Seed Dormancy and Germination

Abstract

Seed dormancy allows seeds to overcome periods that are unfavourable for seedling established and is therefore important for plant ecology and agriculture. Several processes are known to be involved in the induction of dormancy and in the switch from the dormant to the germinating state. The role of plant hormones, the different tissues and genes involved, including newly identified genes in dormancy and germination are described in this chapter, as well as the use transcriptome, proteome and metabolome analyses to study these mechanistically not well understood processes. of 18 The Arabidopsis BookFinch-Savage and Leubner-Metzger, 2006). Dormancy in Arabidopsis should be described as physiologically non-deep, meaning that embryos released from surrounding structures grow normally, and that dormancy is lost through moist chilling (stratification) or after-ripening (Baskin and Baskin, 2004). However, in addition to the testa and endosperm layer surrounding the embryo, the growth potential of the embryo is also important to overcome the constraint of these structures and thereby affects the dormancy state of a seed (Kucera et al., 2006). Since dormancy is regulated at different developmental phases, in interaction with environmental factors, it is difficult to detect when the genetic and physiological differences are established. This difficulty arises because all dormancy assays are based on seed germination, which is the result of the balance between the degree of dormancy and the capacity of the embryo to overcome dormancy. Mechanistically one can distinguish factors that influence dormancy and germination on the basis of their effect on germination, being either inhibiting or promoting. Mutants that germinate better or faster can represent genes that promote dormancy or those that repress germination. A further distinction can be made by defining the timing and site of action of these factors (during maturation or during imbibition of the seeds, in the embryo, the endosperm or in the testa). The interaction between these factors and the large effect of the environment, both during seed development and during imbibition, make seed dormancy a very complex trait.By definition, germination incorporates those events that commence with the uptake of water by the quiescent dry seed and terminates with the elongation of the embryonic axis (Bewley and Black, 1994). Water uptake by a seed is triphasic; phase I rapid initial uptake; phase II plateau phase and in phase III further increase of water uptake, however, only when germination occurs (Schopfer and Plachy, 1984; Bewley, 1997;Manz et al., 2005). The first signs of germination are the resumption of essential processes, including transcription, translation and DNA repair followed by cell-elongation and eventually at the time of radicle protrusion, resumption of cell division (Barroco et al., 2005;Masubelele et al., 2005). Physically germination is a two-stage process, where testa rupture is followed by endosperm rupture. Following rupture of the micropylar endosper...

Molecular identification of a major quantitative trait locus, qLTG3–1 , controlling low-temperature germinability in rice

“…A model system of seed germination and dormancy was proposed from biochemical and molecular information using dicot plants. Germination is determined by the balance between the growth potential of the embryo and the mechanical resistance of the tissues covering the embryo (26)(27)(28)(29). However, the mechanistic basis of the effect of the genes encoding cell wall proteins and hydrolases on seed germination is not well understood.…”

Screening of Sesbania accessions based on seed germination and seedling biomass

“…The higher seed germination (%) is a good syndrome for quality seeds and produces a maximum number of healthy plant populations in the field. It may be occurred due to less seed dormancy and/or genetic effects of collected Sesbania accessions (Bentsink and Koornneef, 2008). The highest emergence and germination percentage of seeds will produce optimum plant population when seeds are sown in the field.…”

Endogenous Quantification of Abscisic Acid and Indole-3-Acetic Acid in Somatic and Zigotic Embryos of Nothofagus alpina (Poepp. & Endl.) Oerst

“…(Robichaud et al, 2004), Q. suber (García-Martín et al, 2005) and J. regia (Vahdati et al, 2008). The decrease in FW and SSE in treatments where ABA was added can be explained by a possible osmotic besides the effect and ABA's capability to inhibit premature germination and control SSE (Bentsink and Koornneef, 2008;Manoj et al, 2008). This generates a greater number of cell divisions along with immature embryo formation in the control treatment, which is reflected in a greater FW in the absence of ABA (T1), matching the results found in Q. ilex (Mauri and Manzanera, 2004).…”

“…ABA has been recognized as a factor for promotion of normal development and maturation of somatic embryos and their uniformity in Quercus ilex L. and Juglans regia L. (Mauri and Manzanera, 2003;Vahdati et al, 2008). Studies show a decrease in fresh weight (FW) and SSE in treatments where ABA was added can be explained by a possible osmotic besides the effect and ABA's capability to inhibit premature germination and control SSE (Bentsink and Koornneef, 2008;Manoj et al, 2008) ABA plays a fundamental role in both somatic embryogenesis and zygotic embryogenesis. At the beginning and middle stages of seed development, an increase in ABA levels controls and regulates protein synthesis, promoting desiccation tolerance.…”

“…At the beginning and middle stages of seed development, an increase in ABA levels controls and regulates protein synthesis, promoting desiccation tolerance. ABA levels are abundant during medium and advanced seed stages as well, promoting the accumulation of mRNA, which encodes reserve proteins known as LEA (Lateembryogenesis-abundant) (Dodeman et al, 1997;Azcón-Bieto and Talón, 2000;Finkelstein et al, 2002;Von Arnold et al, 2002;Pandey et al, 2008).…”