Brittle culm 25, which encodes an UDP-xylose synthase, affects cell wall properties in rice

Because plant mechanical strength influences plant growth and development,the regulatory mechanisms underlying cell-wall synthesis deserve investigation.Rice mutants are useful for such research.We have identified a novel brittle culm 25(bc25)mutant with reduced growth and partial sterility.BC25 encodes an UDP-glucuronic acid decarboxylase involved in cellulose synthesis and belongs to the UXS family.A single-nucleotide mutation in BC25 accounts for its altered cell morphology and cellwall composition.Transmission electron microscopy analysis showed that the thickness of the secondary cell wall was reduced in bc25.Monosaccharide analysis revealed significant increases in content of rhamnose and arabinose but not of other monosaccharides,indicating that BC25 was involved in xylose synthesis with some level of functional redundancy.Enzymatic assays suggested that BC25 functions with high activity to interconvert UDP-glucuronic acid(UDP-Glc A)and UDP-xylose.GUS staining showed that BC25 was ubiquitously expressed with higher expression in culm,root and sheath,in agreement with that shown by quantitative real-time(q RT)-PCR.RNA-seq further suggested that BC25 is involved in sugar metabolism.We conclude that BC25 strongly influences rice cell wall formation.

英国Culm河河漫滩沉积物中磷素时空变化研究

河漫滩上沉积物的沉积伴随着与沉积物相结合的营养和污染物质的沉积。已有研究表明,河漫滩是与沉积物相结合的磷的沉积地。采用137Cs技术,并结合河漫滩沉积物中全磷(TP)含量的剖面信息,可以调查近年河漫滩沉积物中的TP含量,计算TP储量。本文根据英国Devon郡Culm河8个河漫滩采样环沉积物中的数据,重建了在过去40～50年内TP储量和含量的变化。结果表明,在Culm河河漫滩沉积物中,在1963～2000年间TP平均含量为0.60～1.96gkg-1,该值自河流上游向下游和自过去到现在有逐渐增加的趋势;在相同的河漫滩沉积物中,在相同的时期内TP储量为18.62～435.48gm-2,即0.49～11.46gm-2a-1,最大值出现在河流的中游。

Changes in culm surface temperature with maturity of the bamboo species Guadua angustifolia

We used thermal images of bamboo culms of Guadua angustifolia Kunth to analyze the relationship between culm surface temperature and maturity, driven by the hypothesis that young culms may exhibit lower surface temperatures than old ones. The culm surface temperature shows small but constant differences between three age classes of 1, 2, and 3 years. Our findings indicate that surface temperature may be applied as an additional indi- cator to support the determination of maturity of guadua culms besides the visual assessment of the culms.

Elastic Buckling of Bionic Cylindrical Shells Based on Bamboo

High load-bearing efficiency is one of the advantages of biological structures after the evolution of billions of years. Biomimicking from nature may offer the potential for lightweight design. In the viewpoint ofrnechanics properties, the culm of bamboo comprises of two types of cells and the number of the vascular bundles takes a gradient of distribution. A three-point bending test was carried out to measure the elastic modulus. Results show that the elastic modulus of bamboo decreases gradually from the periphery towards the centre. Based on the structural characteristics of bamboo, a bionic cylindrical structure was designed to mimic the gradient distribution of vascular bundles and parenchyma cells. The buckling resistance of the bionic structure was compared with that of a traditional shell of equal mass under axial pressure by finite element simulations. Results show that the load-bearing capacity of bionic shell is increased by 124.8%. The buckling mode of bionic structure is global buckling while that of the conventional shell is local buckling.

Effects of culm carbohydrate partitioning on basal stem strength in a high-yielding rice population

Rice culm carbohydrate transport can simultaneously affect grain filling and stem lodging resistance by regulating non-structural carbohydrate(NSC) and structural carbohydrate(SC) contents. However, the relationship between carbohydrate transposition and culm strength is not well documented. Accordingly, a high-yielding hybrid rice cultivar(Y Liangyou 2) was tested under different N fertilization regimes at two locations, Taoyuan(a special high-yield eco-site), Yunnan province and Danyang(a representative eco-site of the middle and lower Yangtze), Jiangsu province, China. Significantly higher grain yield and basal stem strength were found at Taoyuan than Danyang under all N rates throughout the two-year experiment. At heading stage, soluble sugars, starch, cellulose and lignin contents of the basal culm at Taoyuan were significantly 132.0%, 73.7%, 1.2%, and 62.7% higher than those at Danyang, respectively. At 20 days after heading, soluble sugars and starch content at Taoyuan decreased significantly compared to Danyang, but lignin content remained higher. Culm carbohydrate transport to kernels at Taoyuan was significantly greater than that at Danyang, and the proportion of soluble sugars and starch was correspondingly 62.9%lower. However, the proportion of lignin and cellulose was 22.7% higher at Taoyuan than that at Danyang. Soluble sugars and starch partitioning were significantly reduced under an increased nitrogen application rate, but SC partitioning was little affected. There were significant positive correlations between basal culm bending stress and dry weight and cellulose and lignin proportions at both locations under all N rates, suggesting that the higher SC proportion at 20 days after heading was primarily responsible for culm strength.These results suggest that high-yielding rice populations with greater culm strength require both moderate NSC transport and greater SC accumulation.

Culm form analysis for bamboo, Phyllostachys pubescens

We investigated the culm form for one of the largest bamboo species, Phyllostachys pubescens Mazel ex Houz. in relation to the me- chanical constraint principles, i.e., elastic, stress and geometric similarity. The fine-resolution analysis of the culm taper indicated that the culm for P. pubescens consisted of three or four segments with various forms, except for the butt swell. This implied that the taper of the whole culm for P. pubescens could be expressed by neither of these principles. The regression slope between culm height and diameter at breast height on the double logarithmic coordinates was 0.629, which was significantly different from the values predicted from these principles. In conclusion, none of these mechanical constraint principles can express the culm taper and height-diameter relationship, and there may be a need for a more complicated model to express the culm form for P. pubescens.

Seasonal effect on rooting behaviour of important bamboo species byculm cuttings

We investigated the influence of season on the rooting be- haviour of eight important bamboo species viz., Bambusa balcooa, B. bambos, B. nutans, B. tuMa, B. vulgaris, Dendrocalamus giganteus, D. hamiltonii and D. strictus. We collected 2-3 node culm cuttings in three growing seasons viz. spring （March）, summer （June） and rainy （August） from superior candidate plus clumps （CPCs） centralized in the germplasm garden. Cuttings were placed horizontally in sand and were provided with intermittent misting at regular intervals. Bamboo species exhibited differential rhizogenesis behavior in different seasons. The study reveals significant variation in sprouting and rooting behaviour in different bamboo species. B. bambos had maximum rooting （78.89%）, followed by B. vulgaris （74.44%）. In general, the potential of different bamboo species for rooting was found to be in the order： B. bambos 〉 B. vulgaris 〉 B. balcooa 〉 D. hamiltonii 〉 B. tulda 〉 D. strictus 〉 D. giganteus 〉B. nutans. The maximum rooting was recorded in spring （56.67%）, which was closely followed by summer （54.58%）. In winter season, minimum rooting （36.67%） was observed. The interaction effect of species x season was also significant on sprouting and rooting pa- rameters. In B. balcooa, B. nutans, B. vulgaris, D. hamiltonii and D. strictus, cuttings collected in summer season showed maximum sprouting and rooting, whereas, B. bambos, B. tulda and D. giganteus had maximum rooting in spring. The maximum number of roots developed per cutting was observed in B. tulda （43.8） during spring season.

Cadmium Accumulation and Its Toxicity in Brittle Culm 1(bc1),a Fragile Rice Mutant

Cadmium （Cd） accumulation and toxicity in rice plants were characterized and identified by using brittle culm 1 （bcl）, a fragile rice mutant and its wild type （Shuangkezao, an indica rice） as materials by hydroponics. The low Cd level didn＇t obviously affect the growth parameters in both rice genotypes, but under high Cd levels （1.0 and 5.0 μmol/L）, the growth of both rice plants were substantially inhibited. Moreover, bcl tended to suffer more seriously from Cd toxicity than Shuangkezao. Cd accumulation in both rice plants increased with the increase of Cd levels. There was a significant difference in Cd accumulation between the two rice genotypes with constantly higher Cd concentration in bcl, which also accumulated more Cd at 0, 0.1, and 1.0 μmol/L Cd levels. The same case was found in the two rice plants grown on Cd-contaminated soil. This suggested that cell wall might play an important role in Cd accumulation in rice plants by the physiological mechanisms. The malondialdehyde （MDA） content, superoxide dismutase （SOD） and peroxidase （POD） activities in rice plants were affected differently under Cd treatments, and which implied that POD might play the main role in detoxifying active oxygen free radical. A significant difference in antioxidative system between the two rice genotypes was found with constantly higher MDA content, SOD and POD activities in bcl. In summary, bcl accumulated more Cd and appeared to be more sensitive to Cd stress compared with its wild type.

Discovery of and Preliminary studies on a Rapid-Leafing Rice Genotype at the Vegetative Growth Stage

The leafing rates of fourteen rice varieties were measured in a sowing-time experiment, and a rapid leafing genotype at the vegetative growth stage was discovered in an indica variety Yanhui 559. The leaf number on the main culm of Yanhui 559 was always 4-5 leaves more than that of Lemont, and the leafing rate of Yanhui 559 was significantly higher than that of Lemont based on similar growth durations from sowing to heading. Furthermore, the difference of the leafing rate was significant at the vegetative growth stage, but not distinctive at the panicle initiation stage. Genetic analysis of the leafing rates in the two backcross populations of Yanhui 559 and Lemont showed that major and quantitative genes controlled the expression of rapid leafing character. Based on results of investigation for some plants with similar growth durations in the backcrossing populations, the rapid leafing genotypes exhibited earlier tillering and more tiller numbers per plant, and its yield components including the number of panicles per plant and number of grains per panicle were superior to those of the slow leafing genotypes. Further research and application feasibility of the rapid leafing genotype in breeding were discussed.

Estimation of culm volume reduction factors in five bamboo species(Phyllostachys spp.)

The hollow cylindrical culm is one of the most remarkable morphological characters of most bamboo species.In relation to its hollow structure,there are two different attributes of the culm volume in bamboo:the apparent culm volume(va:the total culm volume including the hollow portion)and the woody culm volume(vw:the volume of the woody walls of the culm).The ratio of vw to va is defined as the reduction factor for culm volume(fv).The quantity fv is useful to quantify the biomass resources of bamboo culms as well as to evaluate the carbon stock of bamboo forests.However,the direct measurement of fv requires destructive sampling,which consumes time and labor.Hence,an alternative method for obtaining fv is desired.In this study,we examined fv in five species of the genus Phyllostachys and proposed alternative methods to estimate fv.Our data showed that fv varied by species,some of which exhibited a dependency of fv on culm sizes.These findings indicate that the intraspecific and interspecific variation in fv should be considered carefully when converting va into vw by fv.Based on our results,we propose here six approaches for predicting fv and we discuss their advantages and disadvantages.Our results are intended to facilitate evaluation of the carbon sequestration capacity of bamboo forests and the commercial utilization of bamboo culms.

Morphological phylogeny among 15 accessions of bamboos growing in Kokrajhar district of the Bodoland Territorial Area Districts,Assam

Bamboo is nature＇s wonderful gift historically associated with the rural population of the Bodoland Territorial Area Districts.However,indiscriminate use of the resource and the ambiguity in the identification of bamboos in the absence of flowering characters pose a potential risk to the bamboo germplasm.Therefore,we considered revising the taxonomic positions and phylogenetic relationships among 15 tropical bamboo species using 35 key morphological descriptors（MD） to assess the reliability of vegetative characters in identifying species.The phylogenetic tree constructed from the similarity matrix,derived from an unweighted pair group method of analysis（UPGMA） of the 35 MDs,marginally deviated from the conventional taxonomic positions of the bamboo species.While the two varieties,one forma of Bambusa vulgaris（var.Vittata,var.Vulgaris,fo.Waminii） and two species of the genus Dendrocalamus（D.giganteus and D.hamiltonii）clustered together in a single clade,and D.strictus was distantly placed from their congeners.This discrepancy with the conventional classification might have ensued since only vegetative characters such as culm anatomy,culm sheath,leaf,and leaf sheath were considered in the present study.While the phylogenetic relationship among the 15 tropical bamboos（computed from exhaustive MDs）grossly corroborate the conventional taxonomic grouping,a molecular-marker-based multidisciplinary approach should resolve the remaining conflicts in bamboo identification.

Comparison of three processing methods for laminated bamboo timber production

Three processing techniques, split-squaring(SS),V-grooving(VG), and split-edging(SE), were evaluated and compared in terms of their processing time and recovery. Semantan bamboo(Gigantochloa scortechinii Gamble) was used as a raw material and the results showed that the VG-method required the longest processing time(32.1 min), followed by the SS-method(18.2 min), and the SE-method(17.9 min). However, the VG-method showed the highest recovery(82.0%) compared to the SS-method and SE-method, 31.0 and 49.4%, respectively. When both processing time and recovery factors were combined with the same weighing factor, the highest value was recorded with the VG-method(49.1), while the SE-method had values of 31.1 and the SS-method 12.8. The results suggest that the VG-method is the best option. However, the V-grooving machine is still a prototype and therefore the SE-method could be an alternative option until the improved V-grooving machine is available.

Changes in foliar nitrogen resorption of Phyllostachys edulis with culm development

Leaf nitrogen resorption is very important to Phyllostachys edulis development because the withdrawn nitrogen can help newly emerging and growing culms.However, few studies have focused on the ontogenetic changes in leaf nitrogen resorption of P. edulis. Here, we examined the variability in mature leaf nitrogen concentrations(Nm), nitrogen resorption efficiency(NRE) and proficiency(NRP or Ns) and leaf-level nitrogen use efficiency(NUE) of the current-, 3 rd-and 5 th-year culms in P.edulis stands under extensive management. Analyses of variance and correlation indicated that patterns of Nm,NRP, NRE and NUE were markedly affected by culm age and leaf nitrogen status. Nm, Nsand NRE were significant higher in younger(current-year) culms with 1-year lifespan leaves, while NUE was markedly higher in older(3 rd-or 5 th-year) culms with 2-year lifespan leaves. Significant linear correlations between Nmand NRP, NRE and NUE,Nmand NUE, Nsand NRE were found for each culm age,and Nmwas significantly positively correlated to NRE for all culms pooled. Higher proficiency in older culms led to higher NUE and lower NRE, these relationships can be modulated by Nm, which in turn, is restrained by leaf N availability and acquisition. Our results revealed that at the intraspecific level, P. edulis can adjust its leaf NRE, NRP,and leaf-level NUE in concert with culm development.Understanding nitrogen resorption characteristics and NUE of P. edulis can help decision-makers design appropriate deforestation strategies and achieve precise N fertilization for sustainable bamboo forest management.

Mathematical expression for the relationship between internode number and internode length for bamboo, Phyllostachys pubescens

We analyzed the relationship between internode number and intemode length for one of the largest bamboo, Phyllostachys pubescens Mazel ex Houz. For 50 sample culms with various sizes felled in a pure stand of P. pubescens, the intemode number was assigned from base to tip and the length for each internode was directly measured. The result indicated that the intemode length should be cumulated from base to tip, and then the cumulated internode length should be relativized by the total culm length. It was inappropriate to relativize the internode length by the maximum intenode length. In addition, the relationship between the relative internode number （the intemode number relativized by the total number of intemodes） and the relative cumulated internode length should be described not by a power function but by a sigmoid function such as the third-order function. The determined function enabled us to estimate the actual internode length, with the root mean squared error being 4 cm. In conclusion, the mathematical expression presented here, i.e., the relativization of the cumulated internode length by the total culm length and the application of the sigmoid function, will be useful in describing the relationship between internode number and internode length for P. pubescens.

Influence of the Age of Bamboo Culm and Its Vertical Position on the Technological Properties of Bamboo Fibers: A Case of Bambusa vulgaris Species from Cameroonian Culture

Due to their interesting properties, bamboo fibers are more and more used as reinforcements in polymer matrices as a substitute for synthetic fibers. For their future service life, it is important to understand their physical and mechanical behavior over time in order to control the aging phenomenon within this fiber. The paper analyzed the influence of the age of the bamboo thatch and the vertical position of the Bambusa vulgaris species cultivated in Cameroon on the physicomechanical properties of the fibers extracted from the thatch. Fibers were mechanically extracted from three bamboo culms aged respectively 3 years (BV3), 4 years (BV4) and 5 years (BV5). The culms were thus identified according to their number of ramifications, and were felled no abated for a total of three culms. A section of about one meter on each of the parts (lower part, middle part, upper part) of these three culms was made for the opposite technological studies. Each age was therefore represented by three portions of thatch, one from the upper part, one from the middle part and the last from the lower part of the thatch, all giving a total number of nine samples taken and marked BV3inf, BV3moy, BV3sup, BV4inf, BV4moy, BV4sup, BV5inf, BV5moy, BV5sup before handling in the laboratory. Physical (density, moisture absorption rate) and mechanical (tensile tests according to DIN EN ISO 13934-1, natural durability) characterizations were used to better understand the mechanisms of this influence. In view of all the results obtained, the fiber from the upper part of the 3-year-old thatch (BV3sup) is the one with the best characteristics and is recommended for a better elaboration of bamboo fiber composites: (Density: 0.83;Absorption rate 11.7%;Young’s modulus: 7.4 GPa;Maximal stress: 64.3 MPa;Elongation at rupture: 1.1;Loss of mass natural durability: 7.63%).

Assessing Growth Parameters from Culm Cuttings of Bambusa vulgaris at the University of Dschang Botanic Garden, West Region of Cameroon: Implications for the Bamboo Resource Base and Rural Livelihoods

Dwindling supplies of bamboo resources and the increase in the demand for bamboo have led to the need for better propagation techniques. This is the only way to ensure the sustainability of the bamboo resource base and improve livelihoods. Thus, this study was carried out to examine the different growth parameters of culm cuttings of Bambusa vulgaris in propagation beds with a substrate consisting of dark soil, manure (compost) and sand in a ratio of 1:1:1. Data on different growth parameters was collected on a daily basis over a three week period and analyzed using appropriate descriptive and inferential statistics. It was found that the different growth parameters (diameter, height, leaves and sheaths) of culm cuttings of B. vulgaris evolved in like manner in three propagation beds. Descriptive statistics for growth parameters of culm cuttings of B. vulgaris showed little or no differences across three shelter/propagation beds (shelter bed 1, shelter bed 2 and shelter bed 3) with 1.4675 ± 1.6172 cm, 93 ± 112 cm, 22 ± 30 leaves, and 4 ± 6 sheaths being the mean diameter, height, number of leaves and number of sheaths for all three propagation beds, respectively. ANOVA test showed no statistically significant variation (p > 0.05) between growth parameters of culm cuttings of B. vulgaris across the three propagation beds, implying that the different growth parameters were relatively similar. Pearson correlation showed the existence of direct and inverse relationships between the different growth parameters of culm cuttings of bamboo. The existence of these direct and inverse relationships could be attributed to the rapid growth rate of bamboo, the substrate used, and the species of bamboo used (B. vulgaris). The study recommends more large-scale propagation projects of this bamboo species in order to ensure the sustainability of the bamboo resource base and improve livelihoods of bamboo dependent rural communities.

Characterization and cloning of a brittle culm mutant (bc88) in rice (Oryza sativa L.)

This study characterizes a brittle culm (bc88) mutant of rice (Oryza sativa L.) obtained by ethylene methylsulfonate (EMS)-induced mutagenesis of Wuyunjing 7. The bc88 mutant exhibits a diversity of pleiotropic phenotypes, including brittle culm at the whole-plant growth stages, withered leaf tips at the seedling stage, and 18-d delay in heading date at the mature stage. Genetic analysis indicates that the bc88 mutant is controlled by a single recessive nuclear gene. The mutated bc88 gene isolated by map-based cloning contains only one point mutation in the 5th exon relative to its wild-type BC88 (LOC_Os09g25490 and Os09g0422500), leading to an amino acid change from P to L in bc88 plants. Alignment of the putative protein sequence with its homologs indicates that the mutation is located in the conserved region of the sequence. Detection of the transcription level of BC88 in rice plants shows that the expression level of BC88 is higher in spikes and culms than in leaves, roots, and leaf sheaths. These contribute to understanding of the molecular mechanism of cellulose synthesis. The target gene BC88 can be a useful tool in molecular marker-assisted selection for rice culm trait breeding.

Isolation of a Novel Lodging Resistance QTL Gene Involved in Strigolactone Signaling and Its Pyramiding with a QTL Gene Involved in Another Mechanism

Lodging has been a major roadblock to attaining increased crop productivity. In an attempt to understand the mechanism for culm strength in rice, we isolated an effective quantitative trait locus （QTL）, STRONG CULM3 （SCM3）, the causal gene of which is identical to rice TEOSINTE BRANCHED1 （OsTB1）, a gene previously reported to positively control strigolactone （SL） signaling. A near-isogenic line （NIL） carrying SCM3 showed enhanced culm strength and increased spikelet number despite the expected decrease in tiller number, indicating that SL also has a positive role in enhancing culm strength and spikelet number. We produced a pyramiding line carrying SCM3 and SCM2, another QTL encoding AP01 involved in panicle development. The NIL-SCM2＋SCM3 showed a much stronger culm than NIL-SCM2 and NIL-SCM3 and an increased spikelet number caused by the additive effect of these QTLs. We discuss the importance of utilizing suitable alleles of these STRONG CULM QTLs without inducing detrimental traits for breeding.

Loss of Gn1a/OsCKX2 confers heavy-panicle rice with excellent lodging resistance

Significant achievements have been made in breeding programs for the heavy-panicle-type(HPT)rice(Oryza sativa) in Southwest China. The HPT varieties now exhibit excellent lodging resistance,allowing them to overcome the greater pressures caused by heavy panicles. However, the genetic mechanism of this lodging resistance remains elusive. Here, we isolated a major quantitative trait locus, Panicle Neck Diameter 1(PND1), andidentified the causal gene as GRAIN NUMBER 1 A/CYTOKININ OXIDASE 2(Gn1 A/Os CKX2). The null gn1 a allele from rice line R498(gn1 aR498) improved lodging resistance through increasing the culm diameter and promoting crown root development.Loss-of-function of Gn1 a/Os CKX2 led to cytokinin accumulation in the crown root tip and accelerated the development of adventitious roots. Gene pyramiding between the null gn1 aR498 allele with two gain-of-function alleles, STRONG CULM 2(SCM2)and SCM3, further improved lodging resistance.Moreover, Gn1 a/Os CKX2 had minimal influence on overall rice quality. Our research thus highlights the distinct genetic components of lodging resistance of HPT varieties and provides a strategy for tailormade crop improvement of both yield and lodging resistance in rice.

A deep learning-integrated micro-CT image analysis pipeline for quantifying rice lodging resistance-related traits

Lodging is a common problemin rice,reducing its yield andmechanical harvesting efficiency.Rice architecture is a key aspect of its domestication and a major factor that limits its high productivity.The ideal rice culm structure,includingmajor_axis_culm,minor axis_culm,andwall thickness_culm,is critical for improving lodging resistance.However,the traditionalmethod ofmeasuring rice culms is destructive,time consuming,and labor intensive.In this study,we used a high-throughput micro-CT-RGB imaging system and deep learning(SegNet)todevelopa high-throughputmicro-CTimageanalysis pipelinethatcanextract 24 riceculmmorphological traits and lodging resistance-related traits.When manual and automatic measurements were compared at themature stage,the mean absolute percentage errors for major_axis_culm,minor_axis_culm,andwall_thickness_culmin 104 indica rice accessionswere 6.03%,5.60%,and 9.85%,respectively,and the R^(2) valueswere 0.799,0.818,and 0.623.We also builtmodels of bending stress using culmtraits at the mature and tillering stages,and the R^(2) values were 0.722 and 0.544,respectively.The modeling results indicated that this method can quantify lodging resistance nondestructively,even at an early growth stage.In addition,we also evaluated the relationships of bending stress toshoot dryweight,culm density,and drought-related traits and found that plants with greater resistance to bending stress had slightly higher biomass,culm density,and culm area but poorer drought resistance.In conclusion,we developed a deep learning-integrated micro-CT image analysis pipeline to accurately quantify the phenotypic traits of rice culms in4.6 min per plant;this pipeline will assist in future high-throughput screening of large rice populations for lodging resistance.