El peso específico como indicador de calidad física y fisiológica en semilla certificada de arroz

the production and utilization of high quality certified rice seed (csr) are important strategies to improve the competitiveness of the venezuelan rice seed industry. official germination and purity trials do not completely evaluate overall quality of crs. this investigation evaluated specific weight of seed (sws) and percentage of field emergence (pfe) as indicators of physical and physiological quality of crs of `araure 4', `cimarron', `fonaiap 1' and `palmar' varieties. in order to determine uniformity, seed samples were immersed in a 96% solution of ammonium sulphate adjusted to six densities ranging from 31.6 to <1 g cc-1 . the associations between varieties, classes of sws, pfe and percentage of germination in the laboratory (plg), were evaluated by field and laboratory trials conducted in the facilities of the agronomy school of the central university of venezuela, located at maracay, venezuela, using a random blocks (rb) desing and a factorial arrangement for varieties and classes of sws. duncan's multiple range test was used for assessment of treatments means. results indicated the separation of eight classes of sws confirming high heterogeneity of commercial crs for all varieties. in all tests performed, always the heaviest seed class (31.6 g cc-1) represented more than 90% of total bulk of csr. also, it was remarkable that results for plg and pfe of the heaviest sws class, were consistently superior than those with sws ￡1.6 g cc-1. the quality of seed belonging to sws class 31.6 g cc-1 showed a highly deteriorated and weedy profile affecting overall quality of csr. these findings seem to justify the innovation in processing procedures, by adding equipment for densimetric analysis to up grade the current level of physical and physiological quality of the csr used by venezuela farmers.