scholarly journals Nitrogen Uptake by Citrus Leaves

1995 ◽  
Vol 120 (3) ◽  
pp. 505-509 ◽  
Author(s):  
John D. Lea-Cox ◽  
James P. Syvertsen
Keyword(s):  
N Uptake ◽  
Leaf Age ◽  
Urea Solution ◽  
Citrus Paradisi ◽  
N Content ◽  
Unit Leaf ◽  
Total Leaf ◽  
Citrus Leaves ◽  
Triton X ◽  
Leaf N

We studied whether foliar-applied N uptake from a single application of low-biuret N-urea or K NO to citrus leaves was affected by N source, leaf age, or whole-shoot N content. In a glasshouse experiment using potted 18-month-old Citrus paradisi (L.) `Redblush' grapefruit trees grown in full sun, 2- and 6-month-old leaves on single shoots were dipped into a 11.2 g N/liter (1.776% atom excess N-urea) solution with 0.1% (v/v) Triton X-77. Two entire trees were harvested 1.5,6,24, and 48 hours after N application. Uptake of N per unit leaf area was 1.6- to 6-fold greater for 2-month-old leaves than for older leaves. The largest proportion of N remained in the treated leaf, although there was some acropetal movement to shoot tips. In a second experiment, 11.2 g N/liter (3.78% atom excess) urea-15N and 3.4 g N/titer (4.92% atom excess) KNO solutions of comparable osmotic potential were applied to 8-week-old leaves on 5-year-old `Redblush' grapefruit field-grown trees of differing N status. Twenty-four percent of the applied N-urea was taken up after 1 hour and 54% after 48 hours. On average, only 3% and 8% of the K NO was taken up after 1 and 48 hours, respectively. Urea increased leaf N concentration by 2.2 mg N/g or 7.5% of total leaf N after 48 hours compared to a 0.5 mg N/g increase (1.8% of total leaf N) for KNO. Foliar uptake of N from urea, however, decreased (P < 0.05) with increasing total shoot N content after 48 hours (r = 0.57).

scholarly journals 504 Urea Uptake and Nitrogen Mobilization by Apple Leaves in Relation to Tree Nitrogen Status in the Fall

HortScience ◽  
2000 ◽  
Vol 35 (3) ◽  
pp. 481D-481
Author(s):  
Lailiang Cheng ◽  
Shufu Dong ◽  
Leslie H. Fuchigami
Keyword(s):  
Leaf Area ◽  
N Uptake ◽  
Urea Solution ◽  
N Content ◽  
Wide Range ◽  
Leaf N Content ◽  
N Status ◽  
Foliar Urea ◽  
Whole Tree ◽  
Leaf N

Bench-grafted Fuji/M26 trees were fertigated with seven nitrogen concentrations (0, 2.5, 5.0, 7.5, 10, 15, and 20 mm) by using a modified Hoagland solution from 30 June to 1 Sept. In Mid-October, plants in each N treatment were divided into three groups. One group was destructively sampled to determine background tree N status before foliar urea application. The second group was painted with 3% 15N-urea solution twice at weekly interval on both sides of all leaves while the third group was left as controls. All the fallen leaves from both the 15N-treated and control trees were collected during the leaf senescence process and the trees were harvested after natural leaf fall. Nitrogen fertigation resulted in a wide range of tree N status in the fall. The percentage of whole tree N partitioned into the foliage in the fall increased linearly with increasing leaf N content up to 2.2 g·m–2, reaching a plateau of 50% to 55% with further rise in leaf N. 15N uptake and mobilization per unit leaf area and the percentage of 15N mobilized from leaves decreased with increasing leaf N content. Of the 15N mobilized back to the tree, the percentage of 15N partitioned into the root system decreased with increasing tree N status. Foliar 15N-urea application reduced the mobilization of existing N in the leaves regardless of leaf N status. More 15N was mobilized on a leaf area basis than that from existing N in the leaves with the low N trees showing the largest difference. On a whole-tree basis, the increase in the amount of reserve N caused by foliar urea treatment was similar. We conclude that low N trees are more effective in utilizing N from foliar urea than high N trees in the fall.

An evaluation of foliar nitrogen and zinc applications to macadamia

2006 ◽  
Vol 46 (10) ◽  
pp. 1373 ◽  
Author(s):  
D. O. Huett ◽  
I. Vimpany
Keyword(s):  
Cellulose Acetate ◽  
N Uptake ◽  
Urea Solution ◽  
Leaf Biomass ◽  
N Content ◽  
Sulfate Heptahydrate ◽  
Foliar Nitrogen ◽  
Uptake Efficiency ◽  
Mature Leaves ◽  
Leaf N

The efficiency and effectiveness of foliar nitrogen (N) applications as urea to macadamia leaves were investigated in field experiments at Alstonville, New South Wales. The first experiment (August 2000) evaluated the effect of 1–8% urea solutions on the evidence of leaf burn. A 2% urea solution produced negligible leaf burn (1% leaves with lesions) whereas the incidence of leaf burn increased with urea concentration; 20% of leaves were affected with an 8% urea solution. In the following month, a second experiment was conducted using a 2% urea solution that was painted onto both sides of leaves to measure N uptake efficiency. The urea was enriched with the stable isotope 15N, which allows a direct measure of urea uptake, a common method for tracing plant N uptake. Leaves were sampled after 3 and 6 days, and cellulose acetate was then applied to remove urea adhering to the surface of leaves. Leaves adjacent to urea-treated leaves were also sampled to account for any transport out of treated leaves. The experiment was repeated in September 2001. In 2000, a mean of 31% of the urea was absorbed by the mature leaves and this increased the N content by 2.2%. In 2001, a mean of 38% of the urea was absorbed by the mature leaves and this increased N content by 1.9%. Leaves from part of a large mature macadamia tree were stripped to provide an estimate of leaf biomass. From this, the increase in leaf N uptake for a mature orchard was calculated to be 3.98 kg/ha in 2000 and 4.57 kg/ha in 2001. The efficiency of application and hence leaf N uptake from a commercial spray would be expected to be lower than that of the present study. Commercial foliar urea applications are unlikely to meet the N requirements of a productive macadamia orchard. In a separate study, the efficiency of zinc (Zn) fertiliser as soil (5–20 g Zn/m2 canopy ground area) and foliar applications were examined at a mature commercial orchard near Alstonville on a Ferrosol soil. In August 2001, a 2% solution of zinc sulfate heptahydrate was thoroughly applied to the canopy of trees using a backpack misting machine and mature leaves were sampled 4 weeks later. Non-sprayed control trees were also sampled. Cellulose acetate was applied to sampled leaves to remove foliar-applied Zn adhering to the surface of leaves. The leaf Zn concentrations were increased (P<0.05) from 11 to 52 mg/kg 4 weeks after foliar Zn application. Sprayed leaf Zn concentrations were stable 18 weeks later, and flush leaves that emerged after spray application had similar (P>0.05) Zn concentrations to control leaves 12 months later indicating that little if any remobilisation of Zn had occurred over these periods. Soil Zn application had no effect (P>0.05) on leaf Zn concentrations 1 and 2 years after application. The effectiveness of a commercial foliar Zn application was evaluated in September 2001 using a low set orchard sprayer and a 1% Zn solution. After 4 weeks, leaf Zn concentrations were increased from 12 to 26 mg/kg. Foliar Zn applications can be recommended to increase leaf Zn concentrations in macadamias despite evidence in the literature for only 1% uptake efficiency.

scholarly journals Effects of ontogenetic stage and leaf age on leaf functional traits and the relationships between traits in Pinus koraiensis

2021 ◽  
Author(s):  
Meng Ji ◽  
Guangze Jin ◽  
Zhili Liu
Keyword(s):  
Significant Positive Correlation ◽  
Leaf Age ◽  
Leaf Traits ◽  
Ontogenetic Stage ◽  
Pinus Koraiensis ◽  
Mature Trees ◽  
N Content ◽  
Ontogenetic Stages ◽  
Leaf N Content ◽  
Leaf N

AbstractInvestigating the effects of ontogenetic stage and leaf age on leaf traits is important for understanding the utilization and distribution of resources in the process of plant growth. However, few studies have been conducted to show how traits and trait-trait relationships change across a range of ontogenetic stage and leaf age for evergreen coniferous species. We divided 67 Pinus koraiensis Sieb. et Zucc. of various sizes (0.3–100 cm diameter at breast height, DBH) into four ontogenetic stages, i.e., young trees, middle-aged trees, mature trees and over-mature trees, and measured the leaf mass per area (LMA), leaf dry matter content (LDMC), and mass-based leaf nitrogen content (N) and phosphorus content (P) of each leaf age group for each sampled tree. One-way analysis of variance (ANOVA) was used to describe the variation in leaf traits by ontogenetic stage and leaf age. The standardized major axis method was used to explore the effects of ontogenetic stage and leaf age on trait-trait relationships. We found that LMA and LDMC increased significantly and N and P decreased significantly with increases in the ontogenetic stage and leaf age. Most trait-trait relationships were consistent with the leaf economic spectrum (LES) at a global scale. Among them, leaf N content and LDMC showed a significant negative correlation, leaf N and P contents showed a significant positive correlation, and the absolute value of the slopes of the trait-trait relationships showed a gradually increasing trend with an increasing ontogenetic stage. LMA and LDMC showed a significant positive correlation, and the slopes of the trait-trait relationships showed a gradually decreasing trend with leaf age. Additionally, there were no significant relationships between leaf N content and LMA in most groups, which is contrary to the expectation of the LES. Overall, in the early ontogenetic stages and leaf ages, the leaf traits tend to be related to a "low investment-quick returns" resource strategy. In contrast, in the late ontogenetic stages and leaf ages, they tend to be related to a "high investment-slow returns" resource strategy. Our results reflect the optimal allocation of resources in Pinus koraiensis according to its functional needs during tree and leaf ontogeny.

N uptake, N partitioning, and photosynthetic N-use efficiency of an old and a new maize hybrid

1994 ◽  
Vol 74 (3) ◽  
pp. 479-484 ◽  
Author(s):  
D. E. McCullough ◽  
A. Aguilera ◽  
M. Tollenaar
Keyword(s):  
Dry Matter ◽  
N Uptake ◽  
N Use Efficiency ◽  
Maize Hybrid ◽  
Unit Leaf ◽  
N Supply ◽  
N Partitioning ◽  
Use Efficiency ◽  
N Use ◽  
Leaf N

An old maize (Zea mays L.) hybrid (Pride 5) has been shown to be less tolerant to N stress than a new maize hybrid (Pioneer 3902) during early phases of development. The objective of this study was to quantify the response of the two hybids to N supply in terms of N uptake, N partitioning, and photosynthetic N–use efficiency. Plants were grown under controlled-environment conditions until the 12-leaf stage at three levels of N supply (i.e., 15 mM N, 2.5 mM N, and 0.5 mM N) and were sampled at the 4-, 8-, and 12-leaf stages. Rates of N uptake per unit ground area were higher for Pioneer 3902 than for Pride 5 under maximum N stress during the 8- to 12-leaf phase, but rates were higher for Pride 5 at high N. Rates of N uptake per unit root weight were higher for Pioneer 3902 than for Pride 5 under both medium and low N supply. The old hybrid (Pride 5) partitioned more dry matter and N to leaves than the new hybrid under low N supply, but leaf N per unit leaf area was higher for the new hybrid. The new hybrid (Pioneer 3902) maintained greater rates of leaf photosynthesis per unit leaf N regardless of N supply. Consequently, results indicate that the higher N-use efficiency of Pioneer 3902 under low N supply is associated with higher N uptake and a higher leaf N per unit leaf area. Key words:Zea mays L., dry matter accumulation, photosynthesis, leaf N

scholarly journals Urea Nitrogen Uptake by Citrus Leaves

HortScience ◽  
2001 ◽  
Vol 36 (6) ◽  
pp. 1061-1065 ◽  
Author(s):  
B.R. Bondada ◽  
J.P. Syvertsen ◽  
L.G. Albrigo
Keyword(s):  
Leaf Age ◽  
Extended Period ◽  
Field Studies ◽  
Urea Nitrogen ◽  
N Source ◽  
Leaf Surfaces ◽  
Young Leaves ◽  
Leaf N Concentration ◽  
Citrus Leaves ◽  
Leaf N

Foliar-applied urea nitrogen (N) has potential to become an important component in fertilizer programs for citrus in Florida and other citrus growing areas as it can reduce nitrate leaching into ground water. We evaluated seasonal absorption characteristics of three urea formulations, Triazone-urea, liquid urea, and spray grade urea by citrus leaves that were from 2 weeks to 6 months old. The effect of leaf age on 15N absorption by N-deficient and N-sufficient leaves, together with urea absorption over an eight-week period were studied using greenhouse-grown and field-grown plants. All foliar N applications were based on a recommended rate of 34 kg N/ha in 469 L of water. In the field studies, leaf N was increased similarly by the three urea formulations one week after three weekly applications. Young leaves (0.25 month and 1 month old) absorbed a greater percentage of N than the older leaves (3 month and 6 month old). Epicuticular wax concentration increased and 15N absorption declined with leaf age. Nitrogen deficient leaves (1.80% N) had greater wax concentration and lower N absorption than N sufficient leaves (2.60% N). Four to 8 weeks after urea applications, Triazone-urea sprayed leaves had significantly greater leaf N concentration than leaves sprayed with liquid urea or nonsprayed control leaves. The greenhouse studies revealed that the 15N absorption was greater through abaxial leaf surfaces than through adaxial surfaces regardless of leaf N level and application time. Applying foliar 15N-urea during night (2000 hr to 2200 hr) resulted in greater absorption of 15N than in the morning (0800 hr to 1000 hr) or afternoon (1200 hr to 1400 hr). It is clear that maximum N absorption from foliar urea sprays occurred at night through the abaxial surfaces of young leaves with sufficient N. Triazone-urea acted as a slow-release N source that could be exploited in supplying N over an extended period of time.

scholarly journals Comparative Nitrogen Uptake and Distribution in Corn and Velvetleaf (Abutilon theophrasti)

Weed Science ◽  
2007 ◽  
Vol 55 (2) ◽  
pp. 102-110 ◽  
Author(s):  
John L. Lindquist ◽  
Darren C. Barker ◽  
Stevan Z. Knezevic ◽  
Alexander R. Martin ◽  
Daniel T. Walters
Keyword(s):  
N Uptake ◽  
Soil Nutrient ◽  
Biomass Accumulation ◽  
Field Studies ◽  
Total Biomass ◽  
N Addition ◽  
N Content ◽  
Area Index ◽  
Leaf N Content ◽  
Leaf N

Weeds compete with crops for light, soil water, and nutrients. Nitrogen (N) is the primary limiting soil nutrient. Forecasting the effects of N on growth, development, and interplant competition requires accurate prediction of N uptake and distribution within plants. Field studies were conducted in 1999 and 2000 to determine the effects of variable N addition on monoculture corn and velvetleaf N uptake, the relationship between plant N concentration ([N]) and total biomass, the fraction of N partitioned to leaves, and predicted N uptake and leaf N content. Cumulative N uptake of both species was generally greater in 2000 than in 1999 and tended to increase with increasing N addition. Corn and velvetleaf [N] declined with increasing biomass in both years in a predictable manner. The fraction of N partitioned to corn and velvetleaf leaves varied with thermal time from emergence but was not influenced by year, N addition, or weed density. With the use of the [N]–biomass relationship to forecast N demand, cumulative corn N uptake was accurately predicted for three of four treatments in 1999 but was underpredicted in 2000. Velvetleaf N uptake was accurately predicted in all treatments in both years. Leaf N content (NL, g N m−2leaf) was predicted by the fraction of N partitioned to leaves, predicted N uptake, and observed leaf area index for each species. Average deviations between predicted and observed corn NLwere < 88 and 12% of the observed values in 1999 and 2000, respectively. Velvetleaf NLwas less well predicted, with average deviations ranging from 39 to 248% of the observed values. Results of this research indicate that N uptake in corn and velvetleaf was driven primarily by biomass accumulation. Overall, the approaches outlined in this paper provide reasonable predictions of corn and velvetleaf N uptake and distribution in aboveground tissues.

scholarly journals FOLIAR NITROGEN EFFECTS ON ONION PRODUCTION AND DAMAGE BY THRIPS AND PURPLE BLOTCH

HortScience ◽  
1990 ◽  
Vol 25 (8) ◽  
pp. 864a-864 ◽  
Author(s):  
Robert Wiedenfeld ◽  
B. Scully ◽  
Marvin Miller ◽  
Jonathan Edelson ◽  
Jiandong Wang
Keyword(s):  
N Uptake ◽  
Leaf Age ◽  
Leaf Tissue ◽  
South Texas ◽  
Thrips Tabaci ◽  
Total N ◽  
Foliar Fertilization ◽  
Nitrogen Concentrations ◽  
Use Efficiency ◽  
Leaf N

Purple blotch (Alternari a porri) and thrips (Thrips tabaci) can seriously reduce yields of short day onions in South Texas. The level of injury caused by these organisms is influenced by the concentration of nitrogen in leaf tissue. Lower levels of tissue nitrogen increase susceptibility to A. porri but decrease susceptibility to thrips. The purpose of this study was to evaluate the effect of tissue N levels on joint susceptibility of 4 onion cultivars to A. porri and thrips. Foliage was fertilized at 0, 4, 8, 12 or 16 lbs N/ac/wk for 6 weeks. Nitrogen concentrations in onion leaves varied over time and by leaf age, but showed very little effect due to foliar fertilization. Significant differences in thrips were noted among cultivars, but not among leaf N concentrations with cultivars. Purple blotch outbreak occurred late in the growing season and was not related to leaf N levels. Total N uptake failed to respond to foliar fertilization, therefore overall use efficiency of the foliar N applied averaged only about 10% relative to the amount taken up in the check plots.

Experiments with solid and liquid N-fertilizers and fungicides on winter wheat at Saxmundham, Suffolk, 1976–9

1983 ◽  
Vol 100 (1) ◽  
pp. 163-173 ◽  
Author(s):  
A. Penny ◽  
F. V. Widdowson ◽  
J. F. Jenkyn
Keyword(s):  
Winter Wheat ◽  
Broad Spectrum ◽  
N Uptake ◽  
Nitrate Solution ◽  
Brown Rust ◽  
N Fertilizer ◽  
Urea Solution ◽  
Puccinia Hordei ◽  
N Content ◽  
Factorial Combination

SUMMARYIn 1976 and 1977 late sprays of a urea-ammonium nitrate solution supplying 50 kg N/ha, and broad spectrum fungicides, were tested in factorial combination with 0, 50, 100 or 150 kg N/ha (as ‘Nitro-Chalk’) given either in April or in May to winter wheat. In 1976 leaf diseases were not assessed. In 1977 brown rust (Puccinia hordei) was prevalent and more severe than either mildew (Erysiphe graminis) or septoria (Septoria spp.). Its severity was decreased by the fungicides and by the late sprays of N. Yield and N content of the grain were increased by each increment of ‘Nitro-Chalk’; though % N in grain was larger, yield and N uptake were smaller when the ‘Nitro-Chalk’ was applied in May. The liquid N-fertilizer increased yield little after giving N in April and decreased yield after giving N in May; nevertheless it always increased N content of the grain. The fungicides increased yield only on plots given N in April; their effects on % N in grain were inconsistent.In 1978 and 1979 isobutylidene di-urea (IBDU) supplying 63 kg N/ha in autumn, ‘Nitro-Chalk’ supplying 0, 50, 100 or 150 kg N/ha in April, late sprays of urea solution supplying 50 kg N/ha, sprays of broad spectrum fungicides and sprays of the rust fungicide benodanil were tested in factorial combination (4 × 24) in a ½ replicate design.In both years septoria was more severe than either brown rust or mildew. The broad spectrum fungicides decreased septoria in 1978, but not in 1979. In 1978 (after wheat) 150 kg N/ha as ‘Nitro-Chalk’ was needed for maximum yield, but in 1979 (after beans) only 100 kg; N content of the grain was increased by each increment of N each year. IBDU in the seed bed was less effective than equivalent ‘Nitro-Chalk’. The urea sprays increased yield and most where the least N was given in spring; they always increased grain N content. In 1978 the broad spectrum fungicides increased yield only with 150 kg N/ha in spring, but in 1979 with each amount of N; they affected % N in the grain inconsistently. The rust fungicide little affected yield, but decreased % N in the grain.The weight of 1000 grains was irregularly affected by ‘Nitro-Chalk’ during 1976–1979. However, in all 4 years, 1000-grain weights were increased both by the liquid N fertilizer and by the broad spectrum fungicides and were largest where both had been sprayed.

scholarly journals The Influence of Foliar-applied Urea Nitrogen and Saline Solutions on Net Gas Exchange of Citrus Leaves

1996 ◽  
Vol 121 (3) ◽  
pp. 501-506 ◽  
Author(s):  
R. Romero-Aranda ◽  
J.P. Syvertsen
Keyword(s):  
Gas Exchange ◽  
Leaf Gas Exchange ◽  
Nitrogen Concentration ◽  
Threshold Value ◽  
Citrus Paradisi ◽  
N Concentration ◽  
Salinity Levels ◽  
Citrus Leaves ◽  
Saline Solutions ◽  
Leaf N

We compared net gas exchange rates of CO2 and H2O vapor of greenhouse-grown `Duncan' grapefruit (Citrus paradisi Macf.) and `Valencia' orange [C. sinensis (L.) Osbeck] leaves after multiple foliar sprays of urea N with and without NaCl: CaCl2 solutions. Highly saline solutions (3.8 dSm-1) caused necrotic burn symptoms after leaf chloride levels reached 7 mmol·m-2. Grapefruit leaves had higher leaf Cl and more burn symptoms than orange leaves. The remaining green areas of all salt-stressed leaves, however, had similar rates of net CO2 assimilation (ACO2) and stomatal conductance (gs) as water-sprayed control leaves. Total leaf N and chlorophyll increased with repeated foliar applications of urea solutions regardless of salinity levels in the spray solution. Thus, salts in solution did not interfere with foliar absorption of N. High urea N solutions (33.6 g·liter-1) without salts caused foliar burn and leaf abscission after one application. Three sprays of urea-N solution (11.2 g·liter-1) increased N concentration of N-deficient leaves about 60% and increased ACO2 rate about 50%. ACO2 did not increase when nitrogen concentration in leaves exceeded a threshold value of about 200 mmol·m-2 so photosynthetic nitrogen use efficiency (PNUE = ACO2/N) decreased with increasing leaf N concentration. Net gas exchange and PNUE was higher for grapefruit than for orange leaves. Leaf Cl levels from foliar-applied salts may not be as detrimental to leaf gas exchange as Cl from salts in soil-applied irrigation water.

scholarly journals 506 Air Temperature, Humidity, Leaf Age, and Solution pH Affect Penetration of Urea Through Citrus Leaf Cuticles

HortScience ◽  
2000 ◽  
Vol 35 (3) ◽  
pp. 482A-482
Author(s):  
Vladimir Orbovic ◽  
Diann Achor ◽  
Peter Petracek ◽  
James P. Syvertsen
Keyword(s):  
Contact Angle ◽  
Air Temperature ◽  
Leaf Age ◽  
Solution Concentration ◽  
Contact Angles ◽  
Urea Solution ◽  
Solution Ph ◽  
Drying Time ◽  
Citrus Leaves ◽  
Cuticle Thickness

We examined the effects of air temperature, relative humidity (RH), leaf age, and solution pH on penetration of urea through isolated cuticles of citrus leaves. Intact cuticles were obtained from adaxial surfaces of different aged grapefruit leaves. A finite dose diffusion system was used to follow movement of 14C-labeled-urea from solution droplets across cuticles throughout a 4-day period. The rate of urea penetration increased as temperature increased from 19 °C to 28 °C, but penetration was not further increased at 38 °C. Increasing RH increased droplet drying time and urea penetration at both 28 °C and 38 °C. Cuticle thickness, weight per area, and the contact angle of urea solution droplets increased as leaves aged. Cuticular permeability to urea decreased as leaf age increased from 3 weeks to 7 weeks, but permeability increased in cuticles from leaves older than 9 weeks. Contact angles decreased with increased urea solution concentration on six 7-week-old leaf surfaces, but solution concentration had no effect on contact angle on cuticles from younger and older leaves. Reducing pH of urea solution from pH 8 to pH 4 accelerated the loss of urea from breakdown, possibly due to hydrolysis.

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