Aplicação do teste de raios x no estudo da morfologia interna e da qualidade fisiológica de aquênios de arnica (Lychnophora pinaster Mart.)

Abstract

The X-ray test is used in seed quality programs to assist morphological and physiological evaluations. Arnica (Lychnophora pinaster Mart.) is considered a medicinal species that has a remarkable number of badly formed seeds at the time of fruit dispersion. Thus, the objective of this study was to verify the influence of the maturation stages on the physiological quality of Arnica seeds by the X-ray test. The seeds used were collected in December 2003 from a natural population in the district of Itumirim, State of Minas Gerais, Brazil. At seed collection the following were considered: the capitulum in which the seeds showed jointed internal papus, less mature stage, without internal papus and seeds that were dispersing. After collection the seeds were dried, cleaning and separated with a vertical blower. The seeds were placed in acrylic transparent plates, radiographed and separated into three categories, full, badly formed and empty seeds according to the internal morphology observed on the radiographs. The time and intensity used during the X-ray test were previously tested. Four replications of 50 seeds for each treatment were used. The seeds were placed in a gerbox on paper towel and kept for 90 days in an incubator (BOD) adjusted at alternating temperature (20-30ºC) and 12-hour photoperiod. The parameters evaluated were speed of germination and final germination percentage. The remaining seeds were subjected to the tetrazolium test to verify seed viability. The X-ray test was shown to be effective for separating the seeds into categories based on their internal morphology. The radiation of 30Kv for 45 seconds allowed visualization of the internal structures of the seeds. The capitulum maturation stage with seeds without internal papus at the time of dispersion was the best for seed collection.