Epidermal Cell Area Research Articles

Response and disease resistance evaluation of sorghum seedlings under anthracnose stress

Sorghum is the world’s fifth-largest cereal crop, and anthracnose (Colletotrichum sublineola) is the main disease affecting sorghum. However, systematic research on the cellular structure, physiological and biochemical, and genes related to anthracnose resistance and disease resistance evaluation in sorghum is lacking in the field. Upon inoculation with anthracnose (C. sublineola) spores, disease-resistant sorghum (gz93) developed a relative lesion area (RLA) that was significantly smaller than that of the disease-susceptible sorghum (gz234). The leaf thickness, length and profile area of leaf mesophyll cells, upper and lower epidermal cells decreased in the lesion area, with a greater reduction observed in gz234 than in gz93. The damage caused by C. sublineola resulted in a greater decrease in the net photosynthetic rate (Pn) in gz234 than in gz93, with early-stage reduction due to stomatal limitation and late-stage reduction caused by lesions. Overall, the activities of superoxide dismutase (SOD) and catalase (CAT), the content of proline (Pro), abscisic acid (ABA), jasmonic acid (JA), salicylic acid (SA), and gibberellic acid (GA3), are higher in gz93 than in gz234 and may be positively correlated with disease resistance. While malondialdehyde (MDA) may be negatively correlated with disease resistance. Disease-resistant genes are significantly overexpressed in gz93, with significant expression changes in gz234, which is related to disease resistance in sorghum. Correlation analysis indicates that GA3, MDA, peroxidase (POD), and disease-resistance genes can serve as reference indicators for disease severity. The regression equation RLA = 0.029 + 8.02 × 10−6 JA–0.016 GA3 can predict and explain RLA. Principal component analysis (PCA), with the top 5 principal components for physiological and biochemical indicators and the top 2 principal components for disease-resistant genes, can explain 82.37% and 89.11% of their total variance, reducing the number of evaluation indicators. This study provides a basis for research on the mechanisms and breeding of sorghum with resistance to anthracnose.

The association analysis of DNA methylation and transcriptomics identified BpCYCD3;2 as a participant in influencing cell division in autotetraploid birch (Betula pendula) leaves

Polyploidization plays a crucial role in plant breeding and genetic improvement. Although the phenomenon of polyploidization affecting the area and number of plant epidermal pavement cells is well described, the underlying mechanism behind this phenomenon is still largely unknown. In this study, we found that the leaves of autotetraploid birch (Betula pendula) stopped cell division earlier and had a larger cell area. In addition, compared to diploids, tetraploids have a smaller stomatal density and fewer stomatal numbers. Genome-wide DNA methylation analysis revealed no significant difference in global DNA methylation levels between diploids and tetraploids. A total of 9154 differential methylation regions (DMRs) were identified between diploids and tetraploids, with CHH-type DMRs accounting for 91.73% of all types of DMRs. Further research has found that there are a total of 2105 differentially methylated genes (DMEGs) with CHH-type DMRs in birch. The GO functional enrichment results of DMEGs showed that differentially methylated genes were mainly involved in terms such as cellular process and metabolic process. The analysis of differentially methylated genes and differentially expressed genes suggests that hyper-methylation in the promoter region may inhibit the gene expression level of BpCYCD3;2 in tetraploids. To investigate the function of BpCYCD3;2 in birch, we obtained overexpression and repressed expression lines of BpCYCD3;2 through genetic transformation. The morphogenesis of both BpCYCD3;2-OE and BpCYCD3;2-RE lines was not affected. However, low expression of BpCYCD3;2 can lead to inhibition of cell division in leaves, and this inhibition of cell proliferation can be compensated for by an increase in cell size. Additionally, we found that the number and density of stomata in the BpCYCD3;2-RE lines were significantly reduced, consistent with the tetraploid. These data indicate that changes in cell division ability and stomatal changes in tetraploid birch can be partially attributed to low expression of the BpCYCD3;2 gene, which may be related to hyper-methylation in its promoter region. These results will provide new insights into the mechanism by which polyploidization affects plant development.

Structural and functional traits underlying the capacity of Calotropis procera to face different stress conditions

Calotropis procera (Aiton) W. T. Aiton, originally native to tropical and sub-tropical regions of northwestern Africa to southwest Asia through the Arabian Peninsula. The present study was engaged to uncover the underlying mechanism (structural and functional) of C. procera sampled from six different ecological regions. The population of normal irrigated agriculture field (IAF) had better growth, high K+ ion content, photosynthetic pigments (chl a chl b, Tchl and caro) and stomatal density. The population of dust and pollution stressed habitat (IWD) exhibited enlarged epidermal cells in stem and leaf, enhanced cortical proportion with largest cells in stem and phloem area in leaf. The population of drought and aridity stressed habitat (ARS) showed increased root cellular area, cortical region thickness and its cell area, and phloem region. The population from salt-affected habitat (SLF) possessed high root and shoot ionic contents (Na+ and Ca2+), total soluble sugars, total antioxidant activity, chlorophyll a/b, widened metaxylem vessels and phloem area in the stem, while intensive sclerification observed in both stem and leaf. The population native to waterlogged and salinity stressed habitat (APC) represented vigorous root growth, total free amino acids, well-developed metaxylem vessels and stomatal area in leaf. The population from drought and salinity-prone habitat (UBL) indicate increased storage of parenchymatous tissue (pith region and its cells area) and epidermal cell area in leaf. It is concluded that C. procera showed much outmost behavior in view of growth, structural and functional attributes in response to prevailing environmental condition.

Morphological and Structural Responses of Albizia lebbeck to Different Lead and Nickel Stress Levels

Lead (Pb) and nickel (Ni) are serious soil pollutants that adversely affect plant growth and development and need to be removed through phytoremediation. The present study aimed to assess the morphological indices of Albizia lebbeck (L.) (Benth.) in relation to anatomical modifications for survival under both Pb and Ni stress. The seedlings of A. lebbeck were established and then subjected to four different concentrations, viz. 0 mM, 25 mM, 50 mM and 75 mM, of Pb and Ni for 14 days in two phases. Morphological traits such as shoot length (70.93%), fresh weight (79.27%), dry weight (83.9%), number of root hairs (65.7%), number of leaves per plant (67.4%) and number of leaflets per plant greatly reduced under Pb or Ni stress. Surprisingly, root length increased rather than decreased with the increase in Pb or Ni concentrations, along with an increase in leaflet width, leaflet length and leaflet area. Moreover, root cortical cell area, metaxylem area and phloem area decreased at 75 mM of Pb and Ni while epidermal thickness and cell area increased. Stem epidermal thickness, cell area and phloem area significantly decreased with the consistent increase in metaxylem area and cortical region thickness under both Pb and Ni stress. Leaf anatomical traits such as midrib thickness, abaxial epidermal thickness and stomatal density and adaxial epidermal thickness and stomatal area significantly increased with increasing Pb or Ni stress. Correlation analysis revealed close relations among morphological and anatomical traits (such as root length with cortical region thickness) for better plant survival under Pb or Ni stress, and a PCA-biplot further verified these correlation analyses. Cluster analyses demonstrated the associations among the morphological and anatomical traits based on different stress levels. Furthermore, we found that the longer exposure (from phase 1 to phase 2) of heavy metals stress is more dangerous for plant survival and can ultimately lead to plant death. Moreover, our results also confirmed that Ni is more harmful or dangerous to plants than Pb at high and moderate concentrations. The anatomical modifications ensured the survival of A. lebbeck in extreme heavy metals stress and therefore unlocked its potential to be used as a natural source of phytoremediation. We also recommend that the genetic potential of A. lebbeck associated with its survival under heavy metal stress be investigated.

Phytoremediation potential modulated by structural and functional traits in a saline desert halophyte Fagonia indica Burm. f.

Using halophytes for phytoremediation is an environmentally friendly technique, now gaining importance all over the world. Fagonia indica Burm. f. (Indian Fagonia) is primarily distributed in salt-affected lands of the Cholistan Desert and surrounding habitats. Four populations with three replications from salt-affected habitats were collected from natural habitats to evaluate structural and functional adaptation for salinity tolerance and phytoremediation of hypersaline habitats. The populations collected from the highest saline sites Pati Sir (PS) and Ladam Sir (LS) had restricted growth habit, increased accumulation of K+ and Ca2+ along Na+ and Cl-, more excretion of Na+ and Cl-, increased cross-sectional area of root and stem, larger exodermal and endodermal cells in roots, and broad metaxylem area. Sclerification in stem was high in population. Specific modifications in leaves were reduced stomatal area and increased adaxial epidermal cell area. Important traits associated with phytoremediation potential of F. indica populations (Pati Sir and Ladam Sir) were deeper roots and taller plants, increased density of salt glands on leaf surface, and high excretion of Na+. Additionally, higher bio-concentration factor, translocation factor, and dilution factor for Na and Cl- in same Ladam Sir and Pati Sir population were identified as key phytoremediation attributes. The plants of F. indica colonizing high salinities (Pati Sir and Ladam Sir) were, therefore, more efficient in phytoremediation of saline soils as these populations accumulated and/or excrete toxic salts. Density of salt glands remarkably increased in the Pati Sir population collected from the highest salinity. This population accumulated and excreted the highest amount of Na+ and Cl-. The dilution factor of Na+ and Cl- ions was also the highest in this population. Anatomical modifications such as root and stem cross-sectional areas, proportion of storage parenchyma, and broad metaxylem vessels were the maximum in Pati Sir population. These modifications indicate not only better salt tolerance of the Pati Sir population but also better in accumulation and excretion of toxic salts. This population can potentially rehabilitate hypersaline uncultivated lands through green reclamation.

Enlarged rete pegs with excessive accumulation of melanosomes leading to darker aging spots revealed by histomorphological measurements of internal structures of the epidermis.

Various histological studies of facial pigmented spot sites such as solar lentigo have been reported, but few studies have used quantitative indices by histomorphometric analysis of the internal structure of pigmented spot sites using non-invasive methods. In the present study, to quantitatively elucidate morphological changes in the epidermis in male, darker-pigmented spots and female, light-pigmented spots, indices that characterize the internal structure of the epidermis in pigmented spot sites were measured using in vivo confocal laser scanning microscopy (CLSM). The darkness of pigmented spots on the cheeks of 69 women and 43 men was analysed using image analysis software. The L* value was calculated from RGB values obtained from facial images. The internal structures of pigmented spots on the cheeks of 13 subjects were observed by CLSM. Various parameters were measured using CLSM images from the surface of the stratum corneum to the bottom of the dermal papillae, including the thickness of the epidermis, melanosome content, and shape of the dermal papillae. Mean ΔL* values between pigmented spots and non-pigmented areas of male subjects were significantly increased in the 40s and 50s compared with those of female subjects. Conspicuous pigmented spots increased in the 40s in male subjects and the 50s in female subjects. In CLSM observations, significant increases in the thickness of the epidermis and melanosome content were confirmed in pigmented spots compared with surrounding non-pigmented areas. In particular, melanosome content in the male subject group with dark-coloured pigmented spots increased significantly to about eight times that of non-pigmented areas, and more than double that of the male subject group with light-coloured pigmented spots. From the measurements of quantitative parameters, morphological changes in the epidermis were clearly related to the surface colour tone of pigmented spots. Darker pigmented spot sites tended to show longer rete pegs in the epidermis. Accumulation of melanosomes in epidermal basal cells could be considered to increase with the degree of elongation of rete pegs at pigmented spot sites and, thus, induce darker pigmented spots.

Plasticity in anatomical traits of Cyperus niveus Retz. along elevational gradient of dry sub-Himalayan mountains

Cyperus niveus Retz., also known as snow white sedge grows in dry mountainous regions of Himalayas. Eight populations of C. niveus were collected from different locations in the Salt Range (Punjab) and Kaghan Valley (Khyber Pakhtoonkhwa) to evaluate role of plasticity in adaptability potential through modification in anatomical traits. This species developed xeric anatomical modifications in roots at higher elevations. These were thick endodermis, formation of sclerenchymatous cells outside endodermis, numerous metaxylem vessels, and increased area of central vessel in roots. Roots were more developed in the Kaghan (K) population, showing the largest root radius (774.7 µm), sclerenchymatous cell area (1429.1 µm2), cortical thickness (147.1 µm), and endodermal cell area (7701.4 µm). Stomatal density (21.7 per mm2) was also the highest in the K population. Formation of aerenchymatous cavities, numerous large vascular bundles with wide metaxylem vessels, and large phloem tissue in stems were the prominent features in the K population at the highest elevation (2078 m a.s.l.). All C. niveus populations showed sclerification around and outside of the vascular bundles, larger adaxial epidermal cell area as compared to abaxial epidermal cells, hypostomatal leaves, and increased storage parenchyma in leaves.

Overexpression of AmCBF1 enhances drought and cold stress tolerance, and improves photosynthesis in transgenic cotton.

China’s main cotton production area is located in the northwest where abiotic stresses, particularly cold and drought, have serious effects on cotton production. In this study, Ammopiptanthus mongolicus C-repeat-binding factor (AmCBF1) isolated from the shrub Ammopiptanthus mongolicus was inserted into upland cotton (Gossypium hirsutum L.) cultivar R15 to evaluate the potential benefits of this gene. Two transgenic lines were selected, and the transgene insertion site was identified using whole-genome sequencing. The results showed that AmCBF1 was incorporated into the cotton genome as a single copy. Transgenic plants had distinctly higher relative water content (RWC), chlorophyll content, soluble sugar content, and lower ion leakage than R15 after drought and cold stress. Some characteristics, such as the area of lower epidermal cells, stomatal density, and root to shoot ratio, varied significantly between transgenic cotton lines and R15. Although the photosynthetic ability of transgenic plants was inhibited after stress, the net photosynthetic rate, stomatal conductance, and transpiration rate in transgenic plants were significantly higher than in R15. This suggested that an enhanced stress tolerance and photosynthesis of transgenic cotton was achieved by overexpressing AmCBF1. All together, our results demonstrate that the new transgenic cotton germplasm has great application value against abiotic stresses, especially in the northwest inland area of China.

Structural responses of differentially adapted Cenchrus setigerus Vahl ecotypes to water deficit

Two ecotypes of Cenchrus setigerus Vahl (birdwood grass) were collected from dry mountains surrounding hyper-saline Kalar Kahar Lake and Gatwala artificial forest plantation. The ramets of the two ecotypes were established in pots for 15 days and then subjected to 100% FC (control) or 75% and 50% FC (field capacity) levels. Growth attributes such as plant height, tillers per plant, leaves per plant, shoot fresh and dry weights were severely affected while root length was the only attribute that increased in both ecotypes under moisture stress. Root anatomical attributes like cortical and pith parenchyma, and vascular region thickness increased in both ecotypes under water stress. Root radius increased in the Faisalabad ecotype at 75% FC, while increased in Salt Range ecotype only at 50% FC. Stem cellular region, sclerenchymatous cell area, vascular bundle area and metaxylem area increased significantly under moderate and severe water deficit only in the Faisalabad ecotype. The Salt Range ecotype exhibited intensive sclerification and large vascular tissue at 50% FC. Leaf anatomical attributes like epidermal cell area, bundle sheath thickness, sclerenchyma thickness and its cell area, and, vascular bundles area significantly increased in the Salt Range ecotype with increasing water deficit. The Faisalabad ecotype showed significant increase in vascular bundle area, metaxylem area and adaxial stomatal area. These findings indicated that both C. setigerus ecotypes mainly relied on water conservation and survival rather than maintaining growth and biomass production. The anatomical modifications at root, stem and leaf levels ensured survival of C. setigerus ecotypes in extreme arid conditions. • Growth attributes were severely affected while root length increased under stress • Root radius increased in the Faisalabad ecotype at 75% FC, while at 50% FC in Salt Range ecotype • Stem area, sclerification and vascular bundle area increased only in Faisalabad ecotype • The Salt Range ecotype exhibited intensive sclerification in leaves and large vascular tissue at 50% FC • The Faisalabad ecotype showed an increase in vascular bundle area, metaxylem area and adaxial stomatal area

Dwarfing and the Underlying Morphological Changes of Poa alpigena Plants in Response to Overgrazing Conditions.

Poa alpigena is a dominant grass species in alpine meadows, which is sensitive to environmental conditions. In this study, we analyzed the characteristics of the anatomical structure of the stems and leaves of Poa alpigena in overgrazed and enclosed conditions in order to determine the dwarfing morphological mechanism associated with overgrazing. The results show that leaf thickness, leaf epidermal thickness, epidermal cell area, and phloem thickness increased with increased grazing intensity (p < 0.05). In contrast, xylem thickness, mesophyll cell area, and guide wall thickness decreased with an increase in grazing intensity (p < 0.05). Mesophyll cell density was relatively unaffected by grazing intensity. Additionally, the plasticity indices of leaf area, upper epidermal cutin layer thickness, and leaf xylem thickness were higher than 0.5. The plasticity indices of stem tube diameter, epidermal cell size, and epidermal cuticle thickness were greater than 0.4. The results of our study indicate that the structural stem and leaf changes in Poa alpigena are induced by the water and mechanical stresses that occur under grazing conditions. Thus, plateau plants adapt to grazing stress by increasing the thickness of their leaves, cuticles, and phloem. The mesophyll cell area, as well as the stem epidermal cell area of Poa alpigena decreased in response to minor variations in grazing intensity, yet overgrazing did not change its density. However, overgrazing induced a shortening of the leaves and stems, indicating that overgrazing has a dwarfing effect on Poa alpigena.

Responses of leaf hydraulic traits of Schoenoplectus tabernaemontani to increasing temperature and CO2 concentrations

BackgroundAgainst the background of a changing climate, the responses of functional traits of plateau wetland plants to increasing temperatures and CO2 concentrations need to be understood. Hydraulic traits are the key for plants to maintain their ecological functions and affect their growth and survival. However, few studies have comprehensively considered the response strategies of wetland plants' hydraulic traits to environmental changes in the context of water and matter transport, loss, and retention. According to the latest IPCC prediction results, we performed experiments under increased temperature (2 °C) and CO2 levels (850 μmol/mol) in an artificial Sealed-top Chamber (STC) to investigate the responses of the hydraulic characteristics of Schoenoplectus tabernaemontani, the dominant species in plateau wetlands in China.ResultsCompared with the CK group, net photosynthetic rate, transpiration rate, stomatal length, cuticle thickness, vascular bundle length, vascular bundle width, and vascular bundle area of S. tabernaemontani in the ET group were significantly reduced, whereas stomatal density and vein density increased significantly. Compared with the CK group, the hydraulic traits of S. tabernaemontani in the EC group were reduced considerably in stomatal length and cuticle thickness but increased dramatically in stomatal density, and there were no significant differences between other parameter values and the control group. Net photosynthetic rate was significantly positively correlated with stomatal length, cuticle thickness, and vascular bundle length, and stomatal conductance was significantly positively correlated with cuticle thickness. The transpiration rate was significantly positively correlated with cuticle thickness, epidermal cell area, vascular bundle length, vascular bundle width, and vascular bundle area. Regarding the hydraulic traits, there was a significant negative correlation between stomatal density and stomatal length, or cuticle thickness, and a significant positive correlation between the latter two. The epidermal cell area was significantly positively correlated with epidermal thickness, vascular bundle length, vascular bundle width, and vascular bundle area.ConclusionsIncreased temperature and CO2 levels are not conducive to the photosynthetic activity of S. tabernaemontani. Photosynthetic rate, stomatal density and size, vein density, epidermal structure size, and vascular bundle size play an essential role in the adaptation of this species to changes in temperature and CO2 concentration. In the process of adaptation, hydraulic traits are not isolated from each other, and there is a functional association among traits. This study provide a scientific basis for the management and protection of plateau wetlands.

A Simple and Effective Bioassay Method Suitable to Comparative In Vitro Study of Tomato Salt Tolerance at Early Development Stages.

In vitro evaluation of tomato seeds and seedlings for salt tolerance has undoubted advantages (high productivity, as well as stability and reproducibility of the obtained experimental data due to the maintenance of constant controlled conditions) in comparison with open-field system and pot experiments. However, even high-quality seeds greatly differ in the uniformity of germination capacity and germination energy. Heterogeneous germination in the habit and developmental stage of plant material significantly distorts the obtaining of relevant experimental data suitable for correct interpretation. In our study, we propose a simple and effective bioassay method suitable to comparative in vitro study of tomato salt tolerance using shoot apex of seedlings at the early first-true-leaf stage. Shoot apexes cultured the on the root induction medium (RIM) supplemented with 0.2 mg/L indole-3-butyric acid (IBA) and NaCl at different concentrations (0–250 mM NaCl) revealed significant differences between two tomato genotypes (line YaLF and cv. Rekordsmen) at the organismal (measurements of CO2 gas exchange), organ (rhizogenesis frequency; number and length of de novo regenerated roots; root fresh (RFW) and dry (RDW) weights; shoot fresh (SFW) and dry (SDW) weights), tissue (the average cross-sectional area of epidermal and mesophylls cotyledonary cells) and cellular (ultrastructure of chloroplast and nuclear compartments) development levels. In addition, a quantitative comparison of proline and photosynthetic pigments contents under 75 and 150 mm NaCl treatments showed a different response between two tomato genotypes. The proposed methodological approach can be used for other plants with a high response to auxin-induced rhizogenesis in vitro, as well as for the comparative in vitro assessment of other abiotic stresses.

Anatomical and Biochemical Traits Associated with Field Resistance of Onion Cultivars to Onion Thrips and the Effect of Mechanical Injury on the Level of Biochemical Compounds in Onion Leaves

Thrips tabaci Lind. is a global pest and also represents a serious threat to onion production in Poland. In 2 years (2015–2016) of field studies, 8 onion cultivars were evaluated to characterize the resistance to onion thrips and to determine if any biochemical and anatomical features of onion plants are associated with antixenotic and/or antibiotic mechanisms of resistance. Additionally, the influence of mechanical injury on the content of several biochemical compounds in onion leaves was made. The resistance to thrips colonization during the migration period, abundance, and thrips damage throughout the whole vegetation season was determined. We identified two cultivars, Tęcza and Wenta, resistant to thrips colonization and abundance, and one cultivar Wenta resistant to thrips damage. A positive correlation between concentrations of the reducing sugars and thrips abundance and conversely negative relationships between the total phenolic content and thrips damage was confirmed in both years. We suspect that a thinner epidermal layer, a smaller area of epidermal and mesophilic cells, and a lower diameter of vascular bundles may favor the resistance of onion cultivars to thrips. Thrips foraging resulted in a decrease in the content of soluble sugars, sucrose, and plant pigments in the leaves of all onion varieties.

Modulation of physiological plasticity through structural and functional modifications in Stipagrostis plumosa L. for adaptability to hyper-arid environments

The role of morpho-physiological attributes along with the antioxidant potential of Stipagrostis plumosa L. populations collected from arid regions in adaptability to aridity was evaluated. Root to shoot length, chlorophyll, carotenoids, and organic osmolytes (total free amino acids, total soluble proteins, glycinebetaine, and proline) increased with more activities of antioxidant enzymes (APX, CAT, POD, and SOD). Root and shoot fresh:dry weight ratio and leaf area decreased with increasing dryness ratio (D: 8.40?30.49) and decreasing precipitation (519 mm to 143 mm). Hyperarid populations [Noorpur Thal - NpT (D: 10.90; P: 400 mm) and Cholistan - Cho (D:30.49; P: 143 mm)] relied on reduced leaf area and plant biomass, longer roots, more activities of antioxidant enzymes with higher accumulation of organic osmolytes, and better compartmentation of ions in root and shoot. Root and leaf epidermal thicknesses, epidermal cell area, the proportion of cortical parenchyma, metaxylem cell area, abaxial stomatal density and area reduced significantly while stem epidermis thickness, cortical cell area, and metaxylem cell area increased in relatively less arid populations [Neela WahnNeW (D: 8.40; P: 519 mm) and Kallar Kahar-KKr (D: 8.99; P: 485 mm)]. In conclusion, survival of S. plumosa under water deficit was directly linked to the plasticity in morpho-physiological and anatomical traits such as epidermal hairs, thick leaves, intense sclerification in roots epidermis, cortex and endodermis, and vascular bundle. These traits not only accounted for the movement of water and solutes but also help conserve water and provided mechanical strength for survival in hyperarid environments.

Insight Into the Multiple Branches Traits of a Mutant in Larix olgensis by Morphological, Cytological, and Transcriptional Analyses.

Larix olgensis is a tall deciduous tree species that has many applications in the wood fiber industry. Bud mutations are somatic mutations in plants and are considered an ideal material to identify and describe the molecular mechanism of plant mutation. However, the molecular regulatory mechanisms of bud mutations in L. olgensis remain unknown. In this study, dwarfed (or stunted), short-leaved, and multi-branched mutants of L. olgensis were found and utilized to identify crucial genes and regulatory networks controlling the multiple branch structure of L. olgensis. The physiological data showed that the branch number, bud number, fresh and dry weight, tracheid length, tracheid length-width ratio, inner tracheid diameter, and epidermal cell area of mutant plants were higher than that of wild-type plants. Hormone concentration measurements found that auxin, gibberellin, and abscisic acid in the mutant leaves were higher than that in wild-type plants. Moreover, the transcriptome sequencing of all samples using the Illumina Hiseq sequencing platform. Transcriptome analysis identified, respectively, 632, 157, and 199 differentially expressed genes (DEGs) in buds, leaves, and stems between mutant plants and wild type. DEGs were found to be involved in cell division and differentiation, shoot apical meristem activity, plant hormone biosynthesis, and sugar metabolism. Furthermore, bZIP, WRKY, and AP2/ERF family transcription factors play a role in bud formation. This study provides new insights into the molecular mechanisms of L. olgensis bud and branch formation and establishes a fundamental understanding of the breeding of new varieties in L. olgensis.

Leaf Size Development Differences and Comparative Transcriptome Analyses of Two Poplar Genotypes

The plant leaf, the main organ of photosynthesis, is an important regulator of growth. To explore the difference between leaf size of Populus deltoides ‘Danhong’ (Pd) and Populus simonii ‘Tongliao1’ (Ps), we investigated the leaf length, leaf width, leaf thickness, leaf area, leaf mass per area (LMA), and cell size of leaves from two genotypes and profiled the transcriptome-wide gene expression patterns through RNA sequencing. Our results show that the leaf area of Pd was significantly larger than that of Ps, but the epidermal cell area was significantly smaller than that of Ps. The difference of leaf size was caused by cell numbers. Transcriptome analysis also revealed that genes related to chromosome replication and DNA repair were highly expressed in Pd, while genes such as the EXPANSIN (EXPA) family which promoted cell expansion were highly expressed in Ps. Further, we revealed that the growth-regulating factors (GRFs) played a key role in the difference of leaf size between two genotypes through regulation of cell proliferation. These data provide a valuable resource for understanding the leaf development of the Populus genus.

Adaptive strategies for ecological fitness in Calotropis procera (Aiton) W. T. Aiton

Fifteen populations of Calotropis procera (Aiton) W.T. Aiton (milkweed) were collected from ecologically different regions of Punjab to evaluate anatomical traits that contribute to the ecological success of this plant in heterogeneous environmental regimes. Structural features relating to stems and leaves showed phenotypic variation. Xeromorphy was high in the desert population possessing thick cuticle and surface hairiness, enhanced xylem vessels, phloem area and deposition of storage parenchymatous tissues (cortex and pith) in the stem and leaves. The population from salt-affected areas showed increased inner phloem area and pubescence in stems, whereas lamina thickness and xylem vessels were greatly enlarged in leaves. The population from mountainous ranges showed the maximum stem area, outer phloem area, cuticle thickness and epidermal cell area. The population along riverbanks showed some prominent features like enlarged bundles of sclerenchyma fibers, and enhanced midrib thickness, cuticle thickness and inner phloem area. The population from the artificial forest plantation had a prominent layer of collenchyma developed under the epidermis, thick lamina and widened xylem vessels. The population from roadsides possessed thick cuticles and enlarged xylem vessels in leaves; in addition, a great proportion of trichomes/hairiness was found on the stem surface. Leaf succulence was the prominent feature of the population adapted to desert and dry mountains. All of these features possibly contribute to C. procera adaptability in a variety of habitats, i.e., desert and semi-desert, salt-affected areas, dry mountains, river/canal banks, roadside and forest plantations, and others.

Arabidopsis thaliana subclass I ACTIN DEPOLYMERIZING FACTORs and vegetative ACTIN2/8 are novel regulators of endoreplication.

Endoreplication is a type of cell cycle where genome replication occurs without mitosis. An increase of ploidy level by endoreplication is often associated with cell enlargement and an enhanced plant growth. Here we report Arabidopsis thaliana subclass I ACTIN DEPOLYMERIZING FACTORs (ADFs) and vegetative ACTIN2/8 as novel regulators of endoreplication. A. thaliana has 11 ADF members that are divided into 4 subclasses. Subclass I consists of four members, ADF1, -2, -3, and -4, all of which constitutively express in various tissues. We found that both adf4 knockout mutant and transgenic plants in which expressions of all of four subclass I ADFs are suppressed (ADF1-4Ri) showed an increased leaf area of mature first leaves, which was associated with a significant increase of epidermal pavement cell area. Ploidy analysis revealed that the ploidy level was significantly increased in mature leaves of ADF1-4Ri. The increased ploidy was also observed in roots of adf4 and ADF1-4Ri, as well as in dark-grown hypocotyls of adf4. Furthermore, double mutants of vegetative ACT2 and ACT8 (act2/8) exhibited an increase of leaf area and ploidy level in mature leaves. Therefore, actin-relating pathway could regulate endoreplication. The possible mechanisms that actin and ADFs regulate endoreplication are discussed.

Effects of experimental warming on Betula nana epidermal cell growth tested over its maximum climatological growth range.

Numerous long-term, free-air plant growth facilities currently explore vegetation responses to the ongoing climate change in northern latitudes. Open top chamber (OTC) experiments as well as the experimental set-ups with active warming focus on many facets of plant growth and performance, but information on morphological alterations of plant cells is still scarce. Here we compare the effects of in-situ warming on leaf epidermal cell expansion in dwarf birch, Betula nana in Finland, Greenland, and Poland. The localities of the three in-situ warming experiments represent contrasting regions of B. nana distribution, with the sites in Finland and Greenland representing the current main distribution in low and high Arctic, respectively, and the continental site in Poland as a B. nana relict Holocene microrefugium. We quantified the epidermal cell lateral expansion by microscopic analysis of B. nana leaf cuticles. The leaves were produced in paired experimental treatment plots with either artificial warming or ambient temperature. At all localities, the leaves were collected in two years at the end of the growing season to facilitate between-site and within-site comparison. The measured parameters included the epidermal cell area and circumference, and using these, the degree of cell wall undulation was calculated as an Undulation Index (UI). We found enhanced leaf epidermal cell expansion under experimental warming, except for the extremely low temperature Greenland site where no significant difference occurred between the treatments. These results demonstrate a strong response of leaf growth at individual cell level to growing season temperature, but also suggest that in harsh conditions other environmental factors may limit this response. Our results provide evidence of the relevance of climate warming for plant leaf maturation and underpin the importance of studies covering large geographical scales.

Adaptive traits for drought tolerance in red-grained wheat (Triticum aestivum L.) landraces

Forty-nine accessions were collected from arid and semi-arid areas of Pakistan to explore adaptive components in red-grained wheat (Triticum aestivum L.). Single-line selections of these accessions were grown on an arid and a control site; that is, Uchkera Farm (UF) and Botanical Garden (BG), Faisalabad. The accessions grown at BG exhibited significantly better biomass and grain yield production than those grown at UF. Accession Ck5 from Chakwal produced the maximum grain yield (17.7 g plant−1) at BG and Jm3 (8.1 g plant−1) at UF. Among the eight accessions selected for further anatomical studies, Dg2 showed increased yield per plant at UF, which was related to root modifications like increased cortical region thickness, endodermal cell area, vascular region thickness, metaxylem area, and root hair length. Stem modifications included increased vascular bundle area, phloem area and stomatal density, while leaves showed increased cuticle thickness, bulliform cell thickness, trichome density, and length. Increased stomatal density and area were also found. Accession Jm3 showed a decrease in yield at UF. Root modifications in Jm3 included increased epidermal cell area, sclerenchymatous thickness, endodermal cell area, and root hair length. Stem modifications in this accession included increased stem cellular region thickness and sclerenchymatous cell area. Leaves had increased abaxial epidermal cell area, trichome number and length, and abaxial stomatal density. In conclusion, morpho-anatomical characteristics varied greatly in the red-grained wheat accessions at both experimental sites that have potential for incorporation into breeding efforts for drought tolerance in modern wheat cultivars.