy. Seeds presenting dormancy indices higher than 25% and physical purity above 98% were submitted to temperatures of 65, 70, 75 and 80 °C for periods of 5, 10 and 15 hours and to immersion in sulphuric acid (98%, 36N) for 15 minutes. At the beginning and at the end of six months storage under uncontrolled laboratory conditions, seeds were evaluated in relation to germination, tetrazolium (viability), first count of germination, seedling shoot lenght, seedling emergence and speed of emergence index. Some specific thermal treatments showed positive effects similar to sulphuric acid treatment in reducing seed dormancy without causing latent physiological deterioration; 70°C/15h was the best thermal treatment to dormancy reduction in cv. Marandu.

ARMAZENAMENTO DE SEMENTES DE IPÊ-BRANCO: TEOR DE ÁGUA E TEMPERATURA DO AMBIENTE

Tabebuia roseo-alba is a tree species largely used in restoration of degraded diverse plant communities and permanent preservation areas, general landscaping and as wood building material. Its seeds present strong variation in quality during storage and also a short period of viability, which hampers its natural dispersal as well as the development of cropping techniques for this tree. Aiming to obtain some informations related to seed preservation, the objective of this research was to study the physiological performance of Tabebuia roseo-alba seeds during storage. Mature fruits were hand collected from mother trees and placed under shade for a short period of natural drying in order to allow easy seed removal. Soon after that, the seed moisture content was determined and a representative portion of the seed lot was removed to constitute the highest moisture level to be studied, which was 10.1%. The remaining seeds were then submitted to drying at 25 °C inside a glass desiccator containing silica gel (anhydrous calcium chloride) in order to obtain 8,3% moisture degree. The two portions, after being divided into five replications, were stored in chambers at 10, 20, and -20 °C. At the beginning (freshly collected seeds) and at 60, 120, 180, 240, 300 and 360 days of storage, the seeds were submitted to the following physiological evaluations: germination, seedling emergence, speed of emergence, and length of the above ground seedling part (hypocotyl). The experiment was a completely randomized design, with two treatments (degrees of moisture) at the beginning of storage and six treatments (2 moisture levels x 3 thermal conditions), in each evaluation period, during storage. Means were compared by the Tukey test at 5%. The preservation of Tabebuia roseo-alba seeds, considering the moisture contents of 10.1% and 8,3%, is favored by storage temperatures of 10 and -20 °C.

Conservação de semente de Cedrela fissilis: teor de água da semente e temperatura do ambiente

The objective of this research was to study the physiological performance of Cedrela fissilis Vellozo seeds during storage in relation to variations in seed moisture content and storage temperature. Mature fruits were hand harvested from selected trees and placed under shade to complete the drying process to allow easy seed extraction from the naturally opened fruits. The initial moisture content of the seed lot was determined and a sample was drawn to represent the highest moisture content to be studied (16,3 %). Following that, the remaining seeds were dried in a forced air dryer at 30o C to obtain the other desired moisture contents (12.4 %, 8.1 % and 4.5 %). The samples corresponding to the different levels of moisture were stored inside chambers set at 10 and 20o C. At the beginning and at 40, 120, 200, 280, and 360 days of storage, seeds were submitted to the following physiological evaluations: germination, emergence and hypocotyl length. A 4 x 2 factorial in a completely random design was used involving four treatments (moisture contents) at the beginning of storage, and eight treatments (4 moisture contents x 2 thermal conditions) at all other storage times. Mean comparison was made by the Tukey test at 5 %. Cedrela fissilis seed preservation, considering the 16.3 % to 4.5 % moisture content interval, is favored by moisture contents between 12.4 % and 4.5 %, at temperatures of 20 and 10o C.

Conservação de sementes de maracujá-amarelo (Passiflora edulis Sims f. flavicarpa Deg.)

