The enzyme catalase (EC 1.11.1.6) is light sensitive and subject to a rapid turnover in light, similar the D1 reaction center protein of photosystem II. After 3 h preadaptation darkness or different intensities (90 520 μmol m−2 s−1 photosynthetic photon flux density), sections rye leaves (Secale cereale L.) were labeled for 4 with l-[35S]methionine. From leaf extracts, was immunoprecipitated an antiserum prepared against purified from leaves. Both incorporation into degradation polypeptide...

ABSTRACT The high mountain plant species Ranunculus glacialis has a low antioxidative scavenging capacity and activity of thermal dissipation excess light energy despite its growth under conditions frequent cold stress. In order to examine whether this is protected from over‐reduction by matching photosystem II (PSII) electron transport (ETR) carbon assimilation, both were analysed simultaneously at various temperatures intensities using infrared gas absorption coupled with chlorophyll...

Five varieties of Sorghum bicolor (L.) Moench., differing in their drought tolerance under field conditions have been used to study the effect individual components stress, namely high light intensity heat stress and water on photosynthetic performance. Chlorophyll content, chlorophyll fluorescence, ribulose-1,5-bisphosphate carboxylase (Rubisco, EC 4.1.1.39) phosphoenolpyruvate (PEPcase, 4.1.1.31) activity oxygen evolution were as key parameters assess The results indicated that...

Abstract: CO 2 assimilation, transpiration and modulated chlorophyll fluorescence of leaves Chenopodium bonus‐henricus (L.) were measured in the laboratory and, at a high altitude location, field. Direct calibration parameters against carbon assimilation presence 1 or 0.5% oxygen (plus ) proved necessary to calculate electron transport under photorespiratory conditions individual experiments. Even when stomata open field, total was two three times higher sunlight than indicated by net gain....

Ranunculus glacialis leaves were tested for their plastid terminal oxidase (PTOX) content and electron flow to photorespiration alternative acceptors. In shade-leaves, the PTOX NAD(P)H dehydrogenase (NDH) markedly lower than in sun-leaves. Carbon assimilation/light Ci response curves not different sun- but photosynthetic capacity was highest Based on calculation of apparent specificity factor ribulose 1.5-bisphosphate carboxylase/oxygenase (Rubisco), magnitude unrelated carboxylation...

ABSTRACT In leaves of three alpine high mountain plants, Homogyne alpina, Ranunculus glacialis and Soldanella alpina , both photosystem II (PSII) the enzyme catalase appeared to he highly resistant photoinactivation under natural field conditions. While Dl protein PSII have a rapid turnover in light require continuous new synthesis non‐adapted little apparent or was induced plants by translation inhibitors at low temperature, suggesting that slow these leaves. vitro rapidly inactivated...

Metabolic profiling using phosphorus nuclear magnetic resonance ((31)P-NMR) revealed that the leaves of different herbs and trees accumulate 2-C-methyl-D-erythritol 2,4-cyclodiphosphate (MEcDP), an intermediate methylerythritol 4-phosphate (MEP) pathway, during bright hot days. In spinach (Spinacia oleracea L.) leaves, its accumulation closely depended on irradiance temperature. MEcDP was only (31)P-NMR-detected MEP pathway intermediate. It remained in chloroplasts a sink for phosphate. The...

Photosynthesis, electron transport to carbon assimilation, photorespiration and alternative transport, light absorption of the two photosystems, antioxidative protection pigment contents were investigated in S. alpina leaves. is an alpine snow-bed plant which can be found with green leaves after snowmelt. At least 24% formed at beginning vegetation period previous year survived consecutive periods under contrasting environmental conditions. In still covered by snow (SNOW), parameters...

Activity of catalase (EC 1.11.1.6) and variable fluorescence (F) were measured in sections rye leaves ( Secale cereale L. cv. Halo) that exposed for 24 h to moderately high irradiance under osmotic or chemical stress conditions (paraquat, DCMU, mannitol, NaCl, CdCl 2 , CuSO 4 Pb(NO 3 ) KNO K SO ). Changes the chlorophyll content enzyme activities related peroxide metabolism, such as glycolate oxidase, glutathione reductase, peroxidase, assayed comparison. In presence herbicides paraquat low...

The cytoplasmic male sterile II (CMSII) mutant lacking complex I of the mitochondrial electron transport chain has a lower photosynthetic activity but exhibits higher rates excess than wild type (WT) when grown at high light intensity. In order to examine cause and determine whether electrons are consumed by photorespiration, light, intercellular CO(2), molar fraction (c(i)) response curves carbon assimilation were measured varying oxygen fractions. While is major acceptor for in CMSII WT...

Abstract: When segments of rye leaves ( Secale cereale L.) grown at 90 μmol m −2 s −1 PAR were incubated a higher photon flux 400–500 μ mol in the presence 0.2‐0.6 M NaCl, preferential loss catalase activity was induced. The extent this decline increased with concentration NaCl. In addition, accumulation alternative antioxidative components, such as ascorbate, glutathione, glutathione reductase, or peroxidase, inhibited. total content H 2 O was, however, lower catalase‐depleted than...

In cold‐hardened leaves (CHL) of winter rye (Secale cereale L.) much higher levels malate were detected by 13C‐NMR than in non‐hardened (NHL). As this was not observed previously, metabolism CHL studied more detail biochemical assays. The activities several enzymes metabolism, NADP‐malate dehydrogenase, NAD‐malate phosphoenolpyruvate carboxylase, and NADP‐malic enzyme, also increased CHL. Short exposures to low temperature 1–3 d did induce increases the content or mature NHL. enzyme declined...

Two high mountain plants Soldanella alpina (L.) and Ranunculus glacialis were transferred from their natural environment to two different growth conditions (22 °C 6 °C) at low elevation in order investigate the possibility of de‐acclimation light cold importance antioxidants metabolite levels. The results compared with lowland crop plant Pisum sativum as a control. Leaves R. grown for 3 weeks 22 more sensitive light‐stress (defined damage photosynthesis, reduction catalase activity (EC...

Climate change effects on snow cover and thermic regime in alpine tundra might lead to a longer growing season, but could also increase risks plants from spring frost events. Alpine snowbeds, i.e. late snowmelt sites, be particularly susceptible such climatic changes. Snowbed communities were grown large monoliths for two consecutive years, under different manipulated treatments, test of early (E) (L) dominant species growth, plant functional traits, leaf area index (LAI) aboveground...

The plastid terminal oxidase PTOX is a plastohydroquinone:oxygen oxidoreductase that important for carotenoid biosynthesis and development. Its role in photosynthesis controversially discussed. Under number of abiotic stress conditions, the protein level increases. thought to act as safety valve under high light protecting photosynthetic apparatus against photodamage. However, transformants with were reported suffer from photoinhibition. To analyze effect on electron transport, tobacco...

ABSTRACT Catalase and photosystem II (PSII) were strongly inactivated during exposure to 4 °C moderate light in 22 °C‐grown non‐hardened leaves (NHL) of winter rye ( Secale cereale L.), but highly resistant photo‐inactivation at low temperature cold‐hardened (CHL). Resistance CHL chilling‐induced catalase PSII depended partially on more efficient de novo synthesis improved protection. Lower rates chloroplast‐mediated inactivation vitro indicated that less reactive oxygen was released by...

Leaves of the two cold-acclimated alpine plant species Ranunculus glacialis and Soldanella alpina and, for comparison, non-acclimated lowland Pisum sativum were illuminated with high light intensity at low temperature. The light- cold-induced changes antioxidants major carbon phosphate metabolites analysed to examine which metabolic pathways might be limiting in pea leaves whether plants are able circumvent such limitation. During illumination temperature accumulated quantities sucrose,...

The significance of total glutathione content was investigated in two alpine plant species with highly differing antioxidative scavenging capacity. Leaves Soldanella alpina and Ranunculus glacialis incubated for 48 h the presence buthionine-sulfoximine had 50% lower contents when compared leaves water. low leaf not compensated by activation other components involved protection or electron consumption. However, normal but increased their ascorbate during high light (HL) treatment (S. alpina)...

1. The enzyme catalase was investigated as a sensitive marker of light stress in Retama raetam stems and Atriplex halimus leaves. While the activity readily photoinactivated vitro when crude extracts from these tissues were exposed to photon flux 500μmolm –2 s –1 photosynthetic active radiation (PAR), no apparent losses extractable activities observed harvested desert plants at noon levels high 2200μmolm PAR. 2. When R. or leaves A. natural daylight 1000μmolm PAR presence cycloheximide...

ABSTRACT The contents of ascorbate and glutathione the activities superoxide dismutase reductase were increased to levels as high those in cold‐hardened leaves (CHL) by incubating non‐hardened (NHL) winter rye ( Secale cereale L.) with precursor substrates L ‐galactonic acid‐ γ ‐lactone 2‐oxothiazolidine‐4‐carboxylate. Reduced was rapidly depleted from NHL after application D , ‐buthionine sulfoximine, an inhibitor its biosynthesis. In spite greatly divergent antioxidant rates...