摘要:

Eleven soil samples derived from a black vertisol (Arcadia form) and a red alfisol (Shortlands form) were investigated by means of X-ray fluorescence as well as standard soil chemical and physical analyses. The profiles developed from Jurassic basalt under identical macro-environmental conditions and were situated 35 m apart. The clay content was significantly higher in the black solum, as were cation exchange capacity and organic matter, while the proportion of secondary iron phases was markedly lower. Differences in the major element composition of the soil fractions as a whole occurred with profile development, with gains in Si concomitant with a depletion of particularly Fe, Mg, Na and Ca. Gains and losses within each profile were most obvious between the two saprolite horizons and at the saprolite/solum boundary. Only small variations occurred within the solums. Trends in the major element composition of the clay fractions with decreasing depth consisted of a linear accumulation of Al and loss of Mg and Si; these were more pronounced in the red solum. Differences in element proportions between the two profiles correlated with parent material characteristics. The contrast in pedochemical development is explicable predominantly in terms of bedrock contours and related lateral movement characteristics of soil solutions and/or clay minerals. The influx of detritus was significant

ISSN:0257-1862    

DOI:10.1080/02571862.1993.10634663

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

A suitable technique for the extraction of wheat flour protein fractions was pursued to assess the effect of quantitative protein composition on the bread-making quality of winter wheat cultivars on a large scale. Nine procedures involving the use of different sequential solvent extractions were quantitatively compared. The distribution of protein components in the different solubility classes was checked by means of sodium dodecyl sulphate Polyacrylamide gel electrophoresis. The most effective procedure to fractionate the four major protein groups sequentially was: albumin (water),' globulin (0.5 M NaCI + 0.05 mM Na-EDTA), gliadin [55% (v/v) propan-2-ol] and glutenin [0.0125 M Na2B4O7, 0.043 M NaOH, 0.5% (m/v) SDS, 1% (v/v)β-mercaptoethanol].To validate this procedure, linear correlations between quality parameters and protein extracted for all localities and cultivars were complemented by principal component and best subset regression analysis. Albumin and globulin were weakly correlated with quality attributes whereas gliadin and glutenin were highly positively correlated. The contribution of relative glutenin content to dough strength was also confirmed. Since these results complied with present concepts on the relationships between protein fractions and functional properties, it was concluded that the technique could be applied for the protein fractionation of South African winter wheat cultivars.

ISSN:0257-1862    

DOI:10.1080/02571862.1993.10634664

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

Die doel met die ondersoek was om vas te stel of die organiese materiaalinhoud van onversteurde ortiese A-horisonte, wat deur rooi apedale, geelbruin apedale en sagte plintiese B-horisonte onderlêword, vanaf beskikbare of maklik meetbare grondeienskappe en klimaatsdata bereken kan word. Onversteurde ortiese bogronde (0–200 mm) is by 41 lokaliteite, wat verspreid in die somerreënvalgebied voorkom (25°—30°S en 24°—30E),gemonster.Die gronde se organiese koolstof- en totale stikstofinhoude, wat tiperende parameters van organiese materiaal is, is met grondeienskappe soos pH, katioonuitruilkapasiteit en deeltjiegrootte- verspreiding asook met klimaatsdata soos gemiddelde jaarlikse reenval, temperatuur en ariditeitsindeks gekorreleer. Statisties betekenisvolle verwantskappe tussen die organiese materiaalinhoud van die gronde en die fynslik-plus-klei-inhoud daarvan (organiese C:r= 0.91 en totale N:r= 0.91), die ariditeitsindeks van die lokaliteite (organiese C:r= 0.90 en totale N:r= 0.89) en die produkte van die ariditeitsindeks van die lokaliteite en die fynslik-plus-klei-inhoude van die gronde (organiese C: r = 0.94 en totale N: r= 0.95) is verkry. Uit die verwantskappe kan afgelei word dat die organiese materiaalinhoud laer is in warm, droër gebiede as in koeler, natter gebiede. In 'n gebied met dieselfde ariditeitsindeks, was die organiese materiaalinhoud direk eweredig aan die fynslik-plus-klei-inhoud. Die regréssievergelykings wat daargestel is, kan gebruik word om die organiese materiaalinhoud van sekere onversteurde ortiese bogronde in die ondersoekgebiedte raam.

ISSN:0257-1862    

DOI:10.1080/02571862.1993.10634665

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

The level of resistance toChilo partelluswas evaluated in 49 commercially available grain sorghum hybrids using artificial infestation in each of two field trials. The assessment of leaf feeding damage on a scale of one to nine indicated levels ranging from susceptibility to intermediate resistance. Hybrid performance in relation to reduction in peduncle length was inconsistent for all seasons. Pronounced differences in yield loss were observed between hybrids within each trial (9–67%) as well as in yields of the same hybrids for all seasons. This was ascribed to tolerance to damage and the ability of the plant to compensate for damage by means of tiller formation. Hybrids CRN 7690, CRN 7692 and PAN 8501 exhibited the greatest tolerance to borer damage, and consequently suffered comparatively low yield losses. This study provides a basis for the evaluation of future progress in grain sorghum resistance breeding.

