The exposition of soybean seeds to alternated cycles of high and low humidity before harvesting, due to frequent rain, dew or daily flotation of the relative humidity of the air, results in deterioration by humidity which can be pointed as the main cause for seeds low quality. Some works have made evident the existence of contrasting genotypes for seeds physiological quality. There are such differences because the presence of seeds with total or partial impermeability for water absorption by the coat that makes them less susceptible to mechanical damages, weather adversities, deterioration by humidity and pathogen occurrence. The objective of this study was to evaluate the physiological quality of seeds from genotypes CD-202 (yellow coat, permeable and susceptible to deterioration) and TP (black coat, semi-permeable and resistent to deterioration) and identify structural differences between the coats of these genotypes. The physiological quality of the seeds was obtained by germination tests and vigour (accelerated ageing and electrical conductivity). To evaluate structural differences, soybean seeds were collected at different development stages (25, 40 and 55 days after the anthesis). These samples were sent to the Laboratory of Immunology and Electronic Microscopy of Embrapa Clima Temperado, where traverse cuts in the seeds coat in ultra-microtome "Leica", with 1µm of thickness were carried out. Coats were stained with methylene blue 1% and borax 1% and visualized in optic microscope Olympus BX 51 in increase of 40x. According to the results genotype TP presented higher physiological quality in relation to genotype CD-202. Structural differences were observed between the coats of the two genotypes which may be related to physiological quality of seeds.
black coat; yellow coat; Glycine max
