ISSN:0190-4167    

DOI:10.1080/01904168609363433

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Iron chlorosis of plants grown on calcareous soils is not induced by an absolute Fe deficiency but rather results from a physiological disorder which affects the mobility of Fe in the entire plant. Evidence is provided that this Fe immobility is caused by an alkaline nutrition which means NO‐3”; as the major, if not as the sole N source combined with HCO‐3. Such alkaline nutritional conditions prevail in calcareous soils. It is supposed that alkaline nutrition results in high pH levels in the leaf apoplast which may bring about a precipitation of Fe. It is also feasible that a high leaf apoplast pH inhibits the plasmalemma located FeIIIreductase which is responsible for the Fe transfer across the plasmamembrane. Measurements which decrease the apoplastic pH such as NH4+nutrition, the application of indole acetic acid or fusicoccin resulted in a regreening of Fe chlorotic leaves.

ISSN:0190-4167    

DOI:10.1080/01904168609363434

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The essential role of Fe in the biological world is impressive and the manner in which the Fe supply is controlled to the plant or organism is unique in making Fe available for use. Each investigator has pursued specific approaches to answer detailed objectives in a designated line of research; these have primarily dealt with the Fe‐stress response mechanism of dicotyledonous plants. These plants respond to Fe‐deficiency stress by (a) release of hydrogen ions and (b) release of reducing compounds from their roots, (c) reduction of Fe3+to Fe2+by their roots, and (d) increases in organic acids (particularly citrate) in their roots. Each of these factors will be discussed in view of existing hypotheses emphasizing reduction by roots at the plasma membrane and with regard to how these factors may compliment each other in the absorption process. Mugeneic acid has been isolated from roots of iron‐deficiency stressed barley and oats and dlbutyl phthalate from sorghum. In each case iron was made available for use by the plant. Hydroxamate siderophores of mlcrobial origin have supplied iron to Fe‐efficient tomato (T3238FER), but not to the Fe‐inefflcient tomato (T3238fer). It has become increasingly apparent In the past few years that noonescheme controls the useof iron in the biological world—except that reduction of Fe3+to Fe2+may be the single most important factor. Other interactions with Fe2+discussed are: K, Mn, N, HCO‐3, and reduction of Fe to Fe by ultra violet light.

ISSN:0190-4167    

DOI:10.1080/01904168609363435

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A stress in crop production is considered as something that decreases yield, and a growth promoter is something the increases yield. Officially, granting and governmental agencies consider that many inputs that improve crop production as not being related to stress. In other words, a stress is an external factor that decreases crop yields from yield maximum to a lower level. Examples are diseases, insects, salinity, and excesses of trace elements. Granting agencies have not considered plant nutrients, growth regulators, or genetic limitation as being directly related to stresses; rather, these factors are considered as promoters of plant yields. This is a fallacy. When plant nutrients are not in optimum amounts and ratios, their deficiency and imbalance are true stresses; they decrease crop yields just as do other stresses. If a yield is not maximum, it is due to the additive accumulation of all stresses. If yields are increased, it is because of removal or overcoming of stresses. Nutrient deficiencies and imbalances are yet a major barrier or stress to obtain the potential of yield maximum. If four different plant nutrients are present in supply and ratio at 90 per cent of optimum and all other nutrients are optimum, the summation of the nutrient stress is 0.90 x 0.90 x 0.90 x 0.90 = 0.66 or 66 per cent of yield maximum. These small departures from optimum collectively are a serious barrier to obtaining yield maximum. In a pot test, iron limited growth of soybeans about 10 per cent, even though there was no chlorosis. This illustrates the importance of research on iron and other plant nutrients and deserves consideration for funding as stress research.

ISSN:0190-4167    

DOI:10.1080/01904168609363436

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Fe chlorosis is commonly associated with calcareous soils. Calcium carbonate has a dominating influence on any system in which it is present due to its properties of high solubility, high buffer capacity and basicity. At the pH of a calcareous soil, approximately 7.4 to 8.5, the equilibrium concentration of total dissolved Fe(III) is approximately 10‐10M, which is considerably less than the 10‐8M concentration which is required for optimum growth of plants in nutrient culture. Therefore, any plant in a calcareous soil is likely in an Fe stress situation. The plant may respond to the Fe stress by exudation of proton and chelate and/or development of an increased capacity for reduction of Fe(III) to Fe(II). These response factors will act to mobilize labile Fe from solid phase soil components, especially the poorly crystalline Fe oxides. Therefore, the crystallinities, particle sizes and reactive surface areas of the soil Fe oxides influence the availability of Fe to plants in calcareous soils.

