摘要:

Effects of calcium (Ca) and magnesium (Mg) on the efflux of solutes and K (Rb) were evaluated using intact barley seedlings. Leakage, as measured by changes in solution conductance, was greater when roots were pretreated with distilled water than with Ca and Mg totalling 12 mM or less. Leakage of K (Rb) was also greater when the external solution was distilled water rather than a solution of Ca and Mg totalling 16 mM. Magnesium did not appear to interfere strongly with Ca function in membrane integrity, although leakage of K (Rb) tended to increase when the ratio of Ca:Mg deviated from unity and Mg rather than Ca was the dominant cation.

ISSN:0190-4167    

DOI:10.1080/01904169009364107

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Previous studies have indicated that under hydroponic conditions, spring wheat (Triticum aestivum) plants produce higher grain yields, more tillers, and increased dry matter when continuously supplied with mixtures of NO3and NH4than when supplied with only NO3. The objective of this study was to determine if mixed N needs to be available before or after flowering, or continuously, in order to elicit increases in growth and yield of wheat. During vegetative development, plants of the cultivar ‘Marshal’ were grown in one of two nutrient solutions containing either a 100/0 or 50/50 mixture of NO3to NH4and, after flowering, half the plants were switched to the other solution. At physiological maturity, plants were harvested, separated into leaves, stems, roots, and grain and the dry matter and N concentration of each part determined. Yield components and the number of productive tillers were also determined. Availability of mixed N at either growth stage increased grain yield over plants receiving continuous NO3, but the increase was twice as large when the mixture was present during vegetative growth. When the N mixture was available only during vegetative growth the yield increase was similar to that obtained with continuous mixed N. The yield increases obtained with mixed N were the result of enhanced tillering and the production of more total biomass. Although plants receiving a mixed N treatment accumulated more total N than those grown solely with NO3, the greatest increase occurred when mixed N was available during vegetative growth. Because availability of mixed N after flowering increased the N concentration over all NO3and pre‐flowering mixed N plants, it appears that the additional N accumulation from mixed N needs to be coupled with tiller development in order to enhance grain yields. These results confirm that mixed N nutrition increases yield of wheat and indicate that the most critical growth stage to supply the N mixture to the plant is during vegetative growth.

ISSN:0190-4167    

DOI:10.1080/01904169009364108

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Euonymus kiautschovicaLoes. ‘Sieboldiana’ plants were grown in small‐volume (450 cm3) or large‐volume (13,500 cm3) plastic containers in the greenhouse in a medium containing sandy loam, perlite, and compost and harvested every 4 weeks for 20 weeks. Plants were fertilized with a nutrient solution several times daily to prevent water and nutrient stress. After 8 to 20 weeks, dry weights of leaves on root‐restricted plants (RRP) were less than those of plants grown in large‐volume containers (controls) but the RRP percent dry weights were higher. There were no differences in dry weights of leaves on the main shoot even after 20 weeks of root restriction. Except for weeks 12 and 16, there was no difference in root/shoot ratio. Root restriction had little or no effect on shoot water potential but reduced the concentration of chlorophyll a, b, and total chlorophyll from weeks 8 through 20 by nearly half. Concentrations of N, P, Ca, Mg, and Cu in the leaves of plants grown in small‐volume containers were 23–48% less than those in large‐volume containers; those of A1 and Fe were 52–68% less, and Mo was 50% greater, but there were no differences in concentrations of K, B, Mn, Zn, Na, or Si. Root restriction caused a pronounced shift in dry matter allocation. The relative distribution of assimilate in the lateral shoots of plants grown in large‐volume and small‐volume containers was 59% and 36% respectively, while that in the main shoot was 21% and 46% respectively. This shift in carbon allocation resulted in a marked suppression of lateral bud growth in root‐restricted plants and suggests that root confinement may induce an imbalance in hormone metabolism and/or nutrient uptake.

