A new optical leaf-clip meter for simultaneous non-destructive assessment of leaf chlorophyll and epidermal flavonoids

Monitoring the vertical profile of leaf chlorophyll (Chl) content within winter wheat canopies is of significant importance for revealing the real nutritional status of the crop. Information on the vertical profile of Chl content is not accessible to nadir-viewing remote or proximal sensing. Off-nadir or multi-angle sensing would provide effective means to detect leaf Chl content in different vertical layers. However, adequate information on the selection of sensitive spectral bands and spectral index formulas for vertical leaf Chl content estimation is not yet available. In this study, all possible two-band and three-band combinations over spectral bands in normalized difference vegetation index (NDVI)-, simple ratio (SR)- and chlorophyll index (CI)-like types of indices at different viewing angles were calculated and assessed for their capability of estimating leaf Chl for three vertical layers of wheat canopies. The vertical profiles of Chl showed top-down declining trends and the patterns of band combinations sensitive to leaf Chl content varied among different vertical layers. Results indicated that the combinations of green band (520 nm) with NIR bands were efficient in estimating upper leaf Chl content, whereas the red edge (695 nm) paired with NIR bands were dominant in quantifying leaf Chl in the lower layers. Correlations between published spectral indices and all NDVI-, SR- and CI-like types of indices and vertical distribution of Chl content showed that reflectance measured from 50°, 30° and 20° backscattering viewing angles were the most promising to obtain information on leaf Chl in the upper-, middle-, and bottom-layer, respectively. Three types of optimized spectral indices improved the accuracy for vertical leaf Chl content estimation. The optimized three-band CI-like index performed the best in the estimation of vertical distribution of leaf Chl content, with R2 of 0.84–0.69, and RMSE of 5.37–5.56 µg/cm2 from the top to the bottom layers, while the optimized SR-like index was recommended for the bottom Chl estimation due to its simple and universal form. We suggest that it is necessary to take into account the penetration characteristic of the light inside the canopy for different Chl absorption regions of the spectrum and the formula used to derive spectral index when estimating the vertical profile of leaf Chl content using off-nadir hyperspectral data.

Intensive vegetable production is commonly associated with excessive nitrogen (N) fertilization and associated environmental problems. Monitoring of crop N status can enhance crop N management. Chlorophyll meters (CMs) could be used to monitor crop N status because leaf chlorophyll (chl) content is strongly related to crop N status. To monitor crop N status, relationships between CM measurements and leaf chl content require evaluation, particularly when excessive N is supplied. The SPAD-502 meter, atLEAF+ sensor, MC-100 Chlorophyll Concentration Meter, and Multiplex sensor were evaluated in sweet pepper with different N supply, throughout the crop, ranging from very deficient to very excessive. CM measurements of all sensors and indices were strongly and positively related to leaf chlorophyll a + b content with curvilinear relationships over the entire range of chl measured (∼0–80 μg cm-2). Measurements with the SPAD-502, and atLEAF+, and of the Multiplex’s simple fluorescence ratio index (SFR) had asymptotic responses to increasing leaf chl. In contrast, the MC-100’s chlorophyll content index (CCI) had a progressively increasing response. At higher chlorophyll a + b contents (e.g., >40 μg cm-2), SPAD-502, atLEAF+ and SFR measurements tended to saturate, which did not occur with CCI. Leaf chl content was most accurately estimated by CCI (R2 = 0.87), followed by the SPAD-502 meter (R2 = 0.85). The atLEAF+ sensor was the least accurate (R2 = 0.76). For leaf chl estimation, CCI measured with the MC-100 meter was the most effective of the four sensors examined because it: (1) most accurately estimated leaf chl content, and (2) had no saturation response at higher leaf chl content. For non-saturating leaf chl content (∼0–40 μg cm-2), all indices were sensitive indicators. As excessive applications of N are frequent in intensive vegetable crop production, the capacity of measuring high leaf chl contents without a saturation response is an important consideration for the practical use of chlorophyll meters.

The soil plant analysis development (SPAD) meter proved effective at estimating leaf Chl content of native and non-native temperate deciduous shrubs. However, due to the change in the relationship between SPAD values and Chl content during the course of autumn senescence, it may be necessary to establish separate calibration equations to cover a range of leaf Chl concentrations. Non-destructive estimates of leaf chlorophyll (Chl) content by hand-held chlorophyll meters such as the Minolta SPAD-502 provide an effective time-efficient method of collecting field data on senescence. To establish useable species-specific calibration equations of relationships between chlorophyll meter readings and leaf Chl content. During autumn, we collected SPAD values and quantum yield of photosystem-II (ΦPSII) over a 10-week period from 1044 leaf samples representing native and non-native temperate deciduous shrub species growing in the wild. Subsequently, Chl was extracted from leaf discs (1 cm diameter), incubated at 65 °C for 2 h in dimethyl sulfoxide, and quantified by spectroscopy. Relationships between extracted Chl and SPAD values were established using linear, quadratic, and exponential equations. Quadratic functions proved the most reliable fit for the data. Interestingly, non-native species tended to have higher leaf Chl content and SPAD values but also exhibited higher variability than native species. The strength (r2) of the SPAD-Chl relationships was weaker than those reported for agricultural or greenhouse-grown plants, but strengthened over time as Chl, ΦPSII, and SPAD values declined. The SPAD meter proved effective at estimating leaf Chl content of native and non-native temperate deciduous shrubs. These estimates may be used in future to validate remote sensing (satellite and near-surface) vegetation indices in late autumn when trees are leafless.

In trying to increase the yield of upland cotton (Gossypium hirsutum L.), breeders have indirectly selected more for increases in harvest index than in photosynthesis. Future cotton yield advances may need increases in both harvest index and photosynthesis. The objectives of this study were to determine if differences in leaf CO2‐exchange rate (CER) existed among cotton genotypes, investigate physiological mechanisms for the gas exchange differences, and determine if gas exchange parameters were related to genotypic lint yield variability. Field studies were conducted from 1990 to 1992 on 18 cotton genotypes. Leaf CER, chlorophyli.(Chl) concentration, soluble protein concentration, specific leaf weight (SLW), lint yield, and yield components were determined each year. In addition, Chl fluorescence measurements were made in 1992. The CER of the 18 genotypes significantly varied about 10% from a low of 26.0 μmol m‐2 s‐1 to a high of 28.8 ltmol m‐2 s‐1. DES 119 and MD 51 ne had higher CER, whereas the CER of Dixie King and Stoneviile 508 were lower. The genotypes differed in leaf Chl and soluble protein concentration in both 1991 and 1992. The CER was positively correlated with leaf Chl concentration (r = 0.768*) and SLW (r = 0.568*) in 1991. No difference in the Fv/Fm parameter of Chi fluorescence was found among the genotypes in 1992. A significant positive association (r2 = 0.205**) was found between lint yield and CER during the boll filling period in 1990 and 1991. CER was positively associated with fiber micronaire (r = 0.772*) and fiber maturity (r 0.797*) in 1992. As some cotton breeders bred for higher yielding genotypes, they may have inadvertently selected for increased photosynthesis.

Research Article| November 01 1999 The Minolta SPAD-502 Leaf Chlorophyll Meter: An Exciting New Tool for Education in the Plant Sciences John Markwell, John Markwell Search for other works by this author on: This Site PubMed Google Scholar Dale Blevins Dale Blevins Search for other works by this author on: This Site PubMed Google Scholar The American Biology Teacher (1999) 61 (9): 672–676. https://doi.org/10.2307/4450800 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Cite Icon Cite Search Site Citation John Markwell, Dale Blevins; The Minolta SPAD-502 Leaf Chlorophyll Meter: An Exciting New Tool for Education in the Plant Sciences. The American Biology Teacher 1 November 1999; 61 (9): 672–676. doi: https://doi.org/10.2307/4450800 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentThe American Biology Teacher Search This content is only available via PDF. Copyright The National Association of Biology Teachers Article PDF first page preview Close Modal You do not currently have access to this content.

Leaf chlorophyll (Chl) concentration can be an indicator of plant health, including photosynthetic potential and nutrient status. In some cases, this measure can indicate the degree to which plants are water-stressed. Traditional methods of measuring Chl concentration have involved a destructive sampling technique: extraction and spectrophotometric analysis. A compatible nondestructive method to measure leaf Chl concentration exists and applies transmittance spectroscopy to plants with a Minolta SPAD-502 meter. These techniques were evaluated by comparing leaf Chl concentration in big bluestem (Andropogon gerardii). Leaves were sampled from plants representing three ecotypes (originating from Central Kansas, Eastern Kansas, and Illinois, USA) and two cultivars of A. gerardii growing in Hays, Kansas, USA. Leaf Chl concentration was measured using nondestructive and destructive techniques. We documented a saturating relationship between destructively measured leaf Chl concentration and SPAD index resulting from a decelerating change in SPAD index as Chl concentration increased. The comparison of A. gerardii ecotypes and cultivars demonstrated highest Chl concentration in the ecotype and cultivar from areas with historically low precipitation, Central Kansas and A. gerardii var. hallii, respectively. A high ratio of Chl a to Chl b is an index of drought adaptation and was also manifested in A. gerardii from drier regions. Thus, drought-adapted ecotypes and cultivars might be able to maintain high photosynthetic productivity and protect photosystem II during dry periods. Conversely, the ecotypes and cultivar originating from areas with higher precipitation had lower leaf Chl and a lower Chl a/b ratio.

Non-destructive determination of maize leaf and canopy chlorophyll content

The role of LAI and leaf chlorophyll on NDVI estimated by UAV in grapevine canopies

SUMMARYThe environmental concern about diffuse pollution from nitrogen (N) fertilizers has led to increased research on the diagnosis of crop N status. The SPAD chlorophyll (Chl) meter is the most commonly used tool for rice (Oryza sativa L.) N status diagnosis, but measurements are conducted at a specific point and readings are affected by different leaf positions. Many measurements per plant must be taken in order to increase the accuracy of N status diagnosis, which limits its application. The present paper attempts to determine rice N status at the canopy level using Multiplex®, a new hand-held optical fluorescence sensor. The fluorescence emission of rice leaves under light excitation was utilized by Multiplex® to non-destructively assess rice leaf Chl and phenolic compound content. A field experiment was conducted in 2011 using a completely randomized split-plot design, with main-plot treatments being six N fertilizer application rates and subplot treatments being different plant densities. Leaf Chl and phenolic compounds were evaluated using the ratio of far-red fluorescence (FRF) to red fluorescence (RF) emission under red light excitation (simple fluorescence ratio, SFR_R) (R2 = 0·35, P < 0·01) and the ratio of decadic logarithm of red to ultra-violet (UV) fluorescence emission (R2 = 0·30, P < 0·01), respectively. Both SPAD reading and fluorescence-based indices including flavonoids (FLAV), nitrogen balance index (NBI_R) and SFR_R could be used to predict rice leaf N contents. The canopy FLAV, SFR_R and NBI_R were all highly correlated to average SPAD readings (R2 > 0·70 in most cases, P < 0·01). Therefore, Multiplex® can be used as an alternative to SPAD to determine rice N status in paddy fields.

Relationships between gross primary production, green LAI, and canopy chlorophyll content in maize: Implications for remote sensing of primary production

BackgroundTea plant is famed in humid and sub-humid of tropical regions, sub-tropical regions, and is a leaf-harvested crop. Nitrogen is the most important nutrient for increasing quality of tea leaves. Therefore, large amounts of nitrogen fertilizer are increasingly applied by tea farmers. Appropriate application of nitrogen fertilizer aroused people’s concern. This research of physiological response to N deficiency stress will be helpful for appropriate application of nitrogen fertilizer for tea farmers and elucidate a mechanistic basis for the reductions in carbon dioxide (CO2) assimilation.ResultsTo elucidate a mechanistic basis for the reductions in carbon dioxide (CO2) assimilation under nitrogen (N) deficiency tea leaves, changes in chlorophyll (Chl), carbohydrates, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and chlorophyll fluorescence transient were examined together with six N treatment (0, 50, 100, 300, 1200 or 6000 μM N). Root, stem and leaves dry weight (DW) increased as N supply increased from 0 to 300 μM, then remained unchanged. The reductions in CO2 assimilation of N-deficient leaves paralleled with high intercellular CO2 concentration. Rubisco activity, protein and Chl content increased linearly or curvilinearly over the range of leaf N content examined except unchanged as leaf N from 2.15 to 2.79 g m−2. Chlorophyll fluorescence transient from N-deficient leaves displayed a depression at the P-step, accompanied by a new step at about 150 μs (L-step). Fv/Fm, REo/ETo, ETo/ABS, Sm, ETo/CSo, PIabs, PItot, abs, were decreased in N-deficient leaves but increased DIo/CSo, DIo/RC and DIo/ABS. Regressive analysis showed that CO2 assimilation decreased linearly or curvilinearly with decreasing initial rubisco, PIabs and Leaf Chl, respectively. Therefore, we concluded the decreased photosynthetic electron transport capacity, leaf chl content and initial rubisco activity are probably the main factors contributing to decreased CO2 assimilation under N deficiency.ConclusionsThe decreased photosynthetic electron transport capacity, leaf Chl content and initial rubisco activity are probably the main factors contributing to decreased CO2 assimilation under N deficiency.

A pot‐culture experiment was conducted under outdoor conditions to determine effects of nitrogen (N) deficiency on big bluestem (Andropogon gerardiiVitman, cv Bonelli) growth, photosynthesis and leaf reflectance (R) properties. Big bluestem was seeded on 14 May 2004 and grown in 120 twelve‐litre pots filled with fine sand and irrigated with Hoagland’s nutrient solution (with 81 mg L−1as N). Treatments initiated at 60 days after sowing (DAS) included: (1) the control (100N) continued receiving the Hoagland’s nutrient solution; (2) reduced N to 20 % of the control (20N); and (3) withheld N from the solution (0N). Chlorophyll (Chl) and N, and reflectance of the uppermost fully expanded leaves were determined at 10‐d intervals from 60 to 115 DAS during the N treatments. Plant growth and developmental parameters were measured at the end of the experiment, 115 DAS. Nitrogen deficiency caused a reduction in leaf Chl content, rate of photosynthesis (A), and dry weight (DW) of biomass components. Deficit N increased leaf reflectance at 555 (R555) and 715 (R715) nm and caused a shift in red‐edge (685–745 nm) to shorter wavelengths. Leaf N and Chl concentrations were linearly correlated with not only the reflectance ratios of R545/R1605 (r2 = 0.82) and R555/R405 (r2 = 0.81), respectively, but also the first derivatives of the reflectance (dR/dλ) in red‐edge centred 690 or 700 nm (r2 = 0.74–0.83). Leaf and panicle DW had the greatest, while root DW had the smallest decrease under N deficiency. It was concluded that the specific reflectance ratios or dR/dλ may be used for rapid and non‐destructive estimation of leaf Chl and plant N status of big bluestem to detect changes in N for appropriate nitrogen management strategies during the growing season.