ISSN:0257-1862    

DOI:10.1080/02571862.1993.10634666

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

Glyphosate [N-(phosphonomethyl) glycine] phytotoxicity was assessed with different sources of natural water carriers to establish to what extent ions in these carriers antagonize glyphosate activity. Glyphosate phytotoxicity with the most antagonistic carrier was 72% less than with deionized water. Antagonistic cations were calcium, sodium and magnesium. Antagonistic anions were bicarbonate, chloride and sulphate. Combinations of ionic factors such as total hardness, total dissolved solids and electrical conductivity were excellent indicators of the antagonistic capability of carriers. Multiple regression analysis indicated that calcium and magnesium and the anion bicarbonate were the most antagonistic ions in combination.

ISSN:0257-1862    

DOI:10.1080/02571862.1993.10634667

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

The carry-over of atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-s-triazine), which occasionally causes damage to susceptible crops grown in rotation with atrazine-treated maize (Zea maysL.), calls for a refinement of the specified recropping intervals. Bioassays were conducted in a glasshouse to evaluate, with nine soils, the tolerance to atrazine shown by dry beans (Phaseolus vulgarisL. cv. Teebus), grain sorghum (Sorghum bicolor(L.) Moench cv. NK222), oats (Avena sativaL. cv. SWK001), soybeans (Glycine max(L.) Merr. cv. Forrest) and sunflower (Helianthus annuusL. cv. S0222). Significant differences between the tolerance of test species in experiments where dry beans/sunflower and oats/soybean combinations were evaluated are inconsistent with the single recrop interval that is stipulated for all four species. The amount of atrazine that was required to elicit a significant response from a particular test crop varied from soil to soil. The variable availability of atrazine in different soils for uptake by crop species needs to be considered to limit the risk when a sensitive follow-up crop is selected for a soil in which the amounts of toxic atrazine residues are known.

ISSN:0257-1862    

DOI:10.1080/02571862.1993.10634668

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

Samples of irrigated ryegrass pasture and natural veld from various parts of Natal were found, with one exception, to lack the amount of Se normally considered sufficient (0.1 mg kg−1) for grazing animals. No soil properties could be identified by multiple regression as causing such a deficiency. Ryegrass was grown in pots filled with a Kranskop topsoil collected from a selenium-deficient pasture. Sodium selenate, selenite (mixed evenly with the soil or placed in a localized application), Selcote (selenate-based, slow-release granules) and fly ash (containing about 10 mg kg−1Se) were factorially compared at Se rates of 0.5, 1 and 2 mg kg−1in the presence of gypsum and lime. Sodium selenate and Selcote (to a lesser degree) increased foliar Se in ryegrass over a 15-week period to levels normally considered toxic to livestock (>4.0mg kg−1). Gypsum and lime decreased Se uptake by one and a half to three times. Selenite boosted foliar Se to adequate (>0.1 mg kg−1) but not toxic concentrations. Fly ash produced adequate foliar Se only at toxic and economically prohibitive concentrations of ash (20% of the soil). Selenite would be safer than selenate-based fertilizers for rectifying Se deficiency in pastures, but would be needed in larger amounts and would therefore be more costly.

ISSN:0257-1862    

DOI:10.1080/02571862.1993.10634669

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

A plant that produced more than one kernel in many of its florets was isolated from breeding material. The condition was found to be transmitted in monogenic fashion as a recessive character. Transmission of the mutation through the egg cells appears to be normal, but transmission through the pollen is considerably lower. Expression of the pistilloid condition in recessive homozygotes appears to be modified by at least one further gene. Three types of pistilloidy were apparent, firstly, the production of additional pistils without the sacrifice of stamens, secondly, the production of 3–4 pistils but no stamens and, thirdly, the development of additional pistils at the expense of a corresponding number of stamens. The mutation is associated with chromosome arm 6BS and recombinationally may be located close to the centromere. A comparison of C-bands showed that chromosome arm 6BS of the mutant line B13, lacks a heterochroma- tic sub-satellite region which is present in‘Chinese Spring’. It is possible that a spontaneous interstitial deletion occurred at this position, resulting in the abnormality.

ISSN:0257-1862    

DOI:10.1080/02571862.1993.10634670

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

An experiment measuring cell membrane stability was conducted on different inbred lines of maize with known drought sensitivity or tolerance. SDS-polyacrylamide gel electrophoresis showed that a 29.5 kD polypeptide was newly synthesized in the drought sensitive inbred line F2834T in response to drought stress in mannitol. This line also showed an increase in drought tolerance between 8 and 12 hours after the application of the stress.

ISSN:0257-1862    

DOI:10.1080/02571862.1993.10634671

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor