Mesophyll Cell Layers Research Articles

Structural changes of mesophyll cells in the rice leaf tissue in response to salinity stress based on the three-dimensional analysis.

Rice leaf blades have intricate-shaped mesophyll cells (MCs) with a large volume of chloroplasts enhancing gas exchange between stroma and intercellular airspace (IAS). Since the rice MCs do not form palisade or spongy tissue cells and are considered monotypic cells, the structural analysis of MCs in the middle part of the leaf tissue has been done, neglecting the various shapes of MCs can be observed on the cross-section of rice leaves. Moreover, the middle MC layer is sandwiched between the upper and lower layers and is more restricted in its demand for light and CO2 entering from the outside. Therefore, the different layers of MCs may differ in their sensitivity to salt stress that causes structural changes in cells. This study aims to elucidate the intra- and extra-cellular structures of MC in different layers of leaf tissue and determine how salinity affects the MC structure in each layer. The mesophyll tissue was divided into adaxial, middle and abaxial layers, and eight MCs and chloroplast regions were selected from each layer and reconstructed into three-dimensional (3D) representations. The whole leaf anatomical and physiological parameters were measured to find the effects of salinity stress on the MC structures. As a result,the 3D analysis of rice leaf tissue revealed the different structures of MCs with greater diversity in the adaxial and abaxial layers than in the middle layer. Salinity stress reduced the size and height of the MCs and coverage of the chloroplast on the cytoplasm periphery of the adaxial and abaxial layers, as well as the chloroplast size of adaxial MCs. Overall,these results reveal the variation of rice MC in leaf tissue and suggest the higher sensitivity to salt stress in the adaxial mesophyll among the layers, which may partly account for the decrease in photosynthetic capacity.

Anatomic-Morphological Structure Features of Leaf Organs of Some Species of the Astragalus L. Genus in Their Ontogenesis

Research relevance: anatomical structure study of Astragalus L. genus plants leaf organs in their ontogenesis is relevant for the reason that results obtained after study can be successfully used in solving systematic and evolutionary issues of higher plants taxonomic categories. Research objectives: to study quantitative indicator characteristics of anatomical structure of leaf organs ontogenesis in 5 species of the Astragalus L., genus belonging to different biomorphs: A. filicaulis Fisch. et C. A. Mey. ex Ledeb. (annual), A. campylorrhynchusFisch. et C. A. Mey. (annual), A. rhacodes, A. rhacodes Bunge (perennial), A. dendroides Kar. et Kir. (shrub) and A. fedtschenkoanus Lipsky (shrub) in order to establish their anatomical and morphological features, using generally accepted ontogenetic and statistical methods. Research materials and methods: Astragalus L. genus species belonging to different biomorphs planted in the soil without any pre-treatment. In plants growth care and development quantitative indicators of the morphological and anatomical structures of leaf organs and their statistical processing, generally accepted methods were used. Research results: species differ from each other in some quantitative indicators of the leaf organs structure, such as the epidermal cells size, the number of stomatal apparatus per unit area, the height of the upper and lower epidermal cells, the number of layers of mesophyll cells and the total thickness of the leaf blade. Conclusions: common feature to the studied species is that the leaf organs in ontogenesis have an amphistomatous structure.

Cellular insights of beech leaf disease reveal abnormal ectopic cell division of symptomatic interveinal leaf areas.

The beech leaf disease nematode, Litylenchus crenatae subsp. mccannii, is recognized as a newly emergent nematode species that causes beech leaf disease (BLD) in beech trees (Fagus spp.) in North America. Changes of leaf morphology before emergence from the bud induced by BLD can provoke dramatic effects on the leaf architecture and consequently to tree performance and development. The initial symptoms of BLD appear as dark green, interveinal banding patterns of the leaf. Despite the fast progression of this disease, the cellular mechanisms leading to the formation of such aberrant leaf phenotype remains totally unknown. To understand the cellular basis of BLD, we employed several types of microscopy to provide an exhaustive characterization of nematode-infected buds and leaves. Histological sections revealed a dramatic cell change composition of these nematode-infected tissues. Diseased bud scale cells were typically hypertrophied and showed a high variability of size. Moreover, while altered cell division had no influence on leaf organogenesis, induction of cell proliferation on young leaf primordia led to a dramatic change in cell layer architecture. Hyperplasia and hypertrophy of the different leaf cell layers, coupled with an abnormal proliferation of chloroplasts especially in the mesophyll cell layers, resulted in the typical interveinal leaf banding. These discrepancies in leaf cell structure were depicted by an abnormal rate of cellular division of the leaf interveinal areas infected by the nematode, promoting significant increase of cell size and leaf thickness. The formation of symptomatic BLD leaves is therefore orchestrated by distinct cellular processes, to enhance the value of these feeding sites and to improve their nutrition status for the nematode. Our findings thus uncover relevant cellular events and provide a structural framework to understand this important disease.

Regulators of early maize leaf development inferred from transcriptomes of laser capture microdissection (LCM)-isolated embryonic leaf cells

The superior photosynthetic efficiency of C4 leaves over C3 leaves is owing to their unique Kranz anatomy, in which the vein is surrounded by one layer of bundle sheath (BS) cells and one layer of mesophyll (M) cells. Kranz anatomy development starts from three contiguous ground meristem (GM) cells, but its regulators and underlying molecular mechanism are largely unknown. To identify the regulators, we obtained the transcriptomes of 11 maize embryonic leaf cell types from five stages of pre-Kranz cells starting from median GM cells and six stages of pre-M cells starting from undifferentiated cells. Principal component and clustering analyses of transcriptomic data revealed rapid pre-Kranz cell differentiation in the first two stages but slow differentiation in the last three stages, suggesting early Kranz cell fate determination. In contrast, pre-M cells exhibit a more prolonged transcriptional differentiation process. Differential gene expression and coexpression analyses identified gene coexpression modules, one of which included 3 auxin transporter and 18 transcription factor (TF) genes, including known regulators of Kranz anatomy and/or vascular development. In situ hybridization of 11 TF genes validated their expression in early Kranz development. We determined the binding motifs of 15 TFs, predicted TF target gene relationships among the 18 TF and 3 auxin transporter genes, and validated 67 predictions by electrophoresis mobility shift assay. From these data, we constructed a gene regulatory network for Kranz development. Our study sheds light on the regulation of early maize leaf development and provides candidate leaf development regulators for future study.

Single-cell transcriptomics sheds light on the identity and metabolism of developing leaf cells.

As the main photosynthetic instruments of vascular plants, leaves are crucial and complex plant organs. A strict organization of leaf mesophyll and epidermal cell layers orchestrates photosynthesis and gas exchange. In addition, water and nutrients for leaf growth are transported through the vascular tissue. To establish the single-cell transcriptomic landscape of these different leaf tissues, we performed high-throughput transcriptome sequencing of individual cells isolated from young leaves of Arabidopsis (Arabidopsis thaliana) seedlings grown in two different environmental conditions. The detection of approximately 19,000 different transcripts in over 1,800 high-quality leaf cells revealed 14 cell populations composing the young, differentiating leaf. Besides the cell populations comprising the core leaf tissues, we identified subpopulations with a distinct identity or metabolic activity. In addition, we proposed cell-type-specific markers for each of these populations. Finally, an intuitive web tool allows for browsing the presented dataset. Our data present insights on how the different cell populations constituting a developing leaf are connected via developmental, metabolic, or stress-related trajectories.

Plant resistance in different cell layers affects aphid probing and feeding behaviour during non-host and poor-host interactions.

Aphids are phloem-feeding insects that cause economic losses to crops globally. Whilst aphid interactions with susceptible plants and partially resistant genotypes have been well characterized, the interactions between aphids and non-host species are not well understood. Unravelling these non-host interactions can identify the mechanisms which contribute to plant resistance. Using contrasting aphid-host plant systems, including the broad host range pest Myzus persicae (host: Arabidopsis; poor-host: barley) and the cereal pest Rhopalosiphum padi (host: barley; non-host: Arabidopsis), we conducted a range of physiological experiments and compared aphid settling and probing behaviour on a host plant vs either a non-host or poor-host. In choice experiments, we observed that around 10% of aphids selected a non-host or poor-host plant species after 24 h. Using the Electrical Penetration Graph technique, we showed that feeding and probing behaviours differ during non-host and poor-host interactions when compared with a host interaction. In the Arabidopsis non-host interaction with the cereal pest R. padi aphids were unable to reach and feed on the phloem, with resistance likely residing in the mesophyll cell layer. In the barley poor-host interaction with M. persicae, resistance is likely phloem-based as phloem ingestion was reduced compared with the host interaction. Overall, our data suggest that plant resistance to aphids in non-host and poor-host interactions with these aphid species likely resides in different plant cell layers. Future work will take into account specific cell layers where resistances are based to dissect the underlying mechanisms and gain a better understanding of how we may improve crop resistance to aphids.

Citron C-05 inhibits both the penetration and colonization of Xanthomonas citri subsp. citri to achieve resistance to citrus canker disease

Citrus canker, caused by Xanthomonas citri subsp. citri (Xcc), is a serious bacterial disease that affects citrus production worldwide. Citron C-05 (Citrus medica) is the only germplasm in the Citrus genus that has been identified to exhibit strong resistance to Xcc. However, it has not been determined when, where, and how Xcc is restricted in the tissues of Citron C-05 during the infection process. In the present study, we investigated the spatiotemporal growth dynamics of an eGFP-labeled virulent Xcc (eGFP-Xcc) strain in Citron C-05 along with five susceptible biotypes (i.e., lemon, pummelo, sour orange, sweet orange, and ponkan mandarin) upon inoculation via the spraying or leaf infiltration of a bacterial suspension. The results from extensive confocal laser scanning microscopy analyses showed that while Xcc grew rapidly in plants of all five susceptible genotypes, Xcc was severely restricted in the epidermal and mesophyll cell layers of the leaves of Citron C-05 in the early stage of infection. Not surprisingly, resistance against Xcc in Citron C-05 was found to be associated with the production of reactive oxygen species and hypersensitive response-like cell death, as well as greater upregulation of several defense-related genes, including a pathogenesis-related gene (PR1) and a glutathione S-transferase gene (GST1), compared with sweet orange as a susceptible control. Taken together, our results not only provide further valuable details of the spatiotemporal dynamics of the host entry, propagation, and spread of Xcc in both resistant and susceptible citrus plants but also suggest that resistance to Xcc in Citron C-05 may be attributed to the activation of multiple defense mechanisms.

Nitrate Defines Shoot Size through Compensatory Roles for Endoreplication and Cell Division in Arabidopsis thaliana.

Precise coordination of cell expansion and cell proliferation underlies growth in multicellular organisms. In addition to endogenous developmental programs, external environmental signals are integrated to modulate organ growth in plants. Nitrate is a nitrogen nutrient that can act as a potent signal to modulate shoot growth, yet the molecular mechanisms involved are largely unexplored in Arabidopsis thaliana or other plant species. Herein, we show that nitrate regulates vegetative growth by modulating cell size and endoreplication. We identified the LGO gene, a CDK inhibitor, as a key cell cycle regulatory factor influencing ploidy and cell-size depending on external nitrate. Nitrate induces LGO gene expression as early as 3days after germination in epidermal and mesophyll cell layers, which undergo endoreplication to increment DNA content and cell size. Our results support a dual role for LGO on endoreplication and cell expansion. Surprisingly, although endoreplication and cell size are greatly reduced in lgo-2 mutant plants and increased in LGO-OX plants, cotyledon size remains unchanged relative to wild type and is set by the amount of nitrate. In lgo-2 mutant plants where cells are unable to endoreplicate fully, cotyledon organ size is achieved through cell division. We conclude nitrate generally controls cotyledon and leaf size by increasing ploidy levels and cell expansion but that cell division can substitute for endoreplication without affecting final organ size or growth in plants.

Fluorescent reporters for functional analysis in rice leaves.

Fluorescent reporters have facilitated non‐invasive imaging in multiple plant species and thus allowed the analysis of processes ranging from gene expression and protein localization to cellular patterning. However, in rice, a globally important crop and model species, there are relatively few reports of fluorescent proteins being used in leaves. Fluorescence imaging is particularly difficult in the rice leaf blade, likely due to a high degree of light scattering in this tissue. To address this, we investigated approaches to improve deep imaging in mature rice leaf blades. We found that ClearSee treatment, which has previously been used to visualize fluorescent reporters in whole tissues of plants, led to improved imaging in rice. Removing epidermal and subtending mesophyll cell layers was faster than ClearSee and also reduced light scattering such that imaging of fluorescent proteins in deeper leaf layers was possible. To expand the range of fluorescent proteins suitable for imaging in rice, we screened twelve whose spectral profiles spanned most of the visible spectrum. This identified five proteins (mTurquoise2, mNeonGreen, mClover3, mKOκ, and tdTomato) that are robustly expressed and detectable in mesophyll cells of stably transformed plants. Using microparticle bombardment, we show that mTurquoise2 and mNeonGreen can be used for simultaneous multicolor imaging of different subcellular compartments. Overall, we conclude that mTurquoise2, mNeonGreen, mClover3, mKOκ, and tdTomato are suitable for high‐resolution live imaging of rice leaves, both after transient and stable transformation. Along with the rapid microparticle bombardment method, which allows transient transformation of major cell types in the leaf blade, these fluorescent reporters should greatly facilitate the analysis of gene expression and cell biology in rice.

Сравнительное изучение анатомического строения листьев Phlox sibirica L. и Phlox sibirica var. borealis (Wherry) B. Boivin

Проведенное сравнительное изучение анатомии листьев Phlox sibirica и Phlox sibirica var. borealis позволило выявить, что морфометрические признаки строения листьев в 95 % случаев достоверно отличаются при уровне значимости P < 0,05. Статистически значимых отличий не было обнаружено только при определении устьичного индекса, значение которого также соответствует другим видам почвопокровных флоксов. Для изученных таксонов характерны закрытые коллатеральные пучки, аномоцитный тип устьичного аппарата и удлиненные, извилистые эпидермальные клетки. Phlox sibirica отличается большим развитием тяжей колленхимы, обеспечивающей жесткость листа даже при потере тургора, ксилемы, наиболее фотосинтетически активного слоя мезофилла (клеток верхнего слоя). Таким образом, в анатомическом строении листьев изученных флоксов выявлены признаки, свойственные для ксерофитно-гелиофитных видов, более выраженные у Phlox sibirica. Анатомия листьев изученных таксонов отражает их адаптацию к условиям с неблагоприятным водным режимом (обеспечивает поддержание нормального водного баланса) и избыточным освещением.

Redundant SCARECROW genes pattern distinct cell layers in roots and leaves of maize.

ABSTRACTThe highly efficient C4 photosynthetic pathway is facilitated by ‘Kranz’ leaf anatomy. In Kranz leaves, closely spaced veins are encircled by concentric layers of photosynthetic bundle sheath (inner) and mesophyll (outer) cells. Here, we demonstrate that, in the C4 monocot maize, Kranz patterning is regulated by redundant function of SCARECROW 1 (ZmSCR1) and a previously uncharacterized homeologue: ZmSCR1h. ZmSCR1 and ZmSCR1h transcripts accumulate in ground meristem cells of developing leaf primordia and in Zmscr1;Zmscr1h mutant leaves, most veins are separated by one rather than two mesophyll cells; many veins have sclerenchyma above and/or below instead of mesophyll cells; and supernumerary bundle sheath cells develop. The mutant defects are unified by compromised mesophyll cell development. In addition to Kranz defects, Zmscr1;Zmscr1h mutants fail to form an organized endodermal layer in the root. Collectively, these data indicate that ZmSCR1 and ZmSCR1h redundantly regulate cell-type patterning in both the leaves and roots of maize. Leaf and root pathways are distinguished, however, by the cell layer in which they operate – mesophyll at a two-cell distance from leaf veins versus endodermis immediately adjacent to root vasculature.

DLT/OsGRAS-32, regulating leaf width and thickness by controlling cell number in Oryza sativa

The improvement of rice leaf morphology is an important goal of rice plant breeding. Studying its molecular development mechanism will facilitate the breeding of a maximally efficient plant type. To further study the developmental mechanism of rice leaves, a dwarf broad-leaf mutant, g44, was obtained by ethyl methanesulfonate mutagenesis of the rice restorer line Jinhui10, and genetic analysis indicated that the trait was controlled by a pair of recessive nuclear gene. The locus was fine mapped on chromosome 6 with 16-kb physical distance. Sequencing revealed that an A-T base substitution occurred in the mutant, resulting in the early termination of LOC_Os06g03710/DLT translation in g44 and yielding only one residual peptide containing 558 amino acids. The phenotypic and sequencing results of the complementary transgenic plants and the allelic mutant g44-1 further confirmed this result. Mutant plants grown under field conditions showed dwarfing, a leaf colour of dark green, leaf widening, and grain enlargement. Paraffin section and cryosection analysis showed that the increase in the number of large vascular bundles and small vascular bundles and the increase in the spacing between adjacent small vascular bundles were the main reasons for the broadening of mutant leaves. In addition, the increase in thickness of the mesophyll cell layer may be the main reason for the increase in leaf colour darkness and net photosynthetic rate. The qPCR results preliminarily predicted that the increase in the number of mutant cells was caused by an enhanced cell division ability, and the DLT/G44 gene was proposed to participate in the regulation of cell division by suppressing the expression of cyclin-related genes.

Chilling-induced physiological, anatomical and biochemical responses in the leaves of Miscanthus × giganteus and maize (Zea mays L.)

Miscanthus × giganteus and Zea mays, closely-related C4 grasses, originated from warm climates react differently to low temperature. To investigate the response to cold (12–14 °C) in these species, the photosynthetic and anatomical parameters as well as biochemical properties of the cell wall were studied. The research was performed using M. giganteus (MG) and two Z. mays lines differentiated for chilling-sensitivity: chilling-tolerant (Zm-T) and chilling-sensitive (Zm-S). The chilled plants of Zm-S line demonstrated strong inhibition of net CO2 assimilation and a clear decrease in F’v/F’m, Fv/Fm and ɸPSII, while in MG and Zm-T plants these parameters were almost unchanged. The anatomical studies revealed that MG plants had thinner leaves, epidermis and mesophyll cell layer as well as thicker cell walls in the comparison to both maize lines. Cold led to an increase in leaf thickness and mesophyll cell layer thickness in the Zm-T maize line, while the opposite response was observed in Zm-S. In turn, in chilled plants of MG and Zm-T lines, some anatomical parameters associated with bundle sheath cells were higher. In addition, Zm-S line showed the strong increase in the cell wall thickness at cold for mesophyll and bundle sheath cells. Chilling-treatment induced the changes in the cell wall biochemistry of tested species, mainly in the content of glucuronoarabinoxylan, uronic acid, β-glucan and phenolic compounds. This work presents a new approach in searching of mechanism(s) of tolerance/sensitivity to low temperature in two thermophilic plants: Miscanthus and maize.

BIOFERTILIZER BASED ON SILICATE SOLUBILIZING BACTERIA IMPROVES PHOTOSYNTHETIC FUNCTION OF BRASSICA JUNCEA

Usage of biofertilizers is one of the important components of integrated nutrientmanagement, as they are renewable source of plant nutrients, ecologically safecompared to chemical fertilizers and cost effective. Silicate solubilizing bacteria(SSB) can play an efficient role not only in solubilizing insoluble forms of silicatesbut also potassium and phosphates, hence increasing soil fertility and therebyenhancing plant productivity. The aim of this study was to investigate the influenceof SSB-enriched biofertilizer on the structural and functional parameters ofphotosynthetic apparatus of Brassica juncea (L.) Czern. The pure culture of SSBwas isolated from the clay substrate, cultivated on Zak–Alexandrov medium andidentified as Bacillus sp. To obtain the biofertilizer, SSB culture (0.6*108 cfu mL-1)was mixed with steriled peat (1:1, v/w) and dried at 35–40°C. Plants were grownfrom seeds during two months in the pots with adding SSB-enriched biofertilizer tothe mixture of clay and soil (1:10, w/w). The clay substrate plus peat without SSBwas used as a control. It was found that addition of SSB-enriched biofertilizer toclay substrate significantly increased the content of total nitrogen, phosphorus andpotassium in the leaves of B. juncea. The thickness of mesophyllic layer and thenumber of mesophyll cells were increased on average by 24 %. It was correlatedwith a sharp increase of photosynthetic pigment content and CO2 uptake (1.5–2.0times). We can conclude that SSB-enriched biofertilizer improves thephotosynthetic function of B. juncea.

Anatomy and ultrastructure of embryonic leaves of the C4 species Setaria viridis.

Setaria viridis is being promoted as a model C4 photosynthetic plant because it has a small genome (~515 Mb), a short life cycle (~60 d) and it can be transformed. Unlike other C4 grasses such as maize, however, there is very little information about how C4 leaf anatomy (Kranz anatomy) develops in S. viridis. As a foundation for future developmental genetic studies, we provide an anatomical and ultrastructural framework of early shoot development in S. viridis, focusing on the initiation of Kranz anatomy in seed leaves. Setaria viridis seeds were germinated and divided into five stages covering development from the dry seed (stage S0) to 36 h after germination (stage S4). Material at each of these stages was examined using conventional light, scanning and transmission electron microscopy. Dry seeds contained three embryonic leaf primordia at different developmental stages (plastochron 1-3 primordia). The oldest (P3) leaf primordium possessed several procambial centres whereas P2 displayed only ground meristem. At the tip of P3 primordia at stage S4, C4 leaf anatomy typical of the malate dehydrogenase-dependent nicotinamide dinucleotide phosphate (NADP-ME) subtype was evident in that vascular bundles lacked a mestome layer and were surrounded by a single layer of bundle sheath cells that contained large, centrifugally located chloroplasts. Two to three mesophyll cells separated adjacent vascular bundles and one mesophyll cell layer on each of the abaxial and adaxial sides delimited vascular bundles from the epidermis. The morphological trajectory reported here provides a foundation for studies of gene regulation during early leaf development in S. viridis and a framework for comparative analyses with other C4 grasses.

Structure, distribution and taxonomic significance of leaf and petiole anatomical characters in five species of Terminalia (L.) (Combretaceae: Magnoliopsida)

This paper presents a synthesis of a comparative leaf anatomy (lamina and petiole) of five species of the genus Terminalia found in southwest Nigeria. Collections of plants were made from different locations in Southwest Nigeria as the geographic locations of the sites of collection were also geo-referenced with a GPS device. The samples were identified at the Herbarium of Botany Department, Obafemi Awolowo University (Ife), Nigeria, and were subjected to anatomical examinations. Quantitative data were subjected to statistical analysis and the characters vary significantly (P = 0.05). Anatomical characters which separate the taxa include petiole outline, epidermal features, vascular pattern, occurence of cortical and pericyclic fibres, presence/absence of, and types of trichomes etc, all found to be useful in identification of different species. The variations in the anatomical traits could be effectively used in taxonomic delimitation of the species and are helpful characters in determining the complexes in the genus such as adaptation of the species to xeric environments. The presence of 2-3 layers of palisade mesophyll cells in Terminalia mantaly, which is an adaptation of the species to drought, is diagnostic for the species. It is suggested that a comprehensive consideration of leaf lamina and petiole anatomy should be used as basis of taxonomy.

The anatomical and compositional basis of leaf mass per area.

Leaf dry mass per unit leaf area (LMA) is a central trait in ecology, but its anatomical and compositional basis has been unclear. An explicit mathematical and physical framework for quantifying the cell and tissue determinants of LMA will enable tests of their influence on species, communities and ecosystems. We present an approach to explaining LMA from the numbers, dimensions and mass densities of leaf cells and tissues, which provided unprecedented explanatory power for 11 broadleaved woody angiosperm species diverse in LMA (33-262g m-2 ; R2 =0.94; P<0.001). Across these diverse species, and in a larger comparison of evergreen vs. deciduous angiosperms, high LMA resulted principally from larger cell sizes, greater major vein allocation, greater numbers of mesophyll cell layers and higher cell mass densities. This explicit approach enables relating leaf anatomy and composition to a wide range of processes in physiological, evolutionary, community and macroecology.

Arundina graminifolia var. revoluta (Arethuseae, Orchidaceae) has fern-type rheophyte characteristics in the leaves.

Morphological and molecular variation between Arundina graminifolia var. graminifolia and the dwarf variety, A. graminifolia var. revoluta, was examined to assess the validity of their taxonomic characteristics and genetic background for identification. Morphological analysis in combination with field observations indicated that A. graminifolia var. revoluta is a rheophyte form of A. graminifolia characterized by narrow leaves, whereas the other morphological characteristics described for A. graminifolia var. revoluta, such as smaller flowers and short stems, were not always accompanied by the narrower leaf phenotype. Molecular analysis based on matK sequences indicated that only partial differentiation has occurred between A. graminifolia var. graminifolia and A. graminifolia var. revoluta. Therefore, we should consider the rheophyte form an ecotype rather than a variety. Anatomical observations of the leaves revealed that the rheophyte form of A. graminifolia possessed characteristics of the rheophytes of both ferns and angiosperms, such as narrower palisade tissue cells and thinner spongy tissue cells, as well as fewer cells in the leaf-width direction and fewer mesophyll cell layers.

Anatomical structure of leaf sectors with different resistance to powdery mildew (Erisiphe cruciferarum Opiz ex. L. Junell) in winter rapeseed chimera

The subject of the study was a sectorial chimera of dihaploid winter rapeseed, obtained with the help of gamma ray treatment (30 Gy) during shoot cloning in vitro. One sector of the plant was infected by &lt;i&gt;Erisiphe cruciferarum&lt;/i&gt; Opiz ex. L. Junell and the other one was resistant. The anatomical structure of a leaf, divided into the two sectors along the midrib, was studied. The infected part of the leaf blade was thinner and built of a smaller number of palisade and spongy mesophyll cell layers. The size of cells in this sector, both in the epidermis and in the mesophyll, as well as the size of nuclei, chloroplasts and intercellular spaces were bigger than those in the resistant portion. On the other hand, the stomata in the infected segment were smaller but their number was higher than that in the healthy part. The study made it possible to analyse the relation between the anatomical structure of the host plant and the pathogen.

Structural and physiological analyses in Salsoleae (Chenopodiaceae) indicate multiple transitions among C3, intermediate, and C4 photosynthesis.

In subfamily Salsoloideae (family Chenopodiaceae) most species are C4 plants having terete leaves with Salsoloid Kranz anatomy characterized by a continuous dual chlorenchyma layer of Kranz cells (KCs) and mesophyll (M) cells, surrounding water storage and vascular tissue. From section Coccosalsola sensu Botschantzev, leaf structural and photosynthetic features were analysed on selected species of Salsola which are not performing C4 based on leaf carbon isotope composition. The results infer the following progression in distinct functional and structural forms from C3 to intermediate to C4 photosynthesis with increased leaf succulence without changes in vein density: From species performing C3 photosynthesis with Sympegmoid anatomy with two equivalent layers of elongated M cells, with few organelles in a discontinuous layer of bundle sheath (BS) cells (S. genistoides, S. masenderanica, S. webbii) > development of proto-Kranz BS cells having mitochondria in a centripetal position and increased chloroplast number (S. montana) > functional C3–C4 intermediates having intermediate CO2 compensation points with refixation of photorespired CO2, development of Kranz-like anatomy with reduction in the outer M cell layer to hypodermal-like cells, and increased specialization (but not size) of a Kranz-like inner layer of cells with increased cell wall thickness, organelle number, and selective expression of mitochondrial glycine decarboxylase (Kranz-like Sympegmoid, S. arbusculiformis; and Kranz-like Salsoloid, S. divaricata) > selective expression of enzymes between the two cell types for performing C4 with Salsoloid-type anatomy. Phylogenetic analysis of tribe Salsoleae shows the occurrence of C3 and intermediates in several clades, and lineages of interest for studying different forms of anatomy.