Rhizome Buds Research Articles

An integrated targeted metabolome of phytohormones and transcriptomics analysis provides insight into the new generation of crops: Polygonatum kingianum var. grandifolium and Polygonatum kingianum.

Huangjing is becoming a new generation of crop. Polygonatum kingianum var. grandifolium (XHJ) is a variant of P. kingianum (DHJ), and they are treated as Huangjing. Unlike other Polygonatum species, the rhizome bud of XHJ can germinate both in spring and autumn, which contributes to its high rhizome yield. However, the molecular mechanism of the autumn shooting of XHJ was still unknown. In the present study, cellular observation, comparative targeted metabolome of phytohormones, and transcriptome analysis between XHJ and DHJ in autumn were conducted. Interestingly, 'Diterpenoid biosynthesis' (ko00904) and 'Plant hormone signal transduction' (ko04075) were commonly enriched by differentially accumulated phytohormones (DAPs) and differentially expressed genes (DEGs) in all tissues, which indicated the high auxin content, low cytokinin (CTK) content, and low abscisic acid/gibberellin (ABA/GA) ratio might contribute to the XHJ rhizome buds' differentiation and germination in autumn. Moreover, according to the weighted gene co-expression network analysis (WCGNA), transcript factors (TFs) related to auxin, CTK, GA, and jasmonic acid (JA) metabolism were screened, such as AP2/ERFs, WRKY, and NAC, which deserve further research. In conclusion, we comprehensively illustrated the mechanism of XHJ natural autumn shooting through cytological, metabolic, and transcriptomic analysis, which improves our understanding of the high yield of XHJ rhizomes and the diversity of shooting mechanisms in Polygonatum to lay the foundation for the further development of the Huangjing industry.

Uncovering PheCLE1 and PheCLE10 Promoting Root Development Based on Genome-Wide Analysis.

Moso bamboo (Phyllostachys edulis), renowned for its rapid growth, is attributed to the dynamic changes in its apical meristem. The CLAVATA3/EMBRYO SURROUNDING REGION-RELATED (CLE) family genes are known to play crucial roles in regulating meristem and organ formation in model plants, but their functions in Moso bamboo remain unclear. Here, we conducted a genome-wide identification of the CLE gene family of Moso bamboo and investigated their gene structure, chromosomal localization, evolutionary relationships, and expression patterns. A total of 11 PheCLE genes were identified, all of which contained a conserved CLE peptide core functional motif (Motif 1) at their C-termini. Based on Arabidopsis classification criteria, these genes were predominantly distributed in Groups A-C. Collinearity analysis unveiled significant synteny among CLE genes in Moso bamboo, rice, and maize, implying potential functional conservation during monocot evolution. Transcriptomic analysis showed significant expression of these genes in the apical tissues of Moso bamboo, including root tips, shoot tips, rhizome buds, and flower buds. Particularly, single-cell transcriptomic data and in situ hybridization further corroborated the heightened expression of PheCLE1 and PheCLE10 in the apical tissue of basal roots. Additionally, the overexpression of PheCLE1 and PheCLE10 in rice markedly promoted root growth. PheCLE1 and PheCLE10 were both located on the cell membrane. Furthermore, the upstream transcription factors NAC9 and NAC6 exhibited binding affinity toward the promoters of PheCLE1 and PheCLE10, thereby facilitating their transcriptional activation. In summary, this study not only systematically identified the CLE gene family in Moso bamboo for the first time but also emphasized their central roles in apical tissue development. This provides a valuable theoretical foundation for the further exploration of functional peptides and their signaling regulatory networks in bamboo species.

Callus induction of red ginger (Zingiber officinale var. rubrum) with 2,4-D and Kinetin combination to enhance total phenolic and flavonoid content

Abstract Plant tissue culture perform as in vitro technique which use any parts of plants under environmental and nutritional control. Tissue culture provides a competitive systems for effective secondary metabolites production, including in red ginger which has many functional properties with high demand in health and pharmaceutical sectors. This study aims to develop an appropriate procedure to cultivate red ginger with in vitro technique to enhance its phenolic and flavonoid content. The rhizome buds were use as explants for callus induction by MS medium with some combination of 2,4-D and kinetin (1:0; 1:1; 1:5; and 5:1). The 70% ethanol, 5,25% sodium hypochlorite, and 10% povidone iodine were used for surface sterilization of bud explants. The result reveals that in 1:0 combination of 2,4-D and Kinetin, the compact callus were initiated on day-16. The other three combinations showed shorter callus forming time in day-14 and they were friable. The 1:1 combination showed the highest percentage (70%) of callus formation compared to other three combinations. In this combination also indicated no contamination occurs. From this in vitro tissue culture, the methanolic extract of callus obtained highest total phenolic content (204,793 µg/mL) than rhizome (130.77 µg/mL). Though, the total flavonoid content of callus extract (0,289 µg/mL) was lower than rhizome extract (6.74 µg/mL). This study showed that the in vitro tissue culture was quite appropriate to enhance total phenolic content in red ginger, although not at the flavonoid content.

Responses of belowground bud bank density of geophytes to environmental perturbations: a meta-analysis

Abstract A belowground bud bank is a collection of asexual propagules produced by the underground storage organs of geophytes. Renewal through belowground bud banks is the main reproductive strategy of geophytes. The belowground bud bank density reflects the potential renewal capacity of geophyte communities. However, the effects of different perturbation regimes and habitats on the belowground bud bank density of geophytes are not comprehensively understood. Moreover, whether different types of belowground bud banks respond differently to perturbations is still unclear. For this meta-analysis, relevant papers on the effects of environmental perturbations on the belowground bud bank density of geophytes were systematically collected. The cumulative effect size of different perturbation regimes and habitats on belowground bud banks among different bud types was analyzed. Overall, the effect of environmental perturbations on belowground bud bank density was small, which may result from opposite or fluctuating responses of bud banks to different perturbations. Drought negatively affected bud bank density. Environmental perturbations decreased rhizome bud density but increased tiller bud density. In wetlands, perturbations decreased belowground bud bank density. However, no significant effect was found for other habitat types. In general, belowground bud banks of geophytes are highly resistant and resilient. Changes in belowground bud bank density depend on the type of perturbations, the habitats in which plants are distributed and the type of bud banks.

High frequency in vitro multiplication of polygonatum verticillatum (l.) All. From rhizome bud explants

This work aims to develop a rapid protocol for the in vitro establishment of Polygonatum verticillatum (L.) All., an astounding medicinal herb of Astavarga group of plants. Successful in vitro establishment was achieved utilizing rhizome bud segments of approx. 0.5 to 1.0 cm size as explants. Sterilized explants were cultured on MS medium containing graded concentration of different plant growth regulators used either singly or in various combinations. Maximum (85±10.0%) per cent shoot induction with maximum shoot length (6.50 ± 0.11cm) were recorded in TDZ (2.0 mg/l) + NAA(1.0 mg/l) + GA3 (2.0 mg/l) supplemented MS medium. NAA (1.0 mg/l) + Kn (0.5 mg/l) and IBA(1.0 mg/l) supplemented full strength MS medium with 3% sugar showed highest 70 ± 5.0% rooting response.½ MS+1.5 % sucrose medium augmented with IBA (1.0mg/l) showed the maximum average number of roots per explants (12.8 ± 1.07) with highest root length(6.12±0.27 cm). After hardening plantlets were transferred to pots in glasshouse produced healthy plants with 56% survival rate. Bangladesh J. Bot. 53(1): 203-208, 2024 (March)

All-Year High IAA and ABA Contents in Rhizome Buds May Contribute to Natural Four-Season Shooting in Woody Bamboo Cephalostachyum pingbianense

To explore the regulation mechanism of endogenous phytohormones on rhizome bud germination in Cephalostachyum pingbianense, the contents of IAA, ABA, GA, and CTK in seven above- and under-ground bamboo structure components were determined using enzyme-linked immunosorbent assays (ELISA). The results showed that a higher content of IAA, GA, and CTK all year was found in above-ground components and dormant rhizome buds. Meanwhile, a higher ABA content in young shoots and a lower ABA content in the culm base and dormant rhizome buds were detected during the peak period of shooting. The amounts of emerging shoots and the grown bamboo culms were positively correlated with the content of IAA and the ratio of IAA/ABA and (IAA + CTK + GA)/ABA, while they were negatively correlated with the ratio of CTK/IAA in dormant rhizome buds. The all-year high contents of IAA (19–31 ng/g) and ABA (114–144 ng/g) in rhizome buds, as well as interactions among four hormones, may be the key physiological mechanisms to maintain rhizome bud germination throughout the year in C. pingbianense. As C. pingbianense is a special bamboo species of multi-season shoot sprouting, the above results may supplement scientific data for a comprehensive understanding of physiological mechanisms within the bamboo subfamily.

Belowground bud banks and land use change: roles of vegetation and soil properties in mediating the composition of bud banks in different ecosystems.

Belowground bud banks play integral roles in vegetation regeneration and ecological succession of plant communities; however, human-caused changes in land use severely threaten their resilience and regrowth. Although vegetation attributes and soil properties mediate such anthropogenic effects, their influence on bud bank size and composition and its regulatory mechanisms under land use change have not been explored. We conducted a field investigation to examine impacts of land use change on bud bank size and composition, vegetation attributes, and soil properties in wetlands (WL), farmlands (FL), and alpine meadow (AM) ecosystems in Zhejiang Province, China. Overall, 63 soil samples in close proximity to the vegetation quadrats were excavated using a shovel, and samples of the excavated soil were placed in plastic bags for onward laboratory soil analysis. The total bud density (1514.727 ± 296.666) and tiller bud density (1229.090 ± 279.002) in wetland ecosystems were significantly higher than in farmland and alpine meadow ecosystems [i.e., total (149.333 ± 21.490 and 573.647 ± 91.518) and tiller bud density (24.666 ± 8.504 and 204.235 ± 50.550), respectively]. While vegetation attributes critically affected bud banks in WL ecosystems, soil properties strongly influenced bud banks in farmland and alpine meadow ecosystems. In wetland ecosystems, total and tiller buds were predominantly dependent on soil properties, but vegetation density played a significant role in farmlands and alpine meadow ecosystems. Root sprouting and rhizome buds significantly correlated with total C in the top 0 - 10 cm layer of farmland and alpine meadow ecosystems, respectively, and depended mainly on soil properties. Our results demonstrate that land use change alters bud bank size and composition; however, such responses differed among bud types in wetland, farmland, and alpine meadow ecosystems.

Identification and Evolutionary Analysis of the Auxin Response Factor (ARF) Family Based on Transcriptome Data from Caucasian Clover and Analysis of Expression Responses to Hormones.

Caucasian clover (Trifolium ambiguum M. Bieb.) is an excellent perennial plant in the legume family Fabaceae, with a well-developed rhizome and strong clonal growth. Auxin is one of the most important phytohormones in plants and plays an important role in plant growth and development. Auxin response factor (ARF) can regulate the expression of auxin-responsive genes, thus participating in multiple pathways of auxin transduction signaling in a synergistic manner. No genomic database has been established for Caucasian clover. In this study, 71 TaARF genes were identified through a transcriptomic database of Caucasian clover rhizome development. Phylogenetic analysis grouped the TaARFs into six (1-6) clades. Thirty TaARFs contained a complete ARF structure, including three relatively conserved regions. Physical and chemical property analysis revealed that TaARFs are unstable and hydrophilic proteins. We also analyzed the expression pattern of TaARFs in different tissues (taproot, horizontal rhizome, swelling of taproot, rhizome bud and rhizome bud tip). Quantitative real-time RT-PCR revealed that all TaARFs were responsive to phytohormones (indole-3-acetic acid, gibberellic acid, abscisic acid and methyl jasmonate) in roots, stems and leaves. These results helped elucidate the role of ARFs in responses to different hormone treatments in Caucasian clover.

Metabolome and transcriptome analyses identify the underground rhizome growth through the regulation of rhizome apices in Panax ginseng

Panax ginseng C. A. Mey. is a well-known oriental medicine as a stimulant and dietary supplement. The ginseng rhizome, as one of the principal medicinal organs, plays an important role in aboveground organ growth and root development, although no studies on ginseng rhizome growth have been recorded. In this study, we identified that shoot apical meristem (SAM) was included in the rhizome bud, which could regulate the underground rhizome growth of ginseng. In microscopic examination, ginseng SAM included the central zone, peripheral zone, rib zone, and organizing center; secondary root structures were observed in ginseng main roots and lateral roots; primary root structures were observed in ginseng fibrous roots; rhizome had a stem structure with pith and discontinuous cambium. The metabolites in different underground ginseng organs were identified using ultra-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS), with oleanane (OA)-type ginsenosides accumulating primarily in the rhizome buds. In addition, ginseng rhizome buds contained a low level of 3-indoleacetonitrile (IAN, one type of auxin), a high amount of abscisic acid (ABA), and a high level of jasmonoyl-isoleucine (JA-Ile, active form of jasmonic acid). ABA and JA-Ile could drastically limit the shooting rate of ginseng embryonic calli, however IAN boosted the rooting rate. Furthermore, the expression of genes involved in ginsenoside biosynthesis, phytohormone production, and shoot stem cell regulatory pathways were studied. This is the first study of SAM in medicinal herbs, and we believe that the results may offer new information about the development of ginseng underground rhizomes.

Identification and characterization of the cupin_1 domain-containing proteins in ma bamboo (Dendrocalamus latiflorus) and their potential role in rhizome sprouting.

Cupin_1 domain-containing protein (CDP) family, which is a member of the cupin superfamily with the most diverse functions in plants, has been found to be involved in hormone pathways that are closely related to rhizome sprouting (RS), a vital form of asexual reproduction in plants. Ma bamboo is a typical clumping bamboo, which mainly reproduces by RS. In this study, we identified and characterized 53 Dendrocalamus latiflorus CDP genes and divided them into seven subfamilies. Comparing the genetic structures among subfamilies showed a relatively conserved gene structure within each subfamily, and the number of cupin_1 domains affected the conservation among D. latiflorus CDP genes. Gene collinearity results showed that segmental duplication and tandem duplication both contributed to the expansion of D. latiflorus CDP genes, and lineage-specific gene duplication was an important factor influencing the evolution of CDP genes. Expression patterns showed that CDP genes generally had higher expression levels in germinating underground buds, indicating that they might play important roles in promoting shoot sprouting. Transcription factor binding site prediction and co-expression network analysis indicated that D. latiflorus CDPs were regulated by a large number of transcription factors, and collectively participated in rhizome buds and shoot development. This study significantly provided new insights into the evolutionary patterns and molecular functions of CDP genes, and laid a foundation for further studying the regulatory mechanisms of plant rhizome sprouting.

Rhizosphere Microbe Affects Soil Available Nitrogen and Its Implication for the Ecological Adaptability and Rapid Growth of Dendrocalamus sinicus, the Strongest Bamboo in the World.

The interaction between soil microbes and plants has a significant effect on soil microbial structure and function, as well as plant adaptability. However, the effect of soil micro-organisms on ecological adaption and rapid growth of woody bamboos remains unclear. Here, 16S rRNA and ITS rRNA genes of rhizosphere micro-organisms were sequenced, and the soil properties of three different types of Dendrocalamus sinicus were determined at the dormancy and germination stages of rhizome buds. The result showed that each type of D. sinicus preferred to absorb ammonia nitrogen (NH4+-N) rather than nitrate nitrogen (NO3--N) and required more NH4+-N at germination or rapid growth period than during the dormancy period. In total, nitrogen fixation capacity of soil bacteria in the straight type was significantly higher than that in the introduced straight type, while the ureolysis capacity had an opposite trend. Saprophytic fungi were the dominant fungal functional taxa in habitat soils of both straight and introduced straight type. Our findings are of great significance in understanding how soil microbes affect growth and adaptation of woody bamboos, but also for soil management of bamboo forests in red soil.

Characterization of phytochemical profile of rhizome of artificial cultured Polygonatum sibiricum with multiple rhizome buds

Rhizome of Polygonatum sibiricum is both a renowned traditional Chinese remedy and a commonly consumed delicacy. Due to the escalating demand and excessive overexploitation, there has been a growing interest in the artificial cultivation of this plant in recent years. To assess the therapeutic benefits of artificially cultivated P. sibiricum, it is crucial to identify and classify its phytochemical components, which are the primary bioactive compounds found in its rhizome. In this study, the phytochemical profile of an artificially cultivated P. sibiricum rhizomes with multiple rhizome buds (ACM) was characterized by using untargeted UHPLC-Q-Orbitrap-MS based approach. In addition, two-wild-types P. sibiricum rhizomes, namely the wild-type with multiple rhizome buds (WTM) and the wild-type with single rhizome bud (WTS), were used for comparison. A total of 183 phytochemicals, including 20 alkaloids, 48 flavonoids, 33 phenolic acids, and 82 terpenoids, were tentatively identified. Generally, the phytochemical profile of ACM was comparable to that of WTM and WTS. In specific, most of the identified alkaloids and phenolic acids, and approximately half of the identified terpenoids, were not significantly different. Notably, several phytochemicals with potent therapeutic properties, such as epiberberine, laetanine, sinapic acid, curcumenol, were present in ACM. Additionally, artificial cultivation increased the abundance of geniposide and naringenin, which have been linked to cardioprotective effects. These findings provide valuable insights for the future utilization of artificially cultivated P. sibiricum.

Molecular identification and high fidelity micropropagation of shell ginger (Alpinia zerumbet)

Alpinia zerumbet is a medicinal and ornamental plant of the Zingiberaceae family cultivated in many parts of the world. The plant is medicinally important and often misidentified with closely related species. The objective of this work was to establish its DNA-based identity and a protocol for high-fidelity micropropagation to support the medicinal plant industry. PCR amplification and subsequent sequencing of RuBisCO large subunit (rbcL) and Maturase K (matK) gene successfully report its DNA barcode. In vitro shoots were induced the best from rhizome buds on Murashige and Skoog (MS) medium supplemented with 6.0 mg L−1 6-benzyl amino purine and 30 g L−1 sucrose. Microshoots were rooted well in MS medium amended with 1.5 mg L−1 naphthalene acetic acid. Plantlets were satisfactorily acclimated to soils maintained in a growth chamber and subsequently in the open air for 10–20 days. Analyzing eight random amplified polymorphic DNA and eight inter-simple sequence repeat primers resulted in 53 and 60 distinct bands, respectively. Uniform banding patterns suggest the genetic uniformity of the micropropagated plants. The results offer an accurate identification of A. zerumbet from any plant tissue. The micropropagation protocol would be helpful for economically feasible and environmentally sustainable exploitation of this valuable plant.

Soil Moisture Rather than Soil Nutrient Regulates the Belowground Bud Bank of Rhizomatous Species Psammochloa villosa in Arid Sand Dunes

In arid and semi-arid sand dune ecosystems, belowground bud bank plays an important role in population regeneration and vegetation restoration. However, the responses of belowground bud bank size and composition to sand burial and its induced changes in soil environmental factors have been rarely studied. In arid sand dunes of Northwestern China, we investigated belowground bud bank size and composition of the typical rhizomatous psammophyte Psammochloa villosa as well as three key soil environmental factors (soil moisture, total carbon and total nitrogen) under different depths of sand burial. Total buds and rhizome buds increased significantly with increasing burial depth, whereas tiller buds first increased and then decreased, with a peak value at the depth of 20–30 cm. Soil moisture increased significantly with sand burial depth, and was positively correlated with the number of all buds and rhizome buds. Soil total carbon concentration first increased and then decreased with sand burial depth, and total nitrogen concentration was significantly lower under deep sand burial than those at shallow depths, and only the number of tiller buds was positively correlated with soil total nitrogen concentration. These results indicate that soil moisture rather than soil nutrient might regulate the belowground bud bank of P. villosa, and that clonal psammophytes could regulate their belowground bud bank in response to sand burial and the most important environmental stress (i.e., soil moisture). These responses, as the key adaptive strategy, may ensure clonal plant population regeneration and vegetation restoration in arid sand dunes.

Regeneration pattern and genome-wide transcription profile of rhizome axillary buds after perennial rice harvest.

Perennial rice is a new type of rice that allows the harvest of rice for multiple years without growing new seedlings annually. This technology represents a green and sustainable agricultural production mode with many advantages for balancing agricultural ecology and food security. However, the differences in regeneration patterns between perennial and annual rice and the gene regulatory pathways of the apical dominance in axillary bud growth after harvest in perennial rice are still unclear. In this study, perennial rice (PR23) and annual rice (Chugeng28) were used to investigate axillary bud growth patterns before and after apical spike removal. After elimination of apical dominance at different development stages, perennial rice rhizome axillary buds at the compression nodes germinated more rapidly than others and developed into new seedlings. The axillary buds at the high-position nodes in annual rice grew faster than those at other nodes. Furthermore, the global gene expression patterns of PR23 rhizome buds at compression nodes grown for 1, 3, 4, and 5 days after apical spike removal were analyzed by transcriptome sequencing. Compared with the control buds without apical removal, 264, 3,484, 2,095, and 3,398 genes were up-regulated, and 674, 3,484, 1,594, and 1,824 genes were down-regulated in the buds grown for 1, 3, 4, and 5 days after apical spike removal, respectively. Trend analysis of the expressed genes at different time points was performed and co-expression network was constructed to identify key genes in rhizome axillary bud regrowth. The results showed that 85 hub genes involved in 12 co-regulatory networks were mainly enriched in the light system, photosynthesis-antenna protein, plant hormone signal transduction, ABC transporter and metabolic pathways, which suggested that hormone and photosynthetic signals might play important roles in the regulation of rhizome axillary bud regeneration in perennial rice. Overall, this study clarified the differences in the regeneration patterns of axillary buds between perennial and annual rice and provided insight into the complex regulatory networks during the regeneration of rhizome axillary buds in perennial rice.

Effects of nitrogen limitation on Leymus Chinensis clonal growth form and bud bank

Nitrogen is an important element which affects the growth and clonal growth of plant species in grassland. Leymus chinensis (Trin.) Tzvel is a dominant species in grasslands with a high nutritional quality; however, data on the effects of low nitrogen concentration on L. chinensis clonal growth strategy are limited. The aim of this study is to evaluate the response of clonal growth of L. chinensis to low nitrogen concentrations. The growth form and biomass allocation ratios of L. chinensis under different low nitrogen concentrations were evaluated, and the quantitative characteristics of three bud types were analyzed. The proportion of spreading ramets was favored by low nitrogen supply, indicating that L. chinensis under low nitrogen conditions primarily exhibits a guerrilla growth form, meaning a long mean spacer length and production of spreading ramets. Under limited nitrogen conditions, biomass distribution was mainly concentrated in underground organs (including the roots and rhizomes), while the high proportion of axillary rhizome buds suggested that L. chinensis grows primarily by occupying effective living spaces under low nitrogen conditions. The balance between two clonal growth form and the change in the proportion of different types of buds is an important strategy for L. chinensis to cope with nutrient limitations.

Deciphering the Ramet System of a Bamboo Plant in Response to Intensive Management

Intensive management is a common practice in bamboo plantations to ensure higher shoot yields. However, the effects of these management practices on ramet systems are understudied. A pot experiment was conducted to explore the process of propagation for potted bamboo seedlings (Phyllostachys praecox C. D. Chu et C. S. Chao “Prevernalis”) from a single mother bamboo to a ramet system exposed to a chronosequence of intensively managed bamboo forest soils. The ramet system of potted bamboo seedlings reached seven branching grades after two growth cycles. During ramet system expansion, the rhizome length and rhizome internodes decreased with increasing branching grade and the extension of intensive management periods. In the bud bank for each branching grade, the front branching grade was dominated by the bud output, which was conducive to consolidating the occupied living space. The back branching grade was dominated by bud input to continue rhizome penetration. With increasing branching, the mulching soil significantly inhibited rhizome bud germination and dormant bud accumulation. The mulching soil was not conducive to branch expansion in the ramet system, and ramet system expansion was predominantly based on the branching of the rhizome modules. With increasing branching and the extension of intensive management periods, rhizome branches decreased markedly. Our findings indicate that bamboo mulching inhibits branching and causes a differential reaction in branching types. The long-term mulching of bamboo forest soil was not conducive to the healthy and sustainable growth of bamboo. These results provide a basis for further research on the relationship between the bamboo ramet system and its productivity, as well as the population construction and maintenance mechanisms of bamboo ramet systems in the field.

Identification of LsPIN1 gene and its potential functions in rhizome turning of Leymus secalinus

BackgroundContinuous tilling and the lateral growth of rhizomes confer rhizomatous grasses with the unique ability to laterally expand, migrate and resist disturbances. They play key roles especially in degraded grasslands, deserts, sand dunes, and other fragile ecological system. The rhizomatous plant Leymus secalinus has both rhizome buds and tiller buds that grow horizontally and upward at the ends of rhizome differentiation and elongation, respectively. The mechanisms of rhizome formation and differentiation in L. secalinus have not yet been clarified.ResultsIn this study, we found that the content of gibberellin A3 (GA3) and indole-3-acetic acid (IAA) were significantly higher in upward rhizome tips than in horizontal rhizome tips; by contrast, the content of methyl jasmonate and brassinolide were significantly higher in horizontal rhizome tips than in upward rhizome tips. GA3 and IAA could stimulate the formation and turning of rhizomes. An auxin efflux carrier gene, LsPIN1, was identified from L. secalinus based on previous transcriptome data. The conserved domains of LsPIN1 and the relationship of LsPIN1 with PIN1 genes from other plants were analyzed. Subcellular localization analysis revealed that LsPIN1 was localized to the plasma membrane. The length of the primary roots (PRs) and the number of lateral roots (LRs) were higher in Arabidopsis thaliana plants overexpressing LsPIN1 than in wild-type (Col-0) plants. Auxin transport was altered and the gravitropic response and phototropic response were stronger in 35S:LsPIN1 transgenic plants compared with Col-0 plants. It also promoted auxin accumulation in root tips.ConclusionOur findings indicated that LsPIN1 plays key roles in auxin transport and root development. Generally, our results provide new insights into the regulatory mechanisms underlying rhizome development in L. secalinus.

Response of under-ground bud bank to degradation in an alpine meadows on the Qinghai-Tibet Plateau, China.

Exploring the diversity and formation mechanism of under-ground bud banks is essential for understanding the renewal of plant populations and community succession. However, there are few studies on the response of bud bank size and composition to different degradation gradients in alpine meadows. In view of this, we investigated the size and composition of bud bank under four degradation gradients (non-degraded:ND, lightly degraded:LD, moderately degraded:MD, and heavily degraded:HD) caused by overgrazing in a typical alpine meadow in Tibet, China, using a unit area excavation sampling method, and analyzed the correlation between above-ground plant community composition and bud bank density. Our results showed that: (i) in the ND alpine meadow, rhizome buds were dominant, in the LD, tiller buds were dominant, and in the MD, root-sprouting buds were dominant; (ii) total bud bank and cyperaceae bud density decreased with increasing degradation gradient, the density of leguminosae was insignificant in each degradation gradient, and the density of gramineae and forb were dominant in LD and MD meadows, respectively; (iii) total bud bank density was significantly and positively correlated with total above-ground biomass in the LD gradient, tiller bud density was significantly positively correlated with the species diversity index of above-ground vegetation under the ND gradient, rhizome bud density was significantly and positively correlated with total above-ground biomass in the LD gradient, and root-sprouting density was significantly negatively correlated with total above-ground biomass in ND meadows, but was significantly positively correlated with the species diversity index of the LD gradient. Therefore, our research shows that rhizome buds are more important in ND meadow habitats, tiller buds are more important in LD meadow habitats, and root-sprouting buds are more important in MD meadows. The response of bud banks to degradation gradient varies with different types of bud banks and different functional groups of plants, and the survival strategy of bud banks is of great value for community restoration and regeneration, which should be paid more attention to in subsequent alpine meadow research.

In Vitro Clonal Propagation of Korarima (Aframomum Corrorima (Braun) P.C.M. Jansen) on Improved Varieties of Bonga and Benchmajji

Korarima (Aframomum corrorima (Braun) P.C.M. Jansen) is a diploid, 2n = 48, monocious, perennial and aromatic herb species under family Zingiberaceae. It is a native plant used as a spice in regular Ethiopian dishes and locally used in traditional medicine. However, commercial exploitation of this crop is hampered due to poor rate of seed germination and slow multiplication rate of the rhizomes along with other agronomic predicaments. Thus, the present study was aimed at in vitro micro propagations of two Aframomum corrorima cultivars of Bonga1 and Benchmajji1. Based on the results, better response was observed in rhizome bud explants with the highest mean number of shoots per explants, 4.33±0.33 and 4.67±0.33 for cv. Bonga1 and Benchmajji1 respectively, whereas 3.33±0.33 and 3.00±0.00 for cv. Bonga1 and Benchmajji1 respectively on the MS medium supplemented with BA 2.0mg/l and KN 0.5 mg/l. For multiplication, the highest mean number of shoots per explants (4.67±0.33) was obtained from the MS medium supplemented with combination of 3.0mg/l BA and 0.5 mg/l KN for cv. Bonga1, and the highest mean number of shoots per explants (4.00±0.00) was obtained from the MS medium supplemented with 2.0mg/l BA from shoot tip explants. For rooting induction, the highest mean number of roots per explants (15.00±1.15) was obtained in the MS supplemented with 1.0mg/l NAA for cv. Bonga1, and the highest mean number of roots per explants (17.33±0.88) was observed in the MS supplemented with 1.5mg/l IBA and 2.0mg/l for genotype cv. Benchmajji1, but the highest root length was obtained in ex vitro rooting with sand and vermi-compost at ratio of 2:1 with 1mg/l IBA three times per a week. Keywords: In vitro clonal propagation, Shoot multiplication, Rooting induction and Ex-vitro DOI: 10.7176/JBAH/12-17-04 Publication date: September 30 th 2022