摘要:

A hydroponic system for nutrient plant culture, designed to overcome the problems of algal contamination, adequate aeration and physical support for the plants is presented. It is based on intermittent floodings of the growth pots, containing lapilli tuff as a supportive medium, with a nutrient solution. The substrate used is capable of holding sufficient water for a relatively long period, yet it maintains good aeration of the roots. The system is simple, inexpensive and requires a low power supply. Detailed technical data are given.

ISSN:0190-4167    

DOI:10.1080/01904168909363994

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Tobacco (Nicotiana tabacumL., cv. ‘Coker 319') plants were grown for 28 days in flowing nutrient culture containing either 1.0 mM NO3‐or 1.0 mM NH4+as the nitrogen source in a complete nutrient solution. Acidities of the solutions were controlled at pH 6.0 or 4.0 for each nitrogen source. Plants were sampled at intervals of 6 to 8 days for determination of dry matter and nitrogen accumulation. Specific rates of NO3‐or NH4+uptake (rate of uptake per unit root mass) were calculated from these data. Net photosynthetic rates per unit leaf area were measured on attached leaves by infrared gas analysis. When NO‐was the sole nitrogen source, root growth and nitrogen uptake rate were unaffected by pH of the solution, and photosynthetic activity of leaves and accumulation of dry matter and nitrogen in the whole plant were similar. When NH4+was the nitrogen source, photosynthetic rate of leaves and accumulation of dry matter and nitrogen in the whole plant were not statistically different from NO3‐‐fed plants when acidity of the solution was controlled at pH 6.0. When acidity for NH4+‐fed plants was increased to pH 4.0, however, specific rate of NH4+uptake decreased by about 50% within the first 6 days of treatment. The effect of acidity on root function was associated with a decreased rate of accumulation of nitrogen in shoots that was accompanied by a rapid cessation of leaf development between days 6 and 13. The decline in leaf growth rate of NH4+‐fed plants at pH 4.0 was followed by reductions in photosynthetic rate per unit leaf area. These responses of NH4+‐fed plants to increased root‐zone acidity are characteristic of the sequence of responses that occur during onset of nitrogen stress.

ISSN:0190-4167    

DOI:10.1080/01904168909363995

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A decrease in the pigment content of pear (Pyrus communisL.) leaves, thought to be related to Fe deficiency, occurs in northeastern Spain where is usually called “pear yellowness”;. A nutritional study has been carried out on a pear orchard affected by this physiological “disease”; and growing in the medium Jalón river valley. Total Fe contents were high both in deficient and control leaves, in good agreement with previous results obtained for Fe deficient crops in the same area. However, K/Ca ratios were low, in sharp contrast with the high K/Ca ratios usually associated with iron chlorosis worldwide. Manganese contents per unit area were significantly lower in the yellow leaves. A new high performance liquid chromatography method confirmed that in Fe deficient leaves most pigments decrease concomitantly with chlorophyll a, in agreement with previous reports from this laboratory. Exceptions to this rule were three carotenoids involved in the violaxanthin cycle, violaxanthin, anteraxanthin and zeaxanthin. The total amount of these pigments actually increased ‐by about 20%‐ when chlorophyll decreased by 60% (mild chlorosis), and decreased only by 25% when chlorophyll decreased by 80% (fully developed chlorosis). In Fe deficient pear leaves and in low light, we found significant amounts of zeaxanthin, suggesting a displacement of the violaxanthin cycle towards this carotenoid.

ISSN:0190-4167    

DOI:10.1080/01904168909363996

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Previously published results on exchange capacities for Ca2+, Mg2+, Mn2+, and K+in the Donnan free space of roots of two ryegrass cultivars (Lolium multiflorumLam. cv. Marshall and Wilo) grown at two Al levels in the nutrient solution (0 and 74 μM) were correlated with the average net uptakes of the same cations. For Al‐treated plants regressed separately, significant correlations r=0.906 and r=0.963 were found for Mn2+and Ca2+/Mg2+, respectively. No significant correlations were observed for these cations in control plants. In contrast, when data of control and Al‐treated plants were combined, significant linear correlations r=0.805, r=0.924, and r=0.968 were found for Ca2+, K+, and K+/(Ca2++Mg2+)1/2, respectively. The influence of cations adsorbed onto the root exchange sites and the effect of Al on the cation uptake processes were discussed.

ISSN:0190-4167    

DOI:10.1080/01904168909363997

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A greenhouse experiment was conducted to determine the effectiveness of three vesicular‐arbuscular mycorrhizal (VAM) species in an Oxisol subjected to simulated erosion usingLeucaena leucocephalaas an indicator host. The extent of colonization of leucaena roots increased significantly due to VAM inoculation of the eroded and uneroded soils. The highest level of VAM colonization was observed when leucaena was grown in association withGlomus aggregatum. followed byG. mosseaeandG. etunicatum. Increased infection associated with inoculation of the eroded soil did not result in enhanced mycorrhizal effectiveness. Inoculation of the uneroded soil, however, led to significant improvement in root colonization as well as in symbiotic effectiveness. Suppression in expression of mycorrhizal effectiveness in the eroded soil appears to be a result of nutrient deficiency. The results suggest the importance of restoring lost nutrients before differences in VAM species could be effectively exploited for a successful establishment of a mycorrhizal plants in eroded soils.

ISSN:0190-4167    

DOI:10.1080/01904168909363998

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The iron (Fe) efficiency of soybean [Glycine max(L.) Merr.] genotypes generally has been evaluated in the field on calcareous soil. A nutrient‐solution system has been developed to permit evaluation of Fe efficiency throughout the year. The objectives of this study were to assess the effectiveness of nutrient‐solution tests for evaluating the Fe efficiency of soybean genotypes and to evaluate alternative nutrient‐solution techniques that could minimize the cost of labor and chemicals. Five bicarbonate (HCO3‐) concentrations and three solution‐change schedules were evaluated in a factorial arrangement. Eight soybean genotypes with a wide range of Fe efficiency were evaluated in each treatment and in replicated field tests on calcereous soil during 3 years. Rank correlation coefficients between mean chlorosis scores of genotypes in nutrient solution and field tests ranged from 0.81 to 0.91 for the three solution‐change schedules and from 0.85 to 0.89 for the five HCO3‐concentrations. Replacing the solution every 4 d was not superior to replacing it only at each stage of plant development or not changing the solution throughout the test. A stepwise increase in HCO3‐level at each stage of plant development was not superior to utilizing a constant level of HCO3‐throughout the test. The most economical evaluation of the Fe efficiency of soybean genotypes in nutrient solution can be achieved with no change in the solution and one or more HCO3‐levels that are held constant throughout the test.

ISSN:0190-4167    

DOI:10.1080/01904168909363999

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Cotton (Gossypium hirsutumL.) is extremely sensitive to Al toxicity. Increasing Si concentration in solution has been reported to alleviate AI toxicity. In this investigation the effects of varying Si concentrations (700, 1400, and 2800 μM Si) on reactive Al (defined as Al reactive with aluminon during 10‐s reaction time, without acidification and heating) was studied in solutions containing either 50, 100 or 200 μM Al during 50 d of aging. An increase in Si concentration had negligible effects on the reactive Al in solutions with 50 or 100 μM Al. However, in solutions with 200 μM Al the reactive Al decreased by 6 to 15% with an increase in Si concentration from 0 to 2800 μM.

ISSN:0190-4167    

DOI:10.1080/01904168909364000

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

An objective and quantitative batch nutrient culture system was developed to assess responses of St. Augustinegrass (Stenotaphrum secundatum[Walt.] Kuntze) cultivars ‘Seville’ (saline tolerant) and ‘Floratam’ (saline sensitive) to salt stress. Vessels containing individual grass plugs growing in solution culture were randomized in a walk‐in growth chamber. Nutrient solutions were supplemented weekly with NaCl to gradually increase the conductivity over a three week period to treatment levels (2.4 [control], 12.4, 22.4, and 32.4 dS m‐1). Plants were sampled at the onset, and at four and eight weeks during the experiment. Cell sap was extracted from grass blades and measured with a vapor pressure osmometer to determine osmolarity and osmotic adjustment. Length and area of sample shoot and root systems and foliage color changes were measured using an adaptation of video image analysis, and dry weight (DW) was measured to determine relative growth rate (RGR). ‘Seville’ responded to increasing salt concentration with uniform stepwise increases in cell osmolarity, whereas ‘Floratam’ showed strong depression of cell osmotic potential only in the highest conductivity treatment. At high salt levels, overall shoot development was initially more inhibited for ‘Floratam’, although RGR analysis indicated recovery in the susceptible cultivar after long salt stress duration. ‘Seville’ reacted to saline stress with increased root length, whereas roots were actually stunted in saline treatments for ‘Floratam’. Stress induced an increase in the optical density of grass blades for both cultivars although foliage color was not visibly affected. A positive linear correlation (r = 0.81–0.97) was obtained between shoot area as determined by image analysis versus DW measurements. Use of this novel system maximizes assessment of turfgrass stress responses, and quantification of resistance characteristics.

ISSN:0190-4167    

DOI:10.1080/01904168909364001

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A nutrient solution‐sand culture study was conducted in a greenhouse to evaluate the response of 35 soft red winter wheat varieties to S. Wheat seedlings were grown for 35 days in sand that was leached every other day with complete nutrient solution containing 0, 1 or 5 mg SO4‐S L‐1. Herbage yield of 5‐week‐old wheat plants was increased an average of fourfold as the level ofsin solution was increased from 0 to 5 mg L‐1. The concentration of S in the herbage was increased an average of three‐fold as the concentration of s was increased from 0 to 5 mg L‐1. Differences were observed among varieties for both dry matter and the concentration of S in plant tissue. However, differences among varieties were not consistent at all three levels of s in solution. Sulfur concentration in wheat herbage explained only 24% of the variability in wheat herbage yield. The study did allow for a general grouping of varieties giving the highest, lowest and intermediate yields. Concentrations of Mg, Cu, P, Fe, Mn and Zn were also affected by the level of SO4‐S.

ISSN:0190-4167    

DOI:10.1080/01904168909364002

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Iron‐inefficient TAM 0–312 and Fe‐efficient Coker 227 oats (Strategy II plants) differ in their release of phytosiderophore in response to iron‐deficiency stress—the Fe‐efficient Coker 227 releases a phytosiderophore whereas the Fe‐inefficient TAM 0–312 does not. The phytosiderophore released by Coker 227 oats in response to Fe‐deficiency stress does not appear to transport Fe into the plant as Fe phytosiderophore. When the Fe‐inefficient TAM 0–312 and Fe‐efficient Coker 227 oats were subjected to Fe supplied as Fe2+(BPDS)3, Fe3+HEDTA, as Fe3+EDDHA, Coker 227 utilized the Fe more efficiently than TAM 0–312 ineverycase. Both cultivars reduced Fe3+as FeCl3to form Fe2+(BPOS)3and responded better to this form of Fe than Fe supplied as the ferric chelate. Reduction of Fe3+at the root appears to be a factor that facilitates iron uptake by Coker 227 oats and the release of a phytosiderophore appears to make more Fe available at the root that can be reduced and transported to plant tops.

ISSN:0190-4167    

DOI:10.1080/01904168909364003

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor