Edvaldo Aparecido Amaral da Silva

Classificação de sementes florestais quanto ao comportamento no armazenamento

The objective of this work was to classify seeds of forest trees regarding storage behaviour and to verify the relation between the classification proposed and the ecological groups of these species. For this study 39 species from remnants of riparian forest from the high and medium Rio Grande-MG were evaluated. The seed viability and the moisture content were obtained from seeds after cleaning; from seeds with the initial moisture content submitted to the storage with semi-permeable packing at temperature of 5oC for 90 days; and from dry seeds submitted to desiccation before and after storage in impermeable packing for 90 days at temperatures of 5oC and -18oC. The statistical analysis was performed by comparison of the overlap of the confidence intervals of the germination percentage averages for each species. The seeds were classified as orthodox and recalcitrant according to storage behavior. The seeds classified as orthodox were from the following species: Alchornea triplinervea, Anadenanthera colubrina, Aspidosperma cylindrocarpon, Aspidosperma polyneuron, Bowdichia virgilioides, Ceiba speciosa, Hymenaea courbaril, Lafoensia pacari, Lecythis pisonis, Lithraea molleoides, Maclura tinctoria, Myroxylon peruiferum, Myrsine umbellata, Rudgea viburnoides, Schinus terebinthifolius, Solanum granuloso-leprosum, Tabebuia crysotricha. The seeds that showed recalcitrant storage behaviour were from the species: Calophyllum brasiliense, Calyptranthes lucida, Cupania vernalis, Eugenia handroana, and Talauma ovata. The species classified as orthodox belonged to the ecological groups pioneer, climax light demanding to seedling growth and climax shade tolerant. The species classified as recalcitrant belonged to the ecological groups climax shade tolerant and climax light demanding.

DESICCATION TOLERANCE AND DNA INTEGRITY IN Eugenia pleurantha O. Berg. (MYRTACEAE) SEEDS 1

The aim of this study was to assess the desiccation tolerance and DNA integrity in Eugenia pleurantha seeds dehydrated to different moisture contents (MCs). Seeds extracted from mature fruits were submmited to drying in silica gel and evaluated at every five percentual points of decrease from the initial MC (35.5%, fresh weight basis). The effects of dehydration on seeds were verified through germination tests and DNA integrity assessment. Undried seeds achieved 87% germination, value reduced to 36% after being dried to 9.8% MC. When dried slightly more, to 7.4% MC, seeds were no longer able to germinate, suggesting an intermediate behavior in relation to desiccation tolerance. It was observed DNA degradation in seeds with 7.4% MC, which might have contributed to the loss of seed germination.

Avaliação da qualidade de sementes de Eugenia pleurantha (Myrtaceae) pelo teste de raios X

The X ray test is a useful tool to evaluate seed physical quality, thatt can be affected by the occurrence of empty seeds and the presence of insects and physical alterations. The objective of this study was also to investigate the efficiency of the X ray test in the evaluation of internal damage in seeds of Eugenia pleurantha, as well as to examine the consequence of this damage in the germination. Seeds of Eugenia pleurantha were placed in supports and exposed to several radiation intensities (35, 45, 50 and 60 Kvp) for 45 and 60 seconds to determine the X ray pattern. According to the anatomy visualized in the X rays, the seeds were classified as full seeds and infested seeds. The seeds were submitted to the germination test with sand as substratum placed at 30°C under continuous light. The 50 Kvp radiation intensity and a 60 second exposure to the X rays allowed clear visualization of the internal damage caused by the presence of insects in the seeds. The internal damage caused by insects prevented Eugenia pleurantha seed germination.

Classificação de sementes de espécies florestais dos gêneros Nectandra e Ocotea (Lauraceae) quanto ao comportamento no armazenamento

Studies on seed storage behaviour allow the establishment of suitable conditions to maintain seed viability, in order to support programs of ex situ conservation and seedling production. Thus, this study aimed to investigate the seed storage behavior of five species of the Lauraceae family which grow in South of Minas Gerais State, Brazil. Seeds of Nectandra grandiflora, Nectandra lanceolata, Nectandra oppositifolia, Ocotea corymbosa and Ocotea pulchella were assessed regarding germination and moisture content before and after artificial drying. The seeds show recalcitrant behaviour due to their desiccation sensitivity.

Gene expression profiling of the green seed problem in Soybean

BackgroundDue to the climate change of the past few decades, some agricultural areas in the world are now experiencing new climatic extremes. For soybean, high temperatures and drought stress can potentially lead to the “green seed problem”, which is characterized by chlorophyll retention in mature seeds and is associated with lower oil and seed quality, thus negatively impacting the production of soybean seeds.ResultsHere we show that heat and drought stress result in a “mild” stay-green phenotype and impaired expression of the STAY-GREEN 1 and STAY-GREEN 2 (D1, D2), PHEOPHORBIDASE 2 (PPH2) and NON-YELLOW COLORING 1 (NYC1_1) genes in soybean seeds of a susceptible soybean cultivar. We suggest that the higher expression of these genes in fully mature seeds of a tolerant cultivar allows these seeds to cope with stressful conditions and complete chlorophyll degradation.ConclusionsThe gene expression results obtained in this study represent a significant advance in understanding chlorophyll retention in mature soybean seeds produced under stressful conditions. This will open new research possibilities towards finding molecular markers for breeding programs to produce cultivars which are less susceptible to chlorophyll retention under the hot and dry climate conditions which are increasingly common in the largest soybean production areas of the world.

Avaliação da perda da tolerância à dessecação e da quantidade de dna nuclear em sementes de Peltophorum dubium (spreng.) taubert durante e após a germinação

The objective of this study was to investigate the loss of desiccation tolerance (DT) in seeds of Peltophorum dubium (Sprengel) Taubert, during and after germination. P. dubium seeds were sown, removed after germination when the primary root lengths reached 1, 3 and 5 mm (68% water content), dehydrated in silica gel until they had reached their initial moisture content (8%), rehydrated and evaluated for survival (resumption of growth and development of normal seedlings). This procedure was also followed in the assays during imbibition, where 4 replications of 25 seeds were subjected to 12, 24, 48, 60 and 72 hours of imbibition. Subsequently, different points were selected (12, 48 and 60 hours of imbibition and radicles 1 mm long) to evaluate the nuclear DNA content in order to relate the beginning of the cell cycle with the loss of DT. For the three radicle lengths sampled, there was no survival of seeds which had been dried and rehydrated. There was a progressive decrease in the survival of P.dubium seeds related to the imbibition period and subsequent drying and rehydration, suggesting that the loss of DT occurs early in germination before radicle protrusion. Seeds imbibed for 12, 24, 48, 60, 72 hours and germinated seeds with 1 mm long radicles showed 98%, 93%, 83%, 35%, 17% and 0% survival, respectively. The assays with the nuclear DNA content do not show any relationship between the resumption of the cell cycle and the loss of DT.

Loss of desiccation tolerance in Copaifera langsdorffii Desf. seeds during germination

This study evaluated the loss of desiccation tolerance in C. langsdorffii seeds during the germination process. Seeds were imbibed for 24, 48, 72, 96, 120 and 144 hours and dried to the initial moisture content, kept in this state for 3 days after which they were submitted to pre-humidification and rehydration. Ultraestructural evaluations were done aiming to observe the cell damage caused by the dry process. Desiccation tolerance was evaluated in terms of the percentage of normal seedlings. Seeds not submitted to the drying process presented 61% of normal seedlings, and after 24 hours of imbibition, followed by drying, the seeds presented the same percentage of survival. However, after 48 hours of imbibition, seeds started to lose the desiccation tolerance. There was twenty six percent of normal seedlings formed from seeds imbibed for 96 hours and later dried and rehydrated. Only 5% of seeds imbibed for 144 hours, dried and rehydrated formed normal seedlings. At 144 hours of imbibition followed the dry process, there was damage into the cell structure, indicating that the seeds were unable to keep the cell structure during the drying process. Copaifera langsdorffii seeds loses the desiccation tolerance at the start of Phase 2 of imbibition.

Swartzia langsdorffii Raddi: morphophysiological traits of a recalcitrant seed dispersed during the dry season

Swartzia langsdorffii seeds have recalcitrant characteristics. Nonetheless, dispersal begins in the month with the lowest precipitation in the studied region, which could lead to seed death by desiccation. Therefore, the objectives of this study were: (1) to characterize the physiological behaviour of S. langsdorffii seeds related to their desiccation sensitivity/tolerance; and (2) to assess the morphophysiological characteristics that enable the seeds to remain viable after dispersal. Fruits and seeds were subjected to biometric evaluation and the anatomical and ultrastructural features of the seeds were determined. Field assessments were performed to determine the capacity of the seeds to maintain viability and to verify the relation between seed viability, diaspore water content and environmental variables. Seeds of this species were found to be recalcitrant and showed pores distributed throughout the seed coat, and contained a large number of stomata in the hypocotyl–radicle axis epidermis. Moreover, phenolic compounds were found throughout the radicle region. Seeds remained viable in the soil for up to 7 months after dispersal without a significant decrease in water content, despite the low precipitation and soil water content. Radicle protrusion began 5 months after dispersal and coincided with partial fruit decomposition at the beginning of the rainy season. Thus, the possible microclimate created by the pericarp, with the moisture content of the aril and the soil, the presence of the structures in the axis, such as the pores and stomata, the chemical composition and the morphology of S. langsdorffii seeds could favour maintenance of their viability until the beginning of the rainy season.

Changes in gene expression during drying and imbibition of desiccation sensitive Magnolia ovata (A. St.-Hil.) spreng. seeds

Seeds of Magnolia ovata were dried to different water contents to assess the viability and transcript abundance of genes related to seed development, cell cycle, cytoskeleton and desiccation tolerance.The expression of development, cell cycle and cytoskeleton relative genes (ABI3, CDC2-like and ACT2) alone could not explain the germination behaviour of M. ovata seeds in relation to drying damage. Irrespective of their initial water content, the seeds performed in the same way during the initial period of germination and the deleterious effects of desiccation only occurred in later stages. Expression of PKABA1, sHSP17.5 and 2-Cys-PRX did not show a relationship with desiccation. However, the expression patterns of PKABA1 and sHSP17.5 suggested the participation of these genes in protective mechanisms during the imbibition of M. ovata seeds..

Variations in desiccation tolerance in seeds of Eugenia pyriformis: dispersal at different stages of maturation

Eugenia pyriformis Cambess., known locally as uvaieira, a species of fruit-bearing tree with both pharmacological and gastronomic potential, has seeds which are sensitive to desiccation. The aim of this study was to analyse whether the degree of tolerance to desiccation of uvaieira seeds depends on the stage of maturation of the seeds at shedding. This, in turn, depends on the environmental conditions in which the seeds develop, including the accumulation of degree-days and rainfall in the period. Seeds were collected from the ripe fruit of parent plants located in the states of Sao Paulo and Minas Gerais, Brazil, submitted to drying and analysed for water content and germination. A completely randomised design was used in a 20 x 3 factorial scheme (source of material x level of drying). The degree of desiccation tolerance differs between region and period of collection, even for the same parent plant when the seeds are collected in different years. The water and thermal conditions of the environment during seed development modify the maturation cycle, the physiological quality and the acquisition of desiccation tolerance. In uvaieira seeds, desiccation tolerance depends on the physiological maturity of the seeds at the time of dispersal, which is associated with the environmental conditions.