Function of the ascorbate‐glutathione cycle in aged sunflower seeds

Abstract

The function of the ascorbate‐glutathione (AsA/GSH) cycle was analyzed in seeds of sunflower (Helianthus annuus L. cv. Peredovik) subjected to accelerated ageing at 43°C and 75% relative humidity for 1 to 11 days. The study was performed using dry seeds and seeds hydrated by imbibition in distilled water for 4 h at 25 °C. Lipid peroxidation was also determined by measuring the malondialdehyde (MDA) level. As the ageing period increased, a progressive loss of seed viability became increasingly evident. Even though high levels of MDA were delected, the MDA level did not change during accelerated ageing, suggesting that lipid peroxidation might occur to some extent. The study of the ascorbate/glutathione (AsA/GSH) cycle revealed that the GSH system is the major detoxifying mechanism in both dry and imbibed sunflower seeds. The GSH system is mainly located in the embryo, and its protective role is mediated by reactions that consume the GSH pool and, thereby, minimize the increase of the oxidized form (GSSG). Seed imbibition activates cellular metabolism and allows some antioxidant enzymes like glutathione reductase (EC 1,6,4,2) to act upon toxic agents. These reactions provide a reducing status, so that repair of damage becomes possible. However, prolonged ageing conditions (11 days) result in an irreversible damage, as evidenced by the appearance of dead seeds when the germination period ended. Multiple regression analysis revealed the effectiveness of the GSH system in aged seeds, especially upon imbibition and until the AsA/GSH cycle became completely functional.

Production and scavenging of reactive oxygen species in Fagus sylvatica seeds during storage at varied temperature and humidity

“…In general, dry seeds of the orthodox category lack ASA. This was confirmed, for example, in Vicia faba (Arrigoni et al, 1992), Heliantus annuus (De Paula et al, 1996), Pinus pinea, and Avena sativa (Tommasi et al, 1999). Our research showed that ASA is present in dry beech seeds, and this seems to support their intermediate character.…”

“…It is characteristic of beech seeds to contain much more GSSG (oxidized form of glutathione) than GSH (reduced form). Such a strong domination of GSSG has not been observed in seeds of other species, such as H. annuus (De Paula et al, 1996) and Citrullus vulgaris (Hsu and Sung, 1997). Such a shift in redox status may decrease the concentration of -SH groups in cells (Alscher, 1989;Kranner and Grill, 1993).…”

“…This indicates that the changes that took place in cells under the influence of ROS are irreversible, and lead to a loss of germinability and seed death. The role of lowmolecular and enzymatic antioxidants in preservation of seed viability has been investigated mainly during accelerated aging of orthodox seeds of species like H. annuus (Bailly et al, 1996;De Paula et al, 1996), C. vulgaris (Hsu and Sung, 1997), Vigna radiata (Murthy et al, 2002) and Gossypium hirsutum (Goel et al, 2003). In all the studies, a high temperature (33-47 1C) and humidity level (80-100% RH) caused a fast decline in seed viability (within 8-11 days), and a decrease in the activity of enzymatic scavengers.…”

Effect of hydro and osmo priming on yield and yield components of Chickpea (Cicer arietinum L.)

“…Different responses among different varieties for the considered traits may be due to genetical differences in varieties which agreed with the findings of Armin et al (2010) who found different responses among the watermelon varieties due to priming treatments Numbers of primary and secondary branches per plant were not significantly affected by seed priming. This finding is in agreeable with the findings of Paula et al (1996) who recorded that mustard seed treated with 1% of KH 2 PO 4 did not show significant difference for number of branches per plant. However, Manigopa et al (2007) reported that seed priming brought considerable increase in lateral branches (primary and /or secondary) per plant in chickpea.…”

Advances in the research on the AsA-GSH cycle in horticultural crops

“…In addition, it has been reported that at chilling acclimation at 0°C for 72 h, the GSH content in strawberry leaves reached the maximal values and it then decreased, but it was significantly higher than the control . de Paula et al (1996) revealed that GSH could inhibit the senescence of sunflower seeds and the AsA-GSH cycle is the major detoxifying mechanism in both dry and imbibed sunflower seeds. However, Devarshi et al (2006) thought that there were no significant changes in the GSH content during drought acclimation, but the GSH/GSSG ratio decreased significantly.…”