Genus Rheum Research Articles

COMPARATIVE ANALYSIS OF THE ANATOMICAL AND MORPHOLOGICAL FEATURES OF RHEUM TATARICUM L. PLANTS FROM DIFFERENT ECOPOPULATIONS

There are about 60 species of the genus Rheum L. (Polygonaceae) distributed mainly in temperate and subtropical Asia, with the largest number (38 species, including 19 endemics) recorded in China. All species of the genus are used as medicinal plants. According to modern pharmacology, the most important property of the rhubarb root is regulation of the stomach and intestine function, due to its laxa-tive effect; rhubarb also has antipyretic properties and antioxidant activity. The high content of dietary fibers provides protection against cardiovascular diseases, and vitamin K is valuable for the prevention of osteoporosis. However, the active ingredients and their mechanism of action have not been sufficiently studied.Rheum tataricum L., known for its high resistance to drought, salinity, and lack of nutrients is the least studied species of wild rhubarb. The whole plant, and especially the leaves, contains several toxic compounds, in particular anthraquinone glycosides and calcium oxalate crystals. Here we present the results of a comparative analysis of the anatomical and morphological structure of Rh. tataricum plants from ecopopulations growing in the Balkhash and Karatal districts of the Almaty region. We identified the differences due to the weather and climatic conditions of the ecopopulations. It is important to note that many idioblasts containing calcium oxalate were found in the rhizomes of Rh. tataricum, which prevent animals from eating plants and getting poisoned. The number of idioblasts in the central circle of the Rh. tataricum rhizome was smaller in the Balkhash district than in the Karatal district, while the idioblasts were larger in size in the former district. The medicinal and nutritional value of Rh. tataricum growing in a semi-desert environment indicates a high potential of the species in plant breeding, medicine, and as a food source.

Studying the species distribution of rhubarbs (Rheum L.) in Kazakhstan

Critical processing of herbarium materials revealed the distribution in Kazakhstan of 10 species of the genus Rheum, including Rheum compactum L., R. wittrokii Lundstr., which are classified as rare and declining in number. R. altaicum Losinsk. was discovered – relict and endemic of Altai. To clarify the distribution in Kazakhstan and compile a summary of species of the genus Rheum, 143 herbarium sheets (1840 – 2024) from the Altai Botanical Garden (ABG), Institute of Botany (AA), and the digital herbarium of Moscow State University (MW) were reviewed and processed. 253 actual places of growth were identified for 10 species of rhubarb from the flora of Kazakhstan, belonging to 5 sections: Rhapontica A. Los., Deserticola Maxim., Orbicularia A. Los., Spiciformia A. Los., Ribesiformia A. Los. A high species diversity of rhubarb was established in the Dzungarian Alatau, Altai, Tarbagatai and Ile Kungei Alatau. Geographically, the most widespread are R. tataricum, R. nanum and R. wittrockii. The research made it possible to systematize, clarify and supplement information on the species diversity and distribution of the genus Rheum in the flora of Kazakhstan.

Seed morphometry of Rheum L. (Polygonaceae) species from Kazakhstan and its implications in taxonomy and species identification

Abstract. Sumbembayev AA, Lagus OA, Nowak S. 2023. Seed morphometry of Rheum L. (Polygonaceae) species from Kazakhstan and its implications in taxonomy and species identification. Biodiversitas 24: 4677-4692. In the article, the evaluation of morphometric and weight parameters of seeds of 7 species of the genus Rheum L. from Kazakhstan is presented, as well as an analysis of their biometric parameters from different ecological and geographical habitats. The purpose of the study was to determine the variability of the seeds of the studied taxa and the importance of the results in determining the taxonomic relationships within the genus. The external structure was described for all species of the genus. Seeds of all studied species are illustrated with photos and scale drawings, and their features are summarized in a table. Stable and taxonomically significant features were identified for the species of the section Ribesiformia, represented by R. cordatum and R. maximowiczii, allowing their identification. The correlation between seed metric parameters and environmental conditions of the site and growth area was established and found a significant relationship between morphometric data and most of the environmental factors studied. The low adaptive potential of rhubarb species in Kazakhstan and the species' narrow ecological range were found. The comparison of the results obtained with the taxonomic relationships and phylogeny of representatives of the genus are briefly discussed.

A chromosome-scale Rhubarb (Rheum tanguticum) genome assembly provides insights into the evolution of anthraquinone biosynthesis

Rhubarb is the collective name for various perennial plants from the genus Rheum L. and the Polygonaceae family. They are one of the most ancient, commonly used, and important herbs in traditional Chinese medicine. Rhubarb is a major source of anthraquinones, but how they are synthesized remains largely unknown. Here, we generate a genome sequence assembly of one important medicinal rhubarb R. tanguticum at the chromosome level, with 2.76 Gb assembled into 11 chromosomes. The genome is shaped by two recent whole-genome duplication events and recent bursts of retrotransposons. Metabolic analyses show that the major anthraquinones are mainly synthesized in its roots. Transcriptomic analysis reveals a co-expression module with a high correlation to anthraquinone biosynthesis that includes key chalcone synthase genes. One CHS, four CYP450 and two BGL genes involved in secondary metabolism show significantly upregulated expression levels in roots compared with other tissues and clustered in the co-expression module, which implies that they may also act as candidate genes for anthraquinone biosynthesis. This study provides valuable insights into the genetic bases of anthraquinone biosynthesis that will facilitate improved breeding practices and agronomic properties for rhubarb in the future.

The genome of the glasshouse plant noble rhubarb (Rheum nobile) provides a window into alpine adaptation

Glasshouse plants are species that trap warmth via specialized morphology and physiology, mimicking a human glasshouse. In the Himalayan alpine region, the highly specialized glasshouse morphology has independently evolved in distinct lineages to adapt to intensive UV radiation and low temperature. Here we demonstrate that the glasshouse structure – specialized cauline leaves – is highly effective in absorbing UV light but transmitting visible and infrared light, creating an optimal microclimate for the development of reproductive organs. We reveal that this glasshouse syndrome has evolved at least three times independently in the rhubarb genus Rheum. We report the genome sequence of the flagship glasshouse plant Rheum nobile and identify key genetic network modules in association with the morphological transition to specialized glasshouse leaves, including active secondary cell wall biogenesis, upregulated cuticular cutin biosynthesis, and suppression of photosynthesis and terpenoid biosynthesis. The distinct cell wall organization and cuticle development might be important for the specialized optical property of glasshouse leaves. We also find that the expansion of LTRs has likely played an important role in noble rhubarb adaptation to high elevation environments. Our study will enable additional comparative analyses to identify the genetic basis underlying the convergent occurrence of glasshouse syndrome.

Medical and medicinal importance of Rheum spp. collected from different altitudes of the Kashmir Himalayan range

Most of the plants are essential due to their medicinal properties and have contributed to the origin and evolution of many traditional herbal therapies. Rheum is also one of the famous and known medicinal plants of Kashmir Himalaya. It ranges from an altitude of 1700-5500 m. Its Roots are long and stout. The stem is erect, hollow, sulcate, glabrous, or strigose. It is native to Asia-Temperate to Asia-Tropical, from China to India, Nepal, and Pakistan. In India, its found in Himachal Pradesh, Jammu and Kashmir, and Uttar Pradesh. Rhubarb is the English name of the genus Rheum (family Polygonaceae). Emodi, Webbianum and Spiciforme are three species of Rheum found in Kashmir Himalaya. Rheum species are well-known medicinal plant and is found on high altitudes. Its leaves and stalks are taken as food and cooked as vegetables. It’s used as medicine and is generally proven more effective against certain ailments like antibacterial, anticancerous, anti-inflammatory, rheumatoid diseases, stomachache, and intestinal problems. It is also used for the treatment of indigestion, abdominal disorders, boils, wounds and flatulence. But Rheum has become endangered due to exploitation. Active compounds like aloe-emodin, rhein, emodin, chrysaphanol and physicion are found in this plant which is anti Cancerian agents. High molecular diversity is also observed in all the three species of Rheum.

Occurrence, Distribution, Conservation, Ethanobotanical and Pharmacological aspects of endangered medicinal herb belonging to Genus Rheum

Rheum is normally known by the name Indian rhubarb, an endangered species of Northern Himalaya and belongs to Polygonaceae family. It is stout perennial herb distributed through the northern Himalayas at a height of 2800 to 3600 M. Rhubarb is efficiently used in Unani, Ayurvedic and Chinese medicine system. Rhubarb is known to be a common ingredient in almost all Ayurvedic medicines related to gastrointestinal diseases. The common phytoconstituents of this species are derivatives of hydroxyanthraquinone like Emodin, Rhein, Aloe-emodin etc. Brief review of literature shows that the component Emodin has the anticancerous property and a great potential to inhibit cell proliferation. Rheum also has antimicrobial, antifungal and antibacterial activity. Along with medicinal uses, this herb is used in cosmetics, dyes and as food colouring agent. Rheum is highly diverse in its genetic constitutes. According to IUCN, this species is rapidly declining in its natural habitat. Thus the regeneration through tissue culture holds a major place for conservation; explants used for regeneration can be shoot tip or excised leaf. The only study about its genetic diversity and population structure in India is in Jammu and Kashmir which shows the way for study in other States also.

Phylogenomic and comparative analyses of Rheum (Polygonaceae, Polygonoideae)

AbstractSpecies of Rheum have high medicinal value, with the center of diversity in the Qinghai–Tibet Plateau (QTP) and adjacent regions. However, phylogenetic relationships of Rheum are still unclear due to fragment markers providing insufficient informative loci. Here, we sequenced and annotated plastomes of nine Rheum species, and compared the genome structure among the novel nine species along with three published species. Comparative analyses revealed that plastomes of Rheum share a relatively conserved structure. Five highly divergent regions (accD, ccsA, matK, ndhF, and ndhH) can be used as valuable molecular markers for further species delimitation and population genetic studies. Twenty‐two accessions representing 17 species were used for phylogenetic analysis, which generated a robust phylogenetic tree and revealed two major clades within Rheum. Phylogenetic results showed that glasshouse structures and cushions of Rheum are results of parallel evolution during adaptation to similar environments. Inconsistent tree topology between concatenated and coalescent methods was detected, implying that incomplete lineage sorting and hybridization may have occurred in the evolutionary history of Rheum. Divergence time estimation based on two fossil calibrations and three secondary calibrations revealed a Miocene to middle Oligocene origin of Rheum. Our study provides valuable genomic resources for the medicinally important genus Rheum, while gaining helpful insights into its systematics and evolution.

Integrating the rapid constituent profiling strategy and multivariate statistical analysis for herb ingredients research, with Chinese official rhubarb and Tibetan rhubarb as an example

The Chinese official rhubarb (COR), from the genus Rheum, is listed in the Chinese Pharmacopoeia, while many rhubarb plant sources include in the Tibetan rhubarb (TR) are not attributable to Chinese Pharmacopoeia. Tibetan rhubarb is widely used as a natural medicine in Tibet; however, the difference in plant endogenous phytochemicals between the COR and TR remains largely unclear. To establish a method for evaluating the chemical composition and metabolic difference between COR and TR. Using UHPLC-QTOF-MS/MS, we established a strategy to quickly and comprehensively identify the chemical components of COR and TR. Furthermore, multivariate statistical analysis was applied to identify the significant metabolic differences between the two. In total, 209 chemical compounds, including 51 anthraquinones, 44 stilbenes, 26 tannins, 52 acyl glycosides, and 36 other compounds, were identified using the data mining strategy. Importantly, 47 compounds may be the potential new compounds, while 35 significant metabolic differences were revealed between COR and TR. This study offers significant insight into the chemical composition and differences between COR and TR that could be used to develop their varieties and clinical applications.

Chemical analysis and bioactivity evaluation of the stem of Rheum tanguticum

Rhubarb (Dahuang in Chinese), belongs to the family Polygonaceae, genus Rheum, has been employed as a traditional Chinese medicinal material for a long time. Rheum officinale, R. palmatum, R. tanguticum, R. rhaponticum, R. ribes, R. franzenbachii, and R. rhabarbarum have been reported to possess many pharmacological active substances that are used to treat diseases. The petioles of R. rhabarbarum, R. ribes, R. rhaponticum are well-known vegetables in some regions of the world. Based on this folk application and active ingredients that may be present in stems, the present study was conducted to analyze the content of nutritional components and active secondary metabolism components, and evaluate the antimicrobial activity and antioxidant activity with prepared solvent extracts. Methods published by the Association of Official Analytical Chemistry (AOAC) was used to determine the total protein, crude fat, crude fiber, vitamin C, ash, and moisture contents. The results showed that the inflorescence stem of R. tanguticum contained a higher content of crude fiber (89.14%) and vitamin C (16.96%). The content of total protein and crude fat was 8.49% and 1.34% respectively. The results showed that the DPPH Radical Scavenging Activity of the extract had a concentration-dependent effect. The highest activity (83.4%) of the methanol extract sample was recorded at 1.0 mg/mL and the lowest activity, 15.56%, was recorded at 0.2 mg/mL. 0.485 mg/mL was needed to achieve a 50% toxicity. The flavonoid and total phenolic contents of the inflorescence stem of R. tanguticum were found to be 0.022 mg/g and 4.138 mg/g respectively. A concentration of 10 mg/mL successfully inhibited the growth of the pathogenic microorganisms, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus subtilis using the paper disc diffusion method. In summary, the results of this study confirm that the inflorescence stem of R. tanguticum contains some rich nutritional components and bioactive secondary metabolism components that are beneficial for human health as edible parts or processed products. The results of bioactivity evaluation in this study also showed that the inflorescence stem of R. tanguticum could be developed natural antioxidant and antibacterial agent as a potential resource. This may possibly provide a feasible solution for non-medicinal parts utilization.

Ethnobotanical Uses, Phytochemistry and Pharmacology of Different Rheum Species (Polygonaceae): A Review.

Today, there is an increased tendency to use herbal remedies. Rhubarb refers to several species of the genus Rheum L. in the Polygonaceae family. This species-rich genus is mainly distributed in Asian countries. Several medicinal effects have been attributed to the Rheum spp. in the traditional and modern medicine such as healing lungs, liver, kidney, womb and bladder diseases, cancer, diabetes, insect bites, relapsing fevers, diarrhea and constipation. Various in vitro, in vivo and clinical studies have investigated the therapeutic effect of extracts, fractions and pure compounds isolated from different species of this genus. Considering the positive findings, several pharmaceutical formulations containing rhubarb extract like capsules, drops, mouthwashes and different topical formulations are now present in the market. However, there are other traditional therapeutic effects of rhubarb that have not been studied yet and it is of great importance to perform confirmatory experiments or clinical investigations. The current review summarizes general information regarding botany, phytochemistry, ethnobotany and pharmacological aspects of Rheum spp. It is hoped that the present review could motivate subsequent research on the other medicinal properties of these plants that have been neglected until today.

Typification of three Linnaean names in the genus Rheum (Polygonaceae)

AbstractThree Linnaean names in the genus Rheum are lectotypified: R. compactum, R. palmatum and R. undulatum.

Application of multifunctional compositions based on Rheum rhaponticum L. extracts for the elaboration of plant protection products

Relevance.Extract-based compositions, combining various types of biological activity were created and tested, to reveal the potential of genus Rheum (Polygonaceae)plants bioactive substances. The aim of the work was to determine the composition of bioactive substances in R. rhaponticum L. plants extracts and assess the possibility of their use as a means of protecting vegetable plants from powdery mildew.Materials and methods. The methods of cultivation and research of R.rhaponticum plant materials was carried out at the Institute of Genetics, Physiology and Plant Protection, Chisinau, Republic of Moldova (2012-2019). The subject of our study the bioactive substances of rhubarb roots and leaves were used. Results.The localization zones of anthracene derivatives were identified: in the main parenchyma of the secondary cortex and the parenchyma of the core rays of the rhubarb root. The amount of flavonoids and phenols in the root extract is 2 times more than in the leaf extract. To study the fungicidal and stimulating properties of rhubarb root extract in the control of powdery mildew, we conducted studies in a greenhouse on vegetable plants using artificial infection of seedlings. It was found that the chlorophyll transmittance index of leaves treated with rhubarb root extract increases until the concentration of the extract (R) reaches 1.5% (157.3 rel. units)(In the control – 119.2 rel. units). With increasing concentration of the extract to 2%, the chlorophyll index falls 1.2 times lower than the control values. The highest immunostimulating and fungicidal activity, intensifying with the addition of rhubarb leaf extract, was shown by rhubarb root extract. Its biological effectiveness was high at any intervals between treatment and infection (4 and 72 hours), and was directly proportional to concentration. Adding rhubarb leaf extract to the rhubarb root extract enhances the activity of the composition, and the risk of developing pesticide resistance among plant pathogens decreased.

ANTHRAQUINONES AND BIOLOGICAL ACTIVITY OF SPECIES OF THE GENUS RHEUM L. (POLYGONACEAE) (REVIEW)

The review of materials on the composition and biological activity of anthraquinones of species of the genus Rheum L. The most well-studied are the representatives of "forest rhubarb", which evolved in the forests of Central and Northern China: Rheum palmatum L., R. officinale Baill., R. emodi Wall. ex Meissn., R. rhabarbarum L. (= R. undulatum L.) and R. compactum L. (= R. rhaponticum L.). The official rhubarb is the Tungut rhubarb R. palmatum L. var. tanguticum Regel, known on the international pharmaceutical market as "Chinese rhubarb". The main aglykones of rhubarb anthraquinones are chrysofanol, emodin, aloe-emodin, fisсion and rhein. Particular attention is paid to various aspects of their impact on the processes that accompany oncological diseases. Emodin was found to inhibit cell proliferation, induce apoptosis induction, and prevent metastases. Emodin and aloe-emodin have high cytotoxic activity against oral squamous cell carcinoma and salivary gland cancer. Rhein inhibits the absorption of glucose in tumor cells and leads to their death. Anthraquinone glycosides, in contrast to aglycons, exhibit moderate cytotoxic activity. Other types of biological activity have been investigated - antimicrobial, antiviral, immunomodulating, antioxidant, molluscicidal etc. It follows from the presented materials that species of the genus Rheum containing anthracene derivatives are promising for practical use and further study.

Adaptive evolution of the rbcL gene in the genus Rheum (Polygonaceae)

ABSTRACTRapid putative radiations of Rheum might be caused by the recent uplifts of the Qinghai–Tibetan Plateau and the quaternary climate oscillations. To better understand the molecular adaptation associated with Rheum radiation, in this study, the adaptive evolution of the chloroplast rbcL gene was analysed using the Phylogenetic Analysis Program. The results showed that two amino acid residues (75F, 203I) were under positive selection. The spatial analysis indicated that the site (75F) was located in the β-sheet of the N-terminal loops involved in subunit interactions in the L8S8 molecule, and the site (203I) was in the α/β-barrel active centre located on the C-terminal domain of the large subunit of Rubisco. These results suggest that potential positive selection in rbcL might have played an important role in the adaption of Rheum species to the extreme environments in Qinghai–Tibetan Plateau regions, and different species lineages might have been subjected to different selective pressures.

Rapid identification and simultaneous analysis of multiple constituents from Rheum tanguticum Maxim. ex Balf. by UPLC/Q-TOF-MS

Rhubarb contains biologically active compounds such as anthraquinones, anthrones, stilbenes and tannins. A rapid and efficient UPLC/Q-TOF-MS/MS method was developed and applied towards identifying the constituents of Rheum tanguticum Maxim. ex Balf. for the first time. Chemical constituents were separated and investigated by UPLC/Q-TOF-MS/MS in the negative ion mode. The ESI-MS2 fragmentation pathways of four types of compounds were interpreted, providing a very useful guidance for the characterisation of different types of compounds. Based on the exact mass information, fragmentation characteristic and LC retention time of 7 reference standards, 30 constituents were tentatively identified from the methanol extract of R. tanguticum. Among them, seven compounds were described for the first time from R. tanguticum and two from the genus Rheum were described for the first time. The analytical tool used here is valuable for the rapid separation and identification of multiple and minor constituents in methanol extracts of R. tanguticum.

Efficacy of Aqueous and Methanolic Extracts of Rheum Spiciformis against Pathogenic Bacterial and Fungal Strains.

Rheum spiciformis is a newly identified edible medicinal plant of genus Rheum. The plant is used to treat various diseases on traditional levels in Kashmir Valley, India. To evaluate the phytochemical screening, antibacterial and antifungal potential of aqueous and methanolic extracts of Rheum spiciformis, a traditionally used edible medicinal plant. Methanolic and aqueous extracts of Rheum spiciformis were tested for their antimicrobial activities against six bacterial strains namely Bacillus subtilis, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus vulgaris and Escherichia coli and four fungal strains Penicillium chrysogenum, Aspergillus fumigatus, Candida albicans and Saccharomyces cerevisiae. The susceptibility of microbial strains to the two extracts was determined using agar well diffusion method. Phytochemical screening was carried out by using various standard procedures. Methanolic extract showed potent antimicrobial activity as compared to aqueous extract at the concentrations of 10, 30, 50, 80 and 100mg/ml. The most susceptible bacterial strains were Staphylococcus aureus with zone of inhibition (25±0.10mm), Klebsiella pneumonia (23±0.25mm), Proteus vulgaris (22±0.10mm) at the concentration of 100mg/ml. Aqueous extracts at the higher concentration were found effective against Proteus vulgaris and Bacillus subtilis with zone of inhibition (17±0.24mm) and (17±0.10mm), respectively. Among fungal strains the most susceptible were Aspergillus fumigatus (21±0.10mm), Saccharomyces cerevisiae (20±0.20mm) and Penicillium Chrysogenum (17±0.15mm) at the concentration of 100mg/ml methanol extract. The zone of inhibition for aqueous extract against fungal strains ranged between 14±0.13mm to 16±0.19mm at the highest concentration of plant extract. Phytochemical analysis revealed the presence of various secondary metabolites like flavonoids, saponins, volatile oils, phenols, steroids, terpenoids and alkaloids. Our results indicate that this plant has enough potential to serve as an excellent candidate for obtaining antimicrobial compounds to combat bacterial and fungal infections.

Morphological variation in leaf dissection of Rheum palmatum complex (Polygonaceae).

Aims Rheum palmatum complex comprises all taxa within section Palmata in the genus Rheum, including R. officinale, R. palmatum, R. tanguticum, R. tanguticum var. liupanshanense and R. laciniatum. The identification of the taxa in section Palmata is based primarily on the degree of leaf blade dissection and the shape of the lobes; however, difficulties in species identification may arise from their significant variation. The aim of this study is to analyze the patterns of variation in leaf blade characteristics within and among populations through population-based sampling covering the entire distribution range of R. palmatum complex.MethodsSamples were taken from 2340 leaves from 780 individuals and 44 populations representing the four species, and the degree of leaf blade dissection and the shape of the lobe were measured to yield a set of quantitative data. Furthermore, those data were statistically analyzed.Important FindingsThe statistical analysis showed that the degree of leaf blade dissection is continuous from lobed to parted, and the shape of the lobe is also continuous from broadly triangular to lanceolate both within and between populations. We suggested that taxa in section Palmata should be considered as one species. Based on the research on the R. palmatum complex, we considered that the quantitative characteristics were greatly influenced by the environment. Therefore, it is not reliable to delimitate the species according to the continuously quantitative vegetative characteristics.

Multiple ITS Copies Reveal Extensive Hybridization within Rheum (Polygonaceae), a Genus That Has Undergone Rapid Radiation

BackgroundDuring adaptive radiation events, characters can arise multiple times due to parallel evolution, but transfer of traits through hybridization provides an alternative explanation for the same character appearing in apparently non-sister lineages. The signature of hybridization can be detected in incongruence between phylogenies derived from different markers, or from the presence of two divergent versions of a nuclear marker such as ITS within one individual.Methodology/Principal FindingsIn this study, we cloned and sequenced ITS regions for 30 species of the genus Rheum, and compared them with a cpDNA phylogeny. Seven species contained two divergent copies of ITS that resolved in different clades from one another in each case, indicating hybridization events too recent for concerted evolution to have homogenised the ITS sequences. Hybridization was also indicated in at least two further species via incongruence in their position between ITS and cpDNA phylogenies. None of the ITS sequences present in these nine species matched those detected in any other species, which provides tentative evidence against recent introgression as an explanation. Rheum globulosum, previously indicated by cpDNA to represent an independent origin of decumbent habit, is indicated by ITS to be part of clade of decumbent species, which acquired cpDNA of another clade via hybridization. However decumbent and glasshouse morphology are confirmed to have arisen three and two times, respectively.ConclusionsThese findings suggested that hybridization among QTP species of Rheum has been extensive, and that a role of hybridization in diversification of Rheum requires investigation.

In vitro micro propagation of Rheum explants supplemented with various types of growth hormones

Rheum species is a perennial stout herb, distributed in the temperate and sub tropical regions of Himalaya from Kashmir to Sikkim . The genus Rheum have been domesticated as medicinal plants for human consumption as its roots and stem are rich in anthraquinones such as Emodin and Rhein.Standardization of protocol for the micro propagation of Rheum using different types of explants and culture media supplemented with various types of growth hormones was carried out. Different parts (seeds, leaves, shoots and rhizomes) of Rheum were used as explants for tissue culture. These explants were first washed in laboline and tween 20 and after surface sterilization using different chemical sterilents, were cultured on different media and in combinations of phytohormones. All the explants showed good germination response with whole plant and roots exhibited about (98%) response each while as seeds exhibited only 95% germination.