Employing variations in seed moisture content and ambient temperature, this research aimed to study the performance of yellow passion fruit (Passiflora edulis Sims f. flavicarpa Deg.) seeds during storage. To do so, the seeds, once extracted from the fruits, were subjected to a turbulent water flow followed by hand rubbing on a wire mesh screen during washing under tap water, in order to remove the mucilage. After elimination of the water from the seed surface through shade drying, a treatment was obtained which consisted of seeds with 26% moisture content. The remaining seeds were submited to oven drying to obtain the other treatments (20, 14, 10 and 8% H2O). The seeds, packaged in polyethylene bags, were stored in a controlled temperature environment at 10 and 20oC; at the beginning and after 35, 70, 105, 140, 175, 210, 245, 280 and 315 days of storage, seeds were evaluated in relation to quality. The preservation of the seeds, considering the storage intervals, is favored by the combination of 10% moisture content with 20oC temperature. On the other hand, the physiological performance showed some random variations with time of storage, suggesting dormancy effects. However, the observed recurrency and ramdomness of this effect, without evident ambient interferences, are not supported by the phenomenology attributed to dormancy by the specialized literature; thus, the subject requires further specific investigations.

Teste de raios X para avaliação do potencial fisiológico de sementes de ipê-roxo

The use of seeds with a high physiological potential is essential to guarantee proper field establishment and seedling development. Several techniques have been used to evaluate seed quality including the X-ray test. The objective of this study was to evaluate the physiological potential of Tabebuia heptaphylla seeds with X-ray and germination tests after grading by color and size. Seeds were classified using the Munsell color chart and screens, in light-yellow larger, light-yellow smaller, dark-yellow larger, dark-yellow smaller, mixture of light-yellow larger, light-yellow smaller and dark-yellow larger and control. Seeds from different fractions were then submitted to X-ray and germination tests. The experimental design was completely randomized with six treatments and five replicationsand mean values were compared by the Scott-Knott test (< 5%). Results showed that the X - ray test effectively evaluates the internal morphology of Tabebuia heptaphylla seeds and its relationship with physiological potential. Seed color and size affect the physiological potential of Tabebuia heptaphyla seeds.

Interpretação de dados obtidos em testes de vigor para a comparação qualitativa entre lotes de sementes de milho

The objective of this research was to study, using corn seed lots, the possibility of establishing relations between vigor data obtained in the laboratory with those observed in the field. To do so, twenty eight corn seed lots (treatments) of the Al Bandeirante open-pollinated variety were standardized regarding seed moisture content, width, length and germination. Afterwards, seed vigor tests were conducted in the laboratory (group A: modified cool germination test; accelerated aging; germination under variations in water availability; radicle, shoot and seedling length under variations in water availability) and in the field (group B: seedling emergence). In order to compare means the 5% Tukey test was used; in addition, the seed lots were assigned points according to a ranking order of performance observed in each evaluation, following criteria of absolute and statistical classifications, so to group them in order of performance in the A and B test groups. Interpretation of vigor data resulting from a group of tests acquires a complexity directly proportional to the number of tests and lots being compared. In this way, the use of absolute classification surpasses the statistical classification in the tasks of qualitatively ranking corn seed lots according to their general performance and, in addition, quantifies the relationship among the responses observed in the laboratory with those obtained in the field

Conservação de sementes de ipê-roxo

The objective of this research was to study the physiological performance of Tabebuia heptaphylla (Vell.) Toledo seeds during storage. Fruits from 15 mother plants were hand picked and placed under shade to finish drying and to ease further manual extraction of seeds. Firstly, the initial moisture content of the seeds was determined, which was 15.6%. Following that, the remaining seeds were submitted to drying at ambient temperature inside a glass desicator in order to obtain the other desired moisture contents (11.5, 8.1 and 4.3%). The samples, corresponding to the different moisture contents were stored inside chambers at temperatures of 10, 20 and -196 °C. At the beginning and after 120, 240 and 360 days of storage, the seeds were submitted to several physiological evaluations. The experiment was a factorial, in a completely randomized design, with 4 treatments (moisture contents) at beginning of storage and 12 treatments (4 moisture contents x 3 thermal conditions), in each evaluation date, during storage. Mean comparison was made by the Tukey test at 5%. It was concluded that the preservation of Tabebuia heptaphylla seeds, at water contents 15.6, 11.5, 8.1 and 4,3% is favored by temperatures from 10 and -196 °C.