Spatiotemporal variations in salicylic acid and hydrogen peroxide in sunflower seeds during transition from dormancy to germination

Abstract

Phytohormones and reactive oxygen species mediate processes such as germination and dormancy. The elucidation of the physiological and biochemical events implicated in the transition from dormancy to germination in different plant species such as sunflower becomes a topic of interest. In this study, we investigated the spatiotemporal variation of salicylic acid (SA), hydrogen peroxide (H 2 O 2 ) and the activity of two antioxidant enzymes (catalase, CAT -EC 1.11.1.6 and ascorbate peroxidase -EC 1.11.1.11) in embryonic axis and cotyledons of dry and imbibed seeds of dormant (B123) and non-dormant (B91) sunflower lines. The results showed that embryonic axis had higher level of SA and H 2 O 2 than cotyledons in both lines. In dry seeds, B123 embryo (embryonic axis + cotyledons) showed a higher SA content than B91. After dry storage at room temperature, SA decreased in B123 embryos to a value close to that registered in B91 embryos. B123 embryonic axis of dry seeds presented higher H 2 O 2 levels than B91. Dry storage led to an increase of H 2 O 2 levels and a decrease of CAT activity in B123 embryonic axis. During imbibition, B123 seeds stored for 33 days displayed an increase in SA level in the embryonic axis (3 h of imbibition) and this lower level correlated with a decrease in H 2 O 2 (6 h of imbibition). Thus, the embryo-imposed dormancy in B123 dry seeds was associated with high levels of SA and low H 2 O 2 , whereas the dormancy release was linked with SA decrease and increase of H 2 O 2 as a consequence of lower CAT activity.

Reactive Oxygen Species (ROS) and Nucleic Acid Modifications during Seed Dormancy

“…ROS accumulate in seeds upon AR and dormancy release and promote germination in several species, as illustrated by studies in A. thaliana, Pisum sativum, Helianthus annuus, Hordeum vulgare, and Triticum aestivum [40,[45][46][47][48]. In A. thaliana and H. annuus AR seeds, while ROS are localized close to the radicle tip of the embryonic axis during imbibition, they do not have a particular distribution in dormant embryos [49][50][51]. It is widely known that ROS act as signalling molecules, but H 2 O 2 seems to be the main responsible for redox signalling, probably because of its stability.…”

The interplay of specific hormonal profile in fruit parts of sunflower inbred lines with contrasting dormancy levels during germination and dormancy breaking by exogenous application of plant growth regulators

“…Previous studies have reported that ABA accumulates during seed development and this in turn leads to the establishment and maintenance of seed dormancy, which is related to inhibition of early germination (Finkelstein, 2010; Shu et al., 2016). Even more, in species such as A. thaliana (L.) Heynh or sunflower, seed dormancy correlates with high ABA levels (Iwasaki et al., 2022; Vigliocco et al., 2019). In agreement with these previous findings, in our study the dormant line Xi3 had higher levels of ABA in the embryo (embryonic axis + cotyledons) than X274, especially in the embryonic axis, which has been proposed as the center where the occurrence of germination is “decided” (Tophan et al., 2010).…”

Developmental responses of perennial ryegrass, red fescue, and Kentucky bluegrass to In vitro chitosan treatments

“…Because ROS could play a role in regulating seed germination by oxidizing the proteins that trigger germination (El-Maarouf-Bouteau et al, 2013) and weakening the endosperm during seed swelling (Müller et al, 2009). In a recent report, the dormancy release was associated with increasing the sunflower seeds' internal H 2 O 2 level (Vigliocco et al, 2019).…”