摘要:

Sand cultures in which P is supplied by a solid‐phase buffer offer several advantages in studies of P nutrition. Phosphorus concentrations may be maintained at realistically low levels, P supply can be localized in the medium, and roots can readily be removed from sand. However, information on pH, P adsorption and P desorption is needed to use solid‐phase buffers effectively to simulate P supply in soil. Experiments were conducted to characterize the effects of acid washing treatments and P concentration on P adsorption by alumina, and subsequent desorption of P from alumina‐P. Increasing the concentration of H in acid washing treatments decreased the equilibrium desorption P concentration and solution pH for any given adsorption P concentration. Increasing P concentration of adsorption solution led to increasing P concentration and pH of desorption solutions. Further experiments were conducted to determine the effect of percentage alumina‐P in sand‐alumina‐P mixtures on P concentration in the solution phase and on P accumulation by maize (Zea maysL.) seedlings. Solution phase P concentration was unaffected by percentage alumina P, but seedling growth and P accumulation increased in a linear manner with increasing percentage alumina‐P. Phosphorus supply in a sand‐alumina‐P mixture was compared to that in a soil‐sand mixture. Sand‐alumina‐P had higher Bray #1 P concentration than soil‐sand, but lower P concentration in an equilibrium solution. When P was added to sand‐alumina‐P or soil‐sand mixtures, P concentrations decreased more rapidly and there was less net increase in P in sand‐alumina‐P than in soil‐sand. Results confirm the utility of sand‐alumina‐P mixtures as a solid medium for studies of P nutrition, and provide the basis for establishing predetermined P concentration and pH in the medium.

ISSN:0190-4167    

DOI:10.1080/01904168909363951

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The response to salinity differs greatly among various plant species. This study was conducted to evaluate the effects of NaCl salinity on growth of corn in terms of dry matter production and nitrogen and water uptake. Dry matter yield and N and water uptake by sweet corn (Zea maysL; cv. “Florida Stay Sweet") under normal (control) and NaCl salinized (3, 6, and 9 bars osmotic pressures) nutrient solutions were investigated in a walk‐in growth chamber. The 7‐day old seedlings were grown for 14 days in complete Hoagland solution before starting salt treatments. Then, osmotic pressures of the nutrient solutions (except the controls) were raised 1 bar every day by adding 24 mmol, 1.404 g L‐1, NaCl until the desired (3, 6, and 9 bars) salinity levels were attained. The levels of the nutrient solutions in the pots were maintained at the 2‐liter mark by addition of deionized water. The added water to each pot was recorded and considered as water absorbed by plants. Thirty days after the completion of salt treatments, plants were harvested and dry matter yield and total N uptake of plants were determined. Increasing the osmotic pressures of culture solutions decreased total dry matter production and N and water uptake by plants. Nitrogen concentration was substantially higher in salinized plants as compared with the controls. Water use efficiency of plants decreased markedly by increasing salinity. Dry matter yield and water uptake were affected to a greater extent than N uptake by plants under salt stress conditions. It appears that any level of NaCl in root medium is detrimental to corn growth in terms of dry matter production and N and water uptake.

ISSN:0190-4167    

DOI:10.1080/01904168909363952

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Toxic levels of aluminum can cause severe yield reduction in alfalfa (Medicago sativaL.), especially in the presence of drought stress. Reactions to Al stress of alfalfa cultivars and germplasms, representing a broad genetic base and the entire range of dormancy types, were evaluated in a Monmouth soil study [26.2% Al saturation (pH 4.8) vs 2.8% Al saturation (pH 5.7)] and in two nutrient solution experiments (0 vs 111 μmol Al; pH 4.5). The soil study, Experiment 1, and Experiment 2 were harvested 28, 40, and 25 d after seeding, respectively.

ISSN:0190-4167    

DOI:10.1080/01904168909363953

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Pepper plants were hydroponically grown in a growth chamber with two levels of light intensity (300 and 240 w/m2) and two NO3:NH4ratios (100:0 and 80:20). Plants grown with both N forms (80:20) under high light regime displayed greater concentrations of free NH4, organic soluble N and insoluble N than NO3, treated plants, this effect was more pronounced for stem, petioles and root. By contrast, nitrate‐ammonium fed plants with light reduced over 25% presented similar concentrations of organic N (soluble and insoluble) as compared to plants supplied with NO3as sole source of N, however, the amount of free NH4in stem and root was increased. Results indicat that NH4supplied at low concentration was more deletereous for pepper plants grown under high light conditions, when light was reduced, plants presented an alleviation of toxic effect of NH4supply. Finally, nitrogen use efficiency is related to form of N nutrition and the light supplied to crop.

ISSN:0190-4167    

DOI:10.1080/01904168909363954

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The influence of nitrogen nutrition and greenbug (Schizaphis graminumRondani) infestation on growth, chlorophyll content, soluble amino acids, and soluble protein of barley plants (Hordeum vulgareL.) was studied in growth chamber experiments. Plants were grown for 21 days using complete or minus nitrogen nutrient solution. First leaves were then fitted with cages containing eight apterous adult greenbugs. After 7 days, the greenbugs were removed and the plants harvested. The plants given complete nutrient solution grew more rapidly than those given minus nitrogen. Plants grown with minus nitrogen had fewer greenbugs per plant but had much higher numbers of greenbugs per square centimeter of total plant leaf area than plants given complete nutrient solution. All leaves of infested plants grown with minus nitrogen had decreased dry weight, decreased chlorophyll, and increased soluble amino acids when compared with minus nitrogen uninfested plants. Infestation of first leaves of plants grown on complete nutrient solution increased soluble amino acids in all leaves. However, there was little change in the dry weight or chlorophyll level in leaves other than the first leaf. It is concluded that adequate nitrogen nutrition produces plants that can better withstand localized greenbug feeding damage than plants deficient in nitrogen.

ISSN:0190-4167    

DOI:10.1080/01904168909363955

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Responses of mycorrhizal and nonmycorrhizal bell peppers (Capsicum annuum) to solution phosphorus (P) concentrations ranging from 0.01 to 1.0 mg/liter were examined in a pot study. Mycorrhizal plants were inoculated at seeding with the vesicular‐arbuscular mycorrhizal fungus (VAMF)Glomus aggregatum(Schenck and Smith emend Koske). The peppers were transplanted Into a fumigated mix of Waialua clay soil (Vertic Haplustoll) and basaltic sand. At solution P concentrations between 0.01 and 0.03 mg/liter, inoculation with the VAMF increased P uptake, total dry matter production and fruit yields, while reducing the time to anthesis. At solution P concentrations above 0.4 mg/liter, mycorrhizal and nonmycorrhizal plants had similar growth and yields. Transplants with higher levels of root infection at transplanting produced greater final dry weights and fruit yields when planted into P‐deficient soil than transplants with lower levels of root infection, even though the highly infected transplants were F‐stressed and smaller than transplants with lower levels of infection. Extensive pretransplanting infection improved subsequent growth by reducing the time required for establishment of a functional mycorrhizal symbiosis following transplanting.

ISSN:0190-4167    

DOI:10.1080/01904168909363956

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

An isotopic dilution method that overcomes the drawbacks of commonly used methods for measuring N2fixation by aquatic N‐fixers such asAzolla pinnata‐Anabaena azollaeassociation (Azolla) is presented. The method was compared with15N2gas (while maintaining CO2) and the difference methods of measuring N2fixation. The isotopic dilution method was used for two conditions: a. For15N‐free growth medium, Azolla was pre‐enriched with15N, and N2fixation was determined by measuring the dilution of15N in the tissue. b. For the growth medium containing N, N2fixation was determined by providing15N enriched ammonium sulfate in the growth medium and measuring15N to14N ratio in the tissue. An airtight chamber, necessary for15N2gas and acetylene reduction methods, was not representative of the growing environment of Azolla. Temperature in the airtight chamber was far from uniform and CO2was rapidly depleted. The isotopic dilution method is simpler, relatively inexpensive, subject to fewer errors and applicable to more diverse conditions, and yet was as accurate as15N2‐gas method.

ISSN:0190-4167    

DOI:10.1080/01904168909363957

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

In hydroponics, cereal crop growth is usually enhanced when the nutrient media contains both nitrate and ammonium compared to either form separately. Identification of genotypic variation between two spring wheat cultivars(Triticum aestivumcv. Len, andTriticum durumcv. Inbar) in their magnitude of growth response to mixed N permits a comparative evaluation of metabolic processes underlying enhanced growth from utilization of N mixtures. The objective of this study was to determine if the additional mixed N‐induced growth, and the difference in response between cultivars, is associated with the uptake or partitioning of N, P, or K during the seedling stage of development. Plants of Len and Inbar were grown hydroponicaily for 21 days in nutrient solutions containing N either as all nitrate or as a 50/50 mixture of nitrate and ammonium. The mean of three experiments showed that whole plant dry weight increased 19% for Len and 41 % for Inbar when the plants were supplied with the N mixture compared to only nitrate. With the N mixture, the increase in biomass was almost entirely due to enhanced shoot production, which was mainly the result of greater tiller formation. Both cultivars absorbed more N, P, and K when grown with mixed N, and the additional N and K uptake of appeared to be associated with the enhanced growth. This conclusion is based on the observation that Inbar absorbed proportionately more N and K, but less P, than Len when grown with mixed N nutrition. These data suggest that the increased dry matter production from the utilization of mixed N nutrition is not directly related to the additional absorption of P, but may be associated with enhanced N and K uptake.

ISSN:0190-4167    

DOI:10.1080/01904168909363958

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Effect of additional nitrate supply on chlorosis development at different levels of Fe stress was examined in iron efficient and inefficient sorghum cultivars. Nitrate reductase, the enzyme primarily responsible for nitrate reduction was estimated in roots and leaves as affected by Fe stress and additional nitrate.

ISSN:0190-4167    

DOI:10.1080/01904168909363959

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0190-4167    

DOI:10.1080/01904168909363950

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor