Partitioning of Nitrogen Between and Within Leaves Grown Under Different Irradiances

1989 ◽  
Vol 16 (6) ◽  
pp. 533 ◽  
Author(s):  
JR Evans
Keyword(s):  
Nitrogen Content ◽  
Photosynthetic Rate ◽  
Protein Complexes ◽  
Leaf Nitrogen ◽  
High Irradiance ◽  
Leaf Nitrogen Content ◽  
Unit Leaf ◽  
Growth Irradiance ◽  
Pigment Protein Complexes ◽  
Nitrogen Contents

The distribution of nitrogen between leaves on individual plants of Phaseolus vulgaris and Cucumis sativus which were grown under different irradiances was examined. For Phaseolus, shading treatments were imposed on individual leaflets when they had reached one-third of full expansion. Adjacent leaflets were either grown under the same irradiance or had different irradiances imposed on them. The nitrogen content of leaves depended on their growth irradiance and not on the growth irradiance of adjacent leaflets, with more nitrogen being found in leaves grown under higher irradiance compared to those grown in shade. For Cucumis, the nitrogen contents of the leaves changed following the imposition of shading treatments. The experiment was repeated four times with different nitrate nutrient treatments, twice in combination with a pretreatment growth irradiance of 40% sunlight. The relative changes in leaf nitrogen content for each irradiance treatment were independent of changes to the leaf nitrogen content of the plant and of the growth irradiance prior to the shading treatments. Again, nitrogen contents were highest in leaves grown at high irradiance. Acclimation of individual leaves to their irradiance treatment was seen for both Phaseolus and Cucumis. Growth under shade resulted in lower rates of oxygen evolution per unit of chlorophyll, when measured at high irradiance, and increased partitioning of nitrogen into pigment-protein complexes. These two changes working in opposition to each other meant that for Cucumis, the relationship between photosynthetic capacity and nitrogen content was similar between irradiance treatments. For Phaseolus, the increased partitioning of nitrogen into pigment-protein complexes at low irradiance was not as great as the reduction in photosynthetic rate per unit of chlorophyll, so that the photosynthetic rate per unit leaf nitrogen was less for leaves grown under low irradiance compared to those grown under high irradiance. It is shown that acclimation to lower irradiance can increase the potential daily photosynthesis for a given leaf nitrogen content.

Effect of Nitrogen Content on the Photosynthetic Characteristics of Sunflower Leaves

1993 ◽  
Vol 20 (3) ◽  
pp. 251 ◽  
Author(s):  
DJ Connor ◽  
AJ Hall ◽  
VO Sadras
Keyword(s):  
Nitrogen Content ◽  
Dark Respiration ◽  
Net Photosynthesis ◽  
Leaf Nitrogen ◽  
Mean Value ◽  
Life Cycles ◽  
High Irradiance ◽  
Response Curves ◽  
Unit Leaf ◽  
Wide Range

Photosynthesis-irradiance response curves and leaf nitrogen contents were measured weekly by destructive sampling over the life cycles of leaves 10, 15, 20 and 25 of sunflower plants (cv. Prosol 35) grown in large pots in the open under optimum conditions of temperature and high irradiance. Individual leaf responses were adequately described by a hyperbola of three parameters, viz. Pmax, the rate of photosynthesis in saturating irradiance; R, the rate of dark respiration adjusted for temperature (30�C); and ε, the apparent quantum efficiency of photosynthesis at low irradiance. Pmax (range 0-40 μmol CO2 m-2 s-1) and R (0-4 μmol CO2 m-2 s-1) were non-linearly related to nitrogen content per unit leaf area (NL) (range 0.3-2.9 g N m-2) across all leaf positions and for all leaf ages. ε (mean value 0.050 mol mol-1, s.e. 0.001) was independent of NL. The equations for net photosynthesis derived from pot studies were shown to explain (r2 =0.80) leaf photosynthesis in a crop of the same cultivar over a wide range of NL and irradiance.

scholarly journals Physiological responses of two tropical weeds to shade: II. Leaf gas exchange and nitrogen content

1999 ◽  
Vol 34 (6) ◽  
pp. 952-961 ◽  
Author(s):  
Moacyr Bernardino Dias-Filho
Keyword(s):  
Nitrogen Content ◽  
Weed Management ◽  
Dark Respiration ◽  
Leaf Gas Exchange ◽  
Co2 Assimilation ◽  
Leaf Nitrogen ◽  
High Irradiance ◽  
Leaf Nitrogen Content ◽  
Light Regimes ◽  
Stachytarpheta Cayennensis

Ipomoea asarifolia (Desr.) Roem. & Schultz (Convolvulaceae) and Stachytarpheta cayennensis (Rich) Vahl. (Verbenaceae), two weeds found in pastures and crop areas in the Brazilian Amazonia, Brazil, were grown in controlled environment cabinets under high (800-1000 µmol m-² s-¹) and low (200-350 µmol m-² s-¹) light regimes during a 40-day period. The objective was to determine the effect of shade on photosynthetic features and leaf nitrogen content of I. asarifolia and S. cayennensis. High-irradiance grown I. asarifolia leaves had significantly higher dark respiration and light saturated rates of photosynthesis than low-irradiance leaves. No significant differences for these traits, between treatments, were observed in S. cayennensis. Low-irradiance leaves of both species displayed higher CO2 assimilation rates under low irradiance. High-irradiance grown leaves of both species had less nitrogen per unit of weight. Low-irradiance S. cayennensis had more nitrogen per unit of leaf area than high-irradiance plants; however, I. asarifolia showed no consistent pattern for this variable through time. For S. cayennensis, leaf nitrogen content and CO2 assimilation were inversely correlated to the amount of biomass allocated to developing reproductive structures. These results are discussed in relation to their ecological and weed management implications.

scholarly journals Novel Combined Spectral Indices Derived from Hyperspectral and Laser-Induced Fluorescence LiDAR Spectra for Leaf Nitrogen Contents Estimation of Rice

2020 ◽  
Vol 12 (1) ◽  
pp. 185
Author(s):  
Lin Du ◽  
Jian Yang ◽  
Bowen Chen ◽  
Jia Sun ◽  
Biwu Chen ◽  
...  
Keyword(s):  
Neural Networks ◽  
Artificial Neural Networks ◽  
Nitrogen Content ◽  
Laser Induced Fluorescence ◽  
Leaf Nitrogen ◽  
Ecological Environment ◽  
Leaf Nitrogen Content ◽  
Spectral Indices ◽  
Crop Monitoring ◽  
Nitrogen Contents

Spectra of reflectance (Sr) and fluorescence (Sf) are significant for crop monitoring and ecological environment research, and can be used to indicate the leaf nitrogen content (LNC) of crops indirectly. The aim of this work is to use the Sr-Sf features obtained with hyperspectral and laser-induced fluorescence LiDAR (HSL, LIFL) systems to construct novel combined spectral indices (NCIH-F) for multi-year rice LNC estimation. The NCIH-F is in a form of FWs* Φ + GSIs* Φ , where Φ is the Sr-Sf features, and FWs and GSIs are the feature weights and global sensitive indices for each characteristic band. In this study, the characteristic bands were chosen in different ways. Firstly, the Sr-Sf characteristics which can be the intensity or derivative variables of spectra in 685 and 740 nm, have been assigned as the Φ value in NCIH-F formula. Simultaneously, the photochemical reflectance index (PRI) formed with 531 and 570 nm was modified based on a variant spectral index, called PRIfraction, with the Sf intensity in 740 nm, and then compared its potential with NCIH-F on LNC estimation. During the above analysis, both NCIH-F and PRIfraction values were utilized to model rice LNC based on the artificial neural networks (ANNs) method. Subsequently, four prior bands were selected, respectively, with high FW and GSI values as the ANNs inputs for rice LNC estimation. Results show that FW- and GSI-based NCIH-F are closely related to rice LNC, and the performance of previous spectral indices used for LNC estimation can be greatly improved by multiplying their FWs and GSIs. Thus, it can be included that the FW- and GSI-based NCIH-F constitutes an efficient and reliable constructed form combining HSL (Sr) and LIFL (Sf) data together for rice LNC estimation.

Photosynthetic Acclimation and Nitrogen Partitioning Within a Lucerne Canopy. II. Stability Through Time and Comparison With a Theoretical Optimum

1993 ◽  
Vol 20 (1) ◽  
pp. 69 ◽  
Author(s):  
JR Evans
Keyword(s):  
Nitrogen Content ◽  
Photosynthetic Rate ◽  
Leaf Nitrogen ◽  
Nitrogen Partitioning ◽  
Photosynthetic Acclimation ◽  
Leaf Nitrogen Content ◽  
Canopy Photosynthesis ◽  
Nitrogen Distribution ◽  
Area Index ◽  
Nitrogen Redistribution

Nitrogen redistribution between and within leaves was examined in a plot of lucerne (Medicago sativa L. cv. Aurora) in relation to potential canopy photosynthesis. The canopy was sampled during regrowth after cutting and just prior to flowering. As leaves were progressively shaded by the newly produced leaves, nitrogen content fell and photosynthetic acclimation occurred. The rate of acclimation in the canopy was the same as occurred following a step change to 23 or 6% sunlight. The profile of leaf nitrogen content was stable with respect to leaf area index and independent of time of sampling. Optimal profiles of nitrogen distribution between leaves, photosynthetic rate per unit chlorophyll and nitrogen partitioning within leaves were calculated from the relationships between photosynthesis and nitrogen in conjunction with the light environment of the preceding 3 days. The optimal nitrogen content of the leaves should vary in proportion to the relative daily irradiance at each leaf. The observed distribution achieved 88% of the potential daily photosynthesis, while a uniform nitrogen distribution yielded only 80%. Photosynthetic acclimation and nitrogen partitioning within each leaf both responded to daily irradiance similarly to the calculated optimum except at the two extremes. At the top of the canopy, photosynthetic rate per unit of chlorophyll did not increase as much as the calculated optimum, while at the base of the canopy, nitrogen partitioning failed to fall as much as the calculated optimum. This may reflect the constraints on the flexibility of the photosynthetic system. Nitrogen redistribution between leaves made a dramatic contribution to increasing the potential photosynthesis by the canopy. Although acclimation to low irradiance reduced the photosynthetic capacity per unit nitrogen by 12%, the considerable reorganisation of proteins within the thylakoids increased potential daily photosynthesis by 20% over that which would have been gained by a 'sun' leaf. However, in terms of canopy photosynthesis, which is dominated by leaves intercepting most of the light, acclimation contributed only a few per cent to the potential daily canopy photosynthesis.

scholarly journals Estimating the Leaf Nitrogen Content with a New Feature Extracted from the Ultra-High Spectral and Spatial Resolution Images in Wheat

2021 ◽  
Vol 13 (4) ◽  
pp. 739
Author(s):  
Jiale Jiang ◽  
Jie Zhu ◽  
Xue Wang ◽  
Tao Cheng ◽  
Yongchao Tian ◽  
...  
Keyword(s):  
Nitrogen Content ◽  
Precision Agriculture ◽  
Field Experiments ◽  
Mean Squared Error ◽  
Growing Season ◽  
Leaf Nitrogen ◽  
Textural Analysis ◽  
Hyperspectral Images ◽  
Leaf Nitrogen Content ◽  
New Feature

Real-time and accurate monitoring of nitrogen content in crops is crucial for precision agriculture. Proximal sensing is the most common technique for monitoring crop traits, but it is often influenced by soil background and shadow effects. However, few studies have investigated the classification of different components of crop canopy, and the performance of spectral and textural indices from different components on estimating leaf nitrogen content (LNC) of wheat remains unexplored. This study aims to investigate a new feature extracted from near-ground hyperspectral imaging data to estimate precisely the LNC of wheat. In field experiments conducted over two years, we collected hyperspectral images at different rates of nitrogen and planting densities for several varieties of wheat throughout the growing season. We used traditional methods of classification (one unsupervised and one supervised method), spectral analysis (SA), textural analysis (TA), and integrated spectral and textural analysis (S-TA) to classify the images obtained as those of soil, panicles, sunlit leaves (SL), and shadowed leaves (SHL). The results show that the S-TA can provide a reasonable compromise between accuracy and efficiency (overall accuracy = 97.8%, Kappa coefficient = 0.971, and run time = 14 min), so the comparative results from S-TA were used to generate four target objects: the whole image (WI), all leaves (AL), SL, and SHL. Then, those objects were used to determine the relationships between the LNC and three types of indices: spectral indices (SIs), textural indices (TIs), and spectral and textural indices (STIs). All AL-derived indices achieved more stable relationships with the LNC than the WI-, SL-, and SHL-derived indices, and the AL-derived STI was the best index for estimating the LNC in terms of both calibration (Rc2 = 0.78, relative root mean-squared error (RRMSEc) = 13.5%) and validation (Rv2 = 0.83, RRMSEv = 10.9%). It suggests that extracting the spectral and textural features of all leaves from near-ground hyperspectral images can precisely estimate the LNC of wheat throughout the growing season. The workflow is promising for the LNC estimation of other crops and could be helpful for precision agriculture.

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