Leaf Color Change Research Articles

SWATH-MS based proteomics reveals the role of photosynthesis related proteins and secondary metabolic pathways in the colored leaves of sweet olive (Osmanthus fragrans)

Colored leaves, a notable horticultural trait, have high research and ornamental value. The evergreen sweet olive (Osmanthus fragrans), one of the top ten traditional flowers in China, has been cultivated for more than two thousand years. However, in recent years, an increasing number of O. fragrans cultivars with colored leaves have been cultivated for their ornamental value. To study the molecular mechanism underlying the observed changes in leaf color, we selected O. fragrans ‘Yinbi Shuanghui’ (Y), which has yellow-white leaves, and O. fragrans ‘Sijigui’ (S), which has green leaves, as materials. Pigment content measurement showed that the chlorophyll, carotenoid and anthocyanin contents in Y were lower than in S. According to the SWATH-MS sequencing results, a total of 3,959 proteins were quantitatively identified, 1,300 of which were differentially expressed proteins (DEPs), including 782 up-regulated and 518 down-regulated proteins in Y compared to S. Functional enrichment analysis of DEPs revealed that down-regulated expression of photosynthesis related proteins may lead to the inhibition of chlorophyll synthesis in Y, this may be the main cause of leaf color change. Moreover, a protein interaction prediction model also showed that proteins such as PetC, PsbO, PsbP, and PsbQ were key proteins in the interaction network, and the up-regulated proteins participating in the anthocyanin and carotenoid pathways may be related to the formation of yellow-white leaves. Taken together, our findings represent the first SWATH-MS-based proteomic report on colored leaf O. fragrans and reveal that chlorophyll synthesis and secondary metabolism pathways contribute to the changes in leaf color.

Unravelling the physiological and molecular mechanisms of leaf color change in Acer griseum through multi-omics analysis

Paperbark maple (Acer griseum), an endemic and endangered wild plant in China, has red-colored autumn leaves of high ornamental and garden application value. Leaf color change serves as a crucial indicator for evaluating garden tree aesthetics; however, research on A. griseum's leaf color change remains limited. This study aims to elucidate the physiological and molecular mechanisms underlying leaf color change in maple leaves through physiological, transcriptional, and metabolic assays. Data analysis encompasses gene expression levels and metabolite changes in three distinct states of maple leaves: green, half-red, and red. The progessive decrease of chlorophyll and carotenoids and the continuous accumulation of anthocyanidins caused a sharp change in leaf coloration, which was most drastic in the green to half-red period. Subsequently, targeted metabolomics analysis was performed, and a total of 71 anthocyanidins were detected, and the content of eight types of anthocyanidins increased significantly in the half-red and red periods, compared with that in the green period; of which the multiplicative difference was the largest for cyanidin-3,5-O diglucoside, delivering the largest multiplicative difference. Thus, it was plausible that cyanidin-3,5-O-diglucoside-dominated compoundswere likely to be the main metabolites associated with leaf reddening. Correlation analysis revealed that 12 key transcription factors (TFs) were significantly correlated with the anthocyanin-related metabolites and structural genes, which play important regulatory roles during the biosynthesis of anthocyanosides in A. griseum. These findings offered useful insights into the molecular basis of leaf color variation in A. griseum; providing valuable information to guide targeted genetic breeding and varietal improvement strategies.

Characterization of Low-Temperature Sensitivity and Chlorophyll Fluorescence in Yellow Leaf Mutants of Tomato

Leaf color mutants serve as valuable models for studying the regulation of plant photosynthesis, alternations in chloroplast structure and function, and the analysis of associated gene functions. A yellow leaf mutant, ylm, was separated from the wild tomato M82, with its yellowing intensity influenced by low temperature. To assess the low-temperature sensitivity of this mutant, the photosynthetic and chlorophyll fluorescence responses of ylm and M82 were examined under different temperature conditions. In this study, the ylm mutant and its wild type, M82, were exposed to three temperature levels, 16, 25, and 30 °C, for 48 h. The impact of these temperature treatments on leaf color change, chlorophyll content, photosynthetic performance, and chlorophyll fluorescence characteristics of mutant ylm was investigated. The results revealed the following: (1) After exposure to 16 °C, the ylm mutant exhibited significant yellowing, a marked reduction in chlorophyll content, and a notable increase in carotenoid content. At 25 °C, the differences were less pronounced, and at 30 °C, the differences between ylm and M82 were minimal. (2) The photosynthetic rate of the ylm mutant was lower than that of M82 at 16 °C, with the gap narrowing as temperature increased, eventually converging at higher temperatures. (3) The fluorescence transient curve (OJIP) of the ylm mutant differed significantly from that of M82 at 16 °C, with higher fluorescence intensity at the O point and lower intensity at the J, I, and P points. This difference was decreased at 25 °C and nearly disappeared at 30 °C. Additionally, the Fv/Fm, Fv/Fo, PIabs, PItotal, ABS/CSm, TRo/CSm, and ETo/CSm values of ylm were lower than those of M82 at 16 °C, while the ABS/RC and DIo/RC values were higher, with no significant differences observed at 30 °C. These findings suggest that the ylm mutant is highly sensitive to low temperature, with pronounced yellowing, reduced light energy absorption and capture efficiency, and impaired electron transport at lower temperature.

Exogenous N Supply on N Transportation and Reuse during the Rice Grain-Filling Stage and Its Relationship with Leaf Color-Changing Parameters

During the later reproductive period of rice growth, the chlorophyll in the leaves degraded, accompanied by the nitrogen (N) transportation from leaves to panicle, resulting in a change in leaf color from green to yellow. This study aimed to investigate the effects of exogenous N supply on leaf color-changing, N accumulation, N transportation, and N loss of indica-japonica hybrid rice during the grain-filling stage. Two indica-japonica hybrid rice cultivars, Chunyou 167 (CY167) and Chunyou 927 (CY927), which exhibited significant differences in leaf color-changing during the grain-filling stage, were selected as materials for field experiment and hydroponic experiment with low, medium, and high N treatments (LN, MN, and HN). The dynamic changes in SPAD value from heading to maturity were measured and fitted with quadratic function to extract leaf color-changing parameters; labeled 15N was used as N source after heading to trace the source of N in the panicle and the remobilization of vegetative organ N. The results showed that 67.37–72.38% of the panicle N was transported from vegetative organs, the N transport efficiency was the upper three leaves > lower leaves > stem, and about 3.1–35.0% of the transported N was lost via volatilization. The effects of exogenous N concentration on N harvest index, N dry matter/grain production efficiency, N reuse efficiency, and N loss were closely related to leaf color-changing parameters. In MN and HN treatment, the N loss was negatively correlated with the onset time of leaf color-changing (T0) and the final leaf color index (CIf), but positively correlated with the leaf color-changing rate (Rmean). Increasing the supply of exogenous N increased T0 and CIf, but decreased Rmean, N transport/reuse efficiency, N harvest index, and N dry matter/grain production efficiency. Compared to the cultivar CY167 with normal leaf color-changing, the “stay-green” cultivar CY927 had higher T0, CIf, and lower Rmean, resulting in less N volatilization loss, lower N harvest index and N transport efficiency, while higher N reuse efficiency. In conclusion, the exogenous N supply affects leaf color by influencing the transportation and reuse of leaf N during the grain-filling stage.

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.

Analysis of plant physiological responses based on leaf color changes through the development and application of a wireless plant sensor

Optical sensing has been used to monitor the physiological responses of plants noninvasively and in real-time. In this study, we developed a low-cost plant sensor that performed a spectroscopic measurement at eight wavelengths in the visible region. The sensor head of the system was attached directly to the underside of the leaf, not blocking the light, and eliminating correction work because of the constant distance between the sensor head and the sample. The collected data was shared in the cloud via a network, thereby enabling remote monitoring. The characteristics of the plant sensor as a spectral photometer were validated, with major wavelengths also showing good correlations with those of a conventional spectrometer. The reflectance of 620 nm in this sensor detected plant aging indicator chlorophyll, and 550 nm detected stress indicator xanthophyll. In the field test, these plant physiological responses, seasonal leaf color changes and environmental stresses, were observed remotely. The results indicate that the novel spectroscopic measurement from the underside of the leaf is effective to realize accurate and stable measurement of the plant leaf. The plant sensor can be a powerful tool in the field of agriculture and ecological study by realizing simultaneous, multi-point and remote monitoring at a low cost.

Selection and Validation of Reliable Reference Genes for Liquidambar formosana Leaves with Different Leaf Colors.

Liquidambar formosana Hance is renowned for its rich leaf color and possesses notable advantages, such as robust adaptability, strong resistance to diseases and pests, and rapid growth, making it a preferred choice for urban greening and carbon sequestration forest initiatives. The completion of whole-genome sequencing of L. formosana has spurred an increased interest in exploring the molecular mechanisms underlying seasonal changes in leaf color, marking a significant focus in L. formosana breeding research. However, there is currently a lack of stable reference genes suitable for analyzing the expression patterns of functional genes in L. formosana exhibiting varying leaf colors. This study selected five L. formosana varieties with significant differences in leaf colors. Through the RT-qPCR analysis, and evaluation using BestKeeper, geNorm, NormFinder, Delta Ct, and RefFinder, the expression stability of 14 candidate reference genes was examined. Consequently, two reference genes (LifEF1-α and LifACT) with stable expression, suitable for RT-qPCR of L. formosana with diverse leaf colors, were identified. The stability of these selected reference genes was further validated by examining the LifbHLH137 gene, which promoted the biosynthesis of anthocyanins. This advancement facilitated molecular biology and genetic breeding investigations of L. formosana, providing essential data for the precise quantification of functional genes associated with leaf color variation.

Genome-Wide Profiling of the Genes Related to Leaf Discoloration in Zelkova schneideriana

Zelkova schneideriana is a landscaping flowering and deciduous plant whose leaf color changes in the fall season. In the discoloration period, the anthocyanin content in the red lines of Z. schneideriana is 3.52 times greater than that in the green lines, whereas the chlorophyll content in the red lines is 20.10 times lower. To understand the molecular mechanism of the leaf discoloration, transcriptome sequencing was performed. A total of 3965 differentially expressed genes (DEGs) were identified between the red and green lines in the discoloration period. These DEGs were mainly involved in plant–pathogen interactions, the MAPK signaling pathway, plant hormone signal transduction, flavonoid biosynthesis, and anthocyanin biosynthesis. Among them, three downregulated genes were involved in chlorophyll synthesis; these genes exhibited a maximum decrease in the red lines that was 11.13 times greater than their expression in the green lines. In contrast, 33 upregulated genes were involved in anthocyanin biosynthesis; they exhibited a maximum increase in the red lines 4645.33 times greater than their expression in the green lines. The results of an association analysis revealed that four transcription factors, including ZeBHLH42, ZeMYB123, ZeMYB113, and ZeWRKY44, positively regulated the anthocyanin synthesis genes. These results explained the mechanism underlying the discoloration of Zelkova leaves and provided a basis for molecular breeding programs of colorful plants.

Variability of agromorphological traits in Portulaca grandiflora through induced mutation using colchicine

Abstract. Aisyah SI, Meiningrum NI, Yudha YS, Nurcholis W. 2024. Variability of agromorphological traits in Portulaca grandiflora through induced mutation using colchicine. Biodiversitas 25: 2484-2493. Portulaca grandiflora Hook is an ornamental plant originating from the Portulacaceae family, and it has been extensively cultivated on various continents. P. grandiflora displays appealing flower shapes and vibrant colors suitable for growth in a tropical landscape. Increased morphological diversity carries significant importance in the aesthetic function of ornamental plants. The higher the variation in the morphological characteristics of ornamental plants, the greater the market value of these plants due to their enhanced aesthetic appeal. Additionally, colchicine, a polyploidy-inducing agent, can enhance the plant genetic diversity. This study aims to investigate the impact of colchicine application on the morphological characters of P. grandiflora. The experiment was conducted for four months at the Leuwikopo Experimental Field, IPB, with two factors of Completely Randomized Block Design: The colchicine treatment comprises five concentration levels (0, 0.05, 0.1, 0.15, and 0.2), with four test genotypes: Orange, Peach, Bicolor, and Banana. A significant reduction in growth was observed in the Bicolor genotype, followed by the Banana genotype, indicating varying tissue sensitivities to colchicine treatment. The study reveals variations in morphological responses for each concentration treatment and genotype used. Statistical results confirm aspects: (i) each genotype displays different performance, (ii) the combined treatment of colchicine significantly influences the growth and development of quantitative traits, and (iii) The interaction (colchicine x genotype) was statistically significant for all quantitative characters of P. grandiflora except stem diameter. Qualitative traits, such as morphological changes in stem color, leaf color, and shape, were observed. Three correlation values are positive and statistically significant: plant length and leaf width, number of branches on shoots and leaves, and number of branches on shoots and flowers. Putative mutants of P. grandiflora exhibiting new traits require in-depth exploration in subsequent generations.

For a Colorful Life: Recent Advances in Anthocyanin Biosynthesis during Leaf Senescence.

Leaf senescence is the last stage of leaf development, and it is accompanied by a leaf color change. In some species, anthocyanins are accumulated during leaf senescence, which are vital indicators for both ornamental and commercial value. Therefore, it is essential to understand the molecular mechanism of anthocyanin accumulation during leaf senescence, which would provide new insight into autumn coloration and molecular breeding for more colorful plants. Anthocyanin accumulation is a surprisingly complex process, and significant advances have been made in the past decades. In this review, we focused on leaf coloration during senescence. We emphatically discussed several networks linked to genetic, hormonal, environmental, and nutritional factors in regulating anthocyanin accumulation during leaf senescence. This paper aims to provide a regulatory model for leaf coloration and to put forward some prospects for future development.

Postharvest practices and loss determinants for interventions among smallholder potato farmers in Tiyo district, Arsi zone, Ethiopia

Postharvest loss reduction, which will contribute to several sustainable development goals (SDGs) including SDG 1, 2, 3, 9, 12 and 13, is an important strategy for food and nutrition security. It requires interventions designed based on timely and reliable statistical data. However, lack of produce-specific loss data and associated factors along the postharvest value chain stages remains a challenge to implement appropriate interventions. Therefore, a survey was conducted on socio-demographic characteristics, postharvest practices, extent and causes of losses, and factors influencing postharvest loss of potato crops in Tiyo district of Arsi Zone, Ethiopia in 2022. A multistage sampling method was used to select a total of 209 smallholder potato farming household heads through a combination of purposive and simple random sampling techniques. Quantitative data collection was carried out online using computer-assisted personal interviewing (CAPI) by programming a semi-structured questionnaire in KoboCollect software for tablets. Descriptive statistics and ordinal probit regression model were used to analyze the collected data and determinant factors influencing postharvest loss of potatoes at various farm-level stages, respectively. An aggregate of 15-46% loss exists between harvesting and marketing. Losses during harvesting, sorting, cleaning, packaging, field-to-storage transport, storage, and storage-to-market transport were 58.9%, 6.2%, 2.9%, 2.4%, 3.8%, 20.1%, and 5.7%, respectively. Elevated loss during harvesting and storage in the area is likely to reflect poor handling and storage practices. The primary causes of losses were poor harvesting and handling techniques, poor storage facility, and insects and worms. Moreover, regression model estimations of categorical losses, as perceived by farmers, reveal that socio-demographic variables and postharvest factors influenced potato loss. During the harvest stage, working family members significantly (p<0.01) increased loss while years of schooling (p<0.05) significantly reduced loss. In addition, harvesting using leaf color change observation as a criterion had significantly (p<0.01) mitigated potato loss. In storage, female respondents (p<0.05), land size (p<0.05), and lack of training (p<0.1) had accentuated loss. During transport, the age of household reduced (p<0.1) loss whereas farming experience promoted (p<0.1) it. To reduce the existing losses, farmers’ awareness should be increased concerning each stage. The study recommends the need for stakeholders’ intervention focusing on postharvest knowledge and skill capacity building, demonstration of simple innovative ventilated storage construction using locally available materials, appropriate packaging (such as reusable plastic crates) and transport methods, and simple value addition methods (such as potato drying using indirect solar dryers and potato flour processing for fortifying local cereals). Key words: CAPI, Ethiopia, ordinal probit regression, postharvest practices, potato loss determinants

Effects of different light intensity on leaf color changes in a Chinese cabbage yellow cotyledon mutant.

Leaf color is one of the most important phenotypic features in horticultural crops and directly related to the contents of photosynthetic pigments. Most leaf color mutants are determined by the altered chlorophyll or carotenoid, which can be affected by light quality and intensity. Our previous study obtained a Chinese cabbage yellow cotyledon mutant that exhibited obvious yellow phenotypes in the cotyledons and the new leaves. However, the underlying mechanisms in the formation of yellow cotyledons and leaves remain unclear. In this study, the Chinese cabbage yellow cotyledon mutant 19YC-2 exhibited obvious difference in leaf color and abnormal chloroplast ultrastructure compared to the normal green cotyledon line 19GC-2. Remarkably, low-intensity light treatment caused turn-green leaves and a significant decrease in carotenoid content in 19YC-2. RNA-seq analysis revealed that the pathways of photosynthesis antenna proteins and carotenoid biosynthesis were significantly enriched during the process of leaf color changes, and many differentially expressed genes related to the two pathways were identified to respond to different light intensities. Remarkably, BrPDS and BrLCYE genes related to carotenoid biosynthesis showed significantly higher expression in 19YC-2 than that in 19GC-2, which was positively related to the higher carotenoid content in 19YC-2. In addition, several differentially expressed transcription factors were also identified and highly correlated to the changes in carotenoid content, suggesting that they may participate in the regulatory pathway of carotenoid biosynthesis. These findings provide insights into the molecular mechanisms of leaf color changes in yellow cotyledon mutant 19YC-2 of Chinese cabbage.

Image Sensing, A Unique Tool for Early Detection of Nitrogen Deficiency of Tomato Grown in Hot and Humid Greenhouses

Protected culture (PC) answers the major issues in conventional agriculture, and thus helps feed the rising world population. Meanwhile, soilless culture has become an integral part of the PC, for sake of catering to the plant nutrient requirements precisely. Therefore, innovative intellective diagnostic systems for diagnosing nutrient deficiency symptoms in protected culture is a timely need. Hence this experiment was conducted to test the effectiveness of “Image Sensing” as a diagnostic tool for nitrogen deficiency under semi-intensive greenhouse management in hot and humid weather. In this study N deficiency symptoms of tomato were detected by leaf color changes, identified through image sensing, and the deficiency was confirmed with respect to retardation of plant growth. Tomato plants were subjected to a series of N treatments by providing 200, 100, 50, 25, and 12.5 percent of the recommended N supply for soilless culture tomatoes. The results showed that morphology changes like stem thickness, leaf area, plant height, and leaf number were significantly reduced along with a reduction of N supply (p<0.05) beginning from 5th week after transplanting (WAT). Leaf images were processed in “ImageJ”, software” to determine the green color intensity of leaves. Image analysis showed that there was a significant difference among treatments since the 3rd WAT. The leaf color chart was less effective for distinguishing leaf color at the early stages of N deficiency. The results revealed that diagnosis of N deficiency in tomato leaves could be effectively done by image sensing much earlier than the use of plant growth parameters or morphological changes. Hence, image sensing can be used as a more effective diagnostic tool for early detection of N deficiency of tomato cultivations in hot and humid greenhouses, that can be used to improve crop management, especially in large large-scale commercial practices.

The effect of giving colchicine on appearance phnotypes of two genotypes in okra (Abelmochus esculentus L. Moench)

Cultivation of okra (Abelmochus esculentus L. Moench) is done to increase productivity by means of mutations to produce populations that have diversity. The aim of this study was to determine the effect of colchicine concentration on phenotypic changes in two genotypes of okra so as to produce plants with polyploidy properties. This research was conducted using a Randomized Block Design (RBD) with 2 treatment factors. First factor is use IPB’s Zahira Varieties: IPB’s Naila Varieties. Second factor was addition with a dose of colchicine 0%, 0.20%, 0.40%, and 0.60% as a solution for soaking okra seeds. Results showed that stomatal density (mm2) and flowering age WAP were significantly different due to variety and colchicine treatments. Variety significantly affected plant height at 5-13 WAP, number of leaves at 6-13 WAP, fruit length, fruit diameter, fruit weight, and number of fruit, colchicine concentration significantly affected height 2-13 WAP, number leaves at 4-9 WAP, flowering age, fruit length, fruit diameter, fruit weight, and number of fruit. Interaction of varieties and administration of colchicine concentrations affected okra plant height at 11-13 WAP, number of leaves at 8 WAP, and fruit weight. The qualitative characters show the results of changes in leaf color and shape.

Pigment Diversity in Leaves of Caladium × hortulanum Birdsey and Transcriptomic and Metabolic Comparisons between Red and White Leaves.

Leaf color is a key ornamental characteristic of cultivated caladium (Caladium × hortulanum Birdsey), a plant with diverse leaf colors. However, the genetic improvement of leaf color in cultivated caladium is hindered by the limited understanding of leaf color diversity and regulation. In this study, the chlorophyll and anthocyanin content of 137 germplasm resources were measured to explore the diversity and mechanism of leaf color formation in cultivated caladium. Association analysis of EST-SSR markers and pigment traits was performed, as well as metabolomics and transcriptomics analysis of a red leaf variety and its white leaf mutant. We found significant differences in chlorophyll and anthocyanin content among different color groups of cultivated caladium, and identified three, eight, three, and seven EST-SSR loci significantly associated with chlorophyll-a, chlorophyll-b, total chlorophyll and total anthocyanins content, respectively. The results further revealed that the white leaf mutation was caused by the down-regulation of various anthocyanins (such as cyanidin-3-O-rutinoside, quercetin-3-O-glucoside, and others). This change in concentration is likely due to the down-regulation of key genes (four PAL, four CHS, six CHI, eight F3H, one F3'H, one FLS, one LAR, four DFR, one ANS and two UFGT) involved in anthocyanin biosynthesis. Concurrently, the up-regulation of certain genes (one FLS and one LAR) that divert the anthocyanin precursors to other pathways was noted. Additionally, a significant change in the expression of numerous transcription factors (12 NAC, 12 bZIP, 23 ERF, 23 bHLH, 19 MYB_related, etc.) was observed. These results revealed the genetic and metabolic basis of leaf color diversity and change in cultivated caladium, and provided valuable information for molecular marker-assisted selection and breeding of leaf color in this ornamental plant.

Integrated Analysis of Metabolome and Transcriptome Revealed Different Regulatory Networks of Metabolic Flux in Tea Plants [Camellia sinensis (L.) O. Kuntze] with Varied Leaf Colors.

Leaf color variations in tea plants were widely considered due to their attractive phenotypes and characteristic flavors. The molecular mechanism of color formation was extensively investigated. But few studies focused on the transformation process of leaf color change. In this study, four strains of 'Baijiguan' F1 half-sib generation with similar genetic backgrounds but different colors were used as materials, including Green (G), Yellow-Green (Y-G), Yellow (Y), and Yellow-Red (Y-R). The results of broadly targeted metabolomics showed that 47 metabolites were differentially accumulated in etiolated leaves (Y-G, Y, and Y-R) as compared with G. Among them, lipids were the main downregulated primary metabolites in etiolated leaves, which were closely linked with the thylakoid membrane and chloroplast structure. Flavones and flavonols were the dominant upregulated secondary metabolites in etiolated leaves, which might be a repair strategy for reducing the negative effects of dysfunctional chloroplasts. Further integrated analysis with the transcriptome indicated different variation mechanisms of leaf phenotype in Y-G, Y, and Y-R. The leaf color formation of Y-G and Y was largely determined by the increased content of eriodictyol-7-O-neohesperidoside and the enhanced activities of its modification process, while the color formation of Y-R depended on the increased contents of apigenin derivates and the vigorous processes of their transportation and transcription factor regulation. The key candidate genes, including UDPG, HCT, CsGSTF1, AN1/CsMYB75, and bHLH62, might play important roles in the flavonoid pathway.

Metabolome combined with transcriptome profiling reveals the dynamic changes in flavonoids in red and green leaves of Populus × euramericana 'Zhonghuahongye'.

Flavonoids are secondary metabolites that have economic value and are essential for health. Poplar is a model perennial woody tree that is often used to study the regulatory mechanisms of flavonoid synthesis. We used a poplar bud mutant, the red leaf poplar variety 2025 (Populus × euramericana 'Zhonghuahongye'), and green leaves as study materials and selected three stages of leaf color changes for evaluation. Phenotypic and biochemical analyses showed that the total flavonoid, polyphenol, and anthocyanin contents of red leaves were higher than those of green leaves in the first stage, and the young and tender leaves of the red leaf variety had higher antioxidant activity. The analyses of widely targeted metabolites identified a total of 273 flavonoid metabolites (114 flavones, 41 flavonols, 34 flavonoids, 25 flavanones, 21 anthocyanins, 18 polyphenols, 15 isoflavones, and 5 proanthocyanidins). The greatest difference among the metabolites was found in the first stage. Most flavonoids accumulated in red leaves, and eight anthocyanin compounds contributed to red leaf coloration. A comprehensive metabolomic analysis based on RNA-seq showed that most genes in the flavonoid and anthocyanin biosynthetic pathways were differentially expressed in the two types of leaves. The flavonoid synthesis genes CHS (chalcone synthase gene), FLS (flavonol synthase gene), ANS (anthocyanidin synthase gene), and proanthocyanidin synthesis gene LAR (leucoanthocyanidin reductase gene) might play key roles in the differences in flavonoid metabolism. A correlation analysis of core metabolites and genes revealed several candidate regulators of flavonoid and anthocyanin biosynthesis, including five MYB (MYB domain), three bHLH (basic helix-loop-helix), and HY5 (elongated hypocotyl 5) transcription factors. This study provides a reference for the identification and utilization of flavonoid bioactive components in red-leaf poplar and improves the understanding of the differences in metabolism and gene expression between red and green leaves at different developmental stages.

Functional Validation and Promoter DNA Methylation Analysis of the OfPAO Gene of Osmanthus fragrans ‘Yinbi Shuanghui’

Osmanthus fragrans ‘Yinbi Shuanghui’ is a colored leaf variety of O. fragrans. To study the mechanism of leaf color formation in O. fragrans ‘Yinbi Shuanghui’, we selected green and colored leaves with two different parts, namely yellow and green, as our research materials. We analyzed the expression changes related to leaf color in genes by performing qRT-PCR in the different leaf parts, finding that OfPAO was significantly up-regulated in the yellow part of colored leaves, and we initially determined that OfPAO was the key gene involved in the formation of colored leaves. Then, we constructed an OfPAO overexpression vector, before transforming it into tobacco through an Agrobacterium-mediated transformation to obtain transgenic plants. We found that the transgenic tobacco leaf color of OfPAO was lighter than that of the null carrier, the chlorophyll content in leaves decreased, and the expression of genes involved in the chlorophyll degradation pathway in OfPAO transgenic tobacco was up-regulated, suggesting that OfPAO regulates chlorophyll degradation, leading to changes in leaf color. According to the results of transcriptome sequencing and the genome data of O. fragrans ‘Rixianggui’, we cloned CDS and the promoter sequence of OfPAO, and the promoter regions 901-1307 of the OfPAO were sequenced through bisulfite genomic sequencing PCR (BSP), finding that the methylation level of CHH in the yellow part of colored leaves was lowest in colored and green leaves at 145 bp. The methylation of CHH in the promoter of OfPAO in O. fragrans ‘Yinbi Shuanghui’ was negatively correlated with the gene expression level, suggesting that the methylation of the promoter of OfPAO may regulate the expression of OfPAO, affecting chlorophyll degradation in the leaves.

Detection of woody species Schinopsis haenkeana using phenological spectral differences and NDVI texture measures in subtropical forests

Schinopsis haenkeana is a native tree species of great importance of South America. Different tree species diverge in their vegetation phenology, providing the opportunity to map their presence based on the seasonal dynamics of vegetation indices. Currently, spatially explicit information on tree species composition provides valuable insights for biodiversity conservation. The objective of this study was to detect the presence of S. haenkeana and its forest status in subtropical forests in central Argentina. We used a combination of RGB-NIR bands and indices (NDVI, EVI, GLI, RGR) derived from Sentinel-2 images. The analyses were processed using the Earth Engine platform and the random forest algorithm was used to discriminate S. haenkeana from other plant species. NDVI texture indices were also used to discriminate different forest states where the species is present. A fruiting period and a leaf color change were detected in July, and spectral differences between fruiting and preceding (May) or subsequent (October) months proved to be highly suitable for discriminating S. haenkeana. The final species presence map achieved an overall accuracy of 91%. Only 0.76% of the total area corresponds to S. haenkeana dense forests. This analysis demonstrated the value of the proposed approach for regularly detecting and mapping S. haenkeana using RGB-NIR spectral information, vegetation indices, and phenological spectral differences. Additionally, it highlighted the importance of using texture indices to differentiate between forests and scrublands, providing suitable data for forest management.

Automated remote sensing system for crops monitoring and irrigation management, based on leaf color change and piecewise linear regression models for soil moisture content predicting

Plants can serve as biological sensors if their “readings” and the feedback they provide us through changes in the colour of their leaves can be correctly interpreted. The study aims to predict soil moisture and, as such, the need for irrigation, using nonlinear mathematical models, describing the relationship between RGB and HSL colour model components and soil moisture and temperature. Nonlinear mathematical models used in the study are based on piecewise linear regression with breakpoint and soil moisture prediction using colour components and soil temperature with a deviation of +-6%. A system for automated irrigation was created and its control program was made, the basic control law of which is based on non-linear piecewise linear models. The automated irrigation management system includes a remote crop monitoring subsystem and an irrigation management subsystem. The program processes the photo received from the camera and activates the actuators when watering is needed. Compared to manual data collection in the first part of the study, the program calculates the average RGB model values from images in the studied row of tomato plantations with an accuracy of over 99% for the R and G components and over 92% for the B component. The program also predicts soil moisture with 98% accuracy. The practical significance of the water-saving efforts of this study lies in the development of a program-controlled automated irrigation system that utilizes plants as biological sensors, employing nonlinear mathematical models based on leaf colour changes to accurately predict soil moisture