The capacity of antioxidant protection during modulated ageing of bean (Phaseolus vulgaris L.) cotyledons. 1. The antioxidant enzyme activities

Abstract

Reactive oxygen species are known to increase in plant senescence. We investigated the participation of antioxidative enzymes in initiation of cotyledon senescence. Senescence of bean (Phaseolus vulgaris L.) cotyledons was modulated by UV C irradiation and by the decapitation of plant apices. Senescence was accompanied by a decrease of protein content and by a decrease of photochemical efficiency. A drop in activity of antioxidative enzymes preceded the onset of senescence in control plants. In cotyledons with prolonged life span, the decrease of antioxidant activities and the markers of senescence onset appeared at a similar age as in controls. Thus we presumed that the period from senescence initiation to cotyledon abscission was extended. On the other hand, in UV C irradiated plants we did not observe actual senescence initiation, and antioxidant enzymes although elevated, did not effectively play their role. The decrease of antioxidant enzymes activity and the markers of senescence appeared at a similar age both in control and in decapitated (D) plants, so we can presume that we prolonged mainly the period from senescence onset to cotyledon abscission in D plants. In UV C irradiated plants the antioxidative enzymes were probably destroyed before the process of senescence could begin.

Polyamines: potent modulators of plant responses to stress

“…Relatively limited information concerning the role of plant PAs toward UV irradiation is available. Recently, effects of UV-C on plants have been reported by many workers (Ehsanpour & Razavizadeh 2005;Prochazkova & Wilhelmova 2007). They are of the view that all types of UV radiations, including UV-C, affect important plant processes.…”

Antioxidant protection during ageing and senescence in chloroplasts of tobacco with modulated life span

“…The solvent system was acetonitrile/methanol/water (80:12:6, v/v/v) followed by 100% methanol; the gradient run was 25 min, flow rate 1 cm min À1 , the detection wavelength was 445 nm. 28 Pigment content was calculated according to Lichtenthaler. 29 The de-epoxidation state of the xanthophyll cycle was calculated as (Z þ 1/2A)/(V þA þ Z) according to Demmig-Adams and Adams.…”

Antioxidant protection during ageing and senescence in transgenic tobacco with enhanced activity of cytokinin oxidase/dehydrogenase

“…For example, Dertinger et al (2003) reported higher SOD, APX and GR activities in old leaves of tobacco with enhanced cytokinin production compared to old leaves of wild type tobacco. Bean cotyledons with prolonged life span by excision of the whole shoots above them showed prolonged period of high activity of antioxidant enzymes as well (Procházková and Wilhelmová 2007b).…”