Laser-induced Chlorophyll Fluorescence Research Articles

Prolonged Use of Insecticide Dimethoate Inhibits Growth and Photosynthetic Activity of Wheat Seedlings: A Study by Laser-Induced Chlorophyll Fluorescence Spectroscopy.

This paper is an extension of the work published in Journal of Fluorescence (2011) 21: 785-791. In the previous work, we studied the effect of dimethoate (50, 100 and 200ppm) on growth and photosynthetic activity of wheat seedlings after 10days of dimethoate treatment. In the present study, new measurement conditions (dimethoate concentration: 25ppm, treatment period: 20days and 30days) were used in addition to those used in the past work. Various plant growth parameters, photosynthetic pigment content, laser-induced chlorophyll fluorescence (LICF) spectra and fluorescence induction kinetics (FIK) curves were recorded after 10, 20 and 30days of dimethoate treatments. LICF spectra were recorded in the region of 650-780nm using violet diode laser (405nm). FIK curves were recorded at 685nm using red diode laser (635nm). Fluorescence intensity ratio (FIR) of two fluorescence peaks around 685 and 730nm, and variable chlorophyll fluorescence decrease ratio (Rfd) were determined from LICF spectra and FIK curves respectively. Curve-fitted parameters of LICF spectra were used for determination of FIR (F685/F730). The effect of treatment of the insecticide dimethoate on growth and photosynthetic activity of wheat seedlings was examined by using these parametersas well as the past work. In 10-days treatment, 25 and 50ppm dimethoate showed stimulatory effect with better stimulation being observed at 25ppm. All studied concentrations higher than 50ppm exhibited inhibitory effect on wheat seedlings. In case of dimethoate treatment studied for longer durations (more than 10days), all concentrations showed inhibitory effect. Lower doses which showed some positive response for short time duration become toxic with the extension of treatment periods. Thus, this study clearly confirms the toxic effect of dimethoate on wheat plants.

Correcting the effect of the detection angular on laser-induced chlorophyll fluorescence

Chlorophyll fluorescence has been widely used to monitor vegetation growth status and quantitative remote sensing monitoring of vegetation biochemical content. Therefore, it is significant to accurately measure the fluorescence information. In this study, the variation in fluorescence intensity of vivo vegetation leaf with the change in detection angle on the basis of laser-induced fluorescence technology was discussed. Experimental results demonstrated that the relationship between the emission fluorescence intensity and detection angles could be explained by the cosine expression. Then, two-step fluorescence intensity correction method was proposed. Firstly, the fluorescence intensity was corrected based on the changing of cosine expression. Secondly, the fluorescence ratio calculated based on the corrected fluorescence intensity. Results demonstrated that the effect of detection angles on fluorescence signals can be efficiently eliminated compared to the traditional spectral ratio method. Findings of this study may be valuable in promoting the applications of laser-induced fluorescence in remote sensing to achieve accurate chlorophyll fluorescence information for quantitative monitoring of plant nutrient stress.

An integrated microfluidic chip for treatment and detection of microalgae cells

As the most economic means of international transportation for massive cargo, marine transportation contributes significantly to the world trading and economics. However, there are large number of microalgae cells and other exotic organisms carried in the ballast water, which may seriously damage the marine ecological environment along the transportation routes of the ships. Microalgae cells and online treatment of the microalgae-rich ballast water have become a pressing demand for ballast water management. Herein, we developed an automatic microfluidic system based on laser-induced chlorophyll fluorescence for real-time detection of microalgae in ballast water samples. This system is highly advantageous compared to the conventional method that requires tedious operation procedures, prolonged detection time, and complex analytical process. Moreover, we introduced chemical methods for fast and effective treatment of the microalgae cells in ballast water. For this purpose, a microfluidic concentration gradient generator was used for fast screening the optimal concentration of chemicals to rapidly reduce the microalgae population in the corresponding ballast water. To the best of our knowledge, this is the first time to combine an automatic high-throughput detection system and a gradient concentration chip for in situ analysis and treatment of ballast water.

Potential of Fluorescence Index Derived from the Slope Characteristics of Laser-Induced Chlorophyll Fluorescence Spectrum for Rice Leaf Nitrogen Concentration Estimation

Leaf nitrogen concentration (LNC) is a major biochemical parameter for estimating photosynthetic efficiency and crop yields. Laser-induced fluorescence, which is a promising potential technology, has been widely used to estimate the growth status of crops with the help of multivariate analysis. In this study, a fluorescence index was proposed based on the slope characteristics of fluorescence spectrum and was used to estimate LNC. Then, the performance of different fluorescence characteristics (proposed fluorescence index, fluorescence ratios, and fluorescence characteristics calculated by principal component analysis (PCA)) for LNC estimation was analyzed based on back-propagation neural network (BPNN) model. The proposed fluorescence index exhibited more stability and reliability for LNC estimation than fluorescence ratios and characteristics calculated by PCA. In addition, the effect of different kernel functions and hidden layer sizes of BPNN model on the accuracy of LNC estimation was discussed for different fluorescence characteristics. The optimal train functions “trainrp,” “trainbr,” and “trainlm” were then selected with higher R2 and lower standard deviation (SD) values than those of other train functions. In addition, experimental results demonstrated that the hidden layer size has a smaller impact on the accuracy of LNC estimation than the kernel function of the BPNN model.

Nondestructive and Rapid Probing of Biochemical Response of Arsenic Stress on the Leaves of Wheat Seedlings Using Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy

ABSTRACTThe goal of the current study is to characterize the changes in the biochemical composition of the leaves of wheat seedlings stressed by arsenic at concentrations of 0.2, 0.3, 0.4, and 0.5 mM using laser induced chlorophyll fluorescence and attenuated total reflectance Fourier transform infrared spectroscopy. The chlorophyll fluorescence spectra of the leaves of control and arsenic treated wheat seedlings showed increase in the intensity and intensity ratios of chlorophyll fluorescence bands indicating decrease in the photosynthesis performance and chlorophyll content of the leaves of wheat seedlings treated with arsenic. The infrared spectra of the leaves of control and arsenic treated wheat seedlings were obtained from 4000 to 485 cm−1 at a resolution of 4 cm−1. Multivariate principle component analysis of the preprocessed spectra suggest significant biochemical discrimination between the control and arsenic treated seedlings. Arsenic treatment decreased the concentration of cellulose while increasing the pectin, hemicellulose, xyloglucan, and lignin levels in the wheat seedling leaves. The exposure to arsenic also increased the spectral signatures of α-helix, β-sheet, amino acids, glutathione, lipids, and carboxyl compounds. These changes in the biochemicals indicate their physiological roles in mediating arsenic stress in wheat seedlings. The study also demonstrates the applicability of spectroscopic techniques for the non-invasive and rapid monitoring of the metabolism and physiology of the vegetation stressed by metals and metalloids before visual signs of toxicity appear.

激光诱导植物叶绿素荧光寿命及光谱特性分析

激光诱导植物叶绿素荧光寿命及光谱特性分析

Water Deficiency Detection of Hevea brasiliensis Clones by Laser Induced Fluorescence

Water is the key nutritional element for the optimal development of plants. A water deficiency leads to lower crop productivity. As the health status of a plant influences the photosynthesis process, a photosynthetic diagnosis of a plant can be carried by laser induced chlorophyll fluorescence, a reliable and fast method that is non-destructive to the sample. In this study, we show that it is possible to detect the water deficiency of rubber tree hevea brasiliensis from the chlorophyll fluorescence ratio. The fluorescence ratio used in this study is called the effective ratio and it corresponds to the both fluorescence peaks ratio. We noticed that the water deficient plants fluorescence ratios were higher than those of normally watered plants. Moreover, the stressed plants' ratios are greater than a threshold value which depends on the duration of water deprivation application.

Potential of spectral ratio indices derived from hyperspectral LiDAR and laser-induced chlorophyll fluorescence spectra on estimating rice leaf nitrogen contents.

Accurate estimation of leaf nitrogen contents (LNCs) is essential for nutrition management in monitoring crop growth status. The aim of this study was to compare the potential of hyperspectral LiDAR (HSL) and laser-induced chlorophyll fluorescence (LIF) data in accurately predicting rice LNC. First of all, the intensity values of HSL at 694 and 742 nm and LIF at ~685 and ~740 nm were selected as the characteristic variables to analyze rice LNC using data collected in 2014 and 2015, respectively. Second, spectral indices derived from HSL (only) and LIF (only) were utilized to estimate LNC of rice, respectively. Third, a combined ratio indices (the ratio indices of reflectance to fluorescence and NDVI-based indices at the above four wavelengths) was developed and evaluated in estimating rice LNC. The statistical method of linking these spectral indices to rice LNC was the artificial neural network, which was to obtain the optimum performance in LNC estimation of rice. The results demonstrated that the combined ratio indices, especially the ratio of reflectance to fluorescence at ~740 nm, showed a moderate relationship with rice LNC (R2 = 0.736, 0.704, and 0.713 for the 2014 first experiment, 2014 second experiment, and 2015 experiment, respectively).

Using Different Regression Methods to Estimate Leaf Nitrogen Content in Rice by Fusing Hyperspectral LiDAR Data and Laser-Induced Chlorophyll Fluorescence Data

Nitrogen is an essential nutrient element in crop photosynthesis and yield improvement. Thus, it is urgent and important to accurately estimate the leaf nitrogen contents (LNC) of crops for precision nitrogen management. Based on the correlation between LNC and reflectance spectra, the hyperspectral LiDAR (HSL) system can determine three-dimensional structural parameters and biochemical changes of crops. Thereby, HSL technology has been widely used to monitor the LNC of crops at leaf and canopy levels. In addition, the laser-induced fluorescence (LIF) of chlorophyll, related to the histological structure and physiological conditions of green plants, can also be utilized to detect nutrient stress in crops. In this study, four regression algorithms, support vector machines (SVMs), partial least squares (PLS) and two artificial neural networks (ANNs), back propagation NNs (BP-NNs) and radial basic function NNs (RBF-NNs), were selected to estimate rice LNC in booting and heading stages based on reflectance and LIF spectra. These four regression algorithms were used for 36 input variables, including the reflectance spectral variables on 32 wavelengths and four peaks of the LIF spectra. A feature weight algorithm was proposed to select different band combinations for the LNC retrieval models. The determination coefficient (R2) and the root mean square error (RMSE) of the retrieval models were utilized to compare their abilities of estimating the rice LNC. The experimental results demonstrate that (I) these four regression methods are useful for estimating rice LNC in the order of RBF-NNs > SVMs > BP-NNs > PLS; (II) The LIF data in two forms, including peaks and indices, display potential in rice LNC retrieval, especially when using the PLS regression (PLSR) model for the relationship of rice LNC with spectral variables. The feature weighting algorithm is an effective and necessary method to determine appropriate band combinations for rice LNC estimation.

The use of laser induced chlorophyll fluorescence (LIF) as a fast and non‑destructive method to investigate water deficit in Arabidopsis

Chlorophyll fluorescence measurements have been widely applied as non-destructive methods to study the photosynthetic efficiency of plants, under control or stress conditions. Compared to most protocols of pulse amplitude modulation (PAM) fluorometry, laser induced chlorophyll fluorescence (LIF) has the advantages of not requiring pulses to be delivered at close range, allowing the remote analysis of a great number of individual plants in a short period of time. Such analyses are extremely useful, for instance, when doing large phenotyping screens of Arabidopsis thaliana mutants or ecotypes. Water deficit is a major abiotic stress compromising plant growth and productivity. Arabidopsis has been adopted as the main model organism in plant sciences and it has been widely used in plant stress studies. However, reports on the applications of LIF techniques to this model plant are scarce. Here we report the use of LIF to investigate changes in chlorophyll a (Chl a) fluorescence signature under progressive drought of potted Arabidopsis plants (Slow Stress) and under fast dehydration of detached leaves (Fast Stress). Results show that the two dehydration methods cause distinct modifications on the red/far-red Chl a fluorescence ratio (F690/F730) and on the wavelengths of Chl a fluorescence maxima. These differences are likely related to distinct changes in water content, photosynthetic pigments, anthocyanins, fatty acid composition and other metabolic adaptations, which are differently regulated in Slow and Fast Stress. Of particular interest are Chl a emission fluorescence changes, which take place under progressive drought, before a substantial decrease in leaf water content. Additionally, no differences were found on LIF emission spectra between fully expanded and young leaves. However, the choice of leaf surface influenced fluorescence emission, with the abaxial surface displaying lower fluorescence and higher F690/F730 ratios. Results suggest that LIF is a fast and non-destructive tool suitable for high-throughput phenotyping of Arabidopsis under water deficit.

Study of laser-induced chlorophyll fluorescence lifetime measurement and its correction

A novel method for laser-induced fluorescence lifetime measurement and correction are presented to improve precision of chlorophyll fluorescence lifetime measurement. Laser was used as excitation source for exciting chlorophyll fluorescence. According to the measured signals characteristics, the fluorescence and background signals were detected respectively by photomultiplier. The chlorophyll fluorescence lifetime can be estimated from deconvolution of the fluorescence and background signals. Based on a number of retrieved results from simulations, a rule of inherent error with deconvolution was found. Therefore, the calibration formula was obtained through the comparison of ideal fluorescence lifetimes and retrieved ones. In actual measurements, the intrinsic fluorescence decay can be separated from the measured signals by deconvolution, and thus, the retrieved fluorescence lifetimes were substituted into a calibration formula to calculate the corrected values. Both simulations and experiments show that the method is a high precision and real-time measurement technique for chlorophyll fluorescence lifetime.

Study the effect of insecticide dimethoate on photosynthetic pigments and photosynthetic activity of pigeon pea: Laser-induced chlorophyll fluorescence spectroscopy

Pigeon pea is one of the most important legume crops in India and dimethoate is a widely used insecticide in various crop plants. We studied the effect of dimethoate on growth and photosynthetic activity of pigeon pea plants over a short and long term exposure. Plant growth parameters, photosynthetic pigment content and chlorophyll fluorescence response of pigeon pea (Cajanus cajan L.) plants treated with various concentrations of the insecticide dimethoate (10, 20, 40 and 80ppm) have been compared for 30days at regular intervals of 10days each. Laser induced chlorophyll fluorescence spectra and fluorescence-induction kinetics (FIK) curve of dimethoate treated pigeon pea plants were recorded after 10, 20 and 30days of treatment. Fluorescence intensity ratio at the two fluorescence maxima (F685/F730) was calculated by evaluating curve-fitted parameters. The variable chlorophyll fluorescence decrease ratio (Rfd) was determined from the FIK curves. Our study revealed that after 10days of treatment, 10ppm of dimethoate showed stimulatory response whereas 20, 40 and 80ppm of dimethoate showed inhibitory response for growth and photosynthetic activity of pigeon pea plants, but after 20 and 30days of treatment all the tested concentrations of dimethoate became inhibitory. This study clearly shows that dimethoate is highly toxic to the pigeon pea plant, even at very low concentration (10ppm), if used for a prolonged duration. Our study may thus be helpful in determining the optimal dose of dimethoate in agricultural practices.

Laser-induced chlorophyll fluorescence lifetime measurement and characteristic analysis

A laser-induced fluorescence lifetime measurement method is presented to evaluate living status for plant growth and the environmental monitoring. A 355 nm laser is used as excitation source for exciting chlorophyll fluorescence, and the fluorescence signals are received by a photomultiplier. Because the measured signal is the convolution of the reliable fluorescence decay signals, laser pulse and instrument response function, according to their characteristics, the time-resolved measurement method is used to estimate the chlorophyll fluorescence and background signals separately; the real fluorescence decay signals are separated by combining a novel deconvolution method, and the chlorophyll fluorescence lifetime can be retrieved. Experiment shows that the method proves to be a high accuracy and real-time monitoring chlorophyll fluorescence lifetime technique; and the chlorophyll solution fluorescence lifetime is measured for different concentrations. The result can prove that the chlorophyll concentration is related to its fluorescence lifetime, and the calibration curves of chlorophyll concentration and fluorescence lifetime is fitted.

Laser-Induced Chlorophyll Fluorescence Measurement System to Assess Photosynthetic Status within Leaves

Chlorophyll (Chl) fluorescence measured on a leaf surface only provides the photosynthetic status of chloroplasts near the surface due to self-shading effect of Chl. Here, we report a laser-induced Chl fluorescence measurement system, which enables measurement of fluorescence induction kinetics at different tissues within a leaf as well as on both leaf surfaces, to assess photosynthetic status within leaves. The logarithmic time-scaled Chl fluorescence induction kinetics obtained from Chenopodium album leaves showed polyphasic transients in which four inflection points designated as O, J, I and P, were observed. Adaxial surface and palisade mesophyll showed significantly higher fluorescence intensities at O than abaxial surface and spongy mesophyll, respectively. In contrast, fluorescence intensities at J, I and P were significantly higher at abaxial surface and spongy mesophyll. Using these fluorescence intensities, the JIP test was performed. The results of JIP test indicated that adaxial surface and palisade mesophyll are characterized by lower maximum quantum yield of photosystem II (PSII) and net rate of PSII closure, but higher rate of energy transfer into electron transport chain than abaxial surface and spongy mesophyll. Considering these dorsiventral and intra-leaf variations in Chl fluorescence parameters, this study suggested the necessity of Chl fluorescence measurements on tissues as well as both surfaces to evaluate photosynthetic status of a whole leaf.

Identifying fruit characteristics for non-invasive detection of sunburn in apple

Sunburn of apple fruit is one of the major problems in fruit production areas with high light and temperature environment. Fruit with sunburn are predisposed to develop postharvest disorders and need to be separated from the fruit considered for mid to long-term storage. In order to identify specific characteristics for non-invasive, automatic selection of fruit with sunburn, the effect of sunburn on external and internal features on sunlit and shaded fruit sides was assessed in ‘Granny Smith’, ‘Fuji’ and ‘Braeburn’ cultivars. It has been shown that shaded sides of apple with and without sunburn generally do not differ in their internal fruit quality characteristics, L ab colour readings and chlorophyll fluorescence intensities. With sunlit fruit sides, sunburn induced changes in L ab values are cultivar specific. The common feature of fruit with sunburn in all tested cultivars is a greater difference between fruit firmness and soluble solids content on shaded and sunlit sides as compared to unaffected fruit. Due to the chlorophyll breakdown in the affected areas, laser-induced chlorophyll fluorescence (LIF) is proposed as an appropriate sensitive technique for the reliable sunburn detection in green and red apple cultivars.

Violet diode laser-induced chlorophyll fluorescence: a tool for assessing mosaic disease severity in cassava (Manihot esculenta Crantz) cultivars

Violet diode laser-induced chlorophyll fluorescence was used in agronomical assessment (disease severity and average yield per plant). Because cassava (Manihot esculenta Crantz) is of economic importance, improved cultivars with various levels of affinity for cassava mosaic disease were investigated. Fluorescence data correlated with cassava mosaic disease severity levels and with the average yield per plant.

Effects of intertidal ­microphytobenthos migration on biomass determination via laser-induced ­fluorescence

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 432:45-52 (2011) - DOI: https://doi.org/10.3354/meps09157 Effects of intertidal ­microphytobenthos migration on biomass determination via laser-induced ­fluorescence Sónia Vieira1,2, Andrei B. Utkin3, Alexander Lavrov3, Nuno M. Santos3, Rui Vilar3,4, Jorge Marques da Silva2, Paulo Cartaxana1,* 1Centro de Oceanografia, Faculdade de Ciências da Universidade de Lisboa, 1749-016 Lisboa, Portugal 2Centro de Biodiversidade, Genómica Integrativa e Funcional (BioFIG), Faculdade de Ciências da Universidade de Lisboa, 1749-016 Lisboa, Portugal 3INOV, Instituto de Engenharia de Sistemas e Computadores, R. Alves Redol 9, 1000-029 Lisboa, Portugal 4Departamento de Engenharia de Materiais, Instituto Superior Técnico, Universidade Técnica de Lisboa, Avenida Rovisco Pais 1, 1049-001 Lisboa, Portugal *Corresponding author. Email: pcartaxana@fc.ul.pt ABSTRACT: Laser-induced fluorescence (LIF) spectra of intertidal microphytobenthos (MPB) communities were obtained in the laboratory with a 532 nm pulsed Nd:YAG laser. The laser-induced chlorophyll (chl) fluorescence emission spectra of MPB in mud and sand sediments were characterized by a band in the red region with a maximum at ca. 685 nm. Biomass accumulation on the surface of the mud due to cell migration caused a shift to longer wavelengths (up to 5 nm) of the red emission maximum and the development and increase of an emission shoulder at the far-red region (maximum at ca. 732 nm), probably owing to increased re-absorption of chl fluorescence within the denser microalgae biofilm. Direct relations were observed between MPB biomass proxies (normalized difference vegetation index [NDVI] and phytobenthos index [PI]) and fluorescence intensity. LIF was used to track migratory rhythms of epipelic benthic microalgae in muddy sediments, which are absent in epipsammic communities in sand: progressive accumulation of biomass occurred at the sediment surface during diurnal low tide periods and was followed by a rapid downward migration before tides began to cover the sampling site. When exposed to high light, surface biomass decreased in migratory biofilms, indicating that diatom cells avoid photoinhibitory light levels. This phenomenon is known as behavioral photoprotection. For the first time, LIF was applied to study intertidal MPB ­communities to adequately describe surface biomass, which included changes due to migration. KEY WORDS: Chlorophyll · Behavioural photoprotection · Benthic diatom · Microalgae biofilm Full text in pdf format PreviousNextCite this article as: Vieira S, Utkin AB, Lavrov A, Santos NM, Vilar R, Marques da Silva J, Cartaxana P (2011) Effects of intertidal ­microphytobenthos migration on biomass determination via laser-induced ­fluorescence. Mar Ecol Prog Ser 432:45-52. https://doi.org/10.3354/meps09157 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 432. Online publication date: June 27, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.

