Effects of fusicoccin and gibberellic acid on the germination of embryos from dormant barley grains: roles of starch degradation and external pH

Abstract

In isolated embryos from dormant barley grains, synergistic effects of fusicoccin (FC) and gibberellic acid (GA3) were observed on the induction of α-amylase mRNA expression. However, no α-amylase mRNA expression could be induced by both agents in embryos from non-dormant grains. Both light- and electron-microscopy studies demonstrated that there were large numbers of starch granules present in mature embryos (mainly in scutellum) from dormant barley grains but none or almost none in embryos from non-dormant grains. Furthermore, the content of reducing sugars in embryos from dormant grains was about half of that from non-dormant grains. In contrast to GA3, FC was able to induce a strong acidification of extracellular pH (pHe). Clamping the pHe to prevent FC-induced acidification, by using 50 mM MES buffer (pH 5.6), caused an inhibition of GA3- or FC-induced α-amylase mRNA expression but did not affect the germination of embryos from dormant grains. In addition, in MES buffer, addition of FC or a combination of FC and GA3increased the germination rate of embryos isolated from dormant grains, though large numbers of starch granules were still present in these embryos. Based on these observations, the presence of starch granules and a low reducing sugar level in embryos from dormant grains is not a factor for control of grain dormancy and germination.

Seed ageing-induced inhibition of germination and post-germination root growth is related to lower activity of plasma membrane H+-ATPase in maize roots

“…The results of the present study imply that the plasma membrane H + -ATPase may play an important role not only for the elongation growth of roots but also for maize seed germination. These results are consistent with the finding that fusicoccin (FC) significantly accelerated germination of dormant barley embryos (Van der Meulen et al, 2000). FC is a fungal toxin, which significantly stimulates the activity of the plasma membrane H + -ATPase (Marré, 1979) through binding to the plasma membrane H + -ATPase and thereby removing the auto-inhibitory C-terminal domain of this enzyme from the catalytic site (Johansson et al, 1993;Palmgren et al, 1991).…”

A Travel through Landscapes of Seed Dormancy

“…Although glucose can also relieve ABA inhibition of expansin genes during late germination [125], exogenous glucose cannot relieve seed dormancy [61]. The latter finding is in agreement with the observation that a low reducing sugar level in embryos of dormant grains (associated with the presence of starch granules) is not a cause (and, thus, it probably is an effect) of dormancy [140].…”

Homeopathically prepared gibberellic acid and barley seed germination

“…Plants are known to respond to very low concentrations of gibberellin. For instance the effect on stem elongation of rice (Oryza sativa L.) and lettuce (Lactuca sativa L.) can be observed in levels as low as 10 À10 g l À1 , 23 and Van der Meulen et al 24 have demonstrated that GA 3 at 10 À8 g l À1 was able to induce germination in dormant barley seed embryos. The HGA 3 4 cH dilution therefore falls within a concentration range of GA 3 which are known to be biologically active in germinating barley embryos.…”