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Various devices and applications are used for the rapid assessment of plant nitrogen nutrition, which give an approximate indication of leaf chlorophyll saturation by giving the relative chlorophyll content or leaf greenness intensity. In this study, chlorophyll content and leaf greenness determined by three devices were compared: SPAD-502 (spectrum technology), Hydro N-Tester, and Samsung smartphone (RGB app). Additionally, laboratory determination of chlorophyll content was compared to soil-plant analysis development (SPAD) values. Based on the results obtained, indices characterising the vegetative or direct state were calculated and the values obtained with these devices were compared. The crops tested were soya, potatoes, wheat and sunflower. The results show a close relationship between the size of the SPAD index and RGB light sources of colour the intensity of red (R), green (G) and blue (B). The indices IPCA and R+G-2B showed a very high negative correlation with SPAD readings (-0.82 and -0.83). Statistical analysis showed that SPAD readings obtained from the two chlorophyll meters showed a high correlation regardless of the crop species tested (R2 = 0.98). The correlation analysis also showed the possibility of substituting equipment and vegetation indices based on readings taken with a smartphone, with an accuracy not much inferior to standard chlorophyll meters. This situation could occur in case of failure or absence of the standard device. [ABSTRACT FROM AUTHOR]

Leaf chlorophyll content (LCC) is an important indicator of plant health. Earth observation facilitates LCC monitoring on large spatial scales and within short time intervals by retrieving canopy LCC from spectral signals. However, in-situ measurements are still necessary to validate the predicted values and the accurate quantification of LCC is labour-intensive and costly. Handheld leaf chlorophyll metres, such as the SPAD-502 (Konica Minolta) promise quick and non-destructive in-situ LCC estimates. SPAD values can be easily converted to LCC by established calibration curves that are based on measurements of single plant species. Due to these practical advantages, the application of SPAD-LCC calibration curves, originally derived in an agricultural context (Markwell et al., 1995), has become common practice in field studies. Although associated with a variety of uncertainties, the transfer of general SPAD-to-LCC calibration equations to natural ecosystems has not yet been comprehensively investigated. In this study, we test the reliability of SPAD-to-LCC conversions in three structurally different semi-natural grassland areas with mixed species compositions. We measured SPAD values in the field and determined the corresponding LCC of the very leaf samples via chemical extraction and spectrophotometry. Our results show that SPAD-to-LCC conversion equations lack accuracy in semi-natural grassland with mixed species compositions (n = 157, R2 = 0.046, p

Measurement of chlorophyll content using destructive methods is not efficient due to a large number of samples, cost, and time needed. Estimationof chlorophyll content by nondestructive methods using handheld chlorophyll meter may be considered to improve efficiency. This research aimed to determine the formula to convert SPAD-502 and atLEAF CHL PLUS values (relative indicator of chlorophyll content) to estimated (absolute) rubber leaves chlorophyll content. Twenty leaves of rubber plant were measured using SPAD-502 and atLEAF CHL PLUS at the same time to determine SPAD-502 and atLEAF CHL PLUS values. The measured leaves were then collected to determine the chlorophyll content using a standard laboratory procedure. Regression and correlation analyses (among 3 methods) were conducted using SAS v.9 software. The results showed that between SPAD-502 and atLEAF CHL PLUS values were closely correlated, hence both of the devices can substitute each other to estimate rubber leaf chlorophyll content. In addition, the relationship between atLEAF CHL PLUS and SPAD-502 values with actual chlorophyll content of rubber clone SP 217, PB 260, GT1, and all clones (general) were significant with high coefficient of determination (R2) as well as low Root Mean Square Error (RMSE) and Coefficient of Variation (CV). Therefore, by using formula determined in this study, both atLEAF CHL PLUS and SPAD-502 can be suggested for accurate, fast, and non-destructive estimation of chlorophyll content of rubber plant leaf.

The nitrogen sufficiency index (NSI) obtained by using a portable chlorophyll meter is a practical alternative to evaluate the N levels in plants. This study aimed at determining the appropriate NSI value for leaves of common bean plants, in order to define the need and amount of N to be applied as topdressing, using the Minolta SPAD-502 portable chlorophyll meter. Three field experiments were conducted using a randomized blocks design, with four replications. Nitrogen doses were applied as topdressing and compared with a treatment in which a high dose of N was used as a reference to calculate the NSI, whose value was 95 %. According to the results observed using the chlorophyll meter and the NSI, for each 0.1 percentage point increase in the NSI to reach the adequate level (95 %), it is necessary to apply 1.1-1.5 kg ha-1 of topdressing N.

Chlorophyll content in lichens is routinely used as an accurate indicator of lichen vigor, interspecific differences, and the effect of site-related environmental parameters. Traditional methods of chlorophyll extraction are destructive, time-consuming, expensive, and inoperable, especially when measuring large quantities of chlorophyll. However, non-destructive methods of measurement using portable chlorophyll meters are rarely used for lichens. Considering the characteristics of lichens such as rough blade surface and absence of chlorophyll b in cyanolichens, we compared the non-destructive methods with traditional methods and evaluated their applicability in studying lichen pigment content. Two instruments, SPAD-502 and CCM-300, were used to measure the pigment content of seven foliose lichen species. These pigment readings were compared with those determined using the dimethyl sulphoxide (DMSO) extraction method. Significant correlations were observed between SPAD/CCM values and pigments (chlorophyll and total carotenoids) extracted from chlorolichens, especially species with a smooth surface. The CCM-300 was more accurate in detecting the pigment content of foliose chlorolichens. However, both instruments showed certain limitations in the determination of pigment content in cyanolichens, especially gelatinous species. For example, CCM-300 often failed to give specific values for some cyanolichen samples, and both instruments showed low measurement accuracy for cyanolichens. Based on the high correlation observed between chlorophyll meter readings and pigments extracted from chlorolichens, equations obtained in this study enabled accurate prediction of pigment content in these lichens. [ABSTRACT FROM AUTHOR]

The utilization of a non-destructive SPAD-502 chlorophyll meter, which enables the measurement of nitrogen status in plant leaves, has gained popularity in agronomic crops. Its application to horticultural crops like coffee remains relatively uncommon. The device provides quick and real-time measurements, helping to provide on-time nitrogen fertilizer to coffee plants before deficiency signs occur. Coffee leaves are characterized by thick and waxy leaves, together with many layers of tree crown. Therefore, the objective of this study was to develop a method for measuring nitrogen levels in coffee plants using the SPAD-502 Chlorophyll meter for an appropriate nitrogen fertilizer application rate in Arabica coffee plants. •Coffee trees were separated into upper, middle and lower levels. Data on SPAD values and total nitrogen were analyzed.•Pearson Correlation Coefficient (R), Coefficient of Determination (R 2 ) and linear regression were calculated for different three levels of both SPAD-502 and total nitrogen values.•The results revealed a strong correlation (R 2  = 0.63) between the SPAD readings of coffee leaves obtained from the upper canopy and their nitrogen content. These findings can provide a good concept of which coffee crown level will be a better part for measuring N content using a SPAD-502 Chlorophyll meter., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Author(s).)

Genetic diversity of plants increases the possibility of choice and provides higher adaptability of plants to adverse environmental conditions. Flax (Linum usitatissimum L.) is one of the crops requiring attention and introduction in agricultural production. In Siberia, Russia already in 1908 the first experiments with flax were started in Tobolsk province. In the 20th century this branch was developed on the farms of Tyumen region. Heat resources, agrochemical properties of soils, water supply are adequate for the cultivation of this crop in the northern latitudes. The study was aimed to explore the effects of seed treatment with phosphemidum on chlorophyll content and morphometric parameters of flax seedlings and plants. Seventeen samples of fibre flax and three samples of linseed of different origin (Russia, Belarus, Ukraine, Canada, Czech Republic, France and Germany) from the collection of the Institute of Biology of Tyumen State University were studied. Air-dried seeds were treated with the solution of chemical agent phosphemidum in concentrations of 0.005, 0.01 and 0.1 %. Laboratory experiments revealed differences in morphometric parameters of plant seedlings. The response to seed treatment with mutagen was studied by the variability of chlorophyll content in the leaves. The samples were found to differ in the dynamics of chlorophyll accumulation by the stages of ontogenesis. All samples reacted to the increase of phosphemidum concentration by the decrease in chlorophyll content in leaves. [ABSTRACT FROM AUTHOR]

In regions around the current high-latitude boundaries of agricultural production, the effects of climate change are likely to affect future growing conditions. Specifically for soybeans (Glycine max (L.) Merr.), this leads to a northward shift of the northernmost limit for cultivation. In two high-latitude regions with cold growing conditions (northwest Germany and southern West Siberia, Russia), similar field trials were conducted under different climate conditions (temperate oceanic, temperate continental). The effect of soybean seed inoculation with Bradyrhizobium japonicum was investigated in comparison to untreated control in five field site-years under organic farming conditions. SPAD meter readings were used to indicate differences in leaf chlorophyll content between inoculation and control at three phenological development stages. To make SPAD values from different varieties and development stages comparable, effect sizes (‘Hedges’ d’ of inoculation against control) were calculated. Inoculation was always successful, and significant numbers of active nodules developed only with inoculation. Effect sizes of SPAD values were significantly positive in inoculated plots at the beginning of seed filling but did not differ earlier. Except for the warmest site-year, inoculation did not affect seed yield. Protein content was significantly higher with inoculation at most varieties tested in Germany but only once in Russia. Protein yield was only in the warmest site-year significantly higher with inoculation. Under cold growing conditions of high-latitude regions, temperature sums seemed to limit soybean yield and the effectiveness of inoculation with B. japonicum. To implement soybeans as legumes in organic farming crop rotations, nevertheless, inoculation is mandatory, since soils at high latitudes lack soy-specific rhizobia bacteria. [ABSTRACT FROM AUTHOR]

The SPAD-502 and the FieldScout CM 1000 chlorophyll meters were compared in their performance in diagnosing the nutritional status of plants. Leaves of a wide range of greenness were used to push the sensitivity of the tools to their limits. Both devices showed high reproducibility when used by different operators. The SPAD-readings were well-correlated with leaf nitrogen (N) concentrations, since leaves from heavily fertilized plants were not included in the sample population. The FieldScout-readings showed a marked saturation curve with the leaf N concentration, thus it cannot be used as a reliable N nutritional status index. The results also showed that the use of SPAD-502 in the diagnosis of the nutritional status of an orchard requires the establishment of specific critical concentrations for cultivars and sampling dates. The SPAD-502 appeared to have potential in the diagnosis of the nutritional status of the orchard for nutrients other than N. [ABSTRACT FROM AUTHOR]

Aim of study: We evaluated the use of dimethylsulfoxide (DMSO) for the photometric determination of chlorophyll (Chla and Chlb) and carotenoids in Quercus ilex L. leaves by comparative analysis using aqueous-acetone extraction. Area of study: a Q. ilex dehesa in Las Majadas del Tietar, Cáceres, Spain Material and methods: Q. ilex leaves were sampled during two vegetative periods. Field SPAD-502 Chlorophyll measurements and photometric chlorophyll determinations were performed. Two procedures were used: extraction of intact foliar discs at 65ºC with DMSO and fine foliar powder with cold aqueous-acetone. Main results: DMSO produced Chlb overestimation and different fitting performance for SPAD vs pigment calibrations (R2=0.64, RMSE=0.20, p

Premise of research: Local adaptation ultimately arises as a result of adaptive divergence in phenotypic characters. Within a species, a large portion of the phenotypic traits that confer local adaptation must be physiological characters. Yet few studies consider adaptive divergence in physiological characters or estimate genetic variation within populations for physiological traits that may confer local adaptation. Here I test the hypothesis that there is genetic variation within and between populations of a C3-C4 intermediate for theCO2 compensation point (G) and other photosynthetic traits. In addition to local adaptation, population-level variation in photosynthetic characters of C3-C4 intermediates reflects the potential for evolution of more C4-like photosynthesis. Methodology: I chose two populations of Mollugo verticillata, one from a relatively cool climate and one from a warm climate. I quantified variation within and between populations by measuring photosynthetic physiology at 247 and 357C, temperatures that match the average maximums during the growing season at the populations' native sites. Pivotal results: I detected little evidence of genetic variation within populations for G and carboxylation efficiency, but there was temperature-dependent population variation for G, where the population from the cool climate had a lower average G at 247C. Apparent chlorophyll concentration was also greater in this population at both temperatures. Conclusions: The results demonstrate that there has been divergence among populations in G. Interestingly, the population from the cooler climate had lower G at 247C. There is little evidence of adaptive evolutionary potential within populations; estimates of broad-sense heritability were not significant even when pooling samples from both populations to increase the overall sample size. Adaptation of more C4-like photosynthesis may proceed through the evolution of other physiological characters not directly related to concentrating carbon. [ABSTRACT FROM AUTHOR]

Cotton aphid ( Aphis gossypii) is considered as one of the most important agriculture pest for the cotton production. However, it is generally labor-intensive and time-consuming to obtain some information of Cotton aphid with conventional methods through direct measurement by sampling in the field. This study explores the potential of using a new method to obtain information of the Cotton aphid rapidly . In our study, the cotton canopy spectral indices ( NDVI, VI_ 2, REDrefc, NIRrefc) and chlorophyll concentration, obtained from hand-held high spectrometer GreenSeeker and chlorophyll meter SPAD-502 and Cotton aphid amount derived from the artificial field-based survey were used to uncover the relationship between Cotton aphid amount and canopy spectral index and SPAD value of the cotton in city of Shihezi, China. The results showed that NDVI and NIRrefc were negatively related to Cotton aphid amount. VI_2 content had a significant and positive relationship with its amount. The non-linear three cubic models with alate Aphid amount as independent variables have been established between VI_2 value and alatae Aphid amount, which could explain 92.37 % of VI_2 value variance. SPAD values were also significantly and negatively correlated to the Aphid amount. The non-linear logarithm model with wingless Aphid amount as independent variables was the best for uncovering the relationship between SPAD value and wingless Aphid amount, which could explain 85.48 % of SPAD value variance. The results demonstrate the establishment of the function model provides a theoretical basis and techniques for indirect and rapid monitoring and management of Cotton aphid. [ABSTRACT FROM AUTHOR]

Biophysical and biochemical plant foliage parameters play a key role in assessing vegetation health. Those plant parameters determine the spectral reflectance and transmittance properties of vegetation; therefore, hyperspectral remote sensing, particularly imaging spectroscopy, can provide estimates of leaf and canopy chemical properties. Based on the relationship between spectral response and biochemical/biophysical properties of the leaves and canopies, the PROSPECT radiative transfer model simulates the interaction of light with leaves. In this study, more than 1100 leaf samples from the Amazon forest of Ecuador were collected at several study sites, some of which are affected by petroleum pollution, and across the vertical profile of the forest. For every sample, field spectroscopy at leaf level was conducted with a spectroradiometer. The goal of this study was to assess leaf optical properties of polluted and unpolluted rainforest canopies across the vertical profile and identify vegetation stress expressed in changes of biophysical and biochemical properties of vegetation. An ANOVA followed by Holme's multiple comparisons of means and a principal component analysis showed that photosynthetic pigments, chlorophyll and carotenoids have significantly lower levels across the vertical profile of the forest, particularly in sites affected by petroleum pollution. On the other hand, foliar water content showed significantly higher levels in the polluted site. Those findings are symptoms of vegetation stress caused by reduced photosynthetic activity and consequently decreased transpiration and water-use efficiency of the plants. Cross-comparison between SPAD-502 chlorophyll content meter index and chlorophyll content showed strong positive correlation coefficients ( r = 0.71 and r = 0.51) which suggests that using the SPAD-502 chlorophyll index itself is sensitive enough to detect vegetation stress in a multispecies tropical forest. Therefore, the SPAD-502 can be used to assess chlorophyll content of vegetation across polluted and non-polluted sites at different canopy layers. The results presented in this paper contribute to the very limited literature on field spectroscopy and radiative transfer models applied to the vertical profile of the Amazon forest. [ABSTRACT FROM AUTHOR]

The effect of different densities of Italian ryegrass (Lolium italicum L.: G1- 5 kg/ha seeds, 60 cm row spacing; G2- 5 kg/ha seeds, 20 cm row spacing; G3- 20 kg/ha seeds, 60 cm row spacing, and G4- 20 kg/ha seeds, 20 cm row spacing) and different rates of applied nitrogen fertilizer (N1- 0 kg N/ha; N2 - 50 kg N/ha; N3- 100 kg N/ha and N4-150 kg N/ha) on SPAD values under interaction between the crop and cleavers (Galium aparine L) was investigated. A tri-factorial trial (4 sowing rates x 4 fertilization rates x 4 sampling times) with three replications was set up in a random block design with plot size 10 m2 on a anthropogenious soil in the Šabac area in 2005/2006. SPAD was measured at 30 random plants of L. italicum and G. aparine on each plot four times during vegetation (V1- tillering; V2 - stem extension; V3- flagleaf, and V4-earing), and nitrogen content in plants was then computed. Relative nitrogen content in plant material was used as a parameter of competitive interaction between the cultivated and weed species. Total nitrogen in plant material was also analyzed. The data acquired showed that SPAD values were normally higher in L. italicum than in G. aparine under almost all crop densities and nitrogen rates applied, and maximum values were recorded in the third growing stage (flagleaf) at G3 density and treatment rate of 100 kg N/ha. The highest biomass yield (6 033.0 kg/ha) and seed yield (1 129.0 kg/ha) of Italian ryegrass were achieved in the same variants, i.e. at crop density of 5 kg/ha seeds, 60 cm row spacing and 100 kg N/ha fertilizer, and the crop developed in competition with the weed species G. aparine at an average population density of 15-25 plants/m2.

In this study, we extended previous work linking the polarization of reflected light from crop canopies with characteristics of the canopy structure, such as the leaf inclination angle. We obtained reflectance and polarized reflectance in 8 spectral bands from the canopies of two varieties of wheat, planted in plots fertilized with a basal dressing and topdressed at the jointing and booting stages. The optical measurements were carried out on 3 clear-sky days when the plants were at the stem-elongation, heading and ripening stages, respectively. On each measurement date, we assessed the leaf orientation geometry of the plants using a Plant Canopy Analyzer (LAI-2000), measured the leaf greenness (an indicator of leaf chlorophyll content) using a handheld SPAD-502 (SPAD) optical sensor, and also measured plant height. Both polarization and leaf greenness observations at the heading stage were able to distinguish the canopies that had received topdressing from those without topdressing. However, no significant correlation was observed between the polarization in the blue, green and red bands and the SPAD (r = 0.425ᵻ0.456, n = 12 observations, p < 0.05). On the other hand, the mean leaf inclination angle (= mean tip angle: MTA) measured by the LAI-2000 was inversely correlated with the polarization in the 3 visible bands (r = −0.85ᵻ−0.88, n = 12, p < 0.001). Adjusting the view zenith angle according to the solar position at the time of measurement improved the accuracy. We tested a linear regression model to predict the MTA of the two wheat varieties based on polarized reflectance in the red band centered at 660 nm (r 2 = 0.73, n = 12, p < 0.001). Validation of this model obtained in the subsequent cropping season confirmed that polarization measurements were potentially useful for estimating the MTA of wheat stands in which the panicles were located below the topmost leaf layer of the canopy.

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The effect of salicylic acid (SA) on pomegranate seedlings (Manfalouty cultivar) infected with root-knot nematode, Meloidogyne javanica was studied in this research. Salicylic acid was applied with different concentrations (0,10 and 40 mM) on foliar and soil drenching. Some traits and characteristics were determined, i.e. shoot and root lengths (cm), shoot and root fresh and dry biomass (g), nematodes reproduction, potassium and magnesium mg/g of both shoot and root, total chlorophyll content and total carbohydrates content (g/100g). Results showed that treated seedlings with SA had a healthier appearance under nematode infection, compare to untreated ones. Moreover, SA significantly enhanced most of vegetative growth parameters, and increased the potassium and magnesium uptake as well as their translocation from root to shoot, and increased the total carbohydrates content. Results also reveal that, all treatments either spraying or drenching significantly reduced all related nematode parameters i.e. number of galls/g root, number of egg masses/g root, as well as number of juveniles/100 g soil (after 45 or 90 days) compared to untreated plants. [ABSTRACT FROM AUTHOR]

Total chlorophyll and nitrogen status in leaves of longkong and rambutan were evaluated by using the SPAD-502 meter. Leaves of both species were sampled from 10 year-old trees grown in an experimental plot at Prince of Songkla University, Hat Yai campus. The relationship between SPAD-502 meter reading (SPAD) and total chlorophyll content analyzed in the laboratory was evaluated in longkong and rambutan, and they were y = -2.68+0.21x, r2 = 0.77** and y = -1.11+0.18x, r2 = 0.77**, respectively. The data recorded by SPAD were also linearly related in a positive manner to nitrogen status in longkong (y = 1.27+0.20x, r2 = 0.82**) and rambutan (y = 1.17+0.02x, r2 = 0.79**). The results show that using the SPAD-502 meter is convenient and fast for the evaluation of total chlorophyll and nitrogen status in leaves of longkong and rambutan.

La medición de la clorofila de la hoja por método de la extracción es un proceso lento costoso y destructi-vo. El objetivo del presente trabajo fue determinar la concentración de la clorofila total en albahaca en etapa de plántula para el trasplante, con un medidor portátil de clorofila SPAD-502 y el método propuesto por Moran, correlacionando ambos datos. El uso del SPAD-502 permitió la determinación confiable de la clorofila, dado que su correlación con el método destructivo generó una ecuación con una R2 de 99.9%

Perennial organ functions of trees living in seasonal environments exhibit temporal changes that can be classified as long-term interannual changes and seasonal fluctuations within single years. However, few studies have separately quantified these changes from longitudinal measurement data or analyzed the relationships between them. We developed a hierarchical Bayesian statistical model consisting of three parts: a long-term interannual change expressed by consecutive annual linear trends, seasonal fluctuations with 26 values for two-week periods in a year, and a random effect for repeated measurements. The model can extract long-term interannual changes and seasonal fluctuations from longitudinal repeated measure data. The pattern of seasonal fluctuation, the amount of seasonal fluctuation, and the net annual change are expressed by the estimated model parameters. We applied our model to foliar chlorophyll (Chl) and nitrogen (N) content measured repeatedly on more than 1-year-old leaves of saplings in four evergreen broad-leaved tree species using nondestructive optical methods. The model successfully explained large variations in the Chl and N content. In general, seasonal fluctuations corresponded to the phenology of current-year leaves; Chl and N tended to decrease from the opening to maturation of new leaves and increased during the rest period. The magnitude of the decrease in the Chl and N content in the growth period of current-year leaves (Δγ) did not decrease noticeably as leaves aged. For the Chl content, Δγ was positively correlated with the maximum value before leaf opening across species. For the N content, Δγ and the maximum value before leaf opening were not clearly correlated across species, but were positively correlated within some species. A model parameter for annual linear trends in Chl and N varied from positive (indicating increasing trends) to negative values (indicating decrease) depending on species and leaf age in years. [ABSTRACT FROM AUTHOR]

