Plant Leaf Color Research Articles

Genome-Wide Identification of the Auxin Response Factor Gene Family in Maple (Acer truncatum) and Transcriptional Expression Analysis at Different Coloration Stages of Leaves

Auxin response factors (ARFs) are involved in the mechanism of plant leaf color regulation, inhibiting chlorophyll synthesis while promoting anthocyanin production. However, it is not clear whether the ARF gene family is involved in autumn leaf color changes in maple. The differentially expressed genes for autumn leaf discoloration were obtained by transcriptome sequencing, and the AtARF family was constructed by homologous gene search. The results show that the AtARFs consist of 21 members distributed on 11 chromosomes and can be divided into three subfamilies, which are mainly distributed in the nucleus. The promoter regions of the AtARFs contain light-responsive elements, abiotic stress-responsive elements, and hormone-responsive elements. The analyses presented in this paper provide comprehensive information on ARFs and help to elucidate their functional roles in leaf color change in Acer truncatum.

Integrated transcriptome and metabolome analysis reveals the mechanism of carotenoid regulation in the yellowing-leaf mutant of pepper (Capsicum annuum L.) in response to different temperatures

Temperature is an important environmental factor affecting plant color, and different temperatures have distinct effects on plant leaf color changes. In order to explore the effects of different temperatures on plant color, we measured the physiological characteristics, transcriptome, and metabolome of the pepper leaf yellowing mutant yl1 and its wild type 6421 under different temperature conditions. Results showed that high temperature treatment compared with the normal temperature treatment significantly increased the contents of chlorophyll a, chlorophyll b, and carotenoids in yl1. At the same time, a total of 28 carotenoid pathway metabolites were detected under three temperature conditions. Among them, β-carotene, zeaxanthin, violaxanthin, neoxanthin, lutein, and antheraxanthin were higher in pepper leaves. The expression levels of ZEP, bHLH104, MYB1R1, and MYB1R1-like were significantly increased under high temperature compared with under normal temperature, while the expression level of crtZ-2 and VDE were significantly decreased. Co-expression network analysis showed that VDE was positively correlated with the bHLH71-like and negatively correlated with MYB1R1-like and bHLH104. These results led to significant differences in the amount of zeaxanthin and antheraxanthin accumulated at different temperatures, which may be the reason for the color change of pepper leaves. However, under the normal and low temperature treatment, it is the opposite, resulting in leaf yellowing. This study provides a reference for further research on the mechanism underlying the impact of temperature on carotenoid metabolism in pepper leaves.

Blue light induces leaf color change by modulating carotenoid metabolites in orange-head Chinese cabbage (Brassica rapa L. ssp. pekinensis)

Carotenoids are involved in the formation of plant leaf color as well as photosystem photoprotection. This study showed that blue light significantly induced up-regulation of the total carotenoid content in the inner leaves of orange-head Chinese cabbage (OHCC). Furthermore, the transcriptomic analysis revealed that blue light treatment induced up-regulation of genes in photosynthesis (BrHY5-2, BrCOP1 and BrDET1) and the methylerythritol 4-phosphate pathways (BrGGPS, BrDXS and BrHDR) upstream of the carotenoid metabolic pathway. Carotenoid metabolomic analysis revealed that the accumulation of several orange and red carotenoids (lycopene, zeaxanthin, β-carotene, lutein, and β-cryptoxanthin) after blue light treatment contributed to the deepening of the leaf coloration, suggesting that short-term blue light treatment could be used to boost nutritional quality. The light signal gene BrHY5-2 participated in the blue light-induced transcriptional regulation of carotenoid biosynthesis in OHCC. Overexpression of BrHY5-2 in Arabidopsis significantly increased the total carotenoid content and the sensitivity to blue light. The above findings revealed new insights about blue-light-induced carotenoid synthesis and accumulation in OHCC lines. They suggested a new engineering approach to increase the nutritional value of vegetables.

Integrated Transcriptome and Metabolome Analysis Revealed the Molecular Mechanism of Anthocyanin Synthesis in Purple Leaf Pepper (Capsicum annuum L.) under Different Light Intensities

Light is a crucial environmental component for plant growth, and light intensity plays a crucial function in controlling pigment anabolism in plants. We performed physiological characterisation, transcriptome, and metabolome investigations on purple leaf peppers treated with different light intensities to evaluate the effect on plant leaf colour. The results showed that the leaves of the peppers became significantly purplish under high light, with significantly higher anthocyanin, chlorophyll a, and carotenoid contents. A total of 44,263 genes were quantified using RNA-Seq, with the photoprotein-related genes LRP and LIP maintaining high expression levels under high and medium light. The anthocyanin synthesis pathway was variously enriched among the comparison groups, according to KEGG. The expression of the genes involved in the anthocyanin synthesis pathway, such as CHI, F3H, DFR, and BZ1, was significantly higher under high light. In addition, MYB and bHLH gene families were the most abundant, and MYB1R1, MYB113-like, and bHLH90-like were significantly expressed under high light and highly positively correlated with the above anthocyanin synthesis genes. According to our metabolomic analysis, delphinidin-3-O-rutinoside and delphinidin-3-O-glucoside accumulated in significant concentrations in purple leaves under high light. This study is useful for understanding the process of anthocyanin synthesis and metabolism in pepper leaves that is generated and regulated by varied light intensity.

The Effects of Dual Ozone and Drought Stresses on the Photosynthetic Properties of Acer rubrum and A. pictum

Ozone (O3) pollution is accompanied by drought stress, especially at high temperatures. Tree species in cities often face dual stresses from O3 and drought. In this study, Acer rubrum ‘Autumn Blaze’ and A. pictum were used as test plants in open-top-chambers (OTCs) to investigate the trees most tolerant to increasing O3 and drought stresses in urban gardens. The results showed that the dual stresses induced a change in A. rubrum’s leaf coloration from green to red. The leaf representation in A. rubrum was more variable than that of A. pictum. The leaf pigment content affected the plant leaf color difference, and the Chl and Car contents of both species were negatively correlated with L*. Under the dual stresses of O3 and drought, the changes in the net photosynthetic rate (Pn) and transpiration rate (Tr) were less variable in A. rubrum than A. pictum. The stomatal conductance (Gs) was more sensitive to higher O3 stress, the effect of which was enhanced by moderate drought (MD) conditions on Gs. The Tr decreased more significantly under drought stress, which mitigated the effect of O3 stress on the stomatal limit value (Ls). A. rubrum displayed differential color changes, resulting in greater structural heterogeneity within the garden landscape. The saplings adjusted their photosynthetic parameters under the dual stresses, whereas the dual stresses played an antagonistic role in protecting A. rubrum, suggesting that A. rubrum can resist O3 and drought. Our study suggests that A. rubrum is an alternative tree species for inclusion in urban gardens exposed to increasing O3 and drought stresses.

Ultraviolet Radiation Management in Greenhouse to Improve Red Lettuce Quality and Yield

The intensity of ultraviolet (UV) radiation affects the yield and quality of red lettuce. The current study aimed to develop a UV management system in a greenhouse to achieve high yield and quality in red lettuce production. The study consisted of two experiments. In the first experiment, the effects of the different UV transparencies of the plastic materials covering the greenhouse on plant growth and the concentration of antioxidants in red lettuce were studied. For this purpose, two greenhouses were covered with polyethene of different transparencies to UV radiation. One greenhouse was covered with a common type of polyethene transparent in a large spectrum of UV radiation (UV-open), while the second greenhouse was covered with polyethene untransparent to ultraviolet radiation (UV-block). The plants were grown in a deep flotation hydroponic system. At the end of the cultivation, plant growth measurements, leaf colour measurements, and the determination of antioxidant components’ concentration were carried out. Red lettuce plants harvested 42 days after planting had an average head weight 42% greater in the UV-block greenhouse compared to plants grown in the UV-open greenhouse. However, the red leaf colour of plants in the UV-block greenhouse lagged significantly compared to that in the UV-open greenhouse. Moreover, the total phenolic content, the total flavonoid content, and the antioxidant capacity of the lettuce leaves in the UV-block greenhouse were significantly lower compared to the corresponding values of the plants in the UV-open greenhouse. During the second experiment, a new cultivation system of red lettuce, which combined a UV-block polyethene film as a greenhouse cover and a pre-harvested supplemental UV light, was tested. For this purpose, various doses of supplemental UV lighting were tested in the UV-block greenhouse for ten days prior to harvest. From these tests, it emerged that applying supplemental UV lighting with a dose of 425 kJ m−2 d−1 for ten days before harvest produces red lettuces of the same quality as those produced in a UV-open greenhouse. This technique of growing red lettuce increases its yield by 30% without a negative effect on the quality of the product.

Integrated Metabolome and Transcriptome Analyses Reveal Dissimilarities in the Anthocyanin Synthesis Pathway Between Different Developmental Leaf Color Transitions in Hopea hainanensis (Dipterocarpaceae).

Changes in plant leaf color during development are directly related to the accumulation or degradation of certain phytochemicals such as anthocyanins. Since some anthocyanins can be beneficial to human health and provide insights into the biology of leaves, the underlying processes and timing by which plants produce these molecules has been the focus of numerous studies. The tree species Hopea hainanensis generally produces green leaves at all growth stages; however, a few explored individuals have been identified possessing red leaves on the top of the seedlings at a young stage. While the phenomenon of leaf color varying with age has been studied in several species, the underlying mechanisms are largely unknown in H. hainanensis. Using a metabolomics approach, the young red leaves in H. hainanensis were found to contain higher levels of anthocyanins and flavonoids than the young green-leaved individuals. Among anthocyanins, pelargonidin and cyanidin were the most likely candidates contributing to the red color of the young leaves. Transcriptome results indicated the genes related to the production of these anthocyanins were significantly upregulated, leading to greater accumulation of red pigments. Specifically, the expression of several MYB and bHLH genes in young red leaf lines was significantly higher than that in the young green leaf lines, especially HhMYB66, HhMYB91, HhMYB6, and HhbHLH70. As such these four transcription factors are probably the main regulatory genes resulting in young red leaves in H. hainanensis. From these results, comparative analyses with other species can be made to better understand the evolution of pigment biosynthesis and how anthocyanins function in plant metabolism and evolution/adaptation.

Advance in mechanism of plant leaf colour mutation

As a common mutation trait in plants, leaf colour mutation is related to the degree of chlorophyll and anthocyanin changes and the destruction of chloroplast structure. This study summarizes the latest research progress in leaf colour mutation mechanism, including the metabolic basis of plant leaf colour mutation, leaf colour mutation caused by gene mutation in the chlorophyll metabolism pathway, leaf colour mutation caused by blocked chloroplast development, leaf colour mutation controlled by key transcription factors and non-coding RNAs, leaf colour mutation caused by environmental factors, and leaf colour mutation due to the involvement of the mevalonate pathway. These results will lay a theoretical foundation for leaf colour development, leaf colour improvement, and molecular breeding for leaf colour among tree species.

Characterization of a novel allele of bc12/gdd1 indicates a differential leaf color function for BC12/GDD1 in Indica and Japonica backgrounds

Leaf color is directly associated with plant photosynthesis. Here, we have isolated and identified a spontaneous rice mutant named yd1 that has yellowish leaves and dwarf stature. Map-based cloning reveals that YD1 encodes a previously reported kinesin protein from the kinesin-4 subfamily, BC12/GDD1. Arginine-328 is replaced by leucine in yd1, BC12328Leu. YD1 is mainly expressed in leaves and is involved in chlorophyll (Chl) synthesis. The yd1 mutant had less Chl and a reduced and disordered thylakoid ultrastructure. In yd1 plants, Chl biosynthesis and photosynthesis associated gene expression was decreased and Chl degradation gene expression was increased, thereby leading to a reduced photosynthesis rate and grain yield. In this study we reveal that the novel BC12328Leu allele of BC12 modulated plant leaf color in yd1 plants, which has not been previously reported in studies of BC12/GDD1/MTD1/SRG1. Gene knockout results indicated that YD1 regulates leaf color in the indica rice background, but not in the japonica rice background. Our study provides new insights into molecular regulation of rice growth by BC12/GDD1 in different genetic backgrounds.

Spectroscopic determination of leaf chlorophyll content and color for genetic selection on Sassafras tzumu

BackgroundReflectance spectroscopy, like IR, VIS–NIR, combined with chemometric, has been widely used in plant leaf chemical analysis. But less studies have been made on the application of NIR reflectance spectroscopy to plant leaf color and pigments analysis and the possibility of using it for genetic breeding selection. Here, we examine the ability of NIR reflectance spectroscopy to determine the plant leaf color and chlorophyll content in Sassafras tzumu leaves and use the prediction results for genetic selection. Fresh and living tree leaves were used for NIR spectra collection, leaf color parameters (a*, b* and L*) and chlorophyll content were measured with standard analytical methods, partial least squares regression (PLSR) were used for model construction, the coefficient of determination (R2) [cross-validation ({text{R}}^{2}_{text{CV}}) and validation ({text{R}}^{2}_{text{V}})] and root mean square error (RMSE) [cross-validation (RMSECV) and validation (RMSEV)] were used for model performance evaluation, significant Multivariate Correlation algorithm was applied for model improvement, to find out the most important region related to the leaf color parameters and chlorophyll model, which have been simulated 100 times for accuracy estimation.ResultsLeaf color parameters (a*, b* and L*) and chlorophyll content were well predicted by NIR reflectance spectroscopy on fresh leaves in vivo. The mean {text{R}}^{2}_{text{CV}} and RMSECV of a*, b*, L* and chlorophyll content were (0.82, 4.43), (0.63, 3.72), (0.61, 2.35) and (0.86, 0.13%) respectively. Three most important NIR regions, including 1087, 1215 and 2219 nm, which were highly related to a*, b*, L* and chlorophyll content were found. NIR reflectance spectra technology can be successfully used for genetic breeding program. High heritability of a*, b*, L* and chlorophyll content (h2 = 0.77, 0.89, 0.78, 0.81 respectively) were estimated. Several families with bright red color or bright yellow color were selected.ConclusionsNIR spectroscopy is promising for the rapid prediction of leaf color and chlorophyll content of living fresh leaves. It has the ability to simultaneously measure multiple plant leaf traits, potentially allowing for quick and economic prediction in situ.

Fine mapping of lcm1, a gene conferring chlorophyll-deficient golden leaf in Chinese cabbage (Brassica rapa ssp. pekinensis)

Leaf color mutants are valuable resources for studying regulatory mechanisms of photosynthetic pigment metabolism. In this study, a chlorophyll-deficient golden leaf mutant lcm1 of Chinese cabbage was identified from its wild-type “FT” by ethyl methanesulfonate (EMS) mutagenesis. The phenotype of the golden leaf mutant lcm1 was that the leaves remained golden throughout development. Pigment measurements showed that the chlorophyll content of the mutant lcm1 was less than that of the wild-type “FT”. There were no obvious grana lamellae observed in the chloroplast microstructure of the mutant lcm1. Genetic analysis revealed that the mutant lcm1 phenotype was controlled by a single recessive nuclear gene, lcm1 (BrChlH). The MutMap method and Kompetitive Allele Specific PCR genotyping were used to predict that Bra006208 encoding a Mg-chelatase H subunit, the candidate gene for the mutant lcm1. The 4249-bp lcm1 gene had five exons and a single nucleotide substitution (G to A) in the third exon that resulted in an amino acid substitution (A to V). This SNP2523351 occurred in the highly conserved CobN-Mg_chel domain of the LCM1 (BrCHLH) protein. This study suggests that lcm1 gene plays an important role in the function of CHLH and provides a solid foundation for further studies on the development of plant leaf color.

Shift in accumulation of flavonoids and phenolic acids in lettuce attributable to changes in ultraviolet radiation and temperature

Environmental conditions influence the content and metabolic profile of phenolic compounds in vegetables. The present study focused on distinguishing between the effects of ultraviolet (UV) radiation and temperature on lettuce plants with green or red leaf color when grown in either a greenhouse or outdoors. A combination of the non-destructive, fluorescence-based method with spectrophotometric and HPLC analyses enabled us to assess the effects of environment, cultivar, and plant-leaf color on concentrations of flavonoids, anthocyanins, and phenolic compounds. The accumulation of total phenolics, flavonoids, anthocyanins, and phenolic acids (benzoic acid derivatives and cinnamic acid derivatives) increased in direct sunlight (high UV radiation, moderate temperature) conditions outdoors as compared to the greenhouse conditions (low UV radiation, high temperature). The comparison of the effects of UV radiation and temperature (indoor-outdoor effect) indicated that the level of UV radiation plays a dominant role in the accumulation of flavonoids, anthocyanins, and methoxycinnamic acid; while temperature predominantly influences the accumulation of phenolic acids (rosmarinic, p-anisic, vanillic acid. Although, the leaf color (green vs. red) was strongly related to the content of majority of studied phytochemicals, environmental conditions affected their concentrations in both color types similarly. The concentrations of compounds estimated with the non-invasive, fluorescence excitation ratio method were highly consistent with those obtained by standard analytical approaches. Our results show that this fast, non-invasive method can be effectively used for determining concentrations of flavonoids and phenolic acids in lettuce plants.

Algorithms for Plant Pathology: Automation of Plant Leaf Colour Chart using Image Processing

Algorithms for Plant Pathology: Automation of Plant Leaf Colour Chart using Image Processing

Visualization of green and red leaf structures in flowering pear Pyrus calleryana using integrated microscopy

Light and electron microscopy has become invaluable tools in plant science research and education. This project critically revisited both light and electron microscopy in the visualization of green and red leaves of flowering pear (Pyrus calleryana). Plant leaf color changes regularly occur in the fall, which is of both science and public interests. We used leaves of the flowering pear because this woody plant is commonly used in landscaping in many cities around the world. In order to visualize and compare the structures of green and red leaves, we prepared hand-sections from both green and red leaves. Sections were examined and imaged with a compound microscope and a laser scanning confocal microscope, respectively. Our data indicated that chlorophyll fluorescence intensity was significantly reduced in the red leaf compared to that of the green leaf. Histological data also showed that the pigment, which is called anthocyanin and makes the leaf red, was located in the leaf palisade and sponge parenchyma cells. Scanning electron microscopy provided detailed cellular pattern and stomatal distribution on leaf lower surfaces. And transmission electron microscopy data clearly revealed the chloroplast ultrastructure in the green leaf and its derivative – gerontoplast structure in the red leaf. This study provides us a new microscopic viewing of the outstanding natural phenomenon in the leaf color change in flowering pear and the microscopic methods described in this paper are useful for plant science research and education in general.

실내에서 LED광질이 관엽식물의 생장에 미치는 영향

In the results of investigating the role of LED light quality in enhancing the ornamental value of indoor foliage plants, amber and red light increased plant height, leaf width, and leaf stalk, and the consequent tree shape decreased the ornamental value. The chlorophyll content increased significantly under white light and compound light. With regard to the effect of plant leaf color on ornamental value, the value of lightness was markedly enhanced by red light. As to the functionality of plants according to photosynthetic activity, plants such as Dieffenbachia, Clusia, and Dracaena were found favorable to those staying indoors for a longtime from morning to evening. Spathiphyllum, and Ficus were found to be recommendable for indoor spaces used actively during afternoon because their photosynthesis was activated in the afternoon. With regard to power consumption according to light quality, white light consumed 119 W/hour, around 45% lower than that of fluorescent lamps, so it is considered the optimal artificial light quality that can enhance energy efficiency. Red light consumed 72 W/hour, only 33% of that of fluorescent lamps, but it was not considered the optimal light quality because plant growth was poor under the light quality. White light and compound light were found to be the ideal light sources for improving the functionality and ornamental value of indoor plants and reducing the cost of maintenance, but because compound light hinders people from recognizing the original color of plants and makes their eyes easily tired, white light was considered the optimal light satisfying all of the ornamental value, economic efficiency and functionality resulting from plant growth.

The cultivation revival of a landrace: pedigree and analytical breeding

This paper aims at improving the legume landrace Fava Santorinis (Lathyrus sp.) through the study of the existing variability, and an intra-landrace pedigree, combined with analytical selection, scheme. The experiments were conducted at the farm of Aristotle University of Thessaloniki during five growing seasons (2005–2009), and the selection was applied on a spaced plant conditions. In the first stage, single-plant frequency distributions of the source landrace for grain yield and pod number plant−1 was studied, and a percentage of 60.80% of non productive plants was found. In the second stage, improvement of grain yield relied on direct pedigree selection, accomplished by analytical selection for the number of pods plant−1, plant leaf color and vigor. This procedure was followed along the first generation progenies, and, later on, along two successive generations on the offsprings of two populations, one with purple and the other with white flower color. In the third stage, the evaluation of the fourth-generation progenies of each population for grain yield, showed superiority ranging from 42.48 to 107.89% compared to the source landrace. Furthermore, the breeding procedure succeeded in: (i) decreasing the coefficient of variability of grain yield and pods plant−1, thus increasing the stability of performance, (ii) reducing by 56.41 and 39.67% the non productive plants for white and purple flower populations, respectively, and (iii) maintaining the mean and the variability for pod traits as in the original landrace. Realized heritability for grain yield was positive during all selection cycle.

Cooling Effect of Shade Trees with Different Characteristics in a Subtropical Urban Park

The effect of shade trees on the air and surface-soil temperature reduction under the canopy was studied in a park in subtropical Taipei City, Taiwan. Ten species of trees and two species of bamboo, which had tightly clustered tall stems and spreading branches resembling trees in shape, were chosen for the study. In the summer of 2007, we measured leaf and canopy characteristics of each species. The microclimate conditions under the tree canopies and an unshaded open space were measured repeatedly at middays without precipitation. In comparison with the nearby unshaded open space, air temperatures under the canopies were 0.64 to 2.52 °C lower, whereas the surface-soil temperatures were 3.28 to 8.07 °C lower. Regression analysis revealed the relative contributions to air cooling effect by the plant's leaf color lightness, foliage density, leaf thickness, and leaf texture (surface roughness) in decreasing order. Foliage density had the greatest contribution to surface-soil cooling followed by leaf thickness, leaf texture, and leaf color lightness in that order. Regression analysis also revealed that solar radiation, wind velocity, and vapor pressure at the site had significant effects on temperature reduction attributable to shade trees or bamboo.

Effects of shade treatments on the photosynthetic capacity, chlorophyll fluorescence, and chlorophyll content of Tetrastigma hemsleyanum Diels et Gilg

Tetrastigma hemsleyanum Diels et Gilg was grown under full sunlight and moderate and high levels of shade for one month to evaluate its photosynthetic and chlorophyll fluorescence response to different light conditions. The results showed that T. hemsleyanum attained greatest leaf size and P n when cultivated with 67% shade. Leaves of seedlings grown with 90% shade were the smallest. Leaf color of plants grown under full sunlight and 50% shade was yellowish-green. The P n value increased rapidly as PPFD increased to 200 μmol m −2 s −1 and then increased slowly to a maximum, followed by a slow decrease as PPFD was increased to 1000 μmol m −2 s −1. P n was highest for the 67% shade treatment and the LSP for this shade treatment was 600 μmol m −2 s −1. Full sunlight and 50% shade treatments resulted in significant reduction of ETR and qP and increased NPQ. Chl a, Chl b and total chlorophyll content increased and Chl a/ b values decreased with increased shading. Results showed that light intensity greater than that of 50% shade depressed photosynthetic activity and T. hemsleyanum growth. Irradiance less than that of 75% shade limited carbon assimilation and led to decreased plant growth. Approximately 67% shade is suggested to be the optimum light irradiance condition for T. hemsleyanum cultivation.

기계시각을 이용한 상추의 엽색 및 건강상태 판정

Image processing systems have been used to measure the plant parameters such as size, shape and structure of plants. There are yet some limited applications for evaluating plant colors due to illumination conditions. This study was focused to present adaptive methods to analyze plant leaf color regardless of illumination conditions. Color patches attached on the calibration bars were selected to represent leaf colors of lettuces and to test a possibility of health monitoring of lettuces. Repeatability of assigning leaf colors to color patches was investigated by two-tailed t-test for paired comparison. It resulted that there were no differences of assignment histogram between two images of one lettuce that were acquired at different light conditions. It supported that use of the calibration bars proposed for leaf color analysis provided color constancy, which was one of the most important issues in a video color analysis. A health discrimination equation was developed to classify lettuces into one of two classes, SOUND group and POOR group, using the machine vision. The classification accuracy of the developed health discrimination equation was 80.8%, compared to farmers` decision. This study could provide a feasible method to develop a standard color chart for evaluating leaf colors of plants and plant health monitoring system using the machine vision.

An Algorithm for Estimating Chlorophyll Content in Leaves Using a Video Camera

Plant leaf colour is commonly used as an index for nutrient diagnosis. We have developed a low-cost diagnostic method that is easy to use to assess the nutrient status of plants, based on the estimation of chlorophyll content of leaves using a portable colour video camera and a personal computer. Relationships between chlorophyll content and various functions derived from red, green and blue wavelengths are examined. Although red-blue and green-blue wavelengths show the highest correlation with chlorophyll content under a limited range of meteorological conditions, the normalized difference (red-blue)/(red+blue) is the most applicable function which can use data collected under different meteorological conditions. The accuracy in estimating chlorophyll content from video images could be improved by correcting with solar radiation data. It is shown that, for practical purposes, the chlorophyll content of leaves can be estimated with sufficient accuracy using a portable video camera.