Plant Chlorophyll Fluorescence Research Articles

Fluorometer “FLS 10s”

Many biological objects have the ability to fluoresce under the influence of electromagnetic radiation in the optical range. Measuring the fluorescence of a biological object helps obtain information about its internal state. Therefore, the creation of instruments for scientific research in the field of studying biological objects has been a pressing task for many areas of human activity for many years. In particular, these are areas such as agriculture, ecology, food industry and medicine. This article is devoted to a description of the recently developed “FLS 10s” device for studying plant chlorophyll fluorescence, as well as description of software for operating the device and analyzing the information obtained. This device provides data of well known OJIP test. Keywords: fluorescence, fluorometer, fluorescence measurement, Kautsky effect, OJIP test, fluorescence induction, fast chlorophyll α fluorescence induction.

Effects of nitrogen addition and Bothriochloa ischaemum and Lespedeza davurica mixture on plant chlorophyll fluorescence and community production in semi-arid grassland.

Grass-legume mixture can effectively improve productivity and stimulate overyielding in artificial grasslands, but may be N-limited in semi-arid regions. This study investigated the effects of N addition on chlorophyll fluorescence and production in the grass-legume mixtures community. An N addition experiment was conducted in the Bothriochloa ischaemum and Lespedeza davurica mixture community, with seven mixture ratios (B0L10, B2L8, B4L6, B5L5, B6L4, B8L2, and B10L0) according to the sowing abundance of B.ischaemum and L.davurica and four N addition levels, N0, N25, N50, and N75 (0,25,50,75kgNhm-2 a-1), respectively. We analyzed the response of chlorophyll fluorescence parameters of the two species, the rapid light-response curves of chlorophyll fluorescence, as well as aboveground biomass (AGB) and overyielding. Our results showed that the two species showed different photosynthetic strategies, with L.davurica having significantly higher initial fluorescence (Fo), effective photochemical quantum yield of PSII (ΦPSII), and coefficient of photochemical fluorescence quenching (qP) than B. ischaemum, consisting with results of rapid light-response curves. N addition and mixture ratio both had significant effects on chlorophyll fluorescence and AGB (p<0.001). The ΦPSII and qP of L.davurica were significantly lowest in B5L5 and B6L4 under N addition, and the effect of N varied with mixture ratio. The photosynthetic efficiency of B. ischaemum was higher in mixture than in monoculture (B10L0), and ΦPSII was significantly higher in N50 than in N25 and N50 at mixture communities except at B5L5. The community AGB was significantly higher in mixture communities than in two monocultures and highest at B6L4. In the same mixture ratio, the AGB was highest under the N50. The overyielding effects were significantly highest under the N75 and B6L4 treatments, mainly attributed to L.davurica. The partial least squares path models demonstrated that adding N increased soil nutrient content, and complementary utilization by B.ischaemum and L.davurica increased the photosynthetic efficiency. However, as the different photosynthetic strategies of these two species, the effect on AGB was offset, and the mixture ratio's effects were larger than N. Our results proposed the B6L4 and N50 treatments were the optimal combination, with the highest AGB and overyielding, moderate grass-legume ratio, optimal community structure, and forage values.

A new method in mitigation of drought stress by chitosan-coated iron oxide nanoparticles and growth stimulant in peppermint

Damage to the plant's photosynthetic system is known as the main symptoms of sensitivity to environmental stresses. Little is known about beneficial role of new chitosan compounds such as Kitoplus®, and chitosan-coated nanomaterials on alleviation of adveres effects of drought stress in plants. In the present study, a factorial experiment was conducted in a split-plot manner based on a randomized complete block design (RCBD) with three replications to evaluate the effects of Kitoplus® growth stimulant and Chitosan-Coated Iron Oxide Nanoparticles (Fe-CTs NPS) on peppermint growth, chlorophyll fluorescence and essential oil biosynthesis under drought stress conditions. Treatments included three levels of drought stress (irrigation at soil moisture levels of 30%, 60%, and 90%), three concentrations of Kitoplus®(control without Kitoplus®, 0.5% and 1%), and three concentrations of Fe-CTs NPs (control without Fe-CTs NPs, 5 and 10 µM). Drought stress, growth stimulation treatment with Kitoplus®, and Fe-CTs NPs had significant dual and triple effects on the studied physiological traits. According to the results, chlorophyll index and stomatal conductance were significantly lower in control plants than in those undergoing drought stress. Under 60% field capacity moisture conditions, the chlorophyll index was increased with 1% Kitoplus® treatment. The maximum fluorescence (Fm) and variable fluorescence (Fv) raised as the drought stress intensity increased. The highest Fm and Fv were observed in plants treated with 1% Kitoplus® and 10 µM Fe-CTs NPS under 30% soil moisture stress . Results also showed that the highest value of menthone (33.31%) was obtained in plants treated with Kitoplus® at 1% and Fe-CTs NPs at 10 μM under drought stress of 60% field capacity. In addition, the highest amount of menthol (26.5%) was observed in plants treated with 0.5% Kitoplus® under drought stress of 30% field capacity. The overall importance of the study lies in devising the simultaneous application of biostimulants and nanomaterials in enhancing essential oils production in the mint plant under drought stress challenges. • Peppermint Vegetative yield improved by increasing the concentration of Kitoplus® and Fe-CTs NPS. • Menthol's highest amount was observed in plants with Kitoplus® (0.5%) and Fe-CTs NPs (10 μM) interaction under 90% FC. • The highest amount of menthol was observed in plants following interaction of Kitoplus® (0.5%) and Fe-CTs NPs (10 μM) under 90% FC. • The maximum menthone obtained in plants treated with Kitoplus® (1%) and Fe-CTs NPs (10 μM) under drought stress of 60% FC. • Chlorophyll fluorescence in plants treated with Kitoplus® and Fe-CTs NPS was significantly higher than that of controls.

Early evaluation of adjuvant effects on topramezone efficacy under different temperature conditions using chlorophyll fluorescence tests

Proper selection of adjuvant applications is an important strategy to enhance herbicide efficacy and reduce active ingredient input especially under adverse environmental conditions. In this study, a two-factor split-plot-design experiment was conducted to evaluate the effects of two adjuvants on the efficacy of topramezone on the grassy weed species giant foxtail (Setaria faberi Herrm.) and the broadleaved weed species velvetleaf (Abutilon theophrasti Medik.) under three different temperature conditions. The two tested adjuvants were methylated seed oil (MSO) and organosilicone. Three temperature levels, 35/30°C, 25/20°C, and 15/10°C (day/night), were used in the laboratory and greenhouse experiment. Plant chlorophyll fluorescence measurements shortly after herbicide application and classic whole-plant bioassay methods were used to evaluate the herbicide efficacy among the different treatments. Results indicated that the maximum quantum efficiency (Fv/Fm) of the top leaf of the weeds treated with topramezone mixed with MSO was significantly lower than that of the weeds treated with topramezone mixed with organosilicone and without an adjuvant at 2–3 days after treatment under all three temperature levels. The herbicide response of the plants treated with topramezone mixed with organosilicone and topramezone alone was not significantly different. These results corresponded well with the results of the classic whole-plant test. MSO has been shown to be good at enhancing the efficacy of topramezone on these weed species under all three temperature conditions. The measurement of chlorophyll fluorescence is a promising technique for evaluating the effects of adjuvants on the efficacy of herbicides shortly after herbicide treatment.

Cooler canopy leverages sorghum adaptation to drought and heat stress

In the present study, individual and combined effects of drought and heat stress were investigated on key physiological parameters (canopy temperature, membrane stability index, chlorophyll content, relative water content, and chlorophyll fluorescence) in two popular sorghum cultivars (Sorghum bicolor cvs. Phule Revati and Phule Vasudha) during the seedling stage. Estimating canopy temperature through pixel-wise analysis of thermal images of plants differentiated the stress responses of sorghum cultivars more effectively than the conventional way of recording canopy temperature. Cultivar difference in maintaining the canopy temperature was also responsible for much of the variation found in critical plant physiological parameters such as cell membrane stability, chlorophyll content, and chlorophyll fluorescence in plants exposed to stress. Hence, the combined stress of drought and heat was more adverse than their individual impacts. The continued loss of water coupled with high-temperature exposure exacerbated the adverse effect of stresses with a remarkable increase in canopy temperature. However, Phule Vasudha, being a drought-tolerant variety, was relatively less affected by the imposed stress conditions than Phule Revati. Besides, the methodology of measuring and reporting plant canopy temperature, which emerged from this study, can effectively differentiate the sorghum genotypes under the combined stress of drought and heat. It can help select promising genotypes among the breeding lines and integrating the concept in the protocol for precision water management in crops like sorghum.

Effect of the Time of Herbicide Application and the Properties of the Spray Solution on the Efficacy of Weed Control in Maize (Zea mays L.) Cultivation

A field experiment was carried out in 2019–2021. The effect of an increased amount of iron in water and the addition of citric acid on the efficacy of herbicides applied in maize cultivation at various times was tested. In the pre-emergence treatment, thiencarbazone-methyl + isoxaflutole were applied, while in the post-emergence treatment, nicosulfuron + tritosulfuron + dicamba were applied once in a full dose or in low dose system at two times in half of the recommended dose with the addition of an adjuvant. In selected combinations, FeSO4 × 7H2O and citric acid were added to the composition of the spray solution. The species composition of weeds and the efficacy of the herbicides used were determined. Plant stress caused by competition from weeds was investigated by measuring the plant chlorophyll fluorescence. The height of the cultivated plants and their yield level were also determined. The lowest efficacy of weed control was observed when the post-emergence herbicides were applied once. Increasing the iron content in water reduced the efficacy of the herbicides, but the addition of citric acid made it possible to decrease this problem.

Phytotoxic Effect of Herbicides on Various Camelina [Camelina sativa (L.) Crantz] Genotypes and Plant Chlorophyll Fluorescence

Camelina is an oil plant classified as a minor crop. The small acreage is the main cause of the small amount of plant protection products that are registered for use on camelina plantations. This contributes to difficulties in the protection of this plant. In the conducted experiment, the genetic similarity of genotypes of camelina was compared. The effect of selected herbicides (propaquizafop at rate 70 g a.i. ha−1, quizalofop-p-ethyl at rate 50 g a.i. ha−1, clopyralid at rate 90 g a.i. ha−1, and picloram at rate 24 g a.i. ha−1 applied in the three-four-leaves growth stage of camelina) on six individual genotypes of the plant and plant chlorophyll fluorescence after the use of these substances was also determined. The Przybrodzka variety showed the lowest level of damage in the assessment carried out 42 days after herbicide application and the damages of plants after quizalofop-p-ethyl and propaquizafop was completely gone. The variety Przybrodzka had the lowest genetic similarity to all analyzed genotypes. In other cases, genetic similarity of analyzed genotypes could not be linked to herbicide-related damage. Picloram contributed to the greatest damage to test plants and had the greatest impact on the operation of photosystem II (PSII). However, the level of plant chlorophyll fluorescence parameter values indicates small PSII damage for all substances and the possibility of subsequent plant regeneration. The results of the presented research indicate that it is worth referring to several plant varieties in phytotoxicity studies of herbicides towards arable crops.

Role of H2O2 on photosynthetic characteristics of soybean genotypes under low water input

Soybean is subjected to abiotic stresses that immensely affect its productivity during its lifespan and threaten food security globally. Recent research recommends that chemical substances could be applied to plants as an alternative to traditional agriculture to better abide abiotic stresses. Hydrogen peroxide (H2O2) is a potential agent that can serve for this purpose. Up to today, responses of exogenous H2O2 on photosynthetic machinery in plants exposed to drought is poorly investigated. Therefore, the effects of exogenous low dose H2O2 on plant chlorophyll fluorescence in two soy bean genotypes (Glycine max L. Merrill), 537 (tolerant) and 520 (susceptible), under drought were evaluated. Drought which we had found significantly reduced water potential of leaves and photosynthetic pigment concentration in two genotypes, did not cause change in Fv/Fm and ΦPSII of tolerant genotype, contrarily subsided qP and ETR values. However, Fv/Fm, ΦPSII, qP and ETR failed in susceptible genotypes under drought. Increases in NPQ were determined under stress in both genotypes. Exogenous H2O2 mitigated the drought-induced impairment in photosystem II efficiency in both genotypes. This data indicates that low dose H2O2 further enhanced the tolerance to drought via regulation of the photochemical process in both genotypes.

基于光程分布方法校正植物叶绿素荧光的影响

基于光程分布方法校正植物叶绿素荧光的影响

Study of laser-induced plant fluorescence lifetime imaging technology for plant remote sensing monitor

Plant fluorescence is too susceptible to interference and unsuitable for plant remote sensing monitor. A plant fluorescence lifetime imaging technology based on plant remote sensing monitor is presented to solve this problem. The technology can be used to analyse plant physiological information for environmental surveillance. The beam expander system was used to expand laser beam at a certain specific wavelengths, and the living plant chlorophyll fluorescence can be excited by this laser beam. Many of the same plant fluorescence signals were excited by continuous laser pulses, and furthermore the start delay time of Intensification Charge Coupled Device was adjusted consecutively in time resolved measurement method. Finally, a complete set of plant continuous fluorescence image was collected by Intensification Charge Coupled Device. The deconvolution can be used to retrieve the high-precision plant fluorescence lifetime of single pixel point in plant continuous fluorescence image. If the plant fluorescence lifetime values from all of pixel points were retrieved, the distribution map of plant fluorescence lifetime can be drawn. The fluorescence lifetime properties of living plants have already been studied preliminarily. The study indicates that the distribution map of plant fluorescence lifetime can more effectively reflect plant chlorophyll content than fluorescence intensity dose. The plant fluorescence lifetime was related to its chlorophyll content in a certain range, and there is a complex and subtle relationship between plant fluorescence lifetime and its physiological information.

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

Remote Laser Fluorimeter to Detect Stress of Plants

One of the promising trends in laser monitoring of natural formations is a vegetation control. A variety of reasons such as plant diseases, deficit of moisture or nutrients in the soil, pests of one sort or another, etc. may cause plant stress (conditions under which normal development of plants is impossible). Often (especially at the early stages) to detect these plant stress conditions by appearance is difficult. Therefore, development of remote methods to detect vegetation stress conditions is of relevance. To date, the method based on detection of plant chlorophyll fluorescence is the only method that allows detection of changes in the photosystem of 2 living plants. The overwhelming majority of papers, as a characteristic of the vegetation fluorescence, use a spectrum shape of the fluorescence irradiance, and the stress conditions of plants are defined by the shape distortion of the fluorescence spectra (as compared with vegetation in the normal condition). The paper presents new experimental data on the spectra of laser-induced fluorescence of plants in normal and stressful conditions (due to various reasons). Their analysis allows us to define a technical configuration of the remote laser fluorimeter to detect the vegetation stress conditions. The papers’ analysis shows that to excite laser-induced fluorescence of plants the second harmonic of a pulsed solid-state YAG-Nd laser with a wavelength of 0.532 μm is the most appropriate in terms of hardware implementation. In this case, the excitation wavelength of 0.532 μm is characterized by high (close to maximum) fluorescence excitation efficiency. The results of experimental studies allow us to find the best options of the laser-induced fluorescence irradiance windows for detection of the plant stress conditions. In the most simple implementation, a laser fluorimeter with 0.532 μm excitation wavelength of fluorescence can detect the laser-induced fluorescence irradiance of plants only in two spectral bands with the central wavelengths 0.685 μm and 0.740 μm.

Effect of carbon/nitrogen ratio on carbohydrate metabolism and light energy dissipation mechanisms in Arabidopsis thaliana

Carbon (C) and nitrogen (N) nutrient sources are essential elements for metabolism, and their availability must be tightly coordinated for the optimal growth and development in plants. Plants are able to sense and respond to different C/N conditions via specific partitioning of C and N sources and the regulation of a complex cellular metabolic activity. We studied how the interaction between C and N signaling could affect carbohydrate metabolism, soluble sugar levels, photochemical efficiency of photosystem II (PSII) and the ability to drive the excess energy in Arabidopsis seedlings under moderated and disrupted C/N-nutrient conditions. Invertase and sucrose synthase activities were markedly affected by C/N-nutrient status depending on the phosphorylation status, suggesting that these enzymes may necessarily be modulated by their direct phosphorylation or phosphorylation of proteins that form complex with them in response to C/N stress. In addition, the enzymatic activity of these enzymes was also correlated with the amount of sugars, which not only act as substrate but also as signaling compounds. Analysis of chlorophyll fluorescence in plants under disrupted C/N condition suggested a reduction of electron transport rate at PSII level associated with a higher capacity for non-radiative energy dissipation in comparison with plants under moderated C/N condition. In conclusion, the tight coordination between C and N not only affects the carbohydrates metabolism and their concentration within plant tissues, but also the partitioning of the excitation energy at PSII level between radiative (electron transport) and non-radiative (heat) dissipation pathways.

Plant chlorophyll fluorescence: active and passive measurements at canopy and leaf scales with different nitrogen treatments.

Most studies assessing chlorophyll fluorescence (ChlF) have examined leaf responses to environmental stress conditions using active techniques. Alternatively, passive techniques are able to measure ChlF at both leaf and canopy scales. However, the measurement principles of both techniques are different, and only a few datasets concerning the relationships between them are reported in the literature. In this study, we investigated the potential for interchanging ChlF measurements using active techniques with passive measurements at different temporal and spatial scales. The ultimate objective was to determine the limits within which active and passive techniques are comparable. The results presented in this study showed that active and passive measurements were highly correlated over the growing season across nitrogen treatments at both canopy and leaf-average scale. At the single-leaf scale, the seasonal relation between techniques was weaker, but still significant. The variability within single-leaf measurements was largely related to leaf heterogeneity associated with variations in CO2 assimilation and stomatal conductance, and less so to variations in leaf chlorophyll content, leaf size or measurement inputs (e.g. light reflected and emitted by the leaf and illumination conditions and leaf spectrum). This uncertainty was exacerbated when single-leaf analysis was limited to a particular day rather than the entire season. We concluded that daily measurements of active and passive ChlF at the single-leaf scale are not comparable. However, canopy and leaf-average active measurements can be used to better understand the daily and seasonal behaviour of passive ChlF measurements. In turn, this can be used to better estimate plant photosynthetic capacity and therefore to provide improved information for crop management.

Physiological stress factors associated with different mine tailings on the chlorophyll fluorescence of plants

Physiological stress factors associated with different mine tailings on the chlorophyll fluorescence of plants

Dynamic response of plant chlorophyll fluorescence to light, water and nutrient availability.

Chlorophyll molecules absorb photosynthetic active radiation (PAR). The resulting excitation energy is dissipated by three competing pathways at the level of photosystem: (i) photochemistry (and, by extension, photosynthesis); (ii) regulated and constitutive thermal energy dissipation; and (iii) chlorophyll-a fluorescence (ChlF). Because the dynamics of photosynthesis modulate the regulated component of thermal energy dissipation (widely addressed as non-photochemical quenching (NPQ)), the relationship between photosynthesis, NPQ and ChlF changes with water, nutrient and light availability. In this study we characterised the relationship between photosynthesis, NPQ and ChlF when conducting light-response curves of photosynthesis in plants growing under different water, nutrient and ambient light conditions. Our goals were to test whether ChlF and photosynthesis correlate in response to water and nutrient deficiency, and determine the optimum PAR level at which the correlation is maximal. Concurrent gas exchange and ChlF light-response curves were measured for Camelina sativa (L.) Crantz and Triticum durum (L.) Desf plants grown under (i) intermediate light growth chamber conditions, and (ii) high light environment field conditions respectively. Plant stress was induced by withdrawing water in the chamber experiment, and applying different nitrogen levels in the field experiment. Our study demonstrated that ChlF was able to track the variations in photosynthetic capacity in both experiments, and that the light level at which plants were grown was optimum for detecting both water and nutrient deficiency with ChlF. The decrease in photosynthesis was found to modulate ChlF via different mechanisms depending on the treatment: through the action of NPQ in response to water stress, or through the action of changes in leaf chlorophyll concentration in response to nitrogen deficiency. This study provides support for the use of remotely sensed ChlF as a proxy to monitor plant stress dynamics from space.

Study of plant fluorescence properties based on laser-induced chlorophyll fluorescence lifetime imaging technology

Plant fluorescence is a susceptible signal in plant fluorescence remote sensing detection. In order to solve this problem, a technique for plant chlorophyll fluorescence lifetime imaging is presented to evaluate living status for plant growth and environmental monitoring. A concave lens is used to expand laser beam at a wavelength of 355 nm, and the living plant is exposed in this laser light source to excite chlorophyll fluorescence. And the chlorophyll fluorescence signals are detected by an intensification charge coupled device. Time resolved measurement method is used in this article, so that every time the same fluorescence signals can be excited by the same laser pulse. Meanwhile, the delay time needed for triggering intensification charge coupled device should be changed consecutively, and the whole discrete fluorescence signal can be obtained. The discrete fluorescence signals from the particular location points of the plant are fitted. An improved method of forward iterative deconvolution is used to retrieve the corresponding fluorescence lifetime, and the high-precision fluorescence lifetime can be obtained. Furthermore, the fluorescence lifetime values at all the location points are retrieved to obtain the distribution map of chlorophyll fluorescence lifetime. This method can give the chlorophyll fluorescence image efficiently. The distribution map of fluorescence lifetime can more effectively reflect the plant chlorophyll concentration than the fluorescence intensity image does. The physical property of chlorophyll fluorescence lifetime from living plants has been studied preliminarily, indicating that the plant physiological status is related to its fluorescence lifetime to a certain extent; and the chlorophyll fluorescence lifetime and plant environment have a subtle and complex correlation. In the future, the relationship between chlorophyll fluorescence lifetime and plant environment will be expected to study with the cooperation of biophysicist.

Atrazine and Methyl Viologen Effects on Chlorophyll‐a Fluorescence Revisited—Implications in Photosystems Emission and Ecotoxicity Assessment

In this work, we use the effect of herbicides that affect the photosynthetic chain at defined sites in the photosynthetic reaction steps to derive information about the fluorescence emission of photosystems. The interpretation of spectral data from treated and control plants, after correction for light reabsorption processes, allowed us to elucidate current controversies in the subject. Results were compatible with the fact that a nonnegligible Photosystem I contribution to chlorophyll fluorescence in plants at room temperature does exist. In another aspect, variable and nonvariable chlorophyll fluorescence were comparatively tested as bioindicators for detection of both herbicides in aquatic environment. Both methodologies were appropriate tools for this purpose. However, they showed better sensitivity for pollutants disconnecting Photosystem II-Photosystem I by blocking the electron transport between them as Atrazine. Specifically, changes in the (experimental and corrected by light reabsorption) red to far red fluorescence ratio, in the maximum photochemical quantum yield and in the quantum efficiency of Photosytem II for increasing concentrations of herbicides have been measured and compared. The most sensitive bioindicator for both herbicides was the quantum efficiency of Photosystem II.

Early Detection of Soybean Plant Injury from Glyphosate by Measuring Chlorophyll Reflectance and Fluorescence

Early detection of crop injury from off-target drift of herbicide is critical in crop production. Subtle changes in canopy reflectance could present useful information to detect the onset of crop stress. This study was conducted in a greenhouse to evaluate a portable spectroradiometer and a portable chlorophyll fluorometer for the detection of crop injury caused by glyphosate spray. Non-glyphosate resistant soybean (Glycine max L. Merr.) plants were sprayed with glyphosate using a pneumatic track sprayer in a spray chamber. Four plants received a rate of 0.86 kg ae/ha glyphosate and four plants received 0.086 kg ae/ha. Additional four non-sprayed plants were used as controls. After the glyphosate spray, the chlorophyll reflectance of the plants was measured with the spectroradiometer at 4, 24, 48, and 72 hours to determine the plant response to herbicide. Simultaneously, fluorescence induction kinetics of the crop under stress was measured with the portable chlorophyll fluorometer. Results of the statistical mean separation indicated that the plant chlorophyll reflectance measurement could be used to differentiate crop stress from glyphosate at 24 hours after spray among treatments and to identify the effect of herbicide at 24 hours after spray in each treatment. Moreover, linear discriminant analysis with the reflectance data showed that the crop stress of the soybean plants from glyphosate could be identified at 24 hours or more post application. Results of the statistical mean separation also indicated that use of plant chlorophyll fluorescence measurement could not differentiate crop stress until 48 hours after spray among treatments while it could identify the effect of herbicide 24 hours after spray in each treatment. These findings demonstrate that chlorophyll reflectance and fluorescence measurements both could be used for early detection of crop stress.

Analysis of in vivo chlorophyll fluorescence spectra to monitor physiological state of tomato plants growing under zinc stress

The effects of zinc (Zn) on plant chlorophyll fluorescence were investigated in 10-day-old tomato ( Solanum lycopersicum) seedlings subjected for 7 days to a series of zinc (10, 50, 100 and 150 μM) applied via the nutrient solution. The chlorophyll fluorescence spectra of leaves were recorded in the spectral region 650–800 nm using the spectroscopic technique of ultraviolet light emitting diode induced fluorescence spectroscopy (UV-LED IFS). These spectra have been used to analyze the effect of several doses of zinc on the photosynthetic activities of tomato plants. The fluorescence intensity ratios (FIR) at the two maxima ( F 690/ F 735) of control as well as treated tomato plants were calculated by evaluating curve-fitted parameters using a Gaussian spectral function. The variable chlorophyll fluorescence decrease ratio ( R Fd) values were determined from the fluorescence induction kinetics curves recorded at 690 nm and 735 nm. In addition, Zn accumulation in plants, plant growth, photosynthetic pigments content and malondialdehyde level (MDA, an index of lipid peroxidation) were also estimated. The results indicated that the plants treated with 10 μM of zinc exhibited better growth, however, higher concentrations of zinc were harmful for plants. Excess Zn induced a decrease in the R Fd values, which was associated with a strong decline of the total chlorophylls content and an increase of MDA level. The total chlorophylls content decline could also be followed via an increase of the chlorophyll fluorescence ratio F 690/ F 735.