• Leaf chlorophyll content (LCC) is often assessed in-situ with the SPAD instrument. • We test this approach for herbs and grasses in temperate grasslands across seasons. • Potential uncertainties in the LCC-SPAD relationship were assessed. • Several species with distinct traits were not suitable for SPAD-LCC measures. • Related uncertainties in LCC assessments have to be considered in applications. Leaf chlorophyll content (LCC) is an important indicator of plant health. Earth observation facilitates LCC monitoring on large spatial scales and within short time intervals by retrieving canopy LCC from spectral signals. However, in-situ measurements are still necessary to validate the predicted values and the accurate quantification of LCC is labour-intensive and costly. Handheld leaf chlorophyll metres, such as the SPAD-502 (Konica Minolta) promise quick and non-destructive in-situ LCC estimates. SPAD values can be easily converted to LCC by established calibration curves that are based on measurements of single plant species. Due to these practical advantages, the application of SPAD-LCC calibration curves, originally derived in an agricultural context (Markwell et al., 1995), has become common practice in field studies. Although associated with a variety of uncertainties, the transfer of general SPAD-to-LCC calibration equations to natural ecosystems has not yet been comprehensively investigated. In this study, we test the reliability of SPAD-to-LCC conversions in three structurally different semi-natural grassland areas with mixed species compositions. We measured SPAD values in the field and determined the corresponding LCC of the very leaf samples via chemical extraction and spectrophotometry. Our results show that SPAD-to-LCC conversion equations lack accuracy in semi-natural grassland with mixed species compositions (n = 157, R2 = 0.046, p < 0.05, for all sites). This study highlights the uncertainties in optical approaches for in-situ LCC assessments. It further underlines the need to find feasible and reliable solutions for a quick and efficient chlorophyll determination in natural habitats with mixed species compositions towards a reliable monitoring of ecosystem properties. [ABSTRACT FROM AUTHOR]

In situ optical meters are widely used to estimate leaf chlorophyll concentration, but non-uniform chlorophyll distribution causes optical measurements to vary widely among species for the same chlorophyll concentration. Over 30 studies have sought to quantify the in situ/in vitro (optical/absolute) relationship, but neither chlorophyll extraction nor measurement techniques for in vitro analysis have been consistent among studies. Here we: (1) review standard procedures for measurement of chlorophyll; (2) estimate the error associated with non-standard procedures; and (3) implement the most accurate methods to provide equations for conversion of optical to absolute chlorophyll for 22 species grown in multiple environments. Tests of five Minolta (model SPAD-502) and 25 Opti- Sciences (model CCM-200) meters, manufactured from 1992 to 2013, indicate that differences among replicate models are less than 5%. We thus developed equations for converting between units from these meter types. There was no significant effect of environment on the optical/absolute chlorophyll relationship. We derive the theoretical relationship between optical transmission ratios and absolute chlorophyll concentration and show how non-uniform distribution among species causes a variable, non-linear response. These results link in situ optical measurements with in vitro chlorophyll concentration and provide insight to strategies for radiation capture among diverse species. [ABSTRACT FROM AUTHOR]

Models were developed to estimate nondestructively chlorophyll (Chl) content per unit of leaf area (Chl area) and nitrogen content per unit of leaf area (N area) using readings of two optical meters for five warm-temperate, evergreen, broadleaved tree species ( Castanopsis sieboldii, Cinnamomum tenuifolium, Eurya japonica, Machilus thunbergii, and Neolitsea sericea). It was determined whether models should be adjusted seasonally. Readings (were obtained six times during a year period and Chl area and N area were determined using destructive methods. Bayesian inference was used to estimate parameters of models that related optical meter readings to Chl area or N area for each species. Deviance information criterion values were used to select the best among models, including the models with seasonal adjustment. The selected models were species-specific and predicted Chl area accurately ( R2 = 0.93–0.96). The best model included parameters with seasonal adjustments for one out of five species. Model-based estimates of N area were not as accurate as those for Chl area, but they were still adequate ( R2 = 0.64–0.82). For all species studied, the best models did not include parameters with seasonal adjustments. The estimation methods used in this study were rapid and nondestructive; thus, they could be used to assess a function of many leaves and/or repeatedly on individual leaves in the field. [ABSTRACT FROM AUTHOR]

Urban trees are frequently subjected to stress-causing environmental factors and cultural practices, requiring a permanent monitoring of their health condition. Stress detection in woody plants usually relies on a visual assessment of symptoms: inventories are mostly based on the parameters of the percentage of foliage reduction and leaf colour, both of which require a subjective interpretation. The main goal of this study was to detect whether the foliar chlorophyll (Chl) and nitrogen contents of linden trees, in an urban environment, can be useful and objective diagnostic indicators of the plant health and physiological performance, and whether it was possible to evaluate these data through a quick technique. Furthermore, as the ectomycorrhizal (ECM) community is a well-known bioindicator of the plant health status, its potential association with both variations in the Chl content and the different degrees of tree decline was verified. By determining the mathematical relationship between the instrument (SPAD-502) readings, the foliar Chl and nitrogen contents and the association with significant variations in the ECM community, the different stages of the visual symptoms of decline were accurately determined. This approach should help to integrate the methodology used for tree health inventories with new universal methods that do not entail individual interpretation. [ABSTRACT FROM AUTHOR]

The effectiveness of eight spectral reflectance indices for estimating chlorophyll (Chl) content in leaves of Eugenia uniflora L., a tropical tree species widely distributed throughout the world and a key species for ecosystem restoration projects, was evaluated. Spectral reflectance indices were tested using sun and shade leaves with a broad variation in leaf mass per area (LMA). Shortly after plants were exposed to chilling temperatures, there was a dramatic visible change in some sun leaves from green to red. Prior to testing Chl-related reflectance indices, the green and red leaves were separated according to the anthocyanin reflectance index (ARI). Slightly green to dark green leaves corresponded to an ARI value less than 0.11 ( n = 107), whereas slightly red to red leaves corresponded to an ARI value greater than 0.11 ( n = 35). To estimate leaf Chl, two simple reflectance indices (SR and SR), two normalized difference indices (ND and ND), two modified reflectance indices (mSR and mND705), a modified Chl absorption ratio index (mCARI) and an index insensitive to the presence of anthocyanins (CI) were evaluated. Good estimates of leaf Chl content were obtained using the reflectance indices tested regardless of the presence of anthocyanins and changes in LMA. Based on the coefficients of determination ( r) and the root mean square errors (RMSɛ) the best results were obtained with reflectance indices measured at wavelengths of 750 and 705 nm. Considering the performance of the models the best reflectance indices to estimate Chl contents in E. uniflora leaves with a broad variation in LMA and anthocyanin contents was SR and mCARI. [ABSTRACT FROM AUTHOR]

For Tunisian olive tree orchards, nitrogen deficiency is an important nutritional problem, in addition to the availability of water. Establishment of relationships between nutrients such as nitrogen and ecophysiological parameters is a promising method to manage fertilisation at orchard level. Therefore, a nitrogen stress experiment with one-year-old olive trees ( Olea europaea L. 'Koroneiki' and 'Meski') was conducted with trees respectively subjected to four nitrogen supply regimes (23.96 meq l, 9.58 meq l, 4.79 meq l and 0 meq l NO). The current paper focuses on the use of the SPAD-502 portable chlorophyll (Chl) meter, a nondestructive method for fertilisation management under nitrogen stress conditions of olive trees. Maximum net photosynthetic assimilation rates, chlorophyll fluorescence parameters and the SPAD Chl index were therefore measured simultaneously and the Chl and nitrogen content of the leaves were analysed. Significant correlations were established in the olive tree leaves between SPAD-502 readings on the one hand and Chl content, nitrogen content, photosynthetic assimilation rate, and Chl fluorescence parameters (Φ and ETR) on the other hand. [ABSTRACT FROM AUTHOR]

A hand-held SPAD-502 chlorophyll meter provides rapid and nondestructive measures of chlorophyll content. Integrating this meter into basil production can reduce costs and may improve basil quality. This study determined the relationship between SPAD-502 and the leaf chlorophyll (total, a, b). Over 500 leaf samples were collected from a field study conducted in 2006. Comparisons between chlorophyll contents and meter readings showed that SPAD meter readings were positively correlated to actual chlorophyll content. Regression analysis SPAD readings should be corrected by leaf area. Findings suggest that SPAD meter readings can be used as a tool to improve Basil quality and for assessing the relative chlorophyll content during the growing season. [ABSTRACT FROM AUTHOR]

Summary: Handheld chlorophyll meters have proven to be useful tools for rapid, non-destructive assessment of chlorophyll and nutrient status in various agricultural and arborescent plant species. We proposed that a SPAD-502 chlorophyll meter would provide valuable information when monitoring life cycle changes and intraspecific variation in endangered plant populations, whereby, destruction of plants to obtain this information is impractical. Further, use of this instrument would augment leaf morphometric measurements collected during controlled studies, circumventing the need for leaf harvest. We developed a regression model relating foliar chlorophyll concentration and content to SPAD chlorophyll content indices for a genetically diverse population of the federally listed Lindera melissifolia. Application of the regression to four additional L. melissifolia populations, and to the ecologically widespread congener L. benzoin, proved the SPAD-502 to be an effective tool for non-destructive estimation of total foliar chlorophyll concentration (r 2=0.8230) and content (r 2=0.9029) across a range of plant ages, growing conditions, and genotypes. [Copyright &y& Elsevier]

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The influence of foliar magnesium (Mg) application before flowering on chloroplast pigment indices was investigated in a 2-year field experiment with five soybean cultivars. Acetone extraction of pigments (chlorophyll a and b, total chlorophylls, and carotenoids as well as their ratios) was compared to chlorophyll meter (SPAD-502) readings. The untreated plants showed significant influence of cultivar on pigment concentrations, and pigment ratios were year-dependant. Foliar fertilization with Mg influenced chlorophyll concentration mostly in the year 2004, and carotenoids were not altered by Mg treatment. Cultivar differences prevailed in the next year when Mg treatment was less effective. The interactions among year, cultivar, and Mg application were showed to be significant for a particular parameter. The SPAD-502 readings significantly correlated with pigment concentrations only in the untreated plants in 2005. However, the foliar treatment influenced significantly SPAD readings in 2004, through the interaction with cultivar in once-treated plants and as a single factor in twice-treated plants. Grain yield was under significant positive influence of leaf Mg concentration in both years, and one treatment with Epsom salt was enough for significant grain yield increase. [ABSTRACT FROM AUTHOR]

Chlorophyll content of butterhead lettuce leaves was estimated by correlations between the Minolta SPAD-502 and Minolta chroma meter CR 300. The SPAD-502 readings and extractable chlorophyll (Chl a, Chl b, and total Chlorophyll) contents were related. High linear correlations were obtained for chlorophyll a (R2=0.90), chlorophyll b (R2=0.85), and total chlorophyll (R2=0.92). After that, during the growth cycle of butterhead lettuce grown in soilless culture, leaves were selected and SPAD-502 and chroma meter readings were made. Finally, correlations between SPAD-502 readings and leaf color (L*, a*, b*, C*, and hue angle) determined by the chroma meter were calculated. Hue angle (H°; R2=0.75) and lightness index (L*; R2=0.68) were the parameters that better relate with SPAD-502 readings, so these parameters can also be used for rapid and nondestructive estimates of leaf chlorophyll in situ. [ABSTRACT FROM AUTHOR]

Chlorophyll contents in vegetation depend on soil nitrogen availability and on crop nitrogen uptake, which are important management factors in arable farming. Crop nitrogen uptake is important, as nitrogen is needed for chlorophyll formation, which is important for photosynthesis, i.e. the conversion of absorbed radiance into plant biomass. The objective of this study was to estimate leaf and canopy nitrogen contents by near and remote sensing observations and to link observations at leaf, plant and canopy level. A theoretical base is presented for scaling-up leaf optical properties to whole plants and crops, by linking different optical recording techniques at leaf, plant and canopy levels through the integration of vertical nitrogen distribution. Field data come from potato experiments in The Netherlands in 1997 and 1998, comprising two potato varieties: Eersteling and Bintje, receiving similar nitrogen treatments (0, 100, 200 and 300 kg N ha-1) in varying application schemes to create differences in canopy nitrogen status during the growing season. Ten standard destructive field samplings were performed to follow leaf area index and crop dry weight evolution. Samples were analysed for inorganic nitrogen and total nitrogen contents. At sampling dates, spectral measurements were taken both at leaf level and at canopy level.At leaf level, an exponential relation between SPAD-502 readings and leaf organic nitrogen contents with a high correlation factor of 0.91 was found. At canopy level, an exponential relation between canopy organic nitrogen contents and red edge position (λrep, nm) derived from reflectance measurements was found with a good correlation of 0.82. Spectral measurements (SPAD-502) at leaf level of a few square mm were related to canopy reflectance measurements (CropScan™) of approximately 0.44 m2. Statistical regression techniques were used to optimise theoretical vertical nitrogen profiles that allowed scaling-up leaf chlorophyll measurements to canopy nitrogen values. A nitrogen attenuation coefficient (kN) of 0.41 g N m-2 soil resulted in highest correlation coefficients for scaling-up nitrogen contents from leaf to canopy values. Remote sensing of canopy nitrogen (g N m-2 soil) did not require considering vertical nitrogen profiles, as canopy reflectance measurements were able to integrate organic nitrogen over total canopy depth. The integration of near sensing techniques, theories on the interpretation of reflectance signatures and vertical crop nitrogen distribution allowed scaling between leaf chlorophyll measurements and canopy nitrogen values. This results in more accurate quantification of the nitrogen status of a potato crop, which is important information in potato crop management. [Copyright &y& Elsevier]

The practicality of the portable, non-destructive type nitrogen meter ( Agriexpert PPW-3000) was tested on ten forest species. Also investigated was the potential relationship between leaf nitrogen and chlorophyll (Chl) contents and the readings taken with the PPW-3000 and a Chl meter ( SPAD-502). There was a significantly positive correlation between the readings of PPW-3000 and N content in the same leaves, whereas the correlation between leaf Chl content and the PPW-3000 values was less positive. Similarly there was a significant positive correlation between actual Chl content and the SPAD-502 readings and the less positive correlation between actual N content and the SPAD-502 readings. Thus using both the PPW-3000 and SPAD-502 enables to determine leaf N and Chl contents simply and non-destructively in the field. [ABSTRACT FROM AUTHOR]

A recent non-destructive technique allows estimation of leaf chlorophyll content using the portable SPAD-502 chlorophyll meter. Measurements were taken on four species (winter wheat, maize, soyabean and tobacco) subjected to different nitrogen regimes or senescence status and the non-destructive readings were compared with analytical results obtained by solvent extraction. In general, the relationship between the SPAD measurement and the analytical result was not linear and species was a factor in three out of four crops. Linear, quadratic and exponential curve fitting are presented; only the interpolation with a polynomial exponential function adequately describes the whole data set. The presence of statistically non-significant differences between the estimated values of wheat and maize on the one hand and significant points of difference between those of tobacco and soyabean on the other suggests distinct behaviour patterns for monocots and dicots. This type of response may be explained by differences in the optical properties of pigments with differing spatial distributions (sieve effect) and therefore by in vivo and in vitro different procedures and the structural diversity of leaves belonging to the two subclasses. [ABSTRACT FROM AUTHOR]