ISSN:0190-4167    

DOI:10.1080/01904168609363437

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The bicarbonate ion has been implicated as a causative agent in iron chlorosis induced by high moisture in calcareous soils. Our studies have demonstrated a correlation between soil solution bicarbonate and chlorosis in soybeans in fields in western Minnesota and under growth chamber conditions. In the growth chamber studies, we found that the severity of chlorosis increases with increasing soil moisture to near the saturated water content. At high moisture, soil pores were filled with water and the partial pressure of CO2in the soil air increased. Since the soil pH is strongly buffered by the high cation exchange capacity of the soils, soil pH remained constant and [HCO‐3] increased. In a system in which CaC03is in equilibrium with the solution phase, the [HCO‐3] should be controlled by CaCO3solubility. In soils, however, the soil solutions were as much as 20‐fold over‐saturated with respect to CaCO3solubility and [HCO‐3] was much greater than predicted by solubility calculations.

ISSN:0190-4167    

DOI:10.1080/01904168609363438

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

During the past few years the DTPA soil test (Lindsay and Norvell, 1978) has been widely accepted for the routine estimation of plant available Fe. The strength of the DTPA test lies in the ability of DTPA to extract labile forms of Fe from the soil, as the plant is able to extract these same labile Fe forms. The objective of this study was to determine the most probable sources of labile Fe which are being removed by the DTPA extractant.

ISSN:0190-4167    

DOI:10.1080/01904168609363439

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Two correlation data sets for the DTPA soil test and one for the NH4HCO3‐DTPA soil test were used to evaluate various soil test correlation methods. Visual, graphical, Mitscherlich, Chi‐square, optimum predictive value, and two‐ and three‐class analysis of variance methods were compared. Critical levels were identified for each method and transition or marginal zones were determined for those methods which facilitate their identification. Critical levels ranged from 3.5 to 5.0 ppm NH4HCO3‐DTPA extractable iron and from 3.5 to 4.8 ppm DTPA extractable iron. Generally, transitional zones were very similar for all methods with both soil tests. Based on these results the Chi‐square method, supported by visual and/or graphical methods, is recommended because of their simplicity and ability to identify transition or marginal zones.

ISSN:0190-4167    

DOI:10.1080/01904168609363440

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Hawkeye soybeans(Glycine maxL.), an iron‐efficient cultivar when grown in calcareous Hacienda loam soil low in P and available Fe, did not respond to P, FeEDDHA, NH4+‐N or NO‐3‐N when applied singly nor to Fe + P together; but did give yield response for N + P + Fe applied together. Addition of HCO3‐with N + P + Fe decreased yields by about 10% and decreased Fe in shoots also by 10%. The NH4+ source of N gave 12% higher leaf yield without HCO3‐and 11% higher with HCO3‐than did nitrate N. Bicarbonate alone caused severe damage to the Hawkeye soybeans, while P alone had little effect. In contrast, P was very damaging with less effect from HCO3‐with iron‐inefficient PI‐54619–5–1 soybeans from a companion study. Addition of Fe decreased Zn and Mn concentrations in leaves, while addition of both Fe and P decreased Zn concentration even more. Bicarbonate contributed additionally to low Zn in leaves with treatments of Fe and Fe + P. These Fe‐efficient Hawk‐eye soybeans were less impaired by NO3‐when grown in calcareous soil than were Fe‐inefficient PI‐54619–5–1 soybeans from a companion study.

ISSN:0190-4167    

DOI:10.1080/01904168609363441

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

In greenhouse experiments, applications of Fe and/or Zn in the form of ferrous sulphate and zinc sulphate induced increased chlorophyll ‘a’ and ‘b’ concentrations, indole‐3‐acetic acid, nitrate reductase activity, and dry matter yield of french bean (Phaseoius vulgarisL.) plants. Iron and Zn in combination were more effective in delaying the leaf senescence compared to controls. Chlorophyll destruction was more rapid at the post‐flowering stage in control plants which led to early senescence and reduced photosynthetic duration. A rapid decline in nitrate reductase activity and indole‐3‐acetic acid concentration in control plants after the 50‐day growth stage further induced senescence. Iron alone and in combination of Zn appeared to contribute to the inhibition of senescence in french bean plants.

ISSN:0190-4167    

DOI:10.1080/01904168609363442

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor