Qualidade fisiológica de cipselas de girassol das cultivares Helio 360 e Helio 250

Abstract

The few research papers relating to the possible advantages of acquiring sunflower cypselas of certain sizes diverge as to the results. This fact awakens interest as much on the part of researchers as on those producing seeds. So it is necessary to analyze, in laboratory and field conditions, the physiologic quality of different widths sunflower cypselas, originating from different sowing times. In chapter I, the study had as its objective the analysis of sunflower cypsela width, cultivar Helio 360, and the influence of sowing time on their physiologic quality. Sunflower cypselas were used from three sowing times (22 January, 9 and 12 July 2007). The cypselas from each sowing time were separated using sieves of different openings, according of the width (6,0; 5,5; 5,0 and 4,5 mm). Water content at 70 and 105 °C and the physiologic quality were determined by means of seedling emergence and vigor tests. Since the coefficient of variation for water content and dry matter was lower at 70 °C, it is recommended to dry the cipselas in this temperature. Cypselas with smaller width had higher water content and dry matter and lower percentage of normal seedlings than the others. In chapter II, the work had as its objective to analyze, in vegetation house and under field conditions, the influence of storage for different batches and sunflower cypselas widths of the cultivar Helio 250 (6,0; 5,5; 5,0 and 4,5 mm), on its physiological quality. Cypselas with two years of storage, derived from batch of better initial quality and smaller width, had a higher percentage and emergence speed in a greenhouse, taking sand as substrate. Upon analysis of the sunflower seedling emergency in the field, the percentage, the speed, the average speed and the average time of emergence showed interaction, being the cypselas of batch of better quality and smaller width and the batch of intermediate quality and higher width had the highest percentage and emergence speed. In both experiments, there was a reduction of up to 36,67% in the percentage of emergency for different batches, after two years of storage.