Effects of dormancy-breaking chemicals on ABA levels in barley grain embryos

Abstract

The endogenous ABA contents of dormant and nondormant barley grains were determined following application of different compounds to break dormancy. The chemicals used for breaking of dormancy in intact dormant grains were weak and strong acids, alcohols, hydrogen peroxide, cyanide, nitrate, salicylic acid, gibberellic acid and fusicoccin. The dormancy-breaking compounds could be classified into two major groups: compounds that caused a decrease in endogenous ABA (class I) and compounds which did not affect endogenous ABA (class II). Class I compounds included gibberellic acid, ethanol, hydrogen peroxide, nitrate, salicylic acid; class II compounds were fusicoccin, acid (H2SO4), sodium azide, n-caproic acid. In addition, these dormancy-breaking compounds were able to stimulate the germination rate when applied to embryos isolated from dormant grains. The concentrations necessary for stimulation of germination of isolated embryos were much lower than the concentrations for breaking the dormancy of intact grains. After embryos were isolated from dormant grains and incubated in water, ABA was determined in both embryos and in the incubation media. The class I compounds stated above also reduced ABA content in the incubation medium of isolated embryos, while class II compounds had no effect on ABA content of the medium. External application of ABA could overcome the effect of dormancy-breaking compounds of class I but not of class II. The results suggest that in the presence of the agents belonging to class II, ABA responsiveness of isolated embryos from dormant grains is decreased, compared to nontreated embryos.

Reactive oxygen species, ABA and nitric oxide interactions on the germination of warm-season C4-grasses

“…In contrast, imbibition on peroxide resulted in the simultaneous development of the seedling shoot and root system (Table 2), and imbibition of switchgrass seeds on ABA + H 2 O 2 resulted in a signiWcant enhancement in shoot and root growth as compared to seeds maintained on ABA alone. These data demonstrated that for switchgrass seeds, addition of H 2 O 2 could largely overcome the negative eVects of ABA, possibly by swamping ABA-dependent signaling, as has been suggested for barley (Wang et al 1998). Conceivably, exogenous peroxide could act through several diVerent routes in signiWcantly promoting switchgrass seed germination.…”

“…1; Tables 1and 2) show that treatment with H 2 O 2 as an exogenous source of ROS signiWcantly promotes seed germination in several warm-season C 4 -grasses such as switchgrass, big bluestem and indiangrass. Treating seeds with H 2 O 2 has been shown to promote germination in several other species, including zinnia (Zinnia elegans L.) (Ogawa and Iwabuchi 2001), rice (Oryza sativa L.) (Naredo et al 1998), wheat (Triticum aesitvum L.) (Wahid et al 2007) and barley (H. vulgare L.) (Wang et al 1998). What has not been explored in warm-season grasses is the relationship between H 2 O 2 , NO and ABA during seed germination.…”

“…Conceivably, exogenous peroxide could act through several diVerent routes in signiWcantly promoting switchgrass seed germination. These are: (1) through interactions with existing ROS mediated GA/ABA/NO dependent signaling cascades (Beligni et al 2002;Kwak et al 2003;Malolepsza and Rozalska 2005;Bright et al 2006;Pandey et al 2006); (2) by oxidative destruction of germination inhibitors (Ogawa and Iwabuchi 2001) and enhanced oxygenation of tissues (for example, Wang et al 1998); or (3) by a combination of ABA dependent and ABA-independent mechanisms.…”

Comparison of pre-germination treatments in <em>Lupinus</em> spp. and their effects on germination and related solutes

“…This decrease in ABA has been observed in Arabidopsis seeds in response to a heat treatment at 34 °C (Toh et al 2008). A similar decrease in ABA was observed in Hordeum distichon cv Triumph seeds after applying a treatment with H 2 SO 4 to break dormancy (Wang et al 1998).…”

Assessing Influence of Ozone in Tomato Seed Dormancy Alleviation

“…Exogenous H 2 O 2 stimulates the germination of dormant seeds of barley, Fontaine et al 1994; rice, [37] apple [38] and tomato [20]. Treatment of dormant barley seeds with hydrogen peroxide results in a decrease in endogenous ABA level [39] and alleviation of apple embryo dormancy by cyanide induces a simultaneous increase in H 2 O 2 level and decrease in ABA content [38]. H 2 O 2 promoted seed germination in a dose-dependent manner as did respiratory inhibitors, indicating that H 2 O 2 itself possibly promotes seed germination rather than O 2 [40].…”