摘要:

In the working conditions used for the extraction of iron with 1,10‐phenanthroline (o‐phe) or 2–2’ Bipyridyl (Bipy) from plant material,in vitrophotoreduction of ferric ions occurs. Nevertheless, iron in plant extracts was found to be independent of the illumination conditions where the sample was maintained during the extraction. Ferric iron added to a plant extract was completely reduced in the darkness. These data seem to indicate that if extraction of ferric iron occurred, it would be reduced and measured as ferrous iron. Thus, the form of iron being extracted may be better called “active”; or “labile”; instead of ferrous iron.

ISSN:0190-4167    

DOI:10.1080/01904168409363241

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Iron chlorosis is a wide spread nutritional disorder in the sugarcane growing parts of Western India and results in serious economic losses. It appears that the iron in the chlorotic leaves is physiologically inactive which is probably due to higher P/Fe ratio. This immobilized iron lowers the activities of enzymes in which iron is involved and also disturbs the synthesis of other specific enzyme proteins some of which are stimulated while others are inhibited. The calculated active iron derived from the formula of De Kocket.al. (1979) shows a significant relationship of the active iron contents and the chlorophyll levels in the leaves. The inactive iron not only affects the quantity of chlorophylls but the quality also. As the chlorosis becomes severe the chlorophyll a/b ratio increases. Chlorosis is probably due to the inhibited synthesis of photosynthetic units, whose number is significantly lowered in the leaves as the degree of chlorosis increases. Mesophyll cell chloroplasts are more affected than the bundle sheath cells.

ISSN:0190-4167    

DOI:10.1080/01904168409363242

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Squash cotyledon and corn leaf NADH:nitrate reductase (NR) catalyze the reduction of Fe (III)‐citrate, as shown by trapping the reduced iron with ferrozine. The co‐identity of NR as a catalyst for both nitrate and iron reduction was shown by the co‐purification and co‐electrophoresis of the two activities with both partially pure and homogeneous enzyme forms. In addition, the Fe (III)‐citrate reductase activity had a pH optimum and substrate kinetics consistent with an enzymic reaction, and was inhibited by rabbit antiserum which had been prepared against homogeneous NADH:NR. Our previous studies with various inhibitors showed that Fe (III)‐citrate was directly reduced by NR, but at a site separate from the nitrate reducing site. A role for the Fe (III)‐citrate reductase activity of NR in the remoblization of recently transported iron is described in relation to the role of this enzyme in nitrate assimilation.

ISSN:0190-4167    

DOI:10.1080/01904168409363243

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The influence of Delta‐amino levulinic acid (ALA), synthesized in etiolated barley leaves on the formation of the porphyrins protoheme and protochlorophyll, was examined. A significant amount of protoheme was found under light‐flash conditions which produced high concentrations of ALA but kept low the production of chlorophyllide. Increases In protoheme were also observed after 24 hours of continuous light. It was considered significant that protoheme did not increase in dark‐held controls in which trace amounts of ALA were detected. The content of protoheme seemed to be a reflection of ALA availability. The chlorophyll content after 24 hours of continuous Illumination was about 100 times greater than that of photoconvertable protochlorophyl11de accumulated in etiolated leaves. Results suggest that light‐induced ALA in etiolated barley was utilized for the production of protoheme and chlorophyll.

ISSN:0190-4167    

DOI:10.1080/01904168409363244

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Iron chlorosis‐like symptoms developed in the terminal leaves of susceptible bean (Phaseolus vulgarisL. ‘Astro') plants when grown in growth chambers containing low pressure sodium (LPS) lamps that are deficient in UV and blue wavelengths. Plants grown under broad‐band radiation, provided by cool white fluorescent lamps, did not develop chlorosis. Ultrastructural and metabolic investigations examined the progress of chlorosis in leaves of plants exposed to nutrient end radiation stress under LPS lamps. Addition of full‐strength Hoagland's #1 nutrient solution or Peter's* 20–20–20 fertilizer to plants grown under LPS lamps resulted in the degradation of maturing chloroplasts in the terminal leaves. After the starch reserves were depleted, the internal membrane system degenerated. Well‐formed grana, characteristic of normal chloroplasts, were degraded, giving rise to spherical membrane structures. Chlorophyll and protein were lost and granular accumulations formed in the chloroplasts. This paper discusses the stability of the chloroplasts and mesophyll under LPS radiation and evaluates the ability of the leaves to regreen when the plants are subjected to favorable radiation and nutrient conditions. Soil application of urea and EDU, along with foliar application of sucrose, promoted regreening of the chlorotic leaves. It was concluded that chlorosis in LPS‐grown plants resulted from photodegradation of the more mature chloroplasts rather than from inhibition of lamellar development due to Fe deficiency.

ISSN:0190-4167    

DOI:10.1080/01904168409363245

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The direction and balance of work on iron has been assessed on the basis of recent published work.

ISSN:0190-4167    

DOI:10.1080/01904168409363246

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Iron efficiency in plants appears to be related to several phenomena which differentially function in different species and cultivars of plants although 2 or more of the mechanisms may be coupled and present in the same individual. Proton expulsion from roots is important in iron efficiency in dicots and it may or may not be associated with excess cation uptake where a cation is exchanged for H+. When protons are expelled, the residual OH‐in roots must be oxidized but this oxidation releases electrons for redox reactions which may.be coupled with enzymatic Fe+++reduction. If this set of reactions is related to catylase or peroxidase, the presence of these enzymes in plants would be more rational. Some plants, particularly monocots, do not expel protons unless much of the nitrogen is in the NH4+form. Such plants then cannot acidify or reduce the rhizosphere. There is evidence that these monocot plants produce phytosiderophores which function in iron mobilization and reduction. Monocots take up more anions than cations and hence tend to increase the pH of the rhizosphere. This increase in pH may improve the stability of the phytosiderophores. The differential role of H+efflux in monocots and dicots may be related to low Ca uptake by the latter. It is of interest that the PI54315–9–1 soybean, which is Fe inefficient, has less Ca uptake than efficient Hawkeye soybean.

ISSN:0190-4167    

DOI:10.1080/01904168409363247

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

New ideas are being developed on iron relationships in plants. Older textbooks on plant nutrition are obsolete in respect to iron and some newer textbooks are somewhat obsolete. It is very important that students be kept near the front of this changing field to insure that progress continues. The chapter by Mengel and Kirkby (1982) is excellent although it does not go into siderophores and their possible relationships with iron uptake and to microbial and crop ecology, or deeply into redox in relationship with uptake of iron from synthetic chelating agents, or into iron uptake by plants from organic iron amendments, or into the riboflavin aspect of the iron response mechanism, or into hormonal control of iron transport, or into the role of iron chelates on the flowering ofLemna, or into the role of iron on thylakoid synthesis or much into the diagnosis of iron status of plants and soils as examples, or much into the significance of iron interactions in ecological problems related to lime soils. The chapter does a good work of putting together the iron stress response mechanism and its characteristics although it could expand more into its genetic control.

ISSN:0190-4167    

DOI:10.1080/01904168409363248

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:0190-4167    

DOI:10.1080/01904168409363249

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:0190-4167    

DOI:10.1080/01904168409363170

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor