摘要:

Three cultivars of tomato(Lycopersicon esculentumMill., cvs. Sera, 898, Rohaba) were grown under different levels of NaCl in nutrient solution to determine effects of salt stress on shoot and root dry matter (DM), plant height, water use efficiency (WUE, g DM kg‐1water evapotranspired), shoot sodium (Na) and potassium (K) concentrations, and K versus Na selectivity (SK,Na). Increasing NaCl concentration in nutrient solution adversely affected shoot and root DM, plant height, WUE, K concentration, and K/Na ratio of all cultivars. Shoot Na concentrations increased with increasing NaCl concentration in the nutrient solution. Although increasing salt concentration in the solution adversely affected growth of all cultivars, the cultivar Sera had the highest shoot and root DM than the other two cultivars (898 and Rohaba). Shoot and root DM of cultivar 898 was most affected by salt, while cultivar Rohaba had an intermediate salt sensitivity. The cultivar Sera generally had higher WUE values, shoot K concentrations, and SK,Na, but had lower shoot Na concentrations than the other two cultivars when plants were grown under different salt levels. Greater Na exclusion, higher K uptake and shoot SK,Naare suggested as being plant strategies for salt tolerance.

ISSN:0190-4167    

DOI:10.1080/01904160009381992

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A method has been developed to consistently induce increases in root ferric chelate reductase activity in the fruit tree rootstock GF 677(Prunus amygdalopersica)grown under iron (Fe) deficiency. Clonal GF 677 plants were grown hydroponically in a growth chamber with 0 or 90 μM Fe(III)‐EDTA. Root ferric chelate reductase activity was measuredin vivousing BPDS. Plants grown without Fe developed visible symptoms of chlorosis and had lower root ferric chelate reductase activities than those grown with Fe. Root ferric chelate reductase activities were 0.1–1.9 and 0.6–5.3 nmol of Fe reduced per gram of fresh mass and minute, respectively, in Fe‐deficient and sufficient plants. However, when plants grown without Fe for several days were resupplied with 180 μM of Fe(III)‐EDTA, FC‐R activities increased within 1 day. The FC‐R values after Fe resupply were 20‐fold higher than those found in Fe‐deficient plants and 5‐fold higher than those found in the Fe‐sufficient controls. After three days of the Fe treatments the FC‐R activities had decreased again to the control values. The reduction of Fe was localized at the subapical root zone. In the conditions used we have found no decreases of the nutrient solution pH values, indicating that this type of response is not strong enough to be detected in peach tree rootstocks. Also, no major changes in root morphology have been found in response to Fe deficiency. This ferric chelate reductase induction protocol may be used in screening assays to select rootstock genotypes tolerant to Fe chlorosis.

ISSN:0190-4167    

DOI:10.1080/01904160009381993

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Conservation tillage systems, including ridge‐tillage, have become increasing popular with producers in the central Great Plains because of their effectiveness in controlling soil erosion and conserving water. A major disadvantage of the ridge system is that nutrient placement options are limited by lack of any primary tillage options. The objective of this research was to investigate the effects of method of phosphorus (P) placement and rate on irrigated grain sorghum [Sorghum bicolor(L.) Moench] grown in a ridge‐tillage system on a soil low in available P. This experiment was conducted from 1993 to 1995 on a producer's field near the North Central Kansas Experiment Field at Scandia, Kansas on a Carr sandy loam soil (course, loamy, mixed, calcareous, mesic, Typic Udifuvents). Treatments consisted of fertilizer application methods, surface broadcast, single band starter (5 cm to the side and 5 cm below seed), dual band starter (one band on each side of the row), and knifed in the center of the row middle (38 cm from each adjacent row). Each of these treatments was made at either 22 or 44 kg P2O5ha‐1, and nitrogen (N) also was included at the rate of 13 kg ha‐1. Additional treatments were, a combination of 13 kg N and 44 kg P2O5ha‐1applied half broadcast and half as a single band starter, a 1:1 N:P2O5ratio (44 kg N and 44 kg P2O5ha‐1) applied as a single band starter, and a 3:1 ratio (134 kg N and 44 kg P2O5ha‐1) applied as a single band starter. A no‐P check plot also was included. Broadcast and center‐of‐row middle knife applications were made approximately 1 week before planting. After planting, N was balanced on all plots to give a total of 180 kg ha‐1. Applied P treatments improved grain yield and nutrient uptake and consistently shortened the time from emergence to mid‐bloom in all 3 years of the experiment. On this low soil test P soil, treatments that subsurface banded P increased grain yield by 1.27 Mg ha‐1compared to broadcast treatments. Placing N and P in a single starter band 5 cm to the side and 5 cm below the seed was as effective as placing a band on each side of the row. Knife applying N and P in the center of the row was not as effective as placement beside the row. Single band starter application of N and P in a 1:1 and or 3:1 N:P2O5ratio consistently increased yields and nutrient uptake and shortened the time to mid‐bloom as compared to the single band starter treatment that provided only 13 kg N ha‐1. Over the 3 years of the study, these 1:1 and 3:1 N:P2O5ratio starters were clearly superior to an other treatments.

ISSN:0190-4167    

DOI:10.1080/01904160009381994

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The effect of urea and biuret on leaf burn was investigated. Urea and biuret were applied as foliar sprays in factorial combinations at the rates of 0,1, and 2% (w/v) and 0,0.05,0.1, and 0.15% (w/v), respectively, in late April to 2‐year‐old ‘Braeburn'/'Malling‐Merton 111’ ('MM. 111') apple (Malus domesticaBorkh.) trees in a greenhouse. The experiment was repeated in the field in late May and in August using 11‐year‐old ‘Golden Delicious'/'Malling 7A’ ('M.7A'). In August, additional urea [4% (w/v)] and biuret [0.4% (w/v)] treatments were applied. Biuret alone at all rates did not cause leaf damage. Within the range of concentrations used, urea was largely responsible for leaf burn and chlorosis following foliar sprays. However, presence of both chemicals in the spray solution increased leaf injury in April, but not at the later applications. Growers should use low‐biuret urea within reasonable costs.

ISSN:0190-4167    

DOI:10.1080/01904160009381995

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The effect of the supply of ammonium (NH4+) and phosphorus (P) in gel on the amounts of hydrogen ion (H+) excreted from plant roots was studied withBrachiaria humidicola(a highly acid‐soil tolerant tropical grass) andB. brizantha(less acid‐soil tolerant) grown in soil in a glasshouse. The H+production was measured over 24 h in agar gel containing full nutrient solution with a range of NH/‐N levels (0, 0.25, 0.5, and 5.0 mM NH4+‐N). Highly soluble P, K2HPO4, or relatively insoluble P, rock P, was supplied at four concentrations (0, 11.5, 34.5, or 115 μM p) in the gel. Increasing NH4+concentration in the gel increased H+production for both grasses, but there was some inhibition of growth forB. brizanthaat the highest N concentration. ForB. humidicola,but notB. brizanthaH+production was greater with 34.5 μM K2HPO4than 11.5 μM K2HPO4. At 34.5 μM P for both grasses there was no difference in H+production when P was supplied as rock P or K2HPO4. With 11.5 μM P both grasses produced less acid in the gel with the rock P compared with K2HPO4. The reduced H+production is probably due to a lower availability of P in the rock P compared with K2HPO4. This effect was greater withB. brizanthathanB. humidicola,implying that 11.5 μM rock P was not able to supply sufficient P for the growth ofB. brizantha. Brachiaria humidicolawas able to dissolve more rock P thanB. brizanthaor alternatively, the growth ofB. humidicolawas less adversely affected by the low P supply from rock P thanB. brizantha.Plant‐induced acidity does not seem to occur as a response to a lack of available P, but rather these grasses only produce acid if there are enough nutrients for growth, i.e., both NH4+and P. If either N or P is limiting, growth is limited as is NH4+uptake, so that H+production is curtailed.

ISSN:0190-4167    

DOI:10.1080/01904160009381996

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Maize(Zea MaysL.) seeds were inoculated with the N2‐fixing bacteria,Azospirillum brasilenseandAzorhizobium caulinodans.Shoot growth, shoot nitrogen (N) concentration, and grain yield was determined under dryland production conditions in a silt loam. Fertilizer N was applied according to soil test recommendations at either 0, 50, 75, or 100% of the recommended N requirements for a 7,500 kg ha‐1yield goal. BothA. brasilenseandA. caulinodansincreased shoot dry matter production, shoot N concentration, and grain yield somewhat at the lower N recommended rates. There was no agronomic benefit with eitherA. brasilenseandA. caulinodansinoculations under dryland conditions for high N fertility soils under dryland production conditions in a subhumid or semi‐arid moisture regime.

ISSN:0190-4167    

DOI:10.1080/01904160009381997

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Iron chlorosis tolerant soybeans exhibit chlorosis symptoms in the Red River Valley of North Dakota and Minnesota. Previous research suggests that chlorosis was generally related to high calcium (Ca) carbonate levels in the soil, so a relationship of chlorosis with the presence of Calciaquoll (carcareous at the surface, with very high levels of calcite in the subsurface) and non‐Calciaquoll soil types would be expected. Six sites each in 1996, 1997, and 1998 were studied to identify soil factors correlated with the incidence and degree of chlorosis. Gradients between green soybeans and severely chlorotic plants were established, soil type was determined at the green and chlorotic gradient endpoints, and soil samples were taken at the 0–15 cm depth at each gradient location. Iron chlorosis symptoms were filmed using a video recorder. The images recorded were then analyzed using an image analyzer to give a digital chroma number. The digital values were correlated with soil factors to determine the degree of relationship of symptoms with each factor. Soil type differences were only associated with chlorosis at four of twelve sites. Both Ca carbonate equivalence and soluble salts were most often correlated with chlorosis symptoms. The relationship of iron chlorosis with soluble salts, along with soil carbonate level, appears to be a factor that should be considered in soybean chlorosis resistance breeding for the Red River Valley. A greenhouse experiment was conducted which was unsuccessful in duplicating field chlorosis symptoms when gypsum and Ca carbonate was added to soil obtained from non‐chlorotic areas. The study was able to show a decrease in soybean nodule number with increasing Ca carbonate and gypsum levels.

ISSN:0190-4167    

DOI:10.1080/01904160009381998

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A method for determination of nitrate concentration and estimation of kinetic parameters of nitrate uptake by spectroscopy based on absorbances at multiple wavelengths has been developed to estimate nitrate uptake by barley (Hordeum vulgareL. cv. Steptoe) seedlings. Nitrate concentration in the nutrient solution was determined from the slope of the linear regression line of the absorbances to nitrate absorption coefficients at 12 wavelengths. Interference by root exudates was only due to an absorption component changing with wavelength in correlation with nitrate absorption. The standard error of the determination decreased in reverse proportion to the square root of the number of the wavelengths. A linear form of the net uptake equation, NUR = ImaxC/Km+C‐E, could be expressed as NUR = (Imax‐ E) ‐ KmNUR/C ‐ KmE I/C where NUR is net uptake rate, Imax is maximum influx, C is concentration, Km is the Michaelis constant, and E is an efflux constant. The method described here was used to determine the time course of nitrate depletion by barley seedlings from their nutrient solution. The isotherm of net nitrate uptake rates derived from the time course was analyzed after modifications based on the linear form of the net uptake equation. The analysis yielded highly significant results (P<0.0001).

ISSN:0190-4167    

DOI:10.1080/01904160009381999

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The effect that application of nitrogen (N) rates exerts on some parameters of N metabolism in pepper plants(Capsicum annuumL. cv. Lamuyo) during senescence was studied. All plants were grown under controlled conditions in an experimental greenhouse. The treatments consisted of the application of 4 rates of N at the onset of flowering in the form of KNO3(N1: 6 g m‐2, N2:12 g m‐2, N3:18 g m‐2, N4:24 g m‐2). The results obtained show a optimal effect ofN2 fertilization on uptake, translocation, and assimilation of NO3‐in the leaves. The N2 treatment registered maximums in the concentration of chlorophyll a and b, and in commercial yield. In conclusion, for improved pepper cultivation during senescence, treatment N2 gave the maximum yield, and increased metabolism and efficient utilization of N.

ISSN:0190-4167    

DOI:10.1080/01904160009382000

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Soil reflectance affects spectral irradiance measurements taken in winter wheat at early stages of growth when percent cover is low. The objective of this study was to determine the critical percent vegetation coverage needed for forage nitrogen (N) uptake calibration with indirect spectral irradiance measurements. Two field experiments were conducted at Tipton and Perkins, OK in October 1996. The effect of row spacing (15.2, 19.0, 25.4, and 30.5 cm) and growth stage (Feekes 4 and 5) under various N fertilizer rates (0, 56, 112, and 168 kg N ha‐1) on spectral irradiance measurements from wheat was evaluated. The normalized difference vegetative index (NDVI) was used to characterize wheat canopy irradiance. In general, NDVI decreased with increasing row spacing and increased with N fertilizer rate at Feekes growth stage 4. Row spacing and N rate were independent of each other since no significant interaction was found. High correlation (r=0.81–0.98) was observed between NDVI and vegetation coverage. Percent vegetation coverage was a good predictor of the other dependent variables including forage dry matter, and total N uptake, which could indirectly be determined using NDVI. The coefficients of variation (CV's) from NDVI values decreased with increasing vegetation coverage suggesting that less variable NDVI values (CV less than 10%) might be obtained from plots where vegetation coverage exceeds 50%.

ISSN:0190-4167    

DOI:10.1080/01904160009382001

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor