Nitric oxide, hydrogen cyanide and ethylene are required in the control of germination and undisturbed development of young apple seedlings

Abstract

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are emerging as important regulators of plant development (germination, flowering, senescence), acting as secondary messengers in cooperation with classical phytohormones. Apple seeds are dormant, unless they undergo a 3 month long cold stratification. Deep dormancy of isolated apple embryos can also be broken by short pre-treatment with HCN or NO with the effect associated with enhanced ethylene synthesis. Non-dormant embryos germinate well and young seedlings grown from non-dormant embryos do not exhibit any morphological anomalies, such as asymmetric growth and greening of cotyledons. One of the aims of this work was to investigate the correlation between RNS-mediated (HCN-and NO-dependent) dormancy removal and ROS (H 2 O 2 and O 2 -• ) accumulation in the embryos. The beneficial effect of NO and HCN on germination of dormant apple embryos has been associated with marked increases in H 2 O 2 and O 2 -• concentration in the embryos at early germination stages. We also analyzed growth of young seedlings developed from embryos pretreatment with HCN or NO or exposed to ethylene (ethephone) and its precursor 1-aminocyclopropane-1-carboxylic acid (ACC). ACC and ethephone removed all morphological anomalies of the seedlings (asymmetric growth and greening of cotyledons) but the radicle growth was rather slight. We propose that accumulation of ROS provoked by HCN and NO pre-treatment is required for embryo germination ''sensu stricto'', while ethylene is required for post-germination seedling growth.

Participation of GA3, ethylene, NO and HCN in germination of Amaranthus retroflexus L. seeds with various dormancy levels

“…As the stimulatory effect of HCN on germination of dormant seeds of A. retroflexus could not occur in the presence of cPTIO, the nitric oxide was probably involved in the response to cyanide. A similar relationship was noted in experiments with Arabidopsis (Bethke et al 2006a, b) and Malus domestica (Gniazdowska et al 2010), when HCN was used in combination with cPTIO. Staratified A. retroflexus seeds were sensitive to NO (Table 2), similarly to Arabidopsis seeds (Bethke et al 2004).…”

“…Prevention of the effect of SNP vapors by the commonly used NO scavenger (Table 1), cPTIO, may indicate that NO is responsible for stimulating the germination of dormant seeds of A. retroflexus. Similarly, stimulatory effect of gases released from SNP on the germination of dormant Arabidopsis seeds (Bethke et al 2006a, b) and apple embryos (Gniazdowska et al 2010) did not occur in the presence of cPTIO. As the stimulatory effect of HCN on germination of dormant seeds of A. retroflexus could not occur in the presence of cPTIO, the nitric oxide was probably involved in the response to cyanide.…”

“…Later, many papers considering the effect of NO, by using its different donors, on the germination of dormant and non-dormant seeds were published (Bethke et al 2007). Sodium nitroprusside (SNP), producing both NO and HCN in the light (Feelisch 1998), releases dormancy of lettuce (Beligni and Lamattina 2000), barley (Bethke et al 2004), Arabidopsis (Bethke et al 2004(Bethke et al , 2006a, A. retroflexus seeds (Liu et al 2011) and Malus domestica embryos (Gniazdowska et al 2007(Gniazdowska et al , 2010. Likewise, HCN released from Fe(II)CN or Fe(III)CN can reduce dormancy in Arabidopsis (Bethke et al 2006b), A. retroflexus seeds (Liu et al 2011) and Malus domestica embryos (Gniazdowska et al 2010).…”

X-band Electron Paramagnetic Resonance Investigation of Stable Organic Radicals Present under Cold Stratification in ‘Fuji’ Apple Seeds

“…Recently, it was reported that alleviation of ROS and reactive nitrogen species RNS play important roles in the dormancy under prolonged cold stratification for 70-90 days 11,12 . In fact, in the present experiment, the apple seeds kept in moisture-containing sand and incubated in refrigerator showed a strong EPR signal of radical.…”

“…It is important to note that the radicals in the seeds can be indirect indicator of ROS. ROS and RNS are involved in the regulation of various processes in plants 11,12 .…”