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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. info:eu-repo/semantics/publishedVersion

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.

The techniques utilized to extract chlorophyll from plant materials are destructive and based on methods that use organic solvents. This study proposes the non-destructive quantification of chlorophyll and nitrogen concentration using a portable chlorophyll meter (SPAD-502). Further, was possible to establish relationships between chlorophyll fluorescence and SPAD-502 values. This methodology could save time, space and resources, and could be used for analysis of the photosynthetic processes. Papaya leaves (Solo and Formosa groups) of different ages were collected from 15-month-old plants cultivated in a commercial field in São Francisco de Itabapoana, Rio de Janeiro State (41(0):15W; 21(0):27S). Correlations were established between the chlorophyll content and carotenoids extracted in DMSO, nitrogen content, a chlorophyll a fluorescence (Fphi, Fmax, Fnu/Fmax, qN, qP, NPQ) with readings from SPAD-502 taken on papaya leaves of different ages. The results show that while the q p and the Fnu/Fmax increased with SPAD-502 readings of up to 40, the qN and NPQ variables decreased. The Fmax presented a direct linear correlation with the SPAD-502 values while the Fphi variable did not correlate with the SPAD-502 values. The portable chlorophyll meter was shown to be useful for nondestructive determination of photosynthetic pigments (chlorophyll and carotenoids) and can be used indirectly in advanced interpretation of the photochemical process in Carica papaya L. leaves. Os métodos utilizados para a extração de clorofila em materiais vegetais são destrutivas e baseiam-se em métodos que utilizam solventes orgânicos. Este trabalho propõe a quantificação não-destrutiva dos teores de clorofila e nitrogênio por meio do SPAD-502. Ainda, foi possível estabelecer uma relação entre a fluorescência e os valores obtidos pelo SPAD-502. Tal metodologia poderá proporcionar uma substancial economia de tempo, espaço e recursos contribuindo na melhoria das interpretações dos processos fotossintéticos. Para tanto, foram utilizadas folhas de mamoeiros (grupos 'Solo' e 'Formosa') de diferentes estádios de desenvolvimento, coletadas de plantas com 15 meses de idade, cultivadas em plantio comercial no município de São Francisco de Itabapoana/RJ. Foram estabelecidas correlações entre os teores de clorofila e carotenóides extraídos em DMSO, os teores de nitrogênio, a fluorescência da clorofila a (Ffi, Fmax, Fni/Fmax, qN, qP, NPQ) e as leituras pelo SPAD 502 em folhas da espécie em estudo, dos grupos 'Solo' e 'Formosa'. Os resultados mostraram que enquanto a variável qP e a relação Fni/Fmax foram crescentes, até leituras do SPAD-502 próximas a 40, as variáveis qN e NPQ se mostraram decrescentes. Foi verificado que a variável Fmax apresentou uma correlação linear, direta, em relação aos valores do SPAD-502, enquanto que a variável Ffi não apresentou nenhuma correlação com os valores do SPAD-502. De acordo com os resultados apresentados, concluiu-se que o determinador portátil de clorofila poderá ser utilizado na quantificação dos pigmentos fotossintéticos (clorofilas e carotenóides) e poderá indiretamente auxiliar nas interpretações avançadas do processo fotoquímico da fotossíntese em plantas da espécie Carica papaya L.

Aim of study: We evaluated the use of dimethylsulfoxide (DMSO) for the photometric determination of chlorophyll (Chl a and Chl b ) 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, Caceres, 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 Chl b overestimation and different fitting performance for SPAD vs pigment calibrations ( R 2 =0.64, RMSE=0.20, p

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 ...

The SPAD reading may be used in estimating total nitrogen content (N) in leaves and even in estimating grape yield in grapevines. The objective of this study was to estimate total N content in leaves and grape yield using the SPAD-502 in grapevines submitted to nitrogen fertilization in soils with clayey and sandy texture. In 2008, two experiments were installed in the Southern region of Brazil. In experiment 1, Cabernet Sauvignon grapevines were planted in a soil with clayey texture and with application of 10, 20, 40 and 80 kg·N·ha-1·year-1. In experiment 2, Cabernet Sauvignon grapevines were planted in a soil with sandy texture and with the application of 0, 10, 15, 20, 40, 80 and 120 kg·N·ha-1·year-1. In the grapevines of the two experiments and during the period from 2008 to 2010, SPAD readings were made on leaves throughout the flowering period and at change in color of the berries using the portable chlorophyll meter Minolta-SPAD-502. The leaves were collected, dried, ground and submitted to analysis of the total N content. In addition, grape yield per hectare was evaluated. The SPAD-502 readings estimated the total N content in flowering and at change in color of the berries in the Cabernet Sauvignon grapevines grown on soils with clayey texture and sandy texture, especially in the first year of evaluation. However, the precision of the SPAD-502 readings is low, with there being no relationship between the SPAD-502 readings and grape yield.

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 ( λ rep , 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 m 2 . 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 ( k N ) 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.