排序方式: 共有3条查询结果,搜索用时 15 毫秒
1
1.
The Finnish barley cultivar (Hordeum vulgare L, cv. Hankkija-673)was grown in solution culture for periods of one and two months.The one month old plants had seminal roots, whereas the twomonth old plants grew adventitious roots from the lower nodes.The roots were tested for ADH activity during aeration, during3 d of hypoxic treatment (brought about by passing nitrogenthrough the nutrient solution), and during a 4 d recovery period.The ADH activity, calculated on a protein basis, rose about4-fold during the nitrogen treatment, the greatest increaseoccurring in the adventitious roots. Differences in the kineticproperties of ADH during the hypoxic period were also foundbetween seminal and adventitious roots. The Km for acetaldehydechanged little in the seminal roots during the hypoxic treatment,but in the adventitious roots it decreased considerably. Thephysiological significance of these changes is discussed. Key words: Hordeum vulgare, alcohol dehydrogenase, hypoxia, enzyme kinetics 相似文献
2.
Antioxidants, Oxidative Damage and Oxygen Deprivation Stress: a Review 总被引:64,自引:1,他引:63
Oxidative stress is induced by a wide range of environmentalfactors including UV stress, pathogen invasion (hypersensitivereaction), herbicide action and oxygen shortage. Oxygen deprivationstress in plant cells is distinguished by three physiologicallydifferent states: transient hypoxia, anoxia and reoxygenation.Generation of reactive oxygen species (ROS) is characteristicfor hypoxia and especially for reoxygenation. Of the ROS, hydrogenperoxide (H2O2) and superoxide (O2·) are bothproduced in a number of cellular reactions, including the iron-catalysedFenton reaction, and by various enzymes such as lipoxygenases,peroxidases, NADPH oxidase and xanthine oxidase. The main cellularcomponents susceptible to damage by free radicals are lipids(peroxidation of unsaturated fatty acids in membranes), proteins(denaturation), carbohydrates and nucleic acids. Consequencesof hypoxia-induced oxidative stress depend on tissue and/orspecies (i.e. their tolerance to anoxia), on membrane properties,on endogenous antioxidant content and on the ability to inducethe response in the antioxidant system. Effective utilizationof energy resources (starch, sugars) and the switch to anaerobicmetabolism and the preservation of the redox status of the cellare vital for survival. The formation of ROS is prevented byan antioxidant system: low molecular mass antioxidants (ascorbicacid, glutathione, tocopherols), enzymes regenerating the reducedforms of antioxidants, and ROS-interacting enzymes such as SOD,peroxidases and catalases. In plant tissues many phenolic compounds(in addition to tocopherols) are potential antioxidants: flavonoids,tannins and lignin precursors may work as ROS-scavenging compounds.Antioxidants act as a cooperative network, employing a seriesof redox reactions. Interactions between ascorbic acid and glutathione,and ascorbic acid and phenolic compounds are well known. Underoxygen deprivation stress some contradictory results on theantioxidant status have been obtained. Experiments on overexpressionof antioxidant production do not always result in the enhancementof the antioxidative defence, and hence increased antioxidativecapacity does not always correlate positively with the degreeof protection. Here we present a consideration of factors whichpossibly affect the effectiveness of antioxidant protectionunder oxygen deprivation as well as under other environmentalstresses. Such aspects as compartmentalization of ROS formationand antioxidant localization, synthesis and transport of antioxidants,the ability to induce the antioxidant defense and cooperation(and/or compensation) between different antioxidant systemsare the determinants of the competence of the antioxidant system. 相似文献
3.
1