Vascular Bundle Area Research Articles

Exploring the Impact of High-Temperature Stress on Physiological, Anatomical, Molecular, Productive, and Quality Parameters in Diverse Olive Cultivars

Olive (Olea europaea L.) is one of the most important horticultural crops in Saudi Arabia. High temperatures are typical in most regions during the summer season. This study explored the effect of high temperatures on diverse olive cultivars (Manzanillo, Chemlali, and Picual) grown in three different geographical locations in Saudi Arabia (Sakaka, Basita, and Al-Qurayyat). Sakaka region was classified as a hot region, while the Basita and Al-Qurayyat regions were characterized by relatively mild or low temperatures. Genotypic components were assessed by studying Amplified Fragment Length Polymorphism (AFLP) molecular markers and physiological, anatomical, productive, and oil quality parameters. The evaluated genotypes displayed considerable variation across the three studied locations. Picual exhibited more heat tolerance, followed by Chemlali and Manzanillo. The high temperature in Sakaka negatively impacted critical characteristics related to olive growth, production, and quality. Results revealed that linoleic acid, oil acidity, total phenols, upper epidermis, palisade tissue, vascular bundle area, and mesophyll were the most appropriate parameters for predicting the impact of high temperatures. These traits were highly correlated with Sakaka and were highly and significantly associated with all the studied markers. Also, significant interactions between locations and genotypes showed that the means for most of the studied traits were the highest in Basita region.

Biogas slurry: A potential substance that synergistically enhances rapeseed yield and lodging resistance

Biogas slurry (BS) plays a vital role in improving the efficiency of crop production. On the flip side, the impact of BS on plant lodging factors and yield related traits is still obscure. Hence, we aimed to study the effects of pig and cow BS applications on yield formation, morpho-anatomical, mechanical, physiological properties and transcript expression patterns. The results showed that the yield and lodging resistance of rapeseed were synergistically improved via applying full BS dosage versus nitrogen fertilizer (CK). In addition, the seed yield was significantly increased by 23.9 % by promoting the dry matter accumulation and transport-ability, increasing number of pods by 8.4 % and 1000-seed weight by 5.1 %, respectively. Moreover, BS developed the stem mechanical strength by decreasing lodging index by 34.2 %, which was manifested by an increase in stem thickness and stiffness and a reduction in plant height. Besides, it enhanced the photosynthesis through promoting chlorophyll synthesis, delaying plant senescence, and accumulating N and K concentration. Anatomical observations revealed that BS increased greater number and area of stem vascular bundles, vessels, and maintained a dense microstructure than CK. Also, it boosted pectin, Ca2+ and K+ contents, which were significantly positively correlated with stem mechanical strength and reduced cellulose, lignin and hemicellulose contents. Meanwhile, correlation and structural equation modeling analysis validated the above results. Additionally, the differentially expressed genes were enriched in cell wall formation pathway, especially about the biosynthesis of pectin (PME, PG and PL), cellulose (CesA and CSL), lignin (PAL, POD, CCR, LAC and COMT) and hemicellulose (XTH and Xyl) were identified under BS. The above-mentioned results indicated that BS simultaneously affected lodging behavior by altering structural carbohydrates and modified yield composition by regulating dry-matter accumulation and allocation. This is the first comprehensive strategy on synchronizing rapeseed yield increase and lodging resistance under optimized BS management.

Identification and Analysis of the Mechanism of Stem Mechanical Strength Enhancement for Maize Inbred Lines QY1.

Enhancing stalk strength is a crucial strategy to reduce lodging. We identified a maize inbred line, QY1, with superior stalk mechanical strength. Comprehensive analyses of the microstructure, cell wall composition, and transcriptome of QY1 were performed to elucidate the underlying factors contributing to its increased strength. Notably, both the vascular bundle area and the thickness of the sclerenchyma cell walls in QY1 were significantly increased. Furthermore, analyses of cell wall components revealed a significant increase in cellulose content and a notable reduction in lignin content. RNA sequencing (RNA-seq) revealed changes in the expression of numerous genes involved in cell wall synthesis and modification, especially those encoding pectin methylesterase (PME). Variations in PME activity and the degree of methylesterification were noted. Additionally, glycolytic efficiency in QY1 was significantly enhanced. These findings indicate that QY1 could be a valuable resource for the development of maize varieties with enhanced stalk mechanical strength and for biofuel production.

Histological Variations in Cucumber Grafted Plants and Their Effect on Yield

Cucumber is a vegetable crop of economic importance in Mexico. In 2023, fresh or frozen cucumber and pickle international sales reached USD 783M, placing Mexico in second rank among countries with the highest currency inflow in the world. This crop is mostly grown under protected environments with new production technologies, including rootstocks that are tolerant to biotic and abiotic factors that limit the yield and quality of the harvest. Therefore, the goal of this work was to assess three cucurbits as rootstocks (Cucurbita maxima, Cucurbita moschata and Citrullus lanatus), as well as studying the response of cucumber crop to the tested rootstocks. The following treatments were assessed: T1:PSP = cucumber Cv. Paraizo F1 without rootstock; T2:P/MA = cucumber grafted over Cucurbita maxima; T3:P/MO = cucumber grafted over Cucurbita moschata; T4:P/CL = cucumber grafted over Citrullus lanatus Citroides Var. The assessed variables included the number of fruits per plant (NFPP), fruit weight per plant (PFPP), average fruit weight (PPF), plant dry weight (PSP), xylem vessel area (AVX), number of xylem vessels (NVX), vascular bundle area (AHV) and number of vascular bundles (NHV) in roots (R), basal stalk (TB) and apical stalk (AT). Significant differences among treatments were found in the results for variables: NFPP, highlighting that T2:P/MA was superior by 46.15% versus T1:PSP and by 67.69% versus T3:P/MO. Regarding PFPP, T2:P/MA achieved the highest weight (5445 g), as it proved superior by 99.45% than the cucumber without rootstock (T1:PSP). Regarding PSP, T2:P/MA achieved the highest weight (196.65 g), significantly exceeding T1 by 137.5%. Regarding AVXR, T4:P/CL had the highest value (30,063 µm2). Regarding NHVR, watermelon had (T4:P/CL) 39.33% more vascular bundles than the root system of cucumber (T1:PSP). Treatments T2:P/MA and T4:P/CL had the highest values at AVXTB, while for variable NVXTB, treatments T3:P/MO and T2:P/MA were almost equal, surpassing non-grafted cucumber by 175.47%. However, T2:P/MA showed the greatest AHVTB, and T1:PSP was significantly superior to T3:P/MO, by 34.93%, for NHVTB. Furthermore, positive and significant correlations were found among PFPP, AHVR, and AVXTB, as well as among PSP, AVXTB, and AHVTB. Therefore, we may say that having a larger area of vascular vessels in the roots and a larger area of xylem vessels in the basal stalk leads to higher fruit yields per plant. In the same vein, the use of rootstocks is a sustainable alternative to increase fruit yield.

Characterization of an Excellent Hybrid Rice Restorer Line R382 with Enhanced Lodging Resistance

Hybrid rice needs to prevent lodging due to excessive grain weight during maturity, which can lead to yield loss, grain quality deterioration and difficulty in harvesting. Breeding excellent parents (restorer and male-sterile lines) is the foundation for cultivating lodging-resistant hybrid rice. However, there is still limited information about restorers with improved lodging resistance. To identify a new restorer with significantly enhanced resistance to lodging, the restorer line Huazhan, which has been used for many years in hybrid rice breeding in China, was used as the control, to evaluate the lodging resistance of the new restorer R382. A two-year field experiment was executed to investigate the difference on lodging-related traits of the basal two internodes above-ground, such as out diameters of stems with or without leaf sheath (DWS, DWOS), culm thickness (CT), the section modulus (SM), bending stress (BS), and bending moment at break (M). The results indicated that DWS, CT, BS, M of R382 was at least 19.9%, 13.3%, 36.5% and 52.6% higher than that of Huazhan. However, the negative indicator lodging index of R382 was over 17.5% lower. The number and area of vascular bundles, and the contents of the chemical components of the cell wall including cellulose, lignin, and hemicellulose, together with the accumulation of starch granules, were significantly greater in R382. Furthermore, in the basal stems during the jointing stage, a series of genes that promote cell wall formation exhibited significantly higher expression levels in R382. Meanwhile, there was no significant difference in the yield of R382 and Huazhan. Thus, this new restorer could be a valuable donor in the future hybrid rice breeding programs for improving lodging resistance.

Genome-wide association study of stem structural characteristics that extracted by a high-throughput phenotypic analysis "LabelmeP rice" in rice.

Stem is important for assimilating transport and plant strength; however, less is known about the genetic basis of its structural characteristics. In this study, a high-throughput method, "LabelmeP rice" was developed to generate 14 traits related to stem regions and vascular bundles, which allows the establishment of a stem cross-section phenotype dataset containing anatomical information of 1738 images from hand-cut transections of stems collected from 387 rice germplasm accessions grown over two successive seasons. Then, the phenotypic diversity of the rice accessions was evaluated. Genome-wide association studies identified 94, 83, and 66 significant single nucleotide polymorphisms (SNPs) for the assayed traits in 2 years and their best linear unbiased estimates, respectively. These SNPs can be integrated into 29 quantitative trait loci (QTL), and 11 of them were common in 2 years, while correlated traits shared 19. In addition, 173 candidate genes were identified, and six located at significant SNPs were repeatedly detected and annotated with a potential function in stem development. By using three introgression lines (chromosome segment substitution lines), four of the 29 QTLs were validated. LOC_Os01g70200, located on the QTL uq1.4, is detected for the area of small vascular bundles (SVB) and the rate of large vascular bundles number to SVB number. Besides, the CRISPR/Cas9 editing approach has elucidated the function of the candidate gene LOC_Os06g46340 in stem development. In conclusion, the results present a time- and cost-effective method that provides convenience for extracting rice stem anatomical traits and the candidate genes/QTL, which would help improve rice.

Gradient Variation and Correlation Analysis of Physical and Mechanical Properties of Moso Bamboo (Phyllostachys edulis).

This study aimed to investigate the gradient properties of bamboo at the microscopic level and provide a basis for improving the utilization rate of bamboo. Using moso bamboo (Phyllostachys edulis (Carrière) J. Houz.) as a research subject, the variation of vascular bundle area percentage, chemical content, relative crystallinity (CR), mechanical properties of different bamboo slivers, and correlation between those parameters were analyzed. From the bamboo green layer (BGL) to the bamboo yellow layer (BYL), the distribution of vascular bundles changed from dense to sparse. Cellulose and lignin mass content decreased gently, and hemicellulose mass content showed gradual increases. The CR showed an order of bamboo middle layer (BML) > BGL > BYL. The tensile modulus of elasticity, tensile strength, bending modulus of elasticity, and bending strength decreased from BGL to BYL. The order of influence degree on mechanical properties of moso bamboo was vascular bundle area, hemicellulose content, lignin mass content, density, and CR, and these factors correlated with mechanical properties at a significant level (p < 0.05). Vascular bundle area had a decisive effect on the mechanical properties of bamboo. The vascular bundle area and density were linearly correlated with mechanical properties, while the lignin mass content and CR were curve-linearly correlated with mechanical properties.

Transcriptome-metabolome and anatomy conjoint analysis of vital component change of photosynthesis of Foxtail millet under different drought conditions

Drought caused by extreme climate change has become more severe and unpredictable, causing imperceptible effects on leaf photosynthesis in foxtail millet. To investigate the damage, we performed light drought (LD) and heavy drought (HD) treatments at both the elongation (Y) and booting stages to obtain a comprehensive understanding of the morphological, anatomical, physiological, transcriptome, and metabolome levels. Under drought stress, the length and area of leaves decreased, especially during the HD treatment at the booting stage. The number of mesophyll cells and the area of large vascular bundles were both decreased under LD and HD treatments at the booting stage, as well as with more blurring vascular bundle structure and Kranz anatomy. However, these numbers decreased but with no significance under Y-LD and Y-HD treatments at the elongation stage. The net photosynthetic rate, stomatal conductivity, transpiration rate, and intercellular CO2 concentration significantly decreased at the booting stage. In addition, the efficiency of electron transfers in photosystem II (PS II) decreased. Conjunction analyses of the transcriptome and metabolome were utilized to uncover the underlying mechanism at the booting stage. The results showed that there was no common differentially enriched pathway in the transcriptome and metabolome under LD treatment but thirty-two pathways were enriched in both the transcript and metabolome under HD treatment. Among these, three pathways arginine, proline metabolism, tyrosine metabolism, ubiquinone, and other terpenoid-quinone biosynthesis pathways were differentially enriched in both the transcript and metabolome. The accumulation of Homogentisate, Salidroside, Homoprotocatechuate, L-DOPA, Tyramine, and L-Tyrosine increased under drought stress. Although genes related to PSII and the Calvin cycle were slightly up-regulated under LD conditions, they were down-regulated under HD condition. The metabolites of Ribose-5P, Glycerate-3P, D-Fructosel 1,6P2, and D-Fructose-6P were all decreased in both the LD and HD treatments, especially D-Fructose-6P, confirming that drought stress had a negative effect on the Calvin cycle. The results revealed that regardless of the severity of drought, photosynthetic function was compromised not only at the morphological and anatomical levels but also in terms of impaired ATP synthase and inhibited photosynthetic CO2 assimilation.

Adaptation Strategies of Populus euphratica to Arid Environments Based on Leaf Trait Network Analysis in the Mainstream of the Tarim River

Populus euphratica, a key tree species in the ecologically fragile area of the Tarim River Basin, plays a crucial role in maintaining the ecological balance of the desert. In order to explore the response of Populus euphratica leaves to river water resources and drought climate change, the complex topological relationship between the leaf traits of Populus euphratica was comprehensively analyzed by establishing the leaf trait network of the mainstream of the Tarim River, and the central traits that play a key role in regulating the phenotype of Populus euphratica were identified. The adaptation strategies of Populus euphratica to different environments were clarified from the perspective of the overall leaf trait network. The results show that, with a decrease in river water flow, the internal coordination of the leaf traits weakened, forming a looser network structure. In the hyper-arid region, the leaf traits were more independent, the network was simpler, and it was easier for the leaf to coordinate the aggregation of specific traits. Leaf thickness and the related photosynthetic traits are the key to adaptive strategies, particularly the cuticle thickness and midvein vascular bundle area. Leaf anatomical traits are more critical than stoichiometry traits in drought resistance. Leaves tend to give priority to the relationship between structural traits. Populus euphratica leaves adjust their trait modularization through a trait substitution strategy to manage different drought conditions.

Analyzing the structure of bamboo culms using computer vision and mechanical simulation

Abstract Bamboo culm is a natural material characterized by a graded structure of vascular bundles in the radial direction and a regular distribution of bamboo nodes in the axial direction. To investigate the adaptation of bamboo culm structure to its natural environment, the bamboo culm structure was analyzed using a vascular bundle identification model, complemented by mechanical simulations. The results showed a certain pattern in the macroscopic dimensional characteristics of bamboo from the base to the top: the outer diameter decreased linearly; the internode length initially increased before decreasing; the length-to-diameter ratio gradually increased; and the wall-to-cavity ratio initially decreased before increasing. In response to external forces, bamboo exhibited strong stability, which was attributed to the thin and hollow wall as well as parabolic distribution of bamboo nodes. Along the axial direction, vascular bundle numbers linearly decreased, while the ratio of fiber sheath tissue and the distribution frequency of vascular bundles increased from the base to the top. In the radial direction, the length and area of vascular bundles tended to increase before decreasing, while the width tended to increase, leading to a decreasing length-to-width ratio. Overall, the radial variation pattern of vascular bundles showed nonsignificant variations at different heights.

Invasive success of star weed (Parthenium hysterophorus L.) through alteration in structural and functional peculiarities.

Parthenium weed poses significant threats to cropping systems, socioeconomic structures, and native ecosystems. The pronounced impact is primarily attributed to its rapid and efficient invasion mechanism. Despite that the detrimental effects of Parthenium weed are widely acknowledged, an in-depth scientific comprehension of its invasion mechanism, particularly regarding modifications in structural and functional attributes under natural conditions, is still lacking. To bridge this knowledge gap and formulate effective strategies for alleviating the adverse consequences of Parthenium weed, a study was conducted in the more cultivated and densely populated areas of Punjab, Pakistan. This study was focused on fifteen distinct populations of the star weed (Parthenium hysterophorus L.) to investigate the factors contributing to its widespread distribution in diverse environmental conditions. The results revealed significant variations in growth performance, physiological traits, and internal structures among populations from different habitats. The populations from wastelands exhibited superior growth, with higher accumulation of soluble proteins (TSP) and chlorophyll content (Chl a&b, TChl, Car, and Chl a/b). These populations displayed increased root and stem area, storage parenchyma, vascular bundle area, metaxylem area, and phloem area. Significant leaf modifications included thicker leaves, sclarification around vascular bundles, and widened metaxylem vessels. Roadside populations possessed larger leaf area, enhanced antioxidant activity, increased thickness of leaves in terms of midrib and lamina, and a higher cortical proportion. Populations found in agricultural fields depicted enhanced shoot biomass production, higher levels of chlorophyll b, and an increased total chlorophyll/carotenoid ratio. Additionally, they exhibited increased phloem area in their roots, stems, and leaves, with a thick epidermis only in the stem. All these outcomes of the study revealed explicit structural and functional modifications among P. hysterophorus populations collected from different habitats. These variations were attributed to the environmental variability and could contribute to the widespread distribution of this species. Notably, these findings hold practical significance for agronomists and ecologists, offering valuable insights for the future management of Parthenium weed in novel environments and contributing to the stability of ecosystems.

Regulatory effect of graphene on growth and carbon/nitrogen metabolism of maize (Zea mays L.).

Leakage of graphene into the environment has resulted from its increasing use. Although the impact of graphene on ecosystems is already in full swing, information regarding its impact on plants is lacking. In particular, the effects of graphene on plant growth and development vary, and basic information on the regulation of carbon and nitrogen metabolism is missing. In the current study, the way in which graphene (0, 25, 50, 100, and 200 g kg-1 ) affects maize seedlings was studied in terms of morphological and biochemical indicators. The purpose of this study was to understand better how graphene regulates plant carbon and nitrogen metabolism and to understand its interactions with leaf structure and plant growth. The results showed that 50 g kg-1 graphene increased plant height, stem diameter, leaf area, and dry weight; however, this was inhibited by the high level of graphene (200 g kg-1 ). Further studies indicated that different concentrations of graphene could increase leaf thickness and vascular bundle area as well as the net photosynthetic rate (Pn) of leaves; 25 and 50 g kg-1 graphene enhanced the leaves stomatal conductance (Cond), transpiration rate (Tr), intercellular carbon dioxide (Ci), and chlorophyll content. Higher concentrations decreased the above indicators. At 50 g kg-1 , graphene increased the activity of carbon/nitrogen metabolism enzymes by increasing carbon metabolites (fructose, sucrose, and soluble sugars) and soluble proteins (nitrogen metabolites). These enzymes included sucrose synthase (SS), sucrose phosphate synthase (SPS), nitrate reductase (NR), glutamine synthase (GS), and glutamate synthase (GOGAT). These results indicate that graphene can regulate the activities of key enzymes involved in carbon and nitrogen metabolism effectively and supplement nitrogen metabolism through substances produced by carbon metabolism by improving photosynthetic efficiency, thus maintaining the balance between carbon and nitrogen and promoting plant growth and development. The relationship between these indexes explained the mechanism by which graphene supported the growth of maize seedlings by enhancing photosynthetic carbon metabolism and maintaining metabolic balance. For maize seedling growth, graphene treatment with 50 g kg-1 soil is recommended. © 2023 Society of Chemical Industry.

Survival tactics of an endangered species Withania coagulans (Stocks) Dunal to arid environments.

Withania coagulans is a valuable medicinal plant with high demand, but its wild growth and local usage pose a threat to its natural habitat. This study aims to understand the plant's growth, anatomy, and physiology in different environmental conditions to aid in conservation and re-vegetation efforts. Fifteen differently adapted populations of Withania coagulans were collected from diverse ecological regions, viz., (i) along the roadside, (ii) hilly areas, (iii) barren land, and (iv) wasteland to unravel the adaptive mechanisms that are responsible for their ecological success across heterogenic environments of Punjab, Pakistan. The roadside populations had high values of photosynthetic pigments, total soluble proteins, root endodermis thickness, stem and leaf cortical thickness, and its cell area. The populations growing in hilly areas showed better growth performance such as vigorous growth and biomass production. Additionally, there was enhanced accumulation of organic osmolytes (glycine betaine and proline), chlorophyll content (chl a/b), and enlarged epidermal cells, cortical cells, vascular bundles, metaxylem vessels, and phloem region in roots. In case of stem area, epidermal thickness, cortical thickness, vascular bundle, and pith area showed improved growth. However, the barren land population showed significant increase in carotenoid contents, vascular bundle area, and metaxylem area in roots, and xylem vessels and phloem area in stems and leaves. The wasteland population surpassed the rest of the populations in having greater root dry weight, higher shoot ionic contents, increased root area, thick cortical, and vascular bundle area in roots. Likewise, cortical thickness and its cell area, and pith area in stems, whereas large vascular bundles, phloem region, and high stomatal density were recorded in leaves. Subsequently, natural populations showed the utmost behavior related to tissue organization and physiology in response to varied environmental conditions that would increase the distribution and survival of species.

Effects of 2,4-dichlorophenoxyacetic acid, α-naphthylacetic acid on the variant formation of Valentine Hoya (Hoya kerrii)

Valentine Hoya (Hoya kerrii) is favoured by many people for its richness in leaf shape, colour and flower fragrance. To increase the diversity and abundance of Hoya, leaf samples were transplanted into MS medium supplemented with 2,4-D and α-naphthylacetic acid (NAA) (concentration 4-7 mg/l) to create callus and induce mutations. Calli formation rate was observed at 100% after 15 days of culture in all treatments supplemented with growth regulators, while the control treatment showed no callus formation. The results of rapid callus multiplication showed that the callus-forming leaf sample obtained from the treatment of 5 mg/l 2,4-D gave the largest callus size (2.98 cm). The 45-day-old calli were transferred to MS + 1 mg/l IBA + 3.5 mg/l BAP regeneration medium, the time of shoot appearance for callus samples treated with NAA was 95 days after subculture with the highest regeneration rate of 66.67%, earlier than 2,4-D treated calli (225 days, 50% regeneration rate). The results of genetic divergence analysis using RAPD markers recorded a total of 330 DNA bands with molecular sizes ranging from 170 to 2700 bp. The polymorphism information content index was calculated in the 0.23-0.40 range. Samples treated with 5 mg/l NAA had the lowest similarity coefficient of 0.455, growth parameters such as petiole diameter, dermal tissue thickness, vascular bundle area, and a number of wood bundles recorded in samples treated with 5 mg/l NAA were superior to those of the control.Keywords:α-naphthylacetic acid, Hoya kerrii, polymorphisminformation content, variation, 2,4-D.Classification number:4.6

Changes in the lodging resistance of winter wheat from 1950s to the 2020s in Henan Province of China

BackgroundLodging is a major factor contributing to yield loss and constraining the mechanical harvesting of wheat crops. Genetic improvement through breeding effectively reduced the lodging and improved the grain yield, however, the physiological mechanisms involved in providing resistance to lodging are different in the breeding stage and are not clearly understood. The purpose of this study was to compare the differences in the lodging resistance (LR) of the wheat varieties released during the different decades and to explore the effect of the application of nitrogen (N) fertilizer on the plasticity of LR.ResultsA field study was conducted during the cultivation seasons of 2019–2020 and 2020–2021, in soil supplemented with three N levels: N0 (0 kg ha–1), N180 (200 kg ha–1), and N360 (360 kg ha–1) using eight varieties of wheat released for commercial cultivation from 1950 to date. The results obtained showed that genetic improvement had significantly enhanced the LR and grain yield in wheat. In the first breeding stage (from 1950 to 1980s) the lodging resistant index increased by 15.0%, which was primarily attributed to a reduced plant height and increased contents of cellulose, Si, and Zn. In the second breeding stage (the 1990s–2020s) it increased by 172.8%, which was mainly attributed to an increase in the stem diameter, wall thickness, and the contents of K, Ca, Fe, Mn, and Cu. The application of N fertilizer improved the grain yield but reduced the LR in wheat. This was mainly due to an increase in plant height resulting in an elevation of the plant center of gravity, a decrease in the contents of cellulose, and a reduction in the area of large-sized vascular bundles in the stems, even if N supplementation increased the concentrations of K, Ca, and Si.ConclusionAlthough breeding strategies improved the stem strength, the trade-off between the grain yield and LR was more significantly influenced by the addition of N. Overcoming this peculiar situation will serve as a breakthrough in improving the seed yield in wheat crops in the future.

Microscopical Analysis of Autofluorescence as a Complementary and Useful Method to Assess Differences in Anatomy and Structural Distribution Underlying Evolutive Variation in Loss of Seed Dispersal in Common Bean.

The common bean has received attention as a model plant for legume studies, but little information is available about the morphology of its pods and the relation of this morphology to the loss of seed dispersal and/or the pod string, which are key agronomic traits of legume domestication. Dehiscence is related to the pod morphology and anatomy of pod tissues because of the weakening of the dorsal and ventral dehiscence zones and the tensions of the pod walls. These tensions are produced by the differential mechanical properties of lignified and non-lignified tissues and changes in turgor associated with fruit maturation. In this research, we histologically studied the dehiscence zone of the ventral and dorsal sutures of the pod in two contrasting genotypes for the dehiscence and string, by comparing different histochemical methods with autofluorescence. We found that the secondary cell wall modifications of the ventral suture of the pod were clearly different between the dehiscence-susceptible and stringy PHA1037 and the dehiscence-resistant and stringless PHA0595 genotypes. The susceptible genotype had cells of bundle caps arranged in a more easily breakable bowtie knot shape. The resistant genotype had a larger vascular bundle area and larger fibre cap cells (FCCs), and due to their thickness, the external valve margin cells were significantly stronger than those from PHA1037. Our findings suggest that the FCC area, and the cell arrangement in the bundle cap, might be partial structures involved in the pod dehiscence of the common bean. The autofluorescence pattern at the ventral suture allowed us to quickly identify the dehiscent phenotype and gain a better understanding of cell wall tissue modifications that took place along the bean's evolution, which had an impact on crop improvement. We report a simple autofluorescence protocol to reliably identify secondary cell wall organization and its relationship to the dehiscence and string in the common bean.

Analysis of seed production and seed shattering in a new artificial grassland forage: pigeon pea.

Pigeon pea is a perennial leguminous plant that is widely cultivated as a forage and pharmaceutical plant in subtropical and tropical areas, especially in artificial grasslands. Higher seed shattering is one of the most important factors in potentially increasing the seed yield of pigeon pea. Advance technology is necessary to increase the seed yield of pigeon pea. Through 2 consecutive years of field observations, we found that fertile tiller number was the key component of the seed yield of pigeon pea due to the direct effect of fertile tiller number per plant (0.364) on pigeon pea seed yield was the highest. Multiplex morphology, histology, and cytological and hydrolytic enzyme activity analysis showed that shatter-susceptible and shatter-resistant pigeon peas possessed an abscission layer at the same time (10 DAF); however, abscission layer cells dissolved earlier in shattering-susceptible pigeon pea (15 DAF), which led to the tearing of the abscission layer. The number of vascular bundle cells and vascular bundle area were the most significant negative factors (p< 0.01) affecting seed shattering. Cellulase and polygalacturonase were involved in the dehiscence process. In addition, we inferred that larger vascular bundle tissues and cells in the ventral suture of seed pods could effectively resist the dehiscence pressure of the abscission layer. This study provides foundation for further molecular studies to increase the seed yield of pigeon pea.

Coordination of Density and Nitrogen Fertilization Improves Stalk Lodging Resistance of Strip-Intercropped Maize with Soybeans by Affecting Stalk Quality Traits

To ensure yield in strip-intercropped maize with soybeans (SM), it is crucial to plant at a density comparable to that of monoculture maize (MM). This requires reducing spacing by more than half, increasing intraspecific competition, and altering stalk lodging resistance traits compared with MM. Nitrogen fertilization can effectively mediate stalk lodging resistance. However, it is still unclear how nitrogen rates influence SM’s stalk lodging resistance under high-density conditions and how that resistance compares to MM. The experiment involved four N fertilizer treatments with two planting densities: medium density (60,000 plants/ha) and high density (75,000 plants/ha). Additionally, different planting patterns of strip-cropped (S) and monoculture (M) were implemented. The N fertilizer application rates were N0 (0 kg/ha), N225 (225 kg/ha), N300 (300 kg/ha), and N375 (375 kg/ha). The stalk lodging resistance was represented by the breaking strength of the third basal internode. The study revealed that, at the same planting density, the third basal internode of the stalk exhibited consistent results in terms of its diameter, crushing strength, total number and area of vascular bundles, and N content. Notably, all these traits exhibited a significant positive relationship with breaking strength. The highest values for these parameters and yield were observed under N225 and N300 fertilization rates for medium-density monoculture and strip-cropped maize, respectively. In contrast, the high-density monoculture and strip-cropped maize showed peak performance under N300 and N375 fertilization rates. At both medium and high planting densities, the strip-cropped maize exhibited 8.9% and 10.9% lower breaking strength than the monoculture maize under N225 treatment. However, increasing the N fertilizer application resulted in comparable lodging resistance between the strip-cropped maize and the maximum values of the monoculture maize, at N300 treatment for medium density and N375 treatment for high density. Hence, strip-cropped maize planted at high density (75,000 plants/ha) with a lower nitrogen rate had lower lodging resistance than monoculture maize, but it can be improved to match the monoculture maize by increasing the nitrogen rate.

Reduction of photosynthesis under P deficiency is mainly caused by the decreased CO2 diffusional capacities in wheat (Triticum aestivum L.)

Phosphorus is one of the most important essential mineral elements for plant growth and development. It has been widely recognized that phosphorus deficiency can lead to the significant declines in leaf photosynthetic rate and leaf area. However, the internal mechanism associated with the leaf anatomical traits has not been well understood. In present study, a hydroponic experiment was conducted to study the effect of phosphorus deficiency on leaf growth and photosynthesis in Jimai 22 (JM22, Triticum aestivum L.) and Suk Landarace 26 (SL26, Triticum aestivum L.). With the decrease in phosphorus concentration, leaf photosynthetic rate and leaf area in SL26 and JM22 all decreased significantly, but the decrease in leaf area occurred earlier than that in leaf photosynthetic rate. The thresholds of phosphorus concentration to maintain a high photosynthesis were 145.5 and 138.7 mg m−2, respectively, in SL26 and JM22; and they were 197.5 and 212.0 mg m−2, respectively, for leaf growth. The decrease in leaf photosynthetic rate under low P conditions was mainly caused by the lowered stomatal conductance and mesophyll conductance, and to a less extent by the decrease in biochemical capacities. The decrease in stomatal conductance was attributed to the smaller vascular bundle area, xylem conduits area and the lower leaf hydraulic conductance. However, the reduction in mesophyll conductance was not related to either the cell wall thickness or the development of chloroplast.

Multiple endpoints of polyethylene microplastics toxicity in vascular plants of freshwater ecosystems: A study involving Salvinia auriculata (Salviniaceae)

More recently, the number of studies on the impacts of microplastics (MPs) on plants has drawn attention considerably. However, many of these studies focused on terrestrial plants, with vascular plants from freshwater ecosystems being little studied. Thus, we aimed to evaluate the possible effects of exposure of Salvinia auriculata, for 28 days, to different concentrations of polyethylene MPs (PE MPs – diameter: 35.46 ± 18.17 µm) (2.7 ×108 and 8.1 ×108 particles/m3), using different biomarkers. Our data indicated that exposure to PE MPs caused alterations in plant growth/development (inferred by the lower floating frond number, “root” length, and the number of “roots”), as well as lower dispersion of individuals in the experimental units. Plants exposed to PE MPs also showed lower epidermal thickness (abaxial leaf face) and a longer length of the central leaf vein and vascular bundle area. Ultrastructural analyses of S. auriculata exposed to MPs revealed rupture of some epidermal cells and trichomes on the adaxial and abaxial, leaf necrosis, and chlorosis. In the “roots”, we observed dehydrated filamentous structures with evident deformations in plants exposed to the pollutants. Both on the abaxial leaf face and on the “roots”, the adherence of PE MPs was observed. Furthermore, exposure to PE MPs induced lower chlorophyll content, cell membrane damage, and redox imbalance, marked by reduced catalase and superoxide dismutase activity and increased production of reactive oxygen and nitrogen species as well as malondialdehyde. However, in general, we did not observe the dose-response effect for the evaluated biomarkers. The values of the integrated biomarker response index, the principal component analysis (PCA) results and the hierarchical clustering analysis confirmed the similarity between the responses of plants exposed to different PE MPs concentrations. Therefore, our study sheds light on how PE MPs can affect S. auriculata and reinforces that putting these pollutants in freshwater environments might be hazardous from an ecotoxicological point of view.