摘要:

Polyacrylamide gel electrophoresis of gliadin proteins in an acid medium was used to identify different spring wheat cultivars. Gliadins were extracted from single kernels or corresponding flour samples using different solvents. Gliadin electrophoretogram formulae using relative band mobilities and staining intensities were determined for each cultivar. Distinctive band patterns were obtained enabling the cultivars to be identified. Single kernels and flour samples gave identical band patterns differing only in the intensity of the staining of the bands.

ISSN:0257-1862    

DOI:10.1080/02571862.1993.10634652

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

Die resultate verkry gedurende hierdie ondersoek dui op akkumulasie van water in holtes van 'n golwende kleierige ondergrond onder oorliggende sand van eoliese oorsprong. Seisoenale veranderings in die diepte van watervlakke is die gevolg van seisoenale verspreidingspatrone van reënval. Die watervlak se diepte is 'n funksie van reënval en die gesamentlike effek van paleo- en oppervlaktopografie. Styging van watervlakke na reënbuie is slegs tydelik en die daaropvolgende daling is die gevolg van horisontale vloei op die paleo- oppervlak.

ISSN:0257-1862    

DOI:10.1080/02571862.1993.10634653

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

A previous investigation showed that Langebaan rock phosphate (Langfos) was not an effective substitute for superphosphate. However, in the light of reports that P availability is enhanced when phosphate rock (PR) and monocalcium phosphate are combined, an improvement in Langfos effectiveness was considered possible if mixed with superphosphate. To investigate this, an Avalon sandy loam and a Balmoral clay were treated with a total of 0, 50, 100, 175, 250 and 350 mg P kg−1and.0, 200, 400, 800 and 1600 mg P kg−1, respectively, applied as a mixture of superphosphate and Langfos to provide P from the two sources in the ratios of1:0, 4:1, 2:1, 1:1, 1:2, 1:4 and 0:1. Soils were incubated forfour weeks before planting to maize. Plants were harvested after six weeks and yield data obtained were examined in relation to total P, water soluble P and citric acid soluble P applied, and to the quantities of P extracted by the Bray 1, Ambic, Mehlich 3 and modified Truog extractants. The water and citric acid-soluble P contents of the various mixtures provided a more reliable index of plant available P, than did their total P contents. The relative agronomic effectiveness of the superphosphate—Langfos mixtures increased in close association with an increase in the proportion of superphosphate in the mixture, and there was little evidence to suggest that an interaction between Langfos and superphosphate had occurred. Both the Ambic and Bray 1 extractants provided reliable indices of plant available P.

ISSN:0257-1862    

DOI:10.1080/02571862.1993.10634654

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

Drought stress-induced changes in the water-soluble protein concentration and total number of sulphydryl (-SH) groups were monitored under controlled environmental conditions in four tobacco cultivars (Nicotiana tabacumL.) with different drought tolerances. The drought stress ranged from light (-0.52 MPa) to severe (-2.5 MPa). A statistically significant decline in both water-soluble protein concentration and total number of -SH groups already occurred at a leaf water potential (ψLof−0.77 MPa. The initial rate of decline in both the concentration of water-soluble protein and the number of -SH groups, as well as the end-values reached by both these parameters, differed significantly between the drought-tolerant (GS46 and ELSOMA) and drought-sensitive (TL33 and CDL28) cultivars. In contrast with the fast initial decline observed in GS46 and ELSOMA at light stress levels, which stabilized and occurred more gradually as the drought stress intensified, the concentration of water-soluble protein and the number of -SH groups declined at a slower but continuous rate in TL33 and CDL28 asψLdecreased. At aψLof−2.51 MPa, the number of -SH groups present in GS46 and ELSOMA respectively, was 63.6% and 65.2%, and that of TL33 and CDL28 was 39.9% and 46.8% of their respective control values. Furthermore, the concentration of water-soluble protein of ELSOMA was still 75.5% and that of GS46, 65.4 % of their controls, even at aψof−2.51 MPa, which contrasts with the corresponding values of 46.6% and 55.3% for TL33 and CDL28, respectively. The steep initial decline in the water-soluble protein concentration of ELSOMA and GS46 is explained on the basis of the concept of protein turnover. The known difference in drought tolerance between the four tobacco cultivars was best explained by a combination of the -SH/-SS hypothesis and the concept of protein turnover.

ISSN:0257-1862    

DOI:10.1080/02571862.1993.10634655

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

Die doel van hierdie studie was om die kompetisievermoëvan koring (Triticum aestivumL.) enBromus diandrusRoth, te vergelyk in terme van vegetatiewe groei in veldproewe. Die proewe is ontwerp as 'n verpla- singsmodel met sewe populaslesamestellings (behandelings) en vyf herhalings. Hoewel gunstige groeitoe- stande in beide jare geheers het, toon die betekenisvolle behandelingsverskille dat kompetisie wel voorge- kom het. Koring was meer gevoelig vir kompetisie asB. diandrusmaar alle gemete plantparameters het toegeneem met 'n toename in die aantalBromus-plante in die populasie. intraspecie-kompetisie het dus 'n groter effek op koring gehad as interspecie-kompetisie. Die finale hoofhalmlengte, blaaroppervlakte en droëmassa per plant vanB. diandrusis slegs in 1988 betekenisvol beïnvloed deur die kompetisie, maar het in beide jare geneig om af te neem met 'n toename in die aantal koringplante in die populasie. Digte koringstande kan dus die vegetatiewe groei vanB. diandrusondergunstigegroeitoestandeonderdruk.

