Germinating seedlings of mung bean (Phaseolus vulgaris L. cv. K-16) were treated with different concentrations of cadmium acetate (10, 50 and 100 μM). Cd2+ lowered the chlorophyll and heme levels. The level of lipid peroxides were higher on day 3 than on day 6. However, Cd2+ treatment significantly enhanced the level of lipid peroxides. Similarly, a dose-dependent induction of lipoxygenase (EC 1.13.11.12) activity was observed with Cd2+ treatment. Further, the activities of antioxidant enzymes such as superoxide dismutase (EC 1.15.1.1) and catalase (EC 1.11.1.6) were decreased. Our results suggest that lipoxygenase-mediated accumulation of lipid peroxides on the one hand and inhibition of free radical scavenging enzymes like superoxide dismutase and catalase on the other caused a pronounced reduction in the chlorophyll and heme levels of the seedlings. The experiments conducted on the effect of Cd2+ on dark-grown seedlings did not conform with the result of light-grown seedlings. Though chlorophyll and heme levels decreased in a dose-dependent manner, no accumulation of lipid peroxides was observed, suggesting that the inhibition of chlorophyll synthesis by Cd2+ is achieved both by reaction with constituent biosynthetic enzymes as well as peroxide-mediated degradation.

Phytotoxicity of cadmium ions on germinating seedlings of mung bean (Phaseolus vulgaris): Involvement of lipid peroxides in chlorphyll degradation

Publisher Summary This chapter reviews the roles of jasmonic acid (JA) and related compounds in the regulation of plant development. JA-related compounds are widely distributed among higher plants and are potent inducers of expression of several genes, such as the genes of proteinase inhibitor in tomato plants and the genes of vegetative storage proteins in soybean plants. JA is synthesized from linolenic acid by a series of enzymes. The initial reaction in JA synthesis is catalyzed by lipoxygenase, which is a common enzyme in plant tissues. JA-related compounds are easily extracted from plant materials by methanol, ethanol, or acetone. The material should be homogenized immediately after harvest with sufficient solvent to prevent the enzymatic changes of the compounds. JA has four stereoisomers because of the presence of two chiral carbons at the C-1 and C-2 positions of a cyclopentane ring. Maslenkova et al. examined the effect of JA on the oxygen-evolving activity of chloroplasts isolated from barley leaves. The kinetics characteristics of oxygen evolution indicated that JA decreased the value of the total number of oxygen-evolving centers. JA affects the degree of structuring of the granal region or the structural integrity of the electron transport chain in barley chloroplasts.

The role of jasmonic acid and related compounds in the regulation of plant development.

The qualitative and quantitative control of pigments in ripe olives and in extracted virgin olive oil has increased our knowledge of the influence on these compounds in the areas of ripening of the fruit, storage time in the factory and the oil extraction process. As the harvesting time of the fruits increases, pigment content decreases. During storage, the presence of lipoxygenase has been detected, as well as a considerable decrease in chlorophylls and a small decrease in carotenoids. During the extraction process, the chlorophyllic fraction is destroyed in the greater part, and although the carotenoid fraction is also affected, its concentration increases in the oil with respect to that in the fresh fruit. In the pigment degradation, in addition to the acid-catalyzed reaction, the presence of lipoxygenase suggests a role for this enzyme.

Pigments present in virgin olive oil

Publisher Summary This chapter discusses the advances in plant lipoxygenase A special effort has been made to focus on physiological roles in which LOX might participate. A clear theme emerging from this effort is that a unique physiological role for LOX probably does not exist in plants. It likely has a more general function of responding to plant requirements by synthesizing fatty acid hydroperoxide, the central intermediate for a variety of diverging metabolic pathways. In this regard, the LOX pathway in plants can be similar to the mammalian LOX or cyclo-oxygenase pathways. In animals, the hydroperoxide or endoperoxide products of these two enzymes are transformed into a variety of leukotrienes and prostaglandins, depending on the nature of the cellular stimulus. Substrates for LOX are fatty acids that possess a cis , cis -1,4-pentadiene structure. The most common plant fatty acids that have this structure are linoleic and linolenic acids, but other fatty acids having this structure are also effective substrates to varying degrees.

Annerose Köckritz

Papers

The effects of soybean lipoxygenase-1 on chloroplasts from wheat