Laser-induced chlorophyll fluorescence and reflectance spectroscopy of cadmium treated Triticum aestivum L. plants

The present study deals with laser-induced chlorophyll fluorescence (LICF) spectra, reflectance spectra and fluores- cence induction kinetics (FIK) curves of Triticum aestivum L. plants treated with different concentrations of cadmium (0.01, 0.1 and 1.0 mM). LICF spectra were recorded in the region of 650-780 nm using violet diode laser (405 nm) and FIK curves were recorded at 685 and 730 nm using red diode laser (635 nm) for excitation. Reflectance spectra were recorded in the region of 400-800 nm using spectrophotometer with an integrating sphere. The fluorescence intensity ratios (FIR) were determined from LICF spectra, vitality index (Rfd) from FIK curves and narrow band vegetation index (NBVI) from reflectance spectra. These parameters along with plant growth parameters and photosynthetic pigment contents were used to analyze the effect of cadmium on wheat plants. The results clearly show that lower concentration of Cd (0.01 mM) shows stimulatory response; whereas higher concentrations (0.1 and 1.0 Mm) are hazardous for plant growth, photosynthetic pigments and photosynthetic activity of wheat plants.

Laser-induced chlorophyll fluorescence and reflectance spectroscopy of cadmium treatedTriticum aestivumL. plants

The present study deals with laser-induced chlorophyll fluorescence (LICF) spectra, reflectance spectra and fluorescence induction kinetics (FIK) curves ofTriticum aestivumL. plants treated with different concentrations of cadmium (0.01, 0.1 and 1.0 mM). LICF spectra were recorded in the region of 650–780 nm using violet diode laser (405 nm) and FIK curves were recorded at 685 and 730 nm using red diode laser (635 nm) for excitation. Reflectance spectra were recorded in the region of 400–800 nm using spectrophotometer with an integrating sphere. The fluorescence intensity ratios (FIR) were determined from LICF spectra, vitality index (Rfd) from FIK curves and narrow band vegetation index (NBVI) from reflectance spectra. These parameters along with plant growth parameters and photosynthetic pigment contents were used to analyze the effect of cadmium on wheat plants. The results clearly show that lower concentration of Cd (0.01 mM) shows stimulatory response; whereas higher concentrations (0.1 and 1.0 Mm) are hazardous for plant growth, photosynthetic pigments and photosynthetic activity of wheat plants.

Laser-Induced Chlorophyll Fluorescence: A Technique for Detection of Dimethoate Effect on Chlorophyll Content and Photosynthetic Activity of Wheat Plant

Laser-induced chlorophyll fluorescence (LICF) spectra and fluorescence induction kinetics (FIK) curves of wheat plant leaves treated with different concentrations (50, 100 and 200 ppm) of dimethoate are recorded. LICF spectra are recorded in the region of 650-780 nm using violet diode laser (405 nm) and FIK curve at 685 and 730 nm with red diode laser (635 nm) for excitation. The fluorescence intensity ratios (FIR) are determined from LICF spectra and vitality index (R(fd)) from FIK curves. These parameters along with photosynthetic pigment contents and growth parameters are used to analyze the effect of dimethoate on wheat plants. The result indicates that lower concentration of 50 ppm shows stimulatory response while higher concentrations of dimethoate are hazardous for growth, photosynthetic pigments and activity of wheat plants.