Does Gibberellic Acid Stimulate Seed Germination via Amylase Synthesis?

Abstract

Gibbereilic acid is known to break dormancy of several types of seeds: (a) light-promoted seeds, such as Grand Rapids lettuce seed (Lactuca sativa L. var. Grand Rapids); (b) lightinhibited seeds, such as the seed of the honey-bee plant (Phacelia tanacetifolia Benth; (c) seeds requiring stratification (storage at low temperatures in a moist condition), such as the hazel nut (Corylus avellana L.); (d) seeds requiring after-ripening (storage at room temperature in dry condition), such as the wild oat (Avena fatua L.).Recent findings indicate that when dormant hazel nut seeds are soaked at 5 C for 28 days, which is a natural means of breaking dormancy, the gibberellin-synthesizing mechanism is activated and that actual synthesis of gibberellins takes place when the seeds are transferred to a suitably higher temperature. Accumulation of GA results in germination (10).It has also been suggested that in the phytochrome-controlled germination of Grand Rapids lettuce seeds, the role of Pfr is to activate GA biosynthesis (8).One biochemical reaction known to be enhanced by GA is the synthesis of hydrolases (especially a-amylase) in the endosperm of cereal grains, such as barley (2,9,13). Since starch is a major food reserve in the cereal grains, its breakdown is generally assumed to be an essential process of germination. Many writers have implied that GA stimulates seed germination via amylase synthesis (1,7,12).Drennan and Berrie (5) compared the time course of amylase development in dormant and nondormant wild oats (Avena spp.). Their results indicated that both types of seeds contained traces of amylases. When dormant seeds were soaked, there was neither germination nor a change in the level of amylases. When nondormant seeds were soaked (in water), they germinated in 4 days and from the 6th day, amylase activity increased. Thus, they concluded that buildup of amylases is a postgermination phenomenon, and a lack of amylase synthesis must be eliminated as a possible cause of dormancy.We have investigated the time course relationship of GAinduced germination and amylase development in an attempt to find out if GA-induced germination is mediated by amylase production.

Dormancy and Impotency of Cocklebur Seeds

“…Nevertheless, it is apparent that GA3 was able to cause seed germination by stimulating both the axial and cotyledonary growth, resulting in the slight increase of its abnormality (Table V). These data would support the recent view (2,(4)(5)(6) that GA3-induced biogenesis at hydrolytic enzyme may not be the primary action of GA3 in the stimulation of seed germination.…”

Early Actions of Gibberellic Acid on the Embryo and on the Endosperm of Avena fatua Seeds

“…Therefore, GA cannot stimulate germination via amylase synthesis. It was suggested that GA could act on the embryo proper (4 The intact seeds treated with 10 Mm GA synthesized less amylases than did the endosperm treated with 10 Mm GA (Table I). One might suspect that (a) less GA gets into the intact seeds, or (b) there is an inhibitor of amylase synthesis coming from the embryo.…”

“…Gibberellic acid breaks dormancy of several types of seeds (4). One biochemical reaction known to be enhanced by GA is the synthesis of hydrolases (especially a-amylase) in the endosperm of cereal grains, such as barley (3,9,12).…”

Morphological Characteristics and Germination Conditions of Seeds in Arabis pendula L.

“…본 연구에서 (Abeles, 1986;Kim et al, 2009;Kim and Lee, 2013). GA3에 의해 발아가 촉진되는 종자의 유형으로는 광발아종자, 암발아종자, 층적처리가 필요 한 종자 및 후숙이 필요한 종자 등 다양한 유형의 종자가 GA 3 에 의해 발아가 촉진되며 (Chen and Chang, 1972), GA3의 발아촉 진 효과는 예냉처리를 동시에 처리했을 때 상승하는 것으로 알 려져 있다 (Bretzloff and Pellett, 1979). …”