Vilma Marques Ferreira

Efeito da temperatura e da luz na germinação de sementes de Acacia polyphylla DC.

Acacia polyphylla (Leguminosae-Mimosoideae) is a typical tree species of secondary succession in Brazil, important for restoration of degraded areas. The purpose of this work was to evaluate the seed germination under different temperatures and light conditions. Constant (15, 20, 25 and 30 oC) and alternating (20-30 oC) temperatures were evaluated, at an eight hours photoperiod under white light. Constant temperature of 25 oC was optimal and the light experiments were conducted at that temperature. Seeds were incubated in darkness and at photoperiods from 1 to 12 hours under white light (high red/far-red ratio), as well as at photoperiods under white light initiated and concluded with shade light (low red/far-red ratio). Germination percentage was not affected by the photoperiods under white light tested, but a photoperiod similar or higher than four hours was required for better initial seedling growth. Both germination percentage and speed was not affected by light of a low red/far-red ratio, but they decreased in darkness.

Trocas gasosas e fluorescência da clorofila a em variedades de cana-de-açúcar submetidas à deficiência hídrica

Water stress affects a great part of the worlds agriculture. Thus, this work was conducted to evaluate photosynthetic traits in four varieties of sugarcane (SP79-1011, RB72454, RB98710 and RB92579) submitted to water stress during the early stage of the vegetative period. The plants were cultivated in plastic pots (15 kg of soil). The study was a factorial (4 varieties x 3 levels of soil water content based on available water capacity (AWC)), in a completely randomized design with 5 replications. The levels of water content in the soil were as follows: control (80 to 100% of AWC), moderate water stress (40 to 60% of AWC) and severe water stress (0 to 20% of AWC). Water stress provoked a significant reduction in stomatic condutance (gs), foliar transpiration (E), net photosynthesis (A) and in the water use efficiency of production (WUEy), irrespective of varieties. The varieties SP79-1011 and RB98710 showed greater stomatal sensitivity, reducing gs and E by the 71 days after the beginning of the water stress treatments, even in the control. However, under such conditions A was little affected, indicating that the plants are capable to fixing CO2 with stomata partially closed. Water stress caused a small reduction in the potential photochemical efficiency (Fv/Fm ratio) in the studied varieties.

Photosynthesis and Water Relations in Brazilian Sugarcane

The expansion of sugarcane (Saccharum spp.) in Brazil has been boosted by the growing demand for bio-fuels all over the world and requires the occupation of new agricultural areas, including regions with unfavorable agro-climatic conditions. This observational study makes an analysis of the relationship between stomatal conductance, gas exchange and photosynthesis in sugarcane fields subject to different ambient conditions and growth phases. It was noted that the stomatal conductance had a much higher control on photosynthesis than on transpiration. Even under high stomatal con- ductance, photosynthesis maintained a high correlation to it. Sugarcane had an instantaneous water use efficiency of ap- proximately 4.4 μmol of fixed CO2 for each mmol of H20 expended in transpiration. Lower leaf water potential, besides leading to an internal reduction of CO2, also reduced the instantaneous carboxylation efficiency, indicating that the photo- synthesis apparatus was also affected. The variety RB92579, seems to have good water absorption system, because even under low leaf water potential, it maintained a good stomatal conductance, with a higher transpiration and photosynthesis than the others varieties. These results suggest that this variety has a tolerance mechanism to endure rather than avoid drought.

Caracterização morfológica de frutos e sementes e desenvolvimento pós-seminal de monjoleiro (Acacia polyphylla DC.)

Acacia polyphylla DC. is a typical tree species of the initial stage of the secondary succession, recommended for restoring degraded areas. However, it was not found any reference that mentioned the chemical components, morphological aspects, as well as the aspects of the post-seminal development of this species. The objective of the present work was to characterize and to illustrate fruits and seeds and to quantify some present chemical components in the seeds and accompanying the different stages of the seedling development. The morphological descriptions of the fruits and seeds were done in relation to the form, size, surface, micropile and shape and position of the embryo. For the morphological description of the seedlings, the seeds were placed to germinate in Murashige & Skoog and incubated at 25oC. All germination stages were observed and both normal and abnormal seedlings were described and illustrated. The fruit is a dehiscente legume and contains from eight to 16 flat seeds, with testal coat: embryo axial and invaginated. The germination of seeds is epigeal and the seedlings are phanerocotyledonarious.

Temperaturas cardeais e efeito da luz na germinação de sementes de mutamba

Guazuma ulmifolia Lam., conhecida como mutamba, e uma especie arborea caracteristica dos estadios iniciais da sucessao secundaria, com ampla ocorrencia natural no Brasil. Possui grande potencial para recuperacao ambiental de areas degradadas. Neste trabalho, conduziram-se dois experimentos, nos quais as sementes foram extraidas e escarificadas antes da instalacao dos testes de germinacao. O primeiro experimento foi desenvolvido com sementes colhidas em outubro de 1995 e teve por objetivo definir as temperaturas cardeais para a germinacao das sementes. Foram testadas as temperaturas de 10, 15, 20, 25, 30, 35, 40 e 45 oC, sob fotoperiodo de oito horas. Os resultados mostraram que a temperatura minima e proxima de 10 oC, a maxima se situa entre 35 e 40 oC e as temperaturas de 25 e 30 oC encontram-se dentro da faixa otima. No segundo experimento, visou-se avaliar o requerimento fotoblastico de sementes recem-colhidas (colheita de outubro de 1996) e armazenadas em câmara seca por um ano (colheita de outubro de 1995). Os testes de germinacao foram conduzidos a 30 oC e as sementes recem-colhidas tiveram a germinacao promovida pelas luzes branca e vermelha, mas inibida pela luz vermelha-extrema e ausencia de luz. As sementes armazenadas, entretanto, revelaram-se insensiveis a luz.

Armazenamento e requerimento fotoblástico de sementes de Acacia polyphylla DC

Acacia polyphylla (Mimosaceae) is a native tree species in Brazil, important for restoration of degraded areas. Seeds of this species were stored under both natural and artificial conditions, to evaluate the seed longevity in soil, conserve the seed physiological quality for two years and verify the photoblastic requirement of stored seeds. Under natural conditions, seeds were buried in light gap and under both thin and closed canopies. Under these conditions, fast deterioration was found and seeds were unable to compose the soil seed bank. Under artificial conditions, seeds were packaged in different containers and stored at both room temperature and in a cold chamber for two years. Periodically, seeds were incubated at 25oC in darkness and under an eight hours photoperiod of both white light (high red-far red ratio) and shade light (low red-far red ratio). During the storage period, germination in darkness was lower than under either white or shade lights. Physiological quality was maintained for two years when seeds were packaged in an impermeable container and stored in a cold chamber. Germinative behaviour of the seeds stored for two years was compared with that of the fresh seeds, at both constant and alternating temperatures, and no effect of either seed age or temperature regime on the photoblastic requirement of the seeds was detected.

Sugars levels of four sugarcane genotypes in different stem portions during the maturation phase

Maturation is a characteristic of sugarcane plant (Saccharum spp.) and even when grown under the same soil and climate conditions the varieties differ on the maturation curve. Thus, studies that allow establishing maturation curves of different sugarcane genotypes in the local soil and climate may indicate the proper harvesting period to ensure better quality of the raw material. This study aimed to analyze the levels of soluble sugars during the maturation phase and assess the technological and productivity indexes of four irrigated sugarcane genotypes in the region of Rio Largo, Alagoas. The experiment was conducted in randomized blocks in a 4 x 2 x 5 factorial: four genotypes (RB92579, RB98710, RB99395 and RB961003), two stem portions (internodes 1-4 and internodes 5-8) and five seasons (82, 49, 25, 13 and 3 days before harvesting), each treatment with three replications. Internodes 1-4 showed the highest levels of reducing sugars, while the largest accumulation of sucrose and total soluble solids occurred in internodes 5-8. RB99395 genotype showed more stability in the sugar levels during sugarcane maturation, which can indicate early maturation and high agricultural yield.

Morphological and photosynthetic adaptations of Tabebuia aurea seedlings in the nursery

Tabebuia aurea (Benth. & Hook. f. ex S. Moore) (Bignoniaceae) is a boreal species common in Brazil. It is used for ornamental parks and along sidewalks. Its timber is also used for furniture. The objective of this study was to evaluate the effect of nursery shading on the growth and photosynthesis of T. aurea and their photosynthetic adaptation after being transferred to direct sunlight. The T. aurea seedlings were grown under 0, 50, 70 or 95% shade. The photosynthetic active radiation and leaf gas exchange were measured over two distinct periods: 51 (young seedlings) and 70 days after having been sown under each shade treatment. Immediately after the measurements were taken, the seedlings were transferred into full sunlight and the measurements were repeated two times after 15 min and 3 days under ambient sunlight. T. aurea seedlings showed satisfactory growth up to 50% shade in the nursery, which could be verified both by growth measurement and by total biomass accumulation. Shading greater than 70% reduced the number of leaves, the leaf area and the stem diameter in relation to plants exposed to full sunlight. The results suggest that T. aurea seedlings should be grown under full sunlight or under shading up to 50% to maximize their growth in the nursery and to minimize stress when transferring the seedlings to their final planting sites.

Caracterização morfométrica de sementes e plântulas e germinação de Anadenanthera macrocarpa (Benth.) Brenan

Anadenanthera macrocarpa (Benth.) Brenan is a tree species belonging to the family LeguminosaeMimosoideae which is popularly known as mimosa-black. It features characteristics of early successional, natural occurrence in Brazil and can form clusters almost homogeneous, with great potential in the recovery of degraded areas. This study was conducted at the Center for Agricultural Sciences, University Federal of Alagoas state, aiming at the physical and morphological characterization of seeds, describing the various stages of post-seminal development, and to evaluate various conditions of temperature and substrate to perform the test germination. The seeds were manually extracted, then homogenized, where two samples of 50 seeds were used to determine the initial moisture. Another sample, consisting of eight repetitions of 100 seeds was used to measure the biometry and the number of seeds per fruit. The morphological

CARACTERIZAÇÃO MORFOMÉTRICA, GERMINAÇÃO E CONSERVAÇÃO DE SEMENTES DE Triplaris brasiliana CHAM. (POLYGONACEAE)

The objective of this study was to characterize morphometrically seeds, evaluate the treatments of scarification, and germination temperatures and the potential seed storage Triplaris Brasiliana Cham., a pioneer species, with great potential for recovery of degraded areas, permanent preservation, riparian areas and land. For the morphometric characterization, it was determined the length and thickness, mass of 1000 seeds, color, shape and hilum and micropyle location, such embryos, the location and type of germination. The germination test was evaluated from seeds with and without scarification at different temperatures. The storage was tested in glass and paper packaging and in refrigerator, dry chamber and ambient conditions. The embryo is axial, and the embryonic axis in the central part of the seed of the lower half, the germination is epigeal and the seedlings are fanerocotylar. Sowing the seeds scarified on paper subjected to 30 °C were more favorable for germination and development of Triplaris brasiliana seedlings, and seeds sensitive to dehydration (intermediate), while preserving physiological quality for longer when stored in the refrigerator and camera in the packages used.