Accurate acquisition of plant phenotypic information has raised long-standing concerns in support of crop breeding programs. Different methods have been developed for high throughput plant phenotyping, while they mainly focused on the canopy level without considering the spatiotemporal heterogeneity at different canopy layers and growth stages. This study aims to phenotype spatiotemporal heterogeneity of chlorophyll (Chl) content and fluorescence response within rice leaves and canopies. Multipoint Chl content and high time-resolved Chl a fluorescence (ChlF) transient (OJIP transient) of rice plants were measured at different nitrogen levels and growth stages. Results showed that the Chl content within the upper leaves exhibited an increasing trend from the basal to the top portions but a decreasing pattern within the lower leaves at the most growth stages. Leaf Chl content within the rice canopy was higher in the lower leaves in the vegetative phase, while from the initial heading stage the pattern gradually reversed with the highest Chl content appearing in the upper leaves. Nitrogen supply mainly affects the occurrence time of the reverse vertical pattern. This could be the result of different nutritional demands of leaves transforming from sinks to sources, and it was further confirmed by the fall of the JI phase of OJIP transient in the vegetative phase and the rise in the reproductive phase. We further deduced that the vertical distribution of Chl content could have a defined pattern at a specific growth stage. Furthermore, the reduction of end acceptors at photosystem I (PSI) electron acceptor side per cross section (RE0/CS) was found to be a potential sensitive predictor for identifying the vertical heterogeneity of leaf Chl content. These findings provide prior knowledge on the vertical profiles of crop physiological traits, which explore the opportunity to develop more efficient plant phenotyping tools for crop breeding.

Accurately quantifying leaf photosynthetic capacity and its seasonal dynamics is critical for simulating gross primary productivity of farmland ecosystems. Previous studies found that leaf chlorophyll (Chl) content was a better proxy for leaf photosynthetic capacity than leaf nitrogen (N) content for C3 crops. However, the relationships of leaf photosynthetic capacity with leaf Chl and N contents for C4 crops (i.e. maize) remain unclear. To address this question, we measured leaf N, Chl, carotenoid (Car) contents, and leaf photosynthetic capacity quantified by the maximum PEP carboxylation rate (Vpmax), maximum carboxylation rate (Vcmax) and maximum electron transport rate (Jmax) weekly for a summer maize cropland in North China from the tillering stage to maturity. The results revealed that leaf photosynthetic capacity and leaf biochemistry parameters exhibited distinct dynamic patterns, increasing during vegetative stages and declining during reproductive growth. The relationships between photosynthetic capacity and biochemical variables (i.e., leaf N, Chl, Car contents) differed pre- and post-flowering. The strongest correlation was observed between the maximum carboxylation rate at 25 °C (Vcmax25) and leaf Chl content by area (Chlarea) (R2 = 0.81) before flowering, followed by N content by area (Narea) and Car content by area (Cararea) (R2 = 0.78 and 0.62, respectively). The explanatory power of Chlarea, Narea, and Cararea for Vcmax25 declined to varying degrees after flowering (R2 = 0.74, 0.50, and 0.52, respectively). The Variable Influence on the Projection (VIP) scores and loading analyses also showed that the relationship between Vcmax25 and biochemical variables exhibited growth-stage dependency. Multiple linear regression analysis revealed that the combination of leaf Narea, Chlarea, and Cararea had higher accuracy in estimating Vcmax25 (pre-flowering: R2 = 0.94, RMSE = 1.50 μmol·m−2·s−1; post-flowering: R2 = 0.78, RMSE = 4.44 μmol·m−2·s−1) than individual leaf traits. However, the estimation accuracy of Vcmax25 based on leaf Narea, Chlarea, and Cararea showed R2 value only 0.13 (pre-flowering) and 0.04 (post-flowering) higher than that of leaf Chlarea alone. These findings imply that integrating leaf Chl with growth stage information could enhance the estimation of leaf photosynthetic capacity in C4 crops.

Pre-visual detection of iron and phosphorus deficiency by transformed reflectance spectra