Seed moisture content can be used to accelerate dormancy release during after-ripening of Urochloa humidicola cv. Llanero spikelets/Uso do teor de agua em sementes para acelerar a quebra de dormencia pos-colheita de cariopses de Urochloa humidicola cv. Llanero

• Published in: Ciência rural 2021-01, Vol.51 (1), p.1
• Main Authors: Abrantes, Fabiana Lima, Machado-Neto, Nelson Barbosa, Custódio, Ceci Castilho
• Format: Article
• Language: English
• ISSN: 0103-8478
• DOI: 10.1590/0103-8478cr20200526

Increased demand for livestock products is leading to research on more productive pastures adapted to different environments. Urochloa humidicola is a species adapted to low-fertility conditions and to environments occasionally subjected to temporary flooding and with highly dormant seeds at harvest. Mechanical and sulphuric acid ([H.sub.2]S[O.sub.4) scarification are used to release these seeds from dormancy; although, there are several side effects. Hydrogen peroxide ([H.sub.2][O.sub.2]) is linked to dormancy release in many crop species. The objective of this research was to characterize the dormancy release and [H.sub.2][O.sub.2] accumulation during one year of storage in dormant spikelets of U. humidicola cv. Llanero equilibrated to 4.5% and 50% relative humidity (RH) and stored at 20 [degrees]C, during which time the seeds had moisture contents (MCs) of 0.03 and 0.1 g [H.sub.2]O [g.sup.1] dry weight (DW), respectively. The seeds were evaluated initially and at 3, 6 and 12 months; the seeds from spikelets or just caryopses were evaluated. Germination and dormancy percentage, [H.sub.2][O.sub.2] content, superoxide dismutase (SOD) and peroxidase (PRX) activity were determined. The germination and [H.sub.2][O.sub.2] content increased mainly in the caryopses, and SOD activity increased. Moreover, dormancy and PRX activity decreased during storage. For the first time, it was shown, in U. humidicola cv. Llanero that dormancy release during storage is caused mainly by the accumulation of reactive oxygen species (ROS) in the spikelets even under ultra-dry storage conditions (4.5% RH), and this process could be accelerated by seed storage at a MC of 0.1 g [H.sub.2]O [g.sup.1] DW at 20 [degrees]C. Key words: Brachiaria, germination, oxidative window, ultra-dry storage, ROS. O aumento da demanda de produtos cárneos tem levado a pesquisas de pastagens mais adaptadas para diferentes ambientes. Urochloa humidicola é uma espécie adaptada a solos de baixa fertilidade e sujeitos a alagamentos ocasionais e que apresentam um alto grau de dormência por ocasião da colheita. Escarificação mecânica e por ácido sulfúrico são normalmente usadas para quebrar a dormência nesta espécie, porém com diversos efeitos colaterais. Peróxido de hidrogênio ([H.sub.2][O.sub.2]) está ligado à quebra de dormência em diversas culturas. O objetivo deste trabalho foi caracterizar a perda de dormência e o acúmulo de [H.sub.2][O.sub.2] durante um ano de armazenamento em espiguetas dormentes de U