Role of Abscisic Acid in Seed Dormancy

Abstract

Seed dormancy is an adaptive trait that improves survival of the next generation by optimizing the distribution of germination over time. The agricultural and forest industries rely on seeds that exhibit high rates of germination and vigorous, synchronous growth after germination; hence dormancy is sometimes considered an undesirable trait. The forest industry encounters problems with the pronounced dormancy of some conifer seeds, a feature that can lead to non-uniform germination and poor seedling vigor. In cereal crops, an optimum balance is most sought after; some dormancy at harvest is favored because it prevents germination of the physiologically mature grain in the head prior to harvest (that is, preharvest sprouting), a phenomenon that leads to considerable damage to grain quality and is especially prominent in cool moist environments. The sesquiterpene abscisic acid (ABA) regulates key events during seed formation, such as the deposition of storage reserves, prevention of precocious germination, acquisition of desiccation tolerance, and induction of primary dormancy. Its regulatory role is achieved in part by cross-talk with other hormones and their associated signaling networks, via mechanisms that are largely unknown. Quantitative genetics and functional genomics approaches will contribute to the elucidation of genes and proteins that control seed dormancy and germination, including components of the ABA signal transduction pathway. Dynamic changes in ABA biosynthesis and catabolism elicit hormone-signaling changes that affect downstream gene expression and thereby regulate critical checkpoints at the transitions from dormancy to germination and from germination to growth. Some of the recent developments in these areas are discussed.

Potencial de inibição da regeneração de raízes e plântulas em sementes germinantes de Eugenia pyriformis

“…Porém, pouca atenção tem sido dada aos inibidores. Processos que tenham a participação do ácido abscísico, por exemplo, reconhecidamente um dos inibidores mais importantes em diversos processos vegetais, necessitam ainda ser elucidados, tais como o transporte dentro e entre tecidos da semente (Weyers & Paterson, 2001;Kermode, 2005) Nas sementes não germinantes, 18% das pequenas e 24% das grandes tiveram formação de uma plântula normal na região central, em posição oposta à incisão (categoria II, Figura 2 C), sem formação de uma segunda raiz. Isso pode ser decorrente do fato de que a germinação iniciada na região central, próxima à incisão, permitiu distribuição uniforme de potenciais inibidores por toda a semente.…”

Maturação de sementes de abobrinha menina brasileira

“…Provavelmente, um dos possíveis fatores que atuaram impedindo a germinação das sementes aos 20 DAA, foi à presença de inibidores, como o ácido abscísico, que em grandes concentrações, impede a germinação precoce das sementes favorecendo o acúmulo de suas reservas, assim como a imaturidade do embrião (Kermode, 2005;Marion-Poll, 1997). Vidigal et al (2009) (Vidigal et al, 2009).…”

Seed Dormancy at Molecular Level

“…Several lines of evidence have established that abscisic acid (ABA) induces dormancy during embryo maturation (reviewed in Feurtado and Kermode 2007, Finch-Savage, 2006, Kermode, 2005. In particular, the balance between the levels of ABA and GA hormones and their respective signalling pathways are important in regulating both induction and maintenance of dormancy, and promotion of germination.…”