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

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.

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Dissection of hyperspectral reflectance to estimate nitrogen and chlorophyll contents in tea leaves based on machine learning algorithms

Scientific Reports ◽

10.1038/s41598-020-73745-2 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Hiroto Yamashita ◽

Rei Sonobe ◽

Yuhei Hirono ◽

Akio Morita ◽

Takashi Ikka

Keyword(s):

Machine Learning ◽

Learning Algorithms ◽

Visible Region ◽

Machine Learning Algorithms ◽

Hyperspectral Reflectance ◽

N Content ◽

Green Leaves ◽

Leaf N Content ◽

N Status ◽

Leaf N

Abstract Nondestructive techniques for estimating nitrogen (N) status are essential tools for optimizing N fertilization input and reducing the environmental impact of agricultural N management, especially in green tea cultivation, which is notably problematic. Previously, hyperspectral indices for chlorophyll (Chl) estimation, namely a green peak and red edge in the visible region, have been identified and used for N estimation because leaf N content closely related to Chl content in green leaves. Herein, datasets of N and Chl contents, and visible and near-infrared hyperspectral reflectance, derived from green leaves under various N nutrient conditions and albino yellow leaves were obtained. A regression model was then constructed using several machine learning algorithms and preprocessing techniques. Machine learning algorithms achieved high-performance models for N and Chl content, ensuring an accuracy threshold of 1.4 or 2.0 based on the ratio of performance to deviation values. Data-based sensitivity analysis through integration of the green and yellow leaves datasets identified clear differences in reflectance to estimate N and Chl contents, especially at 1325–1575 nm, suggesting an N content-specific region. These findings will enable the nondestructive estimation of leaf N content in tea plants and contribute advanced indices for nondestructive tracking of N status in crops.

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288 Effects of Foliar Urea on Reserve Nitrogen and Carbohydrates in Young Apple Trees with Different Nitrogen Background

HortScience ◽

10.21273/hortsci.34.3.492a ◽

1999 ◽

Vol 34 (3) ◽

pp. 492A-492

Author(s):

Lailiang Cheng ◽

Sunghee Guak ◽

Shufu Dong ◽

Leslie H. Fuchigami

Keyword(s):

N Content ◽

Carbohydrate Concentration ◽

Whole Plant ◽

Nitrogen Concentrations ◽

The Difference ◽

Natural Leaf ◽

Reserve Carbohydrate ◽

N Status ◽

Foliar Urea ◽

Whole Tree

Bench-grafted Fuji/M26 plants 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, half of the fertigated trees were sprayed with 3% urea twice at weekly intervals, while the other half were left as controls. The plants were harvested after natural leaf fall, stored at 2 °C, and then destructively sampled in January for reserve N and carbohydrate analysis. As N concentration used in fertigation increased, whole-plant reserve N content increased progressively with a corresponding decrease in reserve carbohydrate concentration. Foliar urea application increased whole-plant N content and decreased reserve carbohydrate concentration. The effect of foliar urea on whole-plant reserve N content and carbohydrate concentration was dependent on the N status of the plant, with low-N plants being more responsive than high-N plants. There was a linear relationship between the increase in N content and decrease in carbohydrate concentration caused by foliar urea, suggesting that part of the reserve carbohydrates was used to assimilate N from foliar urea. Regardless of the difference in tree size caused by N fertigation, the increase in the total amount of reserve N by foliar urea application was the same on a whole-tree basis, indicating that plants with low-N background were more effective in using N from urea spray than plants with high-N background.

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

Weed Science ◽

10.1614/ws-06-141.1 ◽

2007 ◽

Vol 55 (2) ◽

pp. 102-110 ◽

Cited By ~ 9

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.

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Nitrogen Uptake by Citrus Leaves

Journal of the American Society for Horticultural Science ◽

10.21273/jashs.120.3.505 ◽

1995 ◽

Vol 120 (3) ◽

pp. 505-509 ◽

Cited By ~ 9

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).

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An evaluation of foliar nitrogen and zinc applications to macadamia

Australian Journal of Experimental Agriculture ◽

10.1071/ea05165 ◽

2006 ◽

Vol 46 (10) ◽

pp. 1373 ◽

Cited By ~ 5

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.

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Nitrogen Uptake and Mobilization by Hydrangea Leaves from Foliar-sprayed Urea in Fall Depend on Plant Nitrogen Status

HortScience ◽

10.21273/hortsci.43.7.2151 ◽

2008 ◽

Vol 43 (7) ◽

pp. 2151-2154 ◽

Cited By ~ 5

Author(s):

Guihong Bi ◽

Carolyn F. Scagel

Keyword(s):

Nitrogen Uptake ◽

N Uptake ◽

N Content ◽

Plant Nitrogen ◽

Hydrangea Macrophylla ◽

Whole Plant ◽

Urea Uptake ◽

N Status ◽

Foliar Urea ◽

Plant Basis

Rooted liners of Hydrangea macrophylla (Thunb.) Ser. ‘Berlin’ were fertigated with different rates of nitrogen (N) from July to Sept. 2007 and leaves were sprayed with 15N-labeled urea in late October to evaluate urea uptake and 15N translocation by hydrangea leaves in relation to plant N status. Four plants from each N fertigation rate were harvested before they were sprayed with urea and 2, 5, 10, and 15 days after urea spray. Increasing rate of N fertigation increased plant N content in October before being sprayed with urea. Leaves rapidly absorbed 15N from urea spray. The highest rate of 15N uptake occurred during the first 2 days after urea spray and then decreased. Export of 15N from leaves occurred rapidly after uptake and the highest rate of 15N export occurred during the first 2 days after urea spray and then decreased. During the first 5 days after urea spray, the rate of 15N uptake by leaves and export from leaves decreased with increasing rate of N fertigation. On a whole plant basis, the total amount of 15N from foliar 15N–urea spray increased with increasing rate of N fertigation; however, the percentage of 15N exported from leaves and the percentage of N that derived from foliar 15N–urea spray decreased with increasing rate of N fertigation. Results suggest that hydrangea plants with lower N status in the fall are more efficient in absorbing and translocating N from foliar urea than plants with higher N status.

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Use of an Active Canopy Sensor and SPAD Chlorophyll Meter to Quantify Geranium Nitrogen Status

HortScience ◽

10.21273/hortsci.47.1.45 ◽

2012 ◽

Vol 47 (1) ◽

pp. 45-50 ◽

Cited By ~ 11

Author(s):

Yun-wen Wang ◽

Bruce L. Dunn ◽

Daryl B. Arnall ◽

Pei-sheng Mao

Keyword(s):

Green Leaf ◽

Fertilizer Treatment ◽

N Content ◽

Chlorophyll Meter ◽

N Concentration ◽

Flower Traits ◽

Leaf N Content ◽

N Rates ◽

N Status ◽

Leaf N

This research was conducted to investigate the potentials of normalized difference vegetation index (NDVI), a Soil-Plant Analyses Development (SPAD) chlorophyll meter, and leaf nitrogen (N) concentration [% dry matter (DM)] for rapid determination of N status in potted geraniums (Pelargonium ×hortorum). Two F1 cultivars were chosen to represent a dark-green leaf cultivar, Horizon Deep Red, and a light-green leaf cultivar, Horizon Tangerine, and were grown in a soilless culture system. All standard 6-inch (15.24-cm) pots filled with a medium received an initial top-dress application of 5 g controlled-release fertilizer (15N–9P–12K), then plants were supplemented with additional N in the form of urea at 0, 50, 100, or 200 mg·L−1 N every few days to produce plants ranging from N-deficient to N-sufficient. The NDVI readings of individual plants from a NDVI pocket sensor developed by Oklahoma State University were collected weekly until the flowering stage. Data on flower traits, including number of pedicels (NOP), number of full umbels per pot (NOFU), total number of flowers per pot (TNF), number of flowers per pedicel (NOF), and inflorescences diameter (IFD), were collected 3 months after initial fertilizer treatment. After measuring flower traits, pedicels were removed from each pot, and SPAD value, NDVI, and leaf N concentration (g·kg−1 DM) were measured simultaneously. Cultivar and N rate significantly affected all but two flower and one N status parameters studied. The coefficient of determination R2 showed that NOP, NOFU, and TNF traits were more related to the N rates and the status parameters studied for ‘Horizon Tangerine’ than for ‘Horizon Deep Red’. For the latter cultivar, NOP and TNF traits were highly related to NDVI and SPAD values than N rates and leaf N content parameters. Correlation analysis indicated that the NDVI readings (R2 = 0.848 and 0.917) and SPAD values (R2 = 0.861 and 0.950) were significantly related to leaf N content (g·kg−1 DM) between cultivars. However, sensitivity of the NDVI and chlorophyll values to N application rate in geranium was slightly less than leaf N content. Strong correlations (R2 = 0.974 and 0.979, respectively) between NDVI and SPAD values were found within cultivars. The results demonstrated NDVI and SPAD values can be used to estimate N status in geranium. Because the pocket NDVI sensor will be cheaper than the SPAD unit, it has an advantage in determining N content in potted ornamentals.