ISSN:0190-4167    

DOI:10.1080/01904169009364109

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

‘Wellspur Delicious’ apple trees received preharvest foliar sprays of CaCl2at rates of 0, 5.9 or 19.6 kg Ca/ha. season. Fruits of uniform size (7.65 to 8.05 cm diameter) were harvested on a single date and were allowed to ripen at 19°C or were placed in controlled atmosphere storage for five months and then allowed to ripen at 19°C. Fruit quality indices were measured at various times during ripening. The CaCl2sprays failed to influence fruit mineral element composition, skin color, soluble solids, titratable acidity, firmness, bitter pit or watercore. At all times during ripening, fruit skin color, soluble solids, titratable acidity and firmness were independent of whole fruit Ca, Mg, K, N and P concentrations, and whole fruit Mg/Ca, K/Ca, (K+Mg)/Ca, K/(Ca+Mg), N/Ca and P/Ca concentration ratios. Fruits with and without bitter pit had identical whole fruit Ca concentrations and K/Ca concentration ratios. Whole fruit mineral element composition was an insensitive predictor of quality indices of harvested ‘Delicious’ apples.

ISSN:0190-4167    

DOI:10.1080/01904169009364110

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Detoxification of aluminum (Al) in the rhizosphere has been proposed as a means whereby some plant species are able to tolerate soluble Al. Two mechanisms have been suggested, viz. increase in rhizosphere pH, and excretion of organic ligands into the rhizosphere. A solution culture experiment was conducted to evaluate these mechanisms as possible reasons for the differential tolerance of twoLotusspp.,L. pedunculatuscv. Grasslands Maku (Al‐tolerant) andL. corniculatuscv. Maitland (Al‐sensitive). Two solution pH treatments (pH adjusted daily to 4.7 or pH not adjusted, declining toc.4.0 after 26 days) and two Al treatments (0 or 10 μM monomeric Al) were imposed. The two species showed a marked difference in response to Al. After 26 days’ growth, the total dry matter yield of Grasslands Maku increased by 27% at 10 μM Al, while that of Maitland decreased by 40%.Tissue analysis indicated that Al toxicity was not associated with deficiencies or toxicities of essential nutrients. Higher concentrations of monovalent cations were present in Grasslands Maku tops and roots, while Maitland contained higher concentrations of divalent cations. The two species did not differ in their effect on solution pH, the amount of Al added to maintain 10 μM monomeric Al in solution, or on the quantity of organically‐bound Al in solution at the end of the experiment. This suggested that detoxification of Al in the rhizosphere (either by change in solution pH or by excretion of organic ligands) was not a reason for differential Al tolerance in these two species.

ISSN:0190-4167    

DOI:10.1080/01904169009364111

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Three experiments were conducted in which roots of two species ofLotuswere immersed for up to 40 min in complete nutrient solutions containing 6, 15 or 25 μM Al. The two species tested wereL. pedunculatuscv. Grasslands Maku (Al‐tolerant) andL. corniculatuscv. Maitland (Al‐sensitive). There was an initial rapid (< 5 min) decrease in solution Al at 25 μM Al. The effect was less marked with solution Al ≤ 15 μM. The decrease in solution Al was greater in the Al‐sensitive Maitland than in the Al‐tolerant Grasslands Maku, particularly when expressed on the basis of root fresh mass and root length. Root cation‐exchange capacity (CEC) was lower in Grasslands Maku than in Maitland, viz. 23.9 vs 36.5 mmol kg‐1dry mass. Maitland roots removed more Al from solution than did those of Maku on the basis of total exchange capacity.

ISSN:0190-4167    

DOI:10.1080/01904169009364112

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Previous studies with one cultivar of each of twoLotusspecies showed thatL. pedunculatuscv. Grasslands Maku is Al‐tolerant whileL. corniculatuscv. Maitland is Al‐sensitive. However, little information exists on the relative Al‐tolerance of other lines in these species or on the variability within lines in response to Al. Two solution culture experiments were conducted to study these aspects. The Al tolerance of Grasslands Maku was confirmed, plant dry mass increasing by > 40%with 10 to 30 μM monomeric Al in solution. In contrast, the yield of Maitland was decreased by > 80 % at 30 μM Al, as was that of the other twoL. corniculatuslines tested, AT‐I and AT‐U. The F1 of a cross between aL. pedunculatusline and aL. corniculatusline (G4712) was intermediate with respect to Al tolerance. Also, there was a wide range of response to Al in the F2, which appeared to have similar morphological characteristics to Maitland. Thus, there would appear to be considerable benefit in selecting for Al tolerance and good agronomic characters in this interspecific cross.

ISSN:0190-4167    

DOI:10.1080/01904169009364113

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0190-4167    

DOI:10.1080/01904169009364114

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0190-4167    

DOI:10.1080/01904169009364106

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor