Stages Of Leaf Development Research Articles

Phenological growth stages of jackfruit (Artocarpus heterophyllus) according to the extended BBCH scale

Jackfruit, the largest known edible fruit bearing tree, is one of the important fruit crops of India. It exhibits wide range of diversity with respect to fruit character and bulb quality. It is an important component of homestead garden because of its multifarious uses (dessert, vegetable and pickle) and high nutritive value. In spite of high food value and market potential, jackfruit is one of the poorly researched crops and there is a dearth of information about its phenology. The present study defines phenological stages of jackfruit according to the extended BBCH (Biologische Bundesantalt, Bundessortenamt und Chemische Industrie) scale using three‐digit numerical system. Eight principal growth stages, namely bud development (stage 0), shoot development (stage 1), leaf development (stage 3), specialised reproductive shoot development (stage 4), reproductive development (stage 5), flowering (stage 6), fruit development (stage 7) and fruit maturation (stage 8) have been described. A total of 42 secondary growth stages have been described and defined. In this study, bearing and non‐bearing footstalks as well as male and female phases have been defined separately. The study will act as an effective tool for providing a consensual unified approach for standardisation of phenophases, as well as for efficient orchard management for ensuring higher yield and fruit quality. The scale may also be effectively used for characterisation and adaptation of germplasm and assessment of climatic impact on crop phenology.

Validation of a Process-Based Agro-Ecosystem Model (Agro-IBIS) for Maize in Xinjiang, Northwest China

Agricultural oasis expansion and intensive management practices have occurred in arid and semiarid regions of China during the last few decades. Accordingly, regional carbon and water budgets have been profoundly impacted by agroecosystems in these regions. Therefore, study on the methods used to accurately estimate energy, water, and carbon exchanges is becoming increasingly important. Process-based models can represent the complex processes between land and atmosphere among agricultural ecosystems. However, before the models can be applied they must be validated under different environmental and climatic conditions. In this study, a process-based agricultural ecosystem model (Agro-IBIS) was validated for maize crops using 3 years of soil and biometric measurements at Wulanwusu agrometeorological site (WAS) located in the Shihezi oasis in Xinjiang, northwest China. The model satisfactorily represented leaf area index (LAI) during the growing season, simulating its peak values within the magnitude of 0–10%. The total biomass carbon was overestimated by 15%, 8%, and 16% in 2004, 2005, and 2006, respectively. The model satisfactorily simulated the soil temperature (0–10 cm) and volumetric water content (VWC) (0–25 cm) of farmland during the growing season. However, it overestimated soil temperature approximately by 4 °C and VWC by 15–30% during the winter, coinciding with the period of no vegetation cover in Xinjiang. Overall, the results indicate that the model could represent crop growth, and seems to be applicable in multiple sites in arid oases agroecosystems of Xinjiang. Future application of the model will impose more comprehensive validation using eddy covariance flux data, and consider including dynamics of crop residue and improving characterization of the final stage of leaf development.

The Use of RNA Sequencing and Correlation Network Analysis to Study Potential Regulators of Crabapple Leaf Color Transformation.

Anthocyanins are plant pigments that contribute to the color of leaves, flowers and fruits, and that are beneficial to human health in the form of dietary antioxidants. The study of a transformable crabapple cultivar, 'India magic', which has red buds and green mature leaves, using mRNA profiling of four leaf developmental stages, allowed us to characterize molecular mechanisms regulating red color formation in early leaf development and the subsequent rapid down-regulation of anthocyanin biosynthesis. This analysis of differential gene expression during leaf development revealed that ethylene signaling-responsive genes are up-regulated during leaf pigmentation. Genes in the ethylene response factor (ERF), SPL, NAC, WRKY and MADS-box transcription factor (TF) families were identified in two weighted gene co-expression network analysis (WGCNA) modules as having a close relationship to anthocyanin accumulation. Analyses of network hub genes indicated that SPL TFs are located in central positions within anthocyanin-related modules. Furthermore, cis-motif and yeast one-hybrid assays suggested that several anthocyanin biosynthetic or regulatory genes are potential targets of SPL8 and SPL13B. Transient silencing of these two genes confirmed that they play a role in co-ordinating anthocyanin biosynthesis and crabapple leaf development. We present a high-resolution method for identifying regulatory modules associated with leaf pigmentation, which provides a platform for functional genomic studies of anthocyanin biosynthesis.

Gene architecture and expression analyses provide insights into the role of glutathione peroxidases (GPXs) in bread wheat (Triticum aestivum L.)

Glutathione peroxidases (GPXs) are redox sensor proteins that maintain a steady-state of H2O2 in plant cells. They exhibit distinct sub-cellular localization and have diverse functionality in response to different stimuli. In this study, a total of 14 TaGPX genes and three splice variants were identified in the genome of Triticum aestivum and evaluated for various physicochemical properties. The TaGPX genes were scattered on the various chromosomes of the A, B, and D sub-genomes and clustered into five homeologous groups based on high sequence homology. The majority of genes were derived from the B sub-genome and localized on chromosome 2. The intron-exon organization, motif and domain architecture, and phylogenetic analyses revealed the conserved nature of TaGPXs. The occurrence of both development-related and stress-responsive cis-acting elements in the promoter region, the differential expression of these genes during various developmental stages, and the modulation of expression in the presence of biotic and abiotic stresses suggested their diverse role in T. aestivum. The majority of TaGPX genes showed higher expression in various leaf developmental stages. However, TaGPX1-A1 was upregulated in the presence of each abiotic stress treatment. A co-expression analysis revealed the interaction of TaGPXs with numerous development and stress-related genes, which indicated their vital role in numerous biological processes. Our study revealed the opportunities for further characterization of individual TaGPX proteins, which might be useful in designing future crop improvement strategies.

TSC1 enables plastid development under dark conditions, contributing to rice adaptation to transplantation shock.

Since its domestication from wild rice thousands of years ago, rice has been cultivated largely through transplantation. During transplantation from the nursery to the paddy field, rice seedlings experience transplantation shock which affects their physiology and production. However, the mechanisms underlying transplantation shock and rice adaptation to this shock are largely unknown. Here, we isolated a transplant-sensitive chloroplast-deficient (tsc1) rice mutant that produces albino leaves after transplantation. Blocking light from reaching the juvenile leaves and leaf primordia caused chloroplast deficiencies in transplanted tsc1 seedlings. TSC1 encodes a noncanonical adenosine triphosphate-binding cassette (ABC) transporter homologous to AtNAP14 and is of cyanobacterial origin. We demonstrate that TSC1 controls plastid development in rice under dark conditions, and functions independently of light signaling. However, light rescued the tsc1 mutant phenotype in a spectrum-independent manner. TSC1 was upregulated following transplantation, and modulated the iron and copper levels, thereby regulating prolamellar body formation during the early P4 stage of leaf development. Therefore, TSC1 is indispensable for plastid development in the absence of light, and contributes to adaptation to transplantation shock. Our study provides insight into the regulation of plastid development and establishes a framework for improving recovery from transplantation shock in rice.

Control of Retrograde Signaling by Rapid Turnover of GENOMES UNCOUPLED1.

The exchange of signals between cellular compartments coordinates development and differentiation, modulates metabolic pathways, and triggers responses to environmental conditions. The proposed central regulator of plastid-to-nucleus retrograde signaling, GENOMES UNCOUPLED1 (GUN1), is present at very low levels, which has hampered the discovery of its precise molecular function. Here, we show that the Arabidopsis (Arabidopsis thaliana) GUN1 protein accumulates to detectable levels only at very early stages of leaf development, where it functions in the regulation of chloroplast biogenesis. GUN1 mRNA is present at high levels in all tissues, but GUN1 protein undergoes rapid degradation (with an estimated half-life of ∼4 h) in all tissues where chloroplast biogenesis has been completed. The rapid turnover of GUN1 is controlled mainly by the chaperone ClpC1, suggesting degradation of GUN1 by the Clp protease. Degradation of GUN1 slows under stress conditions that alter retrograde signaling, thus ensuring that the plant has sufficient GUN1 protein. We also find that the pentatricopeptide repeat motifs of GUN1 are important determinants of GUN1 stability. Moreover, overexpression of GUN1 causes an early flowering phenotype, suggesting a function of GUN1 in developmental phase transitions beyond chloroplast biogenesis. Taken together, our results provide new insight into the regulation of GUN1 by proteolytic degradation, uncover its function in early chloroplast biogenesis, and suggest a role in developmental phase transitions.

Maize Phyllosphere Microbial Community Niche Development Across Stages of Host Leaf Growth.

Background: The phyllosphere hosts a variety of microorganisms, including bacteria, which can play a positive role in the success of the host plant. Bacterial communities in the phylloplane are influenced by both biotic and abiotic factors, including host plant surface topography and chemistry, which change in concert with microbial communities as the plant leaves develop and age. Methods: We examined how the Zea mays L. leaf microbial community structure changed with plant age. Ribosomal spacer length and scanning electron microscopic imaging strategies were used to assess microbial community composition across maize plant ages, using a novel staggered experimental design. Results: Significant changes in community composition were observed for both molecular and imaging analyses, and the two analysis methods provided complementary information about bacterial community structure within each leaf developmental stage. Conclusions: Both taxonomic and cell-size trait patterns provided evidence for niche-based contributions to microbial community development on leaves.

Wpływ Tytanitu na zawartość suchej masy i makropierwiastków w bulwach ziemniaka

This paper analyses the effect of the dose (0.2 L*ha-1 or 0.4 L*ha-1) and date (a single application at the leaf development stage – BBCH 14-16 or at the tuber formation stage – BBCH 41-43, and a double application at the BBCH 14-16 and BBCH 41-43 stages) of the application of Tytanit® (8.5 g Ti per liter in the form of Ti-ascorbate) on the dry matter and macroelement contents in tuber of very early potato cultivars (‘Lord’ and ‘Milek’). Potatoes were harvested 75 days after planting (the end of June). Tytanit® did not affect the content of dry matter and nitrogen, phosphorus, potassium, calcium, magnesium or sulphur in potato tubers. Following Tytanit® application, there was only an increase in sodium content. The sodium content in the immature potato tubers was higher after the application of 0.2 L*ha-1 of the Tytanit®. Regardless of the Tytanit® dose, the sodium content in tubers was the lowest when the growth stimulant was applied only once in the leaf development stage (BBCH 14-16), particularly under the more favorable thermal and moisture conditions for early crop potato culture. Following Tytanit® application, the weight ratios of Ca:P, K:Ca and K:Mg in potato tuber were similar, and the weight ratios of N:S, Na:Ca and Na:Mg were broader compared to the cultivation without the growth stimulant, although the ratio of the sum of univalent cations to the sum of bivalent cations (K+Na):(Ca+Mg) was at the same level, both in the cultivation with and without Tytanit®.

Colleters in the vegetative axis of Aechmea blanchetiana (Bromeliaceae): anatomical, ultrastructural and functional aspects

Colleters are common among eudicotyledons, but few records exist for monocotyledons and other groups of plants. For Bromeliaceae, mucilage secretions that protect the young portions of the plant have been observed only in the reproductive axis, and little is known about the secretory systems behind this or even other kind of secretions in the family. We aimed to describe, for the first time, the occurrence of colleters associated with the vegetative shoot of Aechmea blanchetiana (Baker) L.B.Sm., and elucidate aspects of their structure, ultrastructure and secretory activity. Samples of various portions of the stem axis were prepared according to standard methods for light and electron microscopy. Colleters were found compressed in the axillary portion of leaves and in all leaf developmental stages. Secretory activity, however, was found to be restricted to young and unexpanded leaves. The colleters displayed a flattened hand-like shape formed by a multiseriate stalk and an expanded secretory portion bearing elongated marginal cells. Ultrastructural data confirmed that the secretory role of the colleters is consistent with mucilaginous secretion. The functional roles of the colleters are discussed with regard to environmental context and intrinsic features of the plant, such as the presence of a water-impounding tank.

Phenotypic Analysis and Molecular Markers of Leaf Senescence.

The process of leaf senescence consists of the final stage of leaf development. It has evolved as a mechanism to degrade macromolecules and micronutrients and remobilize them to other developing parts of the plant; hence it plays a central role for the survival of plants and crop production. During senescence, a range of physiological, morphological, cellular, and molecular events occur, which are generally referred to as the senescence syndrome that includes several hallmarks such as visible yellowing, loss of chlorophyll and water content, increase of ion leakage and cell death, deformation of chloroplast and cell structure, as well as the upregulation of thousands of so-called senescence-associated genes (SAGs) and downregulation of photosynthesis-associated genes (PAGs). This chapter is devoted to methods characterizing the onset and progression of leaf senescence at the morphological, physiological, cellular, and molecular levels. Leaf senescence normally progresses in an age-dependent manner but is also induced prematurely by a variety of environmental stresses in plants. Focused on the hallmarks of the senescence syndrome, a series of protocols is described to asses quantitatively the senescence process caused by developmental cues or environmental perturbations. We first briefly describe the senescence process, the events associated with the senescence syndrome, and the theories and methods to phenotype senescence. Detailed protocols for monitoring senescence in planta and in vitro, using the whole plant and the detached leaf, respectively, are presented. For convenience, most of the protocols use the model plant species Arabidopsis and rice, but they can be easily extended to other plants.

Identification and Functional Analysis of Senescence-Associated Genes in Wheat.

Senescence is the final stage of leaf development. During this process, different macromolecules undergo degradation, and the resulting components are transported to developing and storage tissues of the plant. Senescence-associated genes (SAGs) play important roles in this process. Identification and characterization of SAGs are the first steps to interpret the function of these genes and to elucidate the mechanisms of leaf senescence. One of the most effective ways to identify SAGs is to screen for candidate genes using massive genome-scale transcriptomic data such as microarray, RNA-seq, digital RNA expression level data, etc. The basic functional analysis of candidate genes is to observe the phenotypes of transgenic plants, in which the candidate SAGs are overexpressed, knocked down, or knocked out. In this chapter, we outline methods for identifying and characterizing SAGs by microarray analysis in wheat. Methods of gene functional analyses by screening transgenic plants are also described. The protocols described in this chapter could also be used in other plant species, especially for Poaceae plants.

Genetic redundancy of senescence-associated transcription factors in Arabidopsis.

Leaf senescence is a genetically programmed process that constitutes the last stage of leaf development, and involves massive changes in gene expression. As a result of the intensive efforts that have been made to elucidate the molecular genetic mechanisms underlying leaf senescence, 184 genes that alter leaf senescence phenotypes when mutated or overexpressed have been identified in Arabidopsis thaliana over the past two decades. Concurrently, experimental evidence on functional redundancy within senescence-associated genes (SAGs) has increased. In this review, we focus on transcription factors that play regulatory roles in Arabidopsis leaf senescence, and describe the relationships among gene duplication, gene expression level, and senescence phenotypes. Previous findings and our re-analysis demonstrate the widespread existence of duplicate SAG pairs and a correlation between gene expression levels in duplicate genes and senescence-related phenotypic severity of the corresponding mutants. We also highlight effective and powerful tools that are available for functional analyses of redundant SAGs. We propose that the study of duplicate SAG pairs offers a unique opportunity to understand the regulation of leaf senescence and can guide the investigation of the functions of redundant SAGs via reverse genetic approaches.

Biogenic volatile organic compound emissions from senescent maize leaves and a comparison with other leaf developmental stages

Plants are the major source of Biogenic Volatile Organic Compounds (BVOCs) which have a large influence on atmospheric chemistry and the climate system. Therefore, understanding of BVOC emissions from all abundant plant species at all developmental stages is very important. Nevertheless, investigations on BVOC emissions from even the most widespread agricultural crop species are rare and mainly confined to the healthy green leaves. Senescent leaves of grain crop species could be an important source of BVOCs as almost all the leaves senesce on the field before being harvested. For these reasons, BVOC emission measurements have been performed on maize (Zea mays L.), one of the most cultivated crop species in the world, at all the leaf developmental stages. The measurements were performed in controlled environmental conditions using dynamic enclosures and proton transfer reaction mass spectrometry (PTR-MS). The main compounds emitted by senescent maize leaves were methanol (31% of the total cumulative BVOC emission on a mass of compound basis) and acetic acid (30%), followed by acetaldehyde (11%), hexenals (9%) and m/z 59 compounds (acetone/propanal) (7%). Important differences were observed in the temporal emission profiles of the compounds, and both yellow leaves during chlorosis and dry brown leaves after chlorosis were identified as important senescence-related BVOC sources. Total cumulative BVOC emissions from senescent maize leaves were found to be among the highest for senescent Poaceae plant species. BVOC emission rates varied strongly among the different leaf developmental stages, and senescent leaves showed a larger diversity of emitted compounds than leaves at earlier stages. Methanol was the compound with the highest emissions for all the leaf developmental stages and the contribution from the young-growing, mature, and senescent stages to the total methanol emission by a typical maize leaf was 61, 13, and 26%, respectively. This study shows that BVOC emissions from senescent maize leaves cannot be neglected and further investigations in field conditions are recommended to further constrain the BVOC emissions from this important C4 crop species.

Proteome and Acetyl-Proteome Profiling of Camellia sinensis cv. 'Anjin Baicha' during Periodic Albinism Reveals Alterations in Photosynthetic and Secondary Metabolite Biosynthetic Pathways.

Tea leaf color is not only important from an aesthetics standpoint but is also related to tea quality. To investigate the molecular mechanisms that determine tea leaf color, we examined Camellia sinensis cv. ‘Anji Baicha’ (an albino tea cultivar) by tandem mass tag isobaric labeling to generate a high-resolution proteome and acetyl-proteome atlas of three leaf developmental stages. We identified a total of 7,637 proteins and quantified 6,256; of these, 3,232 were classified as differentially accumulated proteins (DAPs). We also identified 3,161 lysine acetylation sites in 1,752 proteins and quantified 2,869 in 1,612 proteins. The acetylation levels at 468 sites were significantly altered across the three developmental stages during periodic albinism; the corresponding proteins were associated with a variety of biological processes. Interestingly, a large number of DAPs and acetylated proteins with increased/decreased acetylation were related to photosynthesis and secondary metabolite biosynthetic pathways, suggesting that the accumulation or acetylation level of these proteins regulates periodic albinism in ‘Anji Baicha.’ Additionally, overlap between succinylome and acetylome among three ‘Anji Baicha’ developmental stages were found. These data provide important insight into the mechanisms of leaf coloration in the tea plant. The mass spectrometry data have been deposited to Proteome X change via the PRIDE partner repository with the data set identifier PXD008134.

Genetic Dissection of Leaf Senescence in Rice.

Leaf senescence, the final stage of leaf development, is a complex and highly regulated process that involves a series of coordinated actions at the cellular, tissue, organ, and organism levels under the control of a highly regulated genetic program. In the last decade, the use of mutants with different levels of leaf senescence phenotypes has led to the cloning and functional characterizations of a few genes, which has greatly improved the understanding of genetic mechanisms underlying leaf senescence. In this review, we summarize the recent achievements in the genetic mechanisms in rice leaf senescence.

Temporal Response of Scattering From Crops for Transmitted Ellipticity Variation in Simulated Compact-Pol SAR Data

In this paper, the received compact polarimetry (CP) parameters are analyzed to infer ellipticity variations related to the transmission of a polarized electromagnetic wave. A generalized $2 \times 2$ CP covariance matrix is created as a function of the transmitting ellipticity and orientation angle. The Stokes parameters, backscattering coefficients, and the m-χ decomposition scattering powers are used to interpret the temporal behavior of crop growth stages with varying transmitted ellipticities. Time series RADARSAT-2 fully polarimetric synthetic aperture radar data acquired during the Soil Moisture Active Passive Validation Experiment 2012 campaign are used to simulate the CP data. The results clearly show that the transmitted ellipticity variation influences the interaction of the radar signal with agricultural targets. It is noted that there is negligible change in the dominant odd-bounce scattering power for corn during its leaf development stage with the transmitted ellipticity varying by $10^\circ $ . In the case of wheat during tillering and inflorescence, the volume scattering power decreases by ∼14% while the odd-bounce and even-bounce scattering powers increase by ∼6% and ∼8%, respectively, with the transmitted ellipticity varying by $10^\circ $ .

Maize Phyllosphere Microbial Community Niche Development Across Stages of Host Leaf Growth

Background: The phyllosphere hosts a variety of microorganisms, including bacteria, which can play a positive role in the success of the host plant. Bacterial communities in the phylloplane are influenced by both biotic and abiotic factors, including host plant surface topography and chemistry, which change in concert with microbial communities as the plant leaves develop and age. Methods: We examined how the Zea mays L. leaf microbial community structure changed with plant age. Ribosomal spacer length and scanning electron microscopic imaging strategies were used to assess microbial community composition across maize plant ages, using a novel staggered experimental design. Results: Significant changes in community composition were observed for both molecular and imaging analyses, and the two analysis methods provided complementary information about bacterial community structure within each leaf developmental stage. Conclusions: Both taxonomic and cell-size trait patterns provided evidence for niche-based contributions to microbial community development on leaves.

Genome-Wide Identification of Mitogen-activated Protein Kinase Cascade Genes and Transcriptional Profiling Analysis during Organ Development in Eucommia ulmoides

The mitogen-activated protein kinase (MAPK) cascades, which play crucial roles in plant development processes, are universal modules of signal transduction in eukaryotes and consist of a core module of three sequentially phosphorylated kinases: MAPK, MAPK kinase (MAPKK), and MAPKK kinase (MAPKKK). This is the first report on the identification and analysis of MAPK cascades in Eucommia ulmoides. We conducted a genome-wide screening and identified 13 EuMAPKs, five EuMAPKKs, and 57 EuMAPKKKs. The construction of phylogenetic trees revealed that EuMAPKs and EuMAPKKs were divided into four groups (A, B, C, and D), and EuMAPKKKs were divided into three subfamilies (MEKK, RAF, and ZIK). These subfamilies were further confirmed by conserved domain/motif analysis and gene structure analysis. Based on the expression profiles of all identified EuMAPK cascades in various organs at different developmental stages, three genes (EuRAF22-2, EuRAF34-1, and EuRAF33-2) with stable expression patterns at all stages of fruit or leaf development, three genes (EuRAF2-3, EuMPK11, and EuMEKK21) with differential expression patterns, and two highly expressed genes (EuZIK1 and EuMKK2) were screened and validated by qRT-PCR. Overall, our results could be used for further research on the precise role of MAPK cascades during organ development in E. ulmoides.

Volatile organic compounds and nitric oxide as responses of a Brazilian tropical species to ozone: the emission profile of young and mature leaves.

The emission profile of volatile organic compounds (VOCs) and nitric oxide (NO) in young and mature leaves of Croton floribundus was assessed in plants exposed to filtered air (FA) and ozone-enriched filtered air (FA+O3). After the period of exposure, leaves were enclosed in polyethylene terephthalate bags and VOCs were collected in young and mature leaves. Both young and mature leaves constitutively emitted the same VOC, but the concentrations were higher in young leaves. O3 exposure induced the emission of sesquiterpenes (mainly β-caryophyllene) known as antioxidant compounds that may scavenge O3. Young leaves were the highest emitters of sesquiterpenes. O3 induced a rapid accumulation of NO in different tissues and leaf developmental stages; this accumulation was marked in palisade and spongy parenchyma cells in young and mature leaves, respectively. O3 altered the levels of the signaling compound methyl salicylate (MeSA). Moreover, our data showed that NO together with VOC emissions, such as geranyl acetate, α-cadiene, trans-farnesol, cis-β-farnesene, and MeSA, participate of plant defense mechanisms against the oxidative damage caused by O3.

Modeling curve dynamics and spatial geometry characteristics of rice leaves

AbstractThe objective of this work was to develop a dynamic model for describing leaf curves and a detailed spatial geometry model of the rice leaf (including sub-models for unexpanded leaf blades, expanded leaf blades, and leaf sheaths), and to realize three-dimensional (3D) dynamic visualization of rice leaves by combining relevant models. Based on the experimental data of different cultivars and nitrogen (N) rates, the time-course spatial data of leaf curves on the main stem were collected during the rice development stage, then a dynamic model of the rice leaf curve was developed using quantitative modeling technology. Further, a detailed 3D geometric model of rice leaves was built based on the spatial geometry technique and the non-uniform rational B-spline (NURBS) method. Validating the rice leaf curve model with independent field experiment data showed that the average distances between observed and predicted curves were less than 0.89 and 1.20 cm at the tilling and jointing stages, respectively. The proposed leaf curve model and leaf spatial geometry model together with the relevant previous models were used to simulate the spatial morphology and the color dynamics of a single leaf and of leaves on the rice plant after different growing days by 3D visualization technology. The validation of the leaf curve model and the results of leaf 3D visualization indicated that our leaf curve model and leaf spatial geometry model could efficiently predict the dynamics of rice leaf spatial morphology during leaf development stages. These results provide a technical support for related research on virtual rice.