Abstract
water soluble protein fraction (WSPF) content along with the SOD and the CAT activities were comparatively monitored in leaf blades, sheaths and roots. S-deprivation progressively diminished WSPF first in the sheaths, two days later in the blades, and four days later in the root. SOD activity per mg WSPF decreased at d2, whilst it increased for the next four days. After d6, SOD activities of roots and sheaths decreased, followed by the blades at d10. CAT activity per mg WSPF at d2 decreased only in blades, whilst increased in both sheaths and roots (more in sheaths). After d6 decreased CAT activity was found only in roots. No other decreases were observed in blades and sheaths. SOD and CAT specific activities on DM basis presented an oscillation pattern with the increase of DM. S-deprivation altered this picture, by reversing the oscillation pattern and by decreasing the trendlines. SOD specific activity initially decreased in –S sheaths and roots, whilst it remained unchanged in –S blades. Then it increased abruptly, decreased in an exponential manner and stabilised in all three organs. S-deprivation caused an early fluctuation of the CAT activity and then diverse responses; in blades a late increase in CAT activity was observed and decreases in the other two organs. S-deprivation seemed to reverse the oscillation pattern of CAT specific activity differentially for each organ type.
Highlights
Various abiotic stresses lead to the overproduction of reactive oxygen species (ROS) in plants, in which the superoxide anion ( O 2 ) and the hydrogen peroxide (H2O2) are included
Raised thirteen-day-old maize plants were subject to S-deprivation for ten days and the fluctuation of water soluble protein fraction (WSPF) content along with the Superoxide dismutase (SOD) and the CAT activities were comparatively monitored in leaf blades, sheaths and roots
To express the enzymatic activity of SOD in nkat, we considered that reaction is completed within 15 min considering that 1 mol of nitro blue tetrazolium (NBT) reacts with 4 mol O 2, 0.225 μmol ΝΒΤ sre−1acatndwitthhus0.19Uμm=o0l.5Onk 2 atwOith 2 in. 15 min or 1 nmol· O2 ·
Summary
Various abiotic stresses lead to the overproduction of reactive oxygen species (ROS) in plants, in which the superoxide anion ( O 2 ) and the hydrogen peroxide (H2O2) are included. Superoxide dismutase (SOD) and catalase (CAT) comprise two enzymatic components of the antioxidant equipment of the various plant tissues. SOD (EC 1.15.1.1) removes O 2 by catalysing its dismutation and producing H2O2 and O2, whilst CAT (EC 1.11.1.6) catalyses dismutation of H2O2 into H2O and O2 and is indispensable for ROS detoxification during stress causing conditions. The balance between SODs and the different H2O2-scavenging enzyme activities in cells is considered to be crusial in determining the steady-state level of O 2 and H2O2. This balance, together with the sequestering of metal ions by ferritin and other metal-binding proteins, prevents the formation of the highly toxic hydroxyl radical (HO ) via the metaldependent Haber-Weiss reaction or the Fenton reaction. New roles for ROS have been identified as controllers and regulators of various biological processes, among them growth, cell cycle, development and abiotic stress responses [2]
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