Number Of Large Vascular Bundles Research Articles

Effect of stem structural characteristics and cell wall components related to stem lodging resistance in a newly identified mutant of hexaploid wheat (Triticum aestivum L.).

In wheat, lodging is affected by anatomical and chemical characteristics of the stem cell wall. Plant characteristics determining the stem strength were measured in lodging tolerant mutant (PMW-2016-1) developed through mutation breeding utilizing hexaploid wheat cultivar, DPW-621-50. Various anatomical features, chemical composition, and mechanical strength of the culms of newly developed lodging-tolerant mutant (PMW-2016-1) and parent (DPW-621-50), were examined by light microscopy, the Klason method, prostate tester coupled with a Universal Tensile Machine, and Fourier Transform Infrared Spectroscopy. Significant changes in the anatomical features, including the outer radius of the stem, stem wall thickness, and the proportions of various tissues, and vascular bundles were noticed. Chemical analysis revealed that the lignin level in the PMW-2016-1 mutant was higher and exhibited superiority in stem strength compared to the DPW-621-50 parent line. The force (N) required to break the internodes of mutant PMW-2016-1 was higher than that of DPW-621-50. The results suggested that the outer stem radius, stem wall thickness, the proportion of sclerenchyma tissues, the number of large vascular bundles, and lignin content are important factors that affect the mechanical strength of wheat stems, which can be the key parameters for the selection of varieties having higher lodging tolerance. Preliminary studies on the newly identified mutant PMW-2016-1 suggested that this mutant may possess higher lodging tolerance because it has a higher stem strength than DPW-621-50 and can be used as a donor parent for the development of lodging-tolerant wheat varieties.

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

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

Multiple areas investigation reveals the genes related to vascular bundles in rice

BackgroundThe vascular bundle in the panicle neck is a crucial trait in rice (Oryza sativa) production that differs between the indica and japonica subspecies. However, the effect of indica/japonica genetic background on the vascular bundles remains unknown.ResultsA series of recombinant inbred lines (RILs) derived from a cross between japonica and indica were planted in three areas. High-throughput sequencing was conducted to determine the indica pedigree percentage and for quantitative trait locus (QTL) analysis. The indica pedigree affected the number of large vascular bundles (LVBs), but not the number of small vascular bundles (SVBs). QTL analysis identified a locus (qLVB9) that was pleiotropic for both LVBs and SVBs in all three areas, and qLVB9 appeared synonymous with DENSE AND ERECT PANICLE 1 (DEP1). Using CRISPR/Cas9 gene editing and gene overexpression technology, we confirmed that the truncated dep1 allele increased the number of LVBs, and resulted in LVBs more closely associated to the indica pedigree. RNA sequencing showed that the truncated dep1 allele downregulated the AP2-like gene family. The double mutant for the DEP1 and AP2-like genes (OsAP2–39) showed decreased endogenous abscisic acid (ABA) level and insensitivity to exogenous ABA treatment, confirming that both DEP1 and OsAP2–39 are involved in the ABA response mechanism.ConclusionsThe present study showed the qLVB9/DEP1 affects LVBs, and involved in ABA signaling via regulating the AP2-like gene family. These results offer new insights into the function of qLVB9/DEP1 in rice.

Characterization of the relationship between vascular bundles features and indica-allelic frequency using a seventh filial generations of indica × japonica rice crosses

The quality and yield of rice are influenced by vascular bundles and highly significant differences about size and number of vascular bundles can be found among rice subspecies. In this study, we divided a series of recombinant inbred lines, which were derived from a cross between the indica variety ‘Luhui 99’ and the japonica variety ‘Shennong 265’ into pre-indica, intermediate and pre-japonica groups using subspecies-specific markers. We completed an in-depth analysis of vascular bundles characteristics at different panicle positions. The results showed that the number of large vascular bundles (LVBs) and the ratio of the number of LVBs to the number of primary branches (V/R ratio) of the three groups was ranked as pre-indica > intermediate > pre-japonica. However, a large variation in the number of LVBs and V/R ratio was observed inside each group. Increases in the LVBs and the V/R ratio did not result in increased numbers of primary branches, but led to an increase in the number of secondary branches. With the increase in the frequency of indica-allelic markers, the differences in the grain setting rate and 1000-grain weight among the upper, middle and lower panicle sections became significant. Thus, we concluded that crosses between subspecies, followed by selection of the vascular bundle related traits and indica pedigree, can optimize the number of LVBs and the frequency of indica alleles. The simultaneous increase in both LVB and primary branch numbers, which might lead to greater rice yields, and may be a goal for breeders and scientists.

Morpho-anatomical traits of two lowest internodes related to lodging resistance in selected genotypes of Triticum

Abstract The cross-sections of first and second internodes were analyzed under a light and fluorescence microscopes in six varieties of Triticum spelta, two varieties of T. polonicum, and one variety of T. aestivum. The morphometric parameters of stem cross-sections were measured. The analyzed wheats were characterized by significant differences in traits associated with lodging resistance ie: internode diameter, lumen diameter, stem wall thickness, mechanical layer thickness, area of transverse section, and area of lumen for the first and second internode and between the internodes. In all varieties, the values of internode diameter, lumen diameter, area of transverse section and area of lumen were higher for the second internode than for the first internode, whereas the reverse was reported for stem wall thickness and mechanical layer thickness The results of the principal component analysis and section modulus values revealed similarities between spring spelt Wirtas and Rubinas and between common wheat Kontesa and winter spelt Poeme and Epanis. The number of large vascular bundles varied across the studied varieties. The average number of vascular bundles in common wheat Kontesa was significantly higher than in spring spelt Rubinas and Wirtas and significantly lower than in Polish wheat Pol-3 and winter spelt Epanis and Poeme.

Genetical and Physiological Basis of Plant Type Model of Erect and Large Panicle Japonica Super Rice in Northern China

The historical changes in rice yields across China were explored. The physiological mechanisms and genetic basis of the erect and large panicle super-high-yield plant type model for breeding japonica super rice were analyzed mainly on the panicle type, number of large vascular bundles (LVB) in the panicle neck, and the panicle type index (PTI). In the production point of view, we suggested that, for the breeding of super-high-yield japonica rice, the erect panicle types with more LVB numbers in the panicle neck and superior upper grains in the secondary branches would be the key factors. The information has potential significance in the rice breeding and productivity not only in China but also throughout the rice production areas of the world.

A gene controlling the number of primary rachis branches also controls the vascular bundle formation and hence is responsible to increase the harvest index and grain yield in rice

The quantitative trait locus controlling the number of primary rachis branches (PRBs) in rice was identified using backcrossed inbred lines of Sasanishiki/Habataki//Sasanishiki///Sasanishiki. The resultant gene was ABERRANT PANICLE ORGANIZATION 1 (APO1). Habataki-genotype segregated reciprocal recombinant lines for the APO1 locus increased both the number of PRB (12-13%) and the number of grains per panicle (9-12%), which increased the grain yield per plant (5-7%). Further recombination dividing this region revealed that different alleles regulated the number of PRB and the number of grains per panicle. The PRB1 allele, which includes the APO1 open reading frame (ORF) and the proximal promoter region, controlled only the number of PRB but not the number of grains per panicle. In contrast, the HI1 allele, which includes only the distal promoter region, increased the grain yield and harvest index in Habataki-genotype plants, nevertheless, the ORF expressed was Sasanishiki type. It also increased the number of large vascular bundles in the peduncle. APO1 expression occurred not only in developing panicles but also in the developing vascular bundle systems. In addition, Habataki plants displayed increased APO1 expression in comparison to Sasanishiki plants. It suggests that APO1 enhances the formation of vascular bundle systems which, consequently, promote carbohydrate translocation to panicles. The HI1 allele is suggested to regulate the amount of APO1 expression, and thereby control the development of vascular bundle systems. These findings may be useful to improve grain yield as well as quality through the improvement of translocation efficiency.

Subspecies characteristics in filial generation of cross between indica and japonica rice under different environments

The recombinant inbred lines (RILs) population derived from the cross between “Zhongyouzao8” (hsien or indica) and “Fengjin” (keng or japonica) was grown in Liaoning and Sichuan Provinces to compare the subspecies characteristics under different environments. The results showed that the distribution of Cheng’s index was japonicalinous. The population was more japonicalinous in Sichuan than that in Liaoning as a whole. Further analysis indicated that indica and indica-cline in Sichuan were more indicalinous than those in Liaoning, japonica and japonica-cline in Sichuan were more japonicalinous than those in Liaoning. The effects of environment on six characteristics of Cheng’s index were different because of different characters, as well as on the correlations between the six characters, the Cheng’s index and the vascular bundle traits. For example, the length of the first and second rachis and leaf pubescence were more japonicalinous in Sichuan than in Liaoning, while the length/width ratio of spikelets and glume color at heading time were more indicalinous in Sichuan than in Liaoning. The vascular bundle characteristics of RILs in different environments changed remarkably. The number of large vascular bundles in panicle neck was less in Sichuan than in Liaoning, while the number of small vascular bundles in panicle neck and second top stem was greater in Sichuan than in Liaoning. The ratio of large to small vascular bundles in panicle neck decreased and the ratio of large vascular bundles between the second top stem and panicle neck increased in Sichuan. Though total trend was the vascular bundle ratio of large to small in indica was greater than that in japonica and the ratio of large vascular bundles in indica was less than that in japonica, it is not appropriate that the vascular bundle ratio of large to small and the ratio of large vascular bundles are regarded as the parameters for subspecies classification in rice. The vascular bundles characteristics from typical indica or japonica were recombined in the population derived from indica and japonica crossing.

Molecular dissection of the genetic relationships of source, sink and transport tissue with yield traits in rice.

Source, sink, and translocation capacity of assimilates play important roles during the formation of grain yield. The present study was conducted to characterize the genetic bases of traits representing source, sink and transport tissue, and their relationships with yield traits in rice, by analyzing QTLs for these traits and various ratios among them. The genetic materials were a recombinant inbred population derived from a cross between two indica cultivars Zhenshan 97 and Minghui 63, the parents of the most-widely grown hybrid rice in China. Using a linkage map that covers a total of 1,796 cM based on 221 molecular marker loci, a total of 81 QTLs were identified for the 15 traits studied (three leaf areas as the source, total spikelets per panicle as the sink, the number of large vascular bundles in the stem as transport tissue, three source to sink ratios, three transport tissue to source ratios, one transport tissue to sink ratio and three yield traits). The amount of variation explained by individual QTLs ranged from 1.12% to 24.14%. Five QTLs were identified to show interaction effects with the environment, which explained from 3.19% to 9.15% of the variation. The results showed that close linkage or pleiotropy is the genetic basis for the correlations of grain yield traits with source, sink, transport tissue and the various ratios among them. Of the 25 QTLs identified for source-sink-transport tissue trait, and 43 for various ratios, 8 and 22 QTLs, respectively, were mapped to the similar genomic blocks harboring QTLs for yield traits, especially for grain weight. Co-location of QTLs for yield traits with those for ratios among source, sink and transport tissue may provide a genetic explanation for the physiological expression of yield traits, and also suggest that improvement in ratios among source, sink and transport tissue may result in improvement in yield potential.

Characteristics of the Rice Plant with the Modified Flag Leaf from the First Bract

There is a contradictory point of view against Matsushima's diagnoses concerning the rice plant of which first bract was modified to the flag leaf. Therefore, the characteristics of the rice plant with the modified flag leaf were investigated. Three types were observed in the morphology of the neck node. The first type developed one or no primary rachis-branch and formed complete annular protuberance around the whole circumference of the neck node. This type is usually seen and is considered as a normal one. The second type had incomplete annular protuberance around the neck node and contained two subtypes. One resembled the normal type but a part of the circumference of the neck node was lacking in protuberance (Fig.1, A). The other had two or three primary rachis-branches on the neck node and a part of its circumference was lacking in protuberance (Fig. 1, B). The third type had twin or triplet whorled primary rachis-branches and had complete annular protuberance around the neck node (Fig. 1, G and D). The rice plant having a normal neck node did not possess a car or a bud in the axil of the flag leaf except for one which had a bud (Table 1). And the bud was true one of a tiller. Many plants with the other two types of neck nodes carried the axillary car or bud at the flag leaf (Tables 1, 2 and Fig. 2, A, B and C), though there were also a lot of plants having none (Tables 1 and 2). The morphology of the ear was as follows. A prophyll was absent (Fig. 3, A). Earlets were formed alternately on the two linear planes of the axis of the ear (Fig. 3, E). 0ne or two basal earlets had a bract-like structure, some of which were developed well (Fig. 3, E). One or two basal earlets had a bract-like structure, some of which were developed well (Fig. 2, B and Fig. 3, B). But it was bladeless (Fig. 3, B) and did not encircle the axis of the ear (Fig. 3, C and D). The axis of the ear was not hollow and showed a typical feature of an atactostele in the transverse section (Fig. 4, A). The number of large vascular bundles in the axis were two and almost one in the second internode and in the third one respectively, regardless of the number of diverged earlets (Table 3 and Fig. 4, A, B and C). The morphology of thirty-nine buds out of forty-three subtended by flag leaves of the rice plants with the second type or the third of the neck node was the undeveloped feature of the ear mentioned above. But about the remaining four, it was undistinguishable whether they were the buds of the ear or of a tiller, for they had only a leaf-primordium-like structure in which none was contained. The lowest elongated internode of the stem was longer or the number of elongated internodes was more by one in the rice plant of which neck node type was the second or the third, when compared with that of the first type (Table 4). From these results, it is considered that the ear in the axil of the flag leaf and the bud of which morphology was the undeveloped ear are not a tiller but a primary rachis-branch. Therefore, such the flag leaf as this is the one to which the first bract has been modified. And this results in the conclusion that the second type of the neck node morphology and the third one are the characteristic expression of the rice plant with the modified flog leaf from the first bract. Then, the problem still remains about rice plants which had undistinguishable buds or none in the axil of their flag leaves, although their neck node morphology was the second or the third type. But, as their feature of the stem internode elongation differed from the rice plant with he normal neck node and was the same as the one of which first bract had definitely been modified, those plants are also the rice plants of their first bract having been modified. [the rest omitted]

Studies on Large Vascular Bundles in Paddy Rice Plant and Panicle Formation : III. Relationships between the changes in number of Lage vascular bundles in the tillers and the panicle formation

1. The number of large vascular bundles in the first (highest) and second elongated internodes was almost invariable throughout each group of the main culms, the primary, the secondary, and the tertiary tillers. The so-called "the same rank-the same number" principle was applicable. The number of large vascular bundles in the first elongated internode varied according to the tiller tank. The number on the main culm was largest, followed in order by the primary tiller, the secondary tiller, and the tertiary tiller. The number decreased at the rate of one in order named. 2. The number of large vascular bundles in the blades of five high-ranking leaves on the main culm as well as on the tillers was almost invariable throughout the leaves of every rank. The so-called "the same rank-the same number" principle was applicable. The number of large vascular bundles in the flag leaf varied according to the tiller rank. The number on the main culm was largest, followed in order by the primary tiller, the secondary tiller, and the tertiary tiller. The number decreased at the rate of one in order named. 3. Throughout the main culm, the primary tiller, the secondary tiller, and the tertiary tiller, there was an increasing tendency in the number of large vascular bundles in the flag leaf on such culm which possessed a lot of large vascular bundles in the first and second elongated internodes.

Studies on Large Vascular Bundles in Paddy Rice Plant and Panicle Formation : I. Relationships between the number of lage vascular bundles in the culm and the plant types

1. In case of early-maturing rice variety Honen-wase, the correlation coefficients between the number of large vascular bundles in the first (highest) internode and the number of the primary branches of the panicle, the number of paddies per panicle, the weight of a panicle were γ=0.903, γ=0.877 and γ=0.850, respectively. And a fairly intimate interrelationship (γ=0.948) was noticed between the number of the primary branches and the number of paddies per panicle. 2. As the difference between the number of large vascular bundles in the first elongated internode and that in the second elongated internode showed the same tendency with the difference in the number of panicles per hill, it was regarded that the ratios of the number of large vascular bundles in the first elongated internodes to that in the second elongated intermode displayed the plant types' own characteristics; that is, the ratios of panicle-number type varieties, biased panicle-number type varieties, medium panicle-number type varieties, biased panicle-weight type varieties, and panicle-weight type varieties, stood at 1:3, 1:2.75, 1:2.5, 1:2.25, and 1:2, respectively.

Effects of Gibberellin on the Morphogenesis in Rice Plants : 6. Effects of gibberellin on the development of vascular bundles in panicles.

1. This study was carried out to make clear the effects of gibberellin upon the development of vascular bundles in rice panicles. 2. Gibberellin was applied to a variety of paddy rice Sachikaze, at the concentration of 100 ppm mixed in nutrient solution, at the stage of panicle primordium differentiation. 3. It was cleared that the number of large vascular bundles in rachis and that of small ones in rachis and primary branches had been increased with the gibberellin treatment, though there had been no change in secondary branches and peduncles. 4. The increase of large and small vascular bundles in rachis was accompanied by the increase of primary branches, and the increase of small vascular bundles in primary branches was considered to be followed by that of secondary branches and peduncles. 5. The number of cells composing vascular bundle had been increased in both large and small vascular bundles at every portion with the treatment, and this tendency had been conspicuous acropetally to the distal region of primary branch. 6. Regarding to the number of cells in each element of vascular bundles, except parenchyma cells, the number of cells in every element, especially those of fibre and xylem vessels, had been increased by gibberellin. Sclerenchymatous cells could be foums remarkably not only in vascular bundle but also in the bundle sheath and the neighbourings. This tendency also had been conspicuous acropetally to the distal region of primary branch. 7. Based on the results previously obtained by the writers in which both the increase of spikelets in number and the occurrence of morphogenic abnormalities in spikelet were frequently found at the distal regions of panicle and primary branches, and on the results above mentioned, it was considered that the morphogenic effects of gibberellin on the panicle development should become conspicuous acropetally from base to tip in rice panicle.