ISSN:0257-1862    

DOI:10.1080/02571862.1993.10634656

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

Die effek van kompetisie tussen koring (Triticum aestivumL.) enBromus diandrusRoth, op reproduktiewe groei is gedurende 1988 en 1989 in veldproewe ondersoek. Die graanopbrengs van koringplante is in beide jare betekenisvol beïnvloed deur kompetisie en verskille in opbrengs het gekorreleer met verskille in die aantal are plant−1. Beide are plant−1en graanopbrengs van die koringplante het toegeneem soos die aantalBromus-plante in die populasie toegeneem het. Die saadopbrengs vanB. diandrusis slegs in 1988 betekenisvol beïnvloed deur die kompetisie tussen koring enB. diandrusen het afgeneem met 'n toename in die aantal koringplante. Die afname in saadopbrengs was positief gekorreleerd met beide die aantal pluime en saadmassa pluim−1. Die relatiewe opbrengstotaal (RYT) vir 1988 toon dat die species wel vir dieselfde groeifaktore gekompeteer het, maar dat koring in 1988 'n meer aggressiewe groeier asB. diandruswas. Hoewel koring dus die groei vanB. diandruskan onderdruk, verhoed dit nie saadproduksie nie.

ISSN:0257-1862    

DOI:10.1080/02571862.1993.10634657

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

The response of wild oat (Avena fatua) to diclofop-methyl and CGA 184′927+S under conditions of water stress was assessed in a pot experiment. Treatments with 0, 8, 16 and 24% polyethylene glycol (PEG 6000) were used to impose water stress. The water stress treatments were initiated when the plants reached the two-leaf stage and continued for seven days prior to and two days after the herbicides were applied. Leaf extension rate was the most sensitive plant parameter to water stress and was decreased by all water stress treatments. Stomatal diffusive resistance of wild oat. Leaves was increased significantly by the 16 and 24% PEG treatments. These water stress treatments caused a reduction in the response of wild oat to diclofopmethyl as illustrated by a continuation of the leaf extension rate during the first week after spraying. The survival and seedhead production of diclofop-methyl-sprayed plants were greatest at the highest water stress level (24% PEG). Water stress did not affect the efficacy of CGA 184′927+S on wild oat. The leaf expansion of plants sprayed with this herbicide stopped within four days after spraying and all plants died within 35 days, irrespective of the water stress level imposed.

ISSN:0257-1862    

DOI:10.1080/02571862.1993.10634658

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

Soil water characteristics can be estimated accurately from the clay content and cation exchange capacity (CEC) values of soils. The clay with its very large adsorption surface and CEC which reflects the negative charge of clays, is jointly responsible for adsorbing di-polar water molecules. Formulae relating clay content and CEC to soil water content at matric potentials of−33,−80,−500 and−1500 kPa were calculated using the results obtained with the pressure membrane technique on 100 soil samples and then validated with a further 200 soil sample measurements. Clay content and CEC accounted for more than 93% of the variability in soil water at the four measurement points.

ISSN:0257-1862    

DOI:10.1080/02571862.1993.10634659

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

The germination rate of cabbage seeds (Brassica oleraceacv. Hercules) exposed to the vapour of the 2,4-dichlorophenoxy iso-octyl ester (2,4-D IOE) was used in a bioassay to determine the effectiveness of commercial adjuvants in reducing the volatility of this hormonal herbicide. The herbicide vapour was generated by a source of known concentration placed on filter paper at the bottom of a closed system. The phytotoxicity of vapours released by the adjuvants was tested in the same manner. Of the six adjuvants tested, (Agripon Super®, Armoblen T600®, Bladbuff 5®, Getdown®, Derimin®and Surfynol®), Surfynol was found to generate phytotoxic vapours which reduced the germination rate of seeds. Although the adjuvants did not reduce the volatility of 2,4-D IOE in the described system, they were found to be effective if filter paper was omitted from the source solution. This reduction was not sufficiently dramatic to warrant the use of these substances for reducing the volatility of hormonal herbicides in agricultural practices.

ISSN:0257-1862    

DOI:10.1080/02571862.1993.10634660

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

Nutrition-element elimination studies on crops in soil with a high fixation capacity using pot experiments are usually problematic where the realistic and accurate application of nutrients is concerned. The possible use of agar gel in plant nutritional studies was investigated. Commercial agar-agar, used for microbiological purposes, was found to have low enough nutrient concentrations to be used. Furthermore, 1.5% agar blocks were found to be stable in soil during glasshouse pot trials and can be effectively used as a nutrient carrier as they will temporarily protect nutrients against sorption and precipitation due to phase difference.

ISSN:0257-1862    

DOI:10.1080/02571862.1993.10634661

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor