摘要:

Specimens of duckweed, stock (single‐ and double‐flowered), soyabean and pea were isotopically enriched in57Fe by growing in nutrient solutions which contained iron, primarily as the57Fe isotope. Whole duckweed and the separated roots, stems and leaves from the other plants were studied by Mössbauer spectroscopy at 77K. Samples of duckweed and pea were also dried in air and studied at room temperature. All specimens showed the presence of iron in the ferric form and, in addition, the pea leaves indicated the presence of some ferrous iron.

ISSN:0190-4167    

DOI:10.1080/01904168209362963

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Samples of57Fe‐enriched duckweed have been studied by Mössbauer spectroscopy at 4.2 and 1.3K and at 4.2K in the presence of both snail and large external magnetic fields. All spectra support the results previously obtained at higher temperatures which suggested that the iron was present exclusively in the ferric form. The present results show that most, if not all, of the iron is antiferromagnetic‐ally‐coupled at low temperatures, although the presence of a small fraction (< 15%) of paramagnetic material, arising from isolated ferric ions in complexes, could not be discounted. The most common antiferromagnetic material found in plants is ferritin, an iron‐storage protein, but a comparison of the present results with those in the literature for ferritin, shows that, if it is responsible for the Mössbauer spectra, its core must be < 15Å diameter, much smaller than the maximum value of 60–70Å.

ISSN:0190-4167    

DOI:10.1080/01904168209362964

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Previous studies have indicated that addition of nitrogen to Fe‐inefficient PI54619–5–1 soybeans, when grown in calcareous Hacienda loam soil, intensified iron chlorosis. It was reasoned that when large amounts of nitrate were taken up, more hydroxyl ions were expelled by roots with resultant less availability of soil Fe. It was further reasoned that if N were fixed symbiotically, cation (K, Ca, Mg) uptake would considerably exceed anion (H2PO4‐, SO4=, Cl‐) uptake with no need for uptake of NO3‐with resultant increase in protons excreted. Iron availability then would be increased and there would be less Fe deficiency. An experiment was conducted with and without innoculation with the PI54619–5–1 soybeans in the calcareous soil to test the ability of nodules to prevent Fe chlorosis. The only plants in the experiment with nodules were those with innoculum added and these plants were most free of Fe chlorosis. Iron analyses indicated that the hypothesis may be correct. It can be concluded that cationanion uptake balance has much to do with the onset of lime‐induced chlorosis. The relative uptake of NH4+and NO3‐species of nitrogen can be important considerations in the cation‐anion balance.

ISSN:0190-4167    

DOI:10.1080/01904168209362965

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Ferritin is present in almost all species and was detected in many cells, mainly in tissues not associated with full photosynthetic activity and throughout the plant life cycle. It is quite interesting that phytoferritin from an algal source has not been reported except soms initial short, indirect evidence on its presence in algae (Abadi and Dubois‐Tylski 1974). Unicells of algae, prokaryotic or eukaryotic. may have a great advantage in the study of ferritin synthesis. In such systems we deal with one independent cell without the involvement of any adjacent tissue, and its botanical function resembles the higher ferritin containing plant cell. Ferritin clusters deposited in plastidal stroma are classified into four categories: F‐l, amorphous, close packed particles; F‐2, scattered macromolecules; F‐3, paracrystalline and F‐4, crystalline array. The main functions of plant ferritin are: as an iron storeroom in a nontoxic form, for sequestering the cellular extra lethal iron in a safe buffered form, and the mobilization of iron to requested sites. Aspects of iron and ferritin mobilization in plant vascular tissues have been presented. There are still several open questions concerning the assembly and function of ferritin molecules in plants. It is hoped that future studies will answer some of these questions.

ISSN:0190-4167    

DOI:10.1080/01904168209362966

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The availability of iron to the plants from the growing medium is influenced by a number of factors. Although the soil may contain sufficient amounts of iron, its uptake and utilization depend on the processes residing within the plant roots and those controlling the transport to the leaves. The absorption and transport of iron were followed in bean plants, young maize seedlings and a few varieties of rice and were compared with a freely mobile element Rb. Studies with59Fe indicate that it is taken up from the nutrient solution and readily transported to stem, leaves and flowers in bean plants, and from old to new leaves of maize during a short period. Further, with increase in days, there is a decrease in iron content in the older leaves. These results suggest that iron is mobile within the plants during a limited growing period of maize. Iron absorption and transport patterns are found to differ significantly among three rice cultivars, namely, Basmati, and B‐36 and B‐63 which are mutants of Basmati. The results can perhaps help in identifying the cultivars which are iron‐stress tolerant and susceptible.

ISSN:0190-4167    

DOI:10.1080/01904168209362967

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

In terms of plant nutrition, Fe2+is extremely important since it may be the active species of iron taken up by root cells and by the symbiotic nitrogen‐fixing bacteria. A bacterial system is proposed as a model to study the mechanisms of Fe2+transmembrane movement. We have established a method to examine the transport of Fe2+in the following bacteria:Rhizobium leguminosarum, Erwinia carotovoraandEscherichia coli. Using59Fe2+as a radiotracer, we have determined that Fe2+transport inE. coliwas energy dependent and displayed an apparent Kmof 2 x 10‐5M. Kinetic analysis of Fe2+transport in the presence of Mg2+and Ca2+indicated that both cations were competitive inhibitors of Fe2+. Other cations which markedly inhibited Fe2+transport included Zn2+, Mn2+, Cu+and La3+. Stimulation of Fe2+transport was observed with K+, Na+, Al3+, Cd2+and NH4+. The effect of Cr2+was difficult to interpret since this ion markedly increased energy independent binding of Fe2+to the cells. Of the various chemical control agents tested, only the glyphosphate herbicide and Malathion significantly inhibited Fe2+transport.

ISSN:0190-4167    

DOI:10.1080/01904168209362968

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Humic acid extracted from a Brunizem soil was purified using cationic and anionic exchange resins and EDTA. The purified humic acid was passed through a column of weakly acid cation exchange resin saturated with iron labelled with59Fe. The Fe‐humate was eluted from the column at pH 2.7.

ISSN:0190-4167    

DOI:10.1080/01904168209362969

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The occurrence of transfer cells in the root epidermis of three dicotyledonous Fe‐efficient species (tobacco, tomato, cucumber)is confirmed by transmission electron microscopy for hydroponically cultured as well as sand grown plants. The transfer cell formation is exclusively confined to a subapical root zone which is characterized by a transient decrease of the elongation rate and the development of dense root hairs. Even the root hairs exhibit the typical transfer cell features such as cell wall protuberances and dense cytoplasm rich in organelles. Excess trace metals (Co, Ni, Zn, Cd) block the differentiation of transfer cells. Evidence is presented that proton extrusion and production of reducing substances ‐ the typical biochemical Fe‐stress response reactions ‐ are confined to the area of transfer cell differentiation. Therefore these highly specialized cells are considered to be functionally integrated in the overall ‘Fe‐stress‐response mechanism1of these three species.

ISSN:0190-4167    

DOI:10.1080/01904168209362970

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Fe exists in soil primarily in the oxidized, and very insoluble Fe3+form. Prior investigations have shown that Fe is absorbed by plant roots primarily, if not entirely, in the Fe2+form. The reduction of Fe3+; in the rhizoplane is accordingly crucial.

ISSN:0190-4167    

DOI:10.1080/01904168209362971

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Iron‐stressed and control bean plants were kept for several days in an apparatus in which the iron reducing capacity of the roots and the pH of the medium could be followed in a single plant without significant changes in its iron status ('Rhizostat'). With increasing iron stress the iron reducing capacity increased in a gradual way, whereas pH changes in the medium occurred in pulses. This suggests that iron reducing capacity and acidification of the medium, both stimulated by iron stress, are regulated in different ways.

ISSN:0190-4167    

DOI:10.1080/01904168209362972

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor