Effect of storage temperature on the dormancy release pattern of sunflower (Helianthus annuus l.) achenes

PAULA BODRONE; DIEGO BATLLA; SEBASTIAN ARISNABARRETA; MARIA VERONICA RODRIGUEZ; ROBERTO LUIS BENECH-ARNOLD

Salvador de Bahia

Congreso; 10 Conference of the International Society for Seed Science-Seed Science in the 21 Century; 2011

The aim of the present work was to investigate the effect of storage temperature on the dormancy release pattern of sunflower achenes, and to estimate in which proportion changes in dormancy level in response to temperature were associated to changes in embryo and/or coat imposed dormancy (pericarp and seed coat). Also, it was evaluated to what extent observed changes in dormancy level were related to changes in achenes sensitivity to abscisic acid (ABA), in embryo ABA content, and/or embryo ABA synthesis capacity. To achieve these objectives recently harvested sunflower achenes showing a relative dormant state were stored under dry conditions at two contrasting temperatures 5 and 25 ºC. At different time intervals during storage achenes were exposed to different tests: 1-germination of achenes at 11ºC and 25ºC, and embryos at 11ºC, 2-germination of achenes and embryos under mediums containing water, Fluridone (an inhibitor of ABA synthesis) and mixtures of Fluridone and different doses of ABA and 3-the ABA content of embryo and cotyledons was measured after incubation of achenes in water for 0, 15 and 14 hs. Obtained results showed that higher storage temperatures (25º C) accelerated the loss of primary dormancy in sunflower achenes compared with that observed for achenes stored at low temperatures (5 º C), and that the higher level of dormancy observed in achenes stored at 5ºC was mainly explained by a higher embryo dormancy than that in embryos of achene stored at 25ºC. This slower dormancy release rate observed at low storage temperature was associated to higher embryo sensitivity to ABA, a higher embryo and cotyledons ABA content and a higher embryo capacity of ABA synthesis in seeds stored at 5ºC compared with that presented by embryos of achenes stored at 25 º C.