摘要:

Hypotheses regarding mechanisms of aluminum (Al) tolerance in higher plants are grouped into two categories. With exclusion tolerance mechanisms, Al is prevented from entering the symplasm and reaching sensitive metabolic sites. With internal tolerance mechanisms, Al enters the symplasm and tolerance is achieved by detoxification, immobilization, or changes in metabolism. Aluminum is clearly immobilized at the root‐soil interface, however, the extent to which exclusion plays a role in the physiology of Al tolerance is not known. Exclusion mechanisms such as immobilization of Al at the cell wall, selective permeability of the plasma membrane, plant‐induced pH changes in the rhizosphere, and exudation of chelate ligands have been suggested, but experimental support is meagre. Chelation of Al in the cytosol by organic acids or proteins, compartmentation of Al in the vacuole and evolution of Al‐tolerant enzymes have been suggested as possible internal tolerance mechanisms. Despite the volume of literature on this subject, a workable hypothesis to explain how plants flourish on Al‐rich substrates is lacking.

ISSN:0010-3624    

DOI:10.1080/00103628809368004

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

An Al‐tolerant cultivar (Atlas‐66) and an Al‐sensitive cultivar (scout‐66) ofTriticum aestivumL. (wheat) were grown in culture solution with different levels of aluminum (Al) to investigate plant growth response and Al uptake and distribution. With 50 uM Al in solution, root and leaf growth of Scout‐66 decreased to 41±1% and 65±5% of the control, however, both root and leaf growth of Atlas‐66 were not affected. At 200 UM Al, root and leaf growth of Scout‐66 were reduced to 28±1% and 49±2% of control, while root growth of Atlas‐66 was not affected and the leaf growth was reduced to 57±5% of the control. With an increase of Al in solution from 50 to 1000 uM, concentrations of Al in the roots of Atlas‐66 increased from 2500+450 to 4000±110 ug g‐1, and for Scout‐66 from 1980±60 to 3830+20 ug g‐1. In both cultivars, concentrations of Al in the leaves were undetectable below 200 uM Al in solution. Between 200 and 1000 uM Al in solution, concentrations of Al in the leaves were higher in Atlas‐66 (50±2 to 180±40 ug g"1) than in Scout‐66 (40+8 to 130+20 ug g‐1). Of the total absorbed Al, a higher percentage was accumulated in roots of Atlas‐66 (91±1% to 97±1%) than Scout‐66 (83±1% to 92±2%). These results suggest that greater accumulation of Al in roots is one of the characteristics of Al‐tolerant plants, but that Al‐tolerance in wheat is not achieved by exclusion of Al from the symplasm. Ihis conclusion, however, must await separation of absorbed Al into apoplasm and symplasm compartments.

ISSN:0010-3624    

DOI:10.1080/00103628809368005

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

To investigate the relationship between aluminum tolerance and the binding capacity of the root plasmalemma for aluminum, root sections were stained with methylene blue and the blue color intensity of protoplasts was measured with a multi‐purpose graphic analyzer connected to a personal computer. Methylene blue stained both the cell wall and the protoplasts. Root sections killed in boiling water were stained with the same intensity as living root sections.

ISSN:0010-3624    

DOI:10.1080/00103628809368006

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Cultivars ofTriticum aestivum(wheat) differ in their ability to grow under conditions of aluminum (Al) stress, a phenomenon aptly called differential tolerance to Al. The physiological basis of differential tolerance to Al may be the result of differences among cultivars in patterns of nitrogen (N) assimilation. If cultivars differ in their relative preference for NH4+and NO3‐in mixed N substrates, this could affect plant‐induced pH of the growth solution, the solubility and speciation of Al and, hence, the expression of Al tolerance. To further test this hypothesis, an Al‐tolerant cultivar (Atlas‐66) and an Al‐sensitive cultivar (Scout‐66) were grown in solution cultures where the relative supply of NH4+and NO3‐was varied. Plant‐induced pH changes in the growth solutions varied among N treatments and between cultivars. As the supply of NH4+was increased, both cultivars induced a more acidic pH in the growth solution. Despite differences in plant‐induced pH among treatments, the relative root weight (RRW) of Atlas‐66 and Scout‐66 were relatively unaffected by N supply. Thus the superior Al tolerance of Atlas‐66 could not be explained solely by its ability to maintain a high, rhizosphere pH in mixed N solutions.

ISSN:0010-3624    

DOI:10.1080/00103628809368007

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

An aluminum‐tolerant cell line was selected by exposing carrot cell suspension cultures to excess Al, and properties of the selected cells were investigated to elucidate the mechanism of Al‐tolerance. One marked physiological property of the selected cells was that they released more citric acid in the medium than the nonselected cells, particularly in the presence of Al. The Al‐tolerance of the selected cell line was related to the chelating effect of citric acid, which was released abundantly to the medium from the cells. The tops and roots of the germinates from the nonselected cells hardly elongated in the presence of 1 mM AlCl3, but those from the selected cells did very well. Results of visual examination on Al‐tolerance by hematoxylin staining of roots agreed with those obtained by the root elongation test.

ISSN:0010-3624    

DOI:10.1080/00103628809368008

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Genetic variability for tolerance to mineral toxicities, and in particular to aluminum and manganese in acid soils, occurs in a number of crops, and has been widely exploited in wheat. Screening techniques in both the laboratory and the field are reviewed and the mode of inheritance to tolerance is indicated for a number of wheat varieties. In several cases a single dominant gene is involved which can be easily and rapidly transferred into otherwise well adapted varieties. Different genes may be involved for tolerance to different levels of toxicity, and to different toxic minerals. Tolerant varieties are now grown widely in many parts of the world making production possible where none was possible before or increasing production in areas which were previously considered to be marginal.

ISSN:0010-3624    

DOI:10.1080/00103628809368009

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Canadian spring wheat cultivars (Triticum aestivumL.) and imported reference cultivars were grown in nutrient solution at varying aluminum concentrations and treatment durations. Relative root lengths, with and without aluminum, and hematoxylin ratings were the criteria used in evaluating aluminum tolerance.

ISSN:0010-3624    

DOI:10.1080/00103628809368010

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A study was conducted to examine the genetic variability for tolerance to aluminum toxicity in several Kenyan cultivars. The F2 seedlings from eleven crosses between tolerant and intolerant cultivars exhibited a wide range of segregation ratios and indicated that aluminum tolerance in this group of parents was conditioned by two or more genes in each cross. Four of the individual crosses fitted a two‐gene model, and none fitted a single gene model. Expression of the tolerance genes in the F2 progeny was dependent on the genetic background. In three out of four crosses between tolerant parents, a high frequency of susceptible segregates was obtained. The segregation ratio tests performed on the F2 seedling populations suggested that the tolerant parents Romany, PF7748, K. Kongoni and K. Tembo had different tolerance genes. The results from crosses involving K. Fahari, K. Swara and Siete Cerros (all susceptible) indicated that aluminum susceptibility was controlled by recessive genes. The F2 progeny from the crosses K. Tembo x Siete Cerros, K. Swara x Romany, K. Kongoni x PF7748, and K. Fahari x PF7748 fitted a 9 tolerant: 7 susceptible ratio, with dominant genes controlling tolerance. F2 test results indicated that new sources of aluminum tolerance could be incorporated into Kenyan wheat cultivars. Results also suggest that the cultivar Romany is almost equal in tolerance to the best aluminum tolerant spring wheat cultivars previously reported in the literature, and that it is equally effective as a donor parent for aluminum tolerance.

ISSN:0010-3624    

DOI:10.1080/00103628809368011

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The ability of roots of acid soil tolerant and intolerant wheat (Triticum aestivumL.) genotypes to grow into and extract water from subsoil acid environments was investigated. The method used to test this minimized the complicating influence of another effect of acidity, interference with uptake and utilization of nutrients. Root growth by 4‐day‐old seedlings estimates plant ability to explore acid subsoils. Root lengths were measured in eight wheat cultivars exhibiting varied tolerance to an acid soil treated with five levels of Ca(OH)2. Length of the longest root per plant was an indicator of plant response, and decreased linearly with soil solution Al concentration. The cultivars were ranked in order of tolerance from lowest to highest by root length (cm) in the zero lime treatment (434 μMAl in soil solution): Hart 1.8, Arthur 2.0, Wampum 4.0, Caldwell 5.5, Logan 6.3, Edwall 7.3, Titan 8.0, and Yecorra Rojo 8.2. Acid‐tolerant Yecorra Rojo was able to extract 2 to 4 times more water than acid‐sensitive Wampum and Hart cultivars from unlimed subsurface soil.

ISSN:0010-3624    

DOI:10.1080/00103628809368012

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A plant breeding program to develop acid soil stress tolerant (AST) sorghum [Sorghum bicolor(L.) Moench] genotypes under subtropical field environmental conditions in the southeastern U.S.A. has evolved into a dual‐phase process. Since sorghum is highly sensitive to acid soil infertility, initial screening of F1hybrids and advanced generation material is conducted concurrently on 6 soil types (Congaree sl ‐ Typic Udifluvents, Dyke cl ‐ Typic Rhodudults, Cedarbluff sil ‐ Fragiaquic Paleudults, Cecil si and cl ‐ Typic Hapludults, Pacolet scl ‐Typic Hapludults, and Appling csl ‐ Typic Hapludults) at 3 locations and at soil pH levels varying from 4.4 to 4.8 = water extraction [KCl = 3.9–4.2] (range of 5 to 15% Al saturation but Mn toxic). Both conventional (pedigree/backcross) and recurrent selection breeding techniques are being used in the program. Advanced generation material that survives the initial screening process at all locations are reciprocally backcrossed and/or backcrossed to known tolerant genotypes before evaluation at soil pH levels of 3.9 to 4.3 = water extraction [KCl = 3.7–3.9] (range of 40 to 60% Al saturation, and <5% Mn saturation). A satellite Colorado State University tissue culture screening procedure [Al toxicity, salt stress, drought (ethylene glycol) stress] is being initiated in conjunction with the field breeding program. Germplasm with regionally adapted agronomic characteristics, disease resistance, and multiple acid soil stress tolerance is emerging from the sequential developmental program involving environmentally controlled and field stress evaluations.

ISSN:0010-3624    

DOI:10.1080/00103628809368013

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor