Aspectos físicos e fisiológicos de sementes de Fimbristylis dicothoma relacionados à germinação e dormência

Abstract

In the seeds of pioneer plants, the application of treatments for breaking dormancy, and selection by colour and size, are strategies for obtaining seeds of less dormancy and better germination performance. The aim of this study was to evaluate the effect of the physical and physiological aspects of seeds of the tall fringe-rush (Fimbristylis dichotoma) on germination and dormancy. To do this, the seeds were submitted to the following treatments in three studies: (i) control, immersion in H<inf>2</inf>SO<inf>4</inf> (98%, 36N) for 1 minute, immersion in KNO<inf>3</inf> (1, 2 and 3%) for 15 minutes, seeding on a substrate moistened with KNO<inf>3</inf> (0.2%) and exposure for 5 and 10 hours in a forced air circulation oven at 40 and 70 °C; (ii) classification of the seeds by colour (light and dark) and application of the following treatments: control, immersion of the seeds in H<inf>2</inf>SO<inf>4</inf> (98%, 36N) for 1 and 2 minutes, immersion in KNO3 (5% and 10%) for 15 and 30 minutes and seeding on a substrate moistened with KNO<inf>3</inf> (0.2%); (iii) classification by size (0.60, 0.50 and 0.40 mm) and germination on a substrate moistened with KNO<inf>3</inf> (0.2%) or distilled H<inf>2</inf>O. The seeds were evaluated by germination test, first count and germination speed index. Moistening the substrate with KNO<inf>3</inf> (0.2%), and heat treatment at 40 °C for 10 hours improve performance in seeds of the tall fringe-rush. Light-coloured seeds do not display dormancy. Mediumsized seeds of the tall fringe-rush show better performance in terms of percentage and speed of germination.