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Efficiency of C4 photosynthesis in Atriplex lentiformis under salinity stress

Functional Plant Biology ◽

10.1071/pp98143 ◽

1999 ◽

Vol 26 (1) ◽

pp. 79 ◽

Cited By ~ 34

Author(s):

Frederick C. Meinzer ◽

Jun Zhu

Keyword(s):

Gas Exchange ◽

Leaf Area ◽

Salinity Stress ◽

Co2 Uptake ◽

Rubisco Activity ◽

N Content ◽

Bisphosphate Carboxylase ◽

Leaf N Content ◽

Leaf N ◽

Atriplex Lentiformis

Photosynthetic gas exchange, carboxylase activities, and leaf tissue carbon isotope discrimination (Δ) were measured in Atriplex lentiformis (Torr.) Wats. (saltbush) plants grown in a glasshouse at five levels of salinity ranging from 0 to 600 mM NaCl. The net CO2 assimilation rate decreased by 64% from the lowest to the highest level of salinity imposed. The quantum yield for CO2 uptake was maximal in plants grown at 50 mM NaCl, and decreased sharply above and below this salinity level. The ratio of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity to that of phosphoenolpyruvate carboxylase (PEPC) decreased from 0.96 in plants grown at 0 mM NaCl to 0.37 in plants grown at 600 mM NaCl because PEPC activity on a leaf area basis increased linearly with increasing salinity, while Rubisco activity remained relatively constant. Compensatory changes in the leaf area/dry weight ratio and area-based leaf N content with increasing salinity suggested that the linear increase in PEPC activity was a passive response to increasing area-based leaf N content, whereas Rubisco activity on a leaf N basis actually dropped sharply. Relative leakage of CO2 from the bundle sheath, calculated from measurements of gas exchange and foliar Δ values, increased with increasing salinity in parallel with the decrease in the ratio of C3 cycle activity relative to C4 cycle activity. These results suggest that salinity stress diminished the inherent efficiency of the C4 CO2 concentrating mechanism in addition to reducing net CO2 uptake.

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The Relationship between Leaf Nitrogen Content and Photosynthesis in Apple Leaves

HortScience ◽

10.21273/hortsci.31.4.578c ◽

1996 ◽

Vol 31 (4) ◽

pp. 578c-578

Author(s):

Lailiang Cheng ◽

Sunghee Guak ◽

Leslie H. Fuchigami

Keyword(s):

Nitrogen Content ◽

Net Photosynthesis ◽

Leaf Nitrogen ◽

Leaf Nitrogen Content ◽

Nitrogen And Phosphorus ◽

N Content ◽

Wide Range ◽

Leaf N Content ◽

The Relationship ◽

Leaf N

Fertigation of young Fuji/M26 apple trees (Malus domestica Borkh.) with different nitrogen concentrations by using a modified Hoagland solution for 6 weeks resulted in a wide range of leaf nitrogen content in recently expanded leaves (from 0.9 to 4.4 g·m–2). Net photosynthesis at ambient CO2, carboxylation efficiency, and CO2-saturated photosynthesis of recently expanded leaves were closely related to leaf N content expressed on both leaf area and dry weight basis. They all increased almost linearly with increase in leaf N content when leaf N < 2.4 g·m–2, leveled off when leaf N increased further. The relationship between stomatal conductance and leaf N content was similar to that of net photosynthesis with leaf N content, but leaf intercellular CO2 concentration tended to decrease with increase in leaf N content, indicating non-stomatal limitation in leaves with low N content. Photosynthetic nitrogen use efficiency was high when leaf N < 2.4 g·m–2, but decreased with further increase in leaf N content. Due to the correlation between leaf nitrogen and phosphorus content, photosynthesis was also associated with leaf P content, but to a lesser extent.

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