Castor Bean Seedlings Research Articles

Phytophthora species causing root and crown rot on castor bean (Ricinus communis) in Brazil

AbstractCastor bean (Ricinus communis) is a crop of great economic importance in Brazil. It is used for producing oil used in the manufacture of cosmetics and biodiesel. The genus Phytophthora contains pathogens with a wide range of host plants, including ornamentals, fruit and vegetable crops. Among the symptoms induced by Phytophthora species are collar and root rot. This study aimed to identify Phytophthora species causing collar and root rot in castor bean seedlings in the Federal District and test their pathogenicity. Samples of symptomatic plants were collected in four satellite cities in Distrito Federal, Brazil. Fourteen isolates were obtained, and they were initially identified through the morphology of reproductive structures. The isolates were subjected to molecular characterization using phylogeny of the sequences from the ITS region and the Cytochrome Oxidase II gene. Ten isolates of the pathogen were tested for pathogenicity on seedlings of two castor bean accessions and species known to be hosts of P. nicotianae. The isolates were identified as P. nicotianae (12 isolates) and P. palmivora (two isolates). In the pathogenicity test, all isolates were capable of causing disease in castor beans. The isolates of P. nicotianae and P. palmivora varied in pathogenicity to other plant species. This is the first report of P. nicotianae causing collar and root rot in castor bean in the Central‐West Region of Brazil. It is also the first report of P. palmivora causing diseases in castor beans in South America.

Uptake and transport of antibiotic kasugamycin in castor bean (Ricinus communis L.) seedlings.

Kasugamycin (KSM), an aminoglycoside antibiotic, has been widely used for the management of plant diseases, especially for the control of rice blast in Asia. However, its uptake mechanism and transport in plants are still obscure. The castor bean (Ricinus communis L.) seeding, a model plant for phloem transport, was used to study the mechanism of uptake and transport of KSM. Results showed that cotyledon-applied KSM could transport into the phloem and distributed in root and shoot of plant. The temperature, concentration, and pH had significant effects on the uptake of KSM, indicating that the uptake of KSM was mediated by an active carrier system. Compared with the control, competitive inhibitors of sugar transporters D-glucose, D-chiro-inositol, and phloridzin inhibited 71.03%, 67.95%, and 61.73% uptake of KSM, respectively. Energy inhibitor dinitrophenol (DNP) and carbonyl cyanide chlorophenylhydrazone (CCCP) also affected the uptake of KSM, and the inhibition rates were 34.23% and 48.06%. All the results showed that the uptake of KSM was mediated by a sugar transporter, and it could transport from shoot to root in plants via the phloem. The study preliminary elucidated the plant–microbe interactions in the context of the transport of microbial secondary metabolites in plants. It has certain significance for scientific application of antibiotics and biological control of plant diseases and provides theoretical basis for the development of bidirectional transport pesticides.

Integrated lipidomic and transcriptomic analysis reveals triacylglycerol accumulation in castor bean seedlings under heat stress

Heat stress is one of the most challenging environmental factors for plants, which have evolved various mechanisms to cope with it. However, the role of lipid remodeling caused by heat stress is not yet fully understood. Here, we integrated UPLC-QTOF/MS-based lipidomic and transcriptomic analyzes to uncover the molecular basis of lipid remodeling under heat stress in castor bean (Ricinus communis), an important non-edible oil crop. We detected 297 lipid compounds in castor bean seedlings, of which 54 displayed altered abundances under heat stress. In particular, polyunsaturated triacylglycerols (TAGs) (e.g., TAG54:6, TAG54:7, TAG54:8, and TAG54:9) and diacylglycerols (DAGs) (DAG36:6) significantly increased, while polyunsaturated monogalactosyldiacylglycerols (MGDGs) (MGDG34:3) markedly decreased. When heat stress was subsequently relieved, these lipid molecules recovered to their normal levels. We found that heat-induced TAGs primarily accumulate in the cytosol. Transcriptomic analysis indicated that polyunsaturated fatty acids (FAs) used for TAGs are not derived from de novo synthesis, but likely from the lipids remodeling via lipase activity, and are subsequently esterified into TAGs via diacylglycerol acyltransferase (DGAT). Our results suggest that TAGs may act as intermediates in lipid turnover and provide one mechanism by which plants respond to heat stress, broadening our understanding of how lipid remodeling functions in plant adaptation to heat stress.

Cultivable rhizobacteria improve castor bean seedlings root and plant growth in Pb–Zn treated soil

Culturable bacteria are widely used in the remediation of heavy metal-contaminated soil associated with different plants. In this study, a pot experiment of castor bean (Ricinus communis L.) was performed to determine the effect of culturable bacterial communities on the growth of castor bean, as well as their response to the presence of Pb and Zn during the 21-day incubation. The results indicated that the inoculation of the cultivable bacterial communities promoted plant growth, whether Pb/Zn-contaminated or not, and a well-developed root system was also detected in the bacterial community after treatment. Under heavy metal stress, the root surface area of castor bean decreased significantly, but after inoculation, it was close to the level of the normal (uncontaminated) samples. Sequence analysis at the phylum and genus taxonomic levels illustrated 13 identified phyla and 125 genera were observed in the control and Pb/Zn-contaminated soil. The input of contaminants affected the bacterial community structure, suggesting that although Proteobacteria, Bacteroidetes, and Actinobacteria were the dominant phyla in the two samples, the Ensifer and Cupriavidus genera were decreased in contaminated soil. However, Arcticibacter, a phosphate-solubilizing bacterium, was enriched by the Pb/Zn treatment. Compared with the control group, Pb and Zn exposure in the treatment group resulted in a new community structure. A microflora consisting of a number of microorganisms undergoing a long duration period of adaptation and symbiosis can possess systematic functions with high stabilities, so it has considerably high potential in intensifying the effect of phytoremediation.

Phloem Delivery of Fludioxonil by Plant Amino Acid Transporter-Mediated Polysuccinimide Nanocarriers for Controlling Fusarium Wilt in Banana.

Fusarium wilt disease poses a serious threat to the global production of bananas. The targeted delivery of fungicides to banana phloem tissues may offer new hope for controlling this hard-to-treat vascular disease. In this study, fludioxonil (FLU)-loaded glycine methyl ester-conjugated polysuccinimide nanoparticles (PGA) were prepared with a loading efficiency (LE) of 27.9%. The obtained nanoparticles (FLU@PGA) exhibited pH-sensitive controlled release, specifically under an alkaline pH in plant phloem. In vivo experiments in potted bananas demonstrated that FLU@PGA can achieve the downward delivery of FLU to banana rhizomes and roots after foliar application, reducing disease severity by 50.4%. The phloem transport studies showed that the phloem loading of FLU@PGA was involved in an active transport mechanism at the organ level (castor bean seedlings). The observation of fluorescein-5-isothiocyanate cadaverine-labeled PGA nanocarriers showed that they could be absorbed by mesophyll cells and loaded into vascular tissues through the symplastic pathway. Furthermore, the interaction of FLU@PGA with the plant amino acid transporter AtLHT1 was observed to enhance transmembrane uptake at the cellular level (Xenopus oocytes). These results suggested that the phloem-targeted delivery of fungicide by transporter-mediated nanocarriers could be a promising new strategy for the management of Fusarium wilt in bananas.

SHELTER BUILDING BY LARVAE OF PHYCITA DIAPHANASTAUDINGER, 1870 (LEPIDOPTERA PYRALIDAE) USING RICINUS COMMUNISL. IN ARID ZONE

In July 2017, in south-eastern Tunisia, larvae of Phycita diaphanawere observed on seedlings of castor bean. Infested pointed lobes of the leaves are characterized by the presence of shelters or nests ranging from oneto six shelters per leaf. The shelter area ranged from 1.01 to 28.27 cm2. In each shelter, we found from one to nine larvae. We conclude thatPh. diaphana spends the whole larval stage protected without changing its feeding habits.The leaf roll may reduce leaf toughness and lower levels of plant defensive chemicals, and hence provides a more easily and more safely eaten food. Larvae of Ph. diaphana use the pointed lobe to build its shelter. As Castor bean is used in several fields of economy, mainly the production of biodiesel fuel, the monitoring of this pest will be important and interesting. Thereby, studying the life cycle of pests constitute a significant element of phytosanitary control.

Cotyledon removal decreases salt tolerance during seedling establishment of Ricinus communis, an oilseed energy crop species

Early seedling growth is the most sensitive and critical periods for most plant establishment in saline environments. Castor bean (Ricinus communis) is an important oilseed crop species worldwide and has good salt tolerance. However, the specific functions of cotyledons during early seedling establishment of this species under salt stress are still not clearly understood. Here, the biomass, gas exchange, chlorophyll fluorescence, leaf ultrastructure, inorganic ion and organic solute contents of Ricinus communis seedlings whose cotyledons were partially or completely removed were measured in both salt and non-salt treatments. The results indicated that cotyledon removal decreased both the growth and photosynthesis of the seedlings under salt stress. The ultrastructure of the chloroplasts was greatly altered and distorted in the leaves of plants whose cotyledons were removed. With increasing salinity, cotyledon removal dramatically increased the Na+ content and simultaneously reduced the K+ content in the castor bean leaves. In addition, cotyledon removal also increased the contents of malondialdehyde (MDA), proline and soluble sugars in the leaves of plants under salt stress. These results suggest that cotyledons can alleviate the reduction in photosynthetic capability caused by stomatal closure in the leaves of castor bean plants and can maintain the structural integrity of chloroplasts under salt stress. Moreover, cotyledons can also counteract Na+ toxicity and alleviate osmotic stress caused by salt stress. Together, these findings provide an improved understanding of cotyledon function in young castor bean seedlings under salt stress.

Physiological Adaptive Strategies of Oil Seed Crop Ricinus communis Early Seedlings (Cotyledon vs. True Leaf) Under Salt and Alkali Stresses: From the Growth, Photosynthesis and Chlorophyll Fluorescence.

Ricinus communis is an important energy crop and is considered as one of the most potential plants for salt-alkali soil improvement in Northeast China. Early seedling stage (such as the cotyledon expansion stage) is always a vulnerable stage but plays a vital role in plant establishment, especially under stress conditions. However, little information exists concerning the function of cotyledon and the relationship between cotyledon and true leaf in the adaptation to salt stress and alkali stress of this species. Here, Ricinus communis seedlings were treated with varying (40, 80 and 120 mM) salinity (NaCl) and alkalinity (NaHCO3), growth, photosynthesis, and chlorophyll fluorescence of cotyledons and true leaves were measured. The results showed that the biomass, photosynthetic parameters, and the qp value of both cotyledons and true leaves decreased with increasing salt-alkali stress, and the decrease in biomass, gs and Tr, of true leaves were much greater than that of cotyledons. Salt-alkali stress only reduced photosynthetic pigments and ΦPSII in cotyledons, but did not affect those in true leaves. Additionally, the Fv/Fm and NPQ between cotyledons and true leaves showed different trends in salinity and alkalinity. The results suggested that alkali stress could cause much more damage to the castor bean seedlings, and different physiological responses and adaptive strategies are found in cotyledons and true leaves under salt-alkali stress. This study will help us develop a better understanding of the adaptation mechanisms of cotyledon and true leaf during early seedling stage of castor bean plant, and also provide new insights into the function of cotyledon in Ricinus communis under salt-alkali stress conditions.

Genetic parameters in agronomic characters for selection of superior lineages of Ricinus communis L

ABSTRACT: Knowledge on the variability and heritability of agronomic characters of interest aid the selection of superior materials. Thus, the objective of this study was to evaluate the genetic parameters of agronomic traits in castor bean plant lineages and to quantify the genetic correlations between them. The study was performed in the experimental area of the Federal University of the Recôncavo da Bahia, Cruz das Almas, Bahia. Seed oil content, vegetative cycle, plant height, and the number and weight of seeds per plant were evaluated in 47 lineages of castor bean seedlings. The coefficient of genetic variation was higher for weight of seeds per plant, revealing greater variability. The broad-sense heritability of individual plots presented a higher value for oil content and a lower value for seed number per plant. Selection precision was moderate for plant height, number and weight of seeds per plant, high for vegetative cycle, and very high for oil content. The genetic parameters allowed superior genotypes to be ranked and selected. Positive correlations between vegetative cycle and plant height, associated with negative correlations for number and weight of seeds, and oil content, allow significant gains for crop productivity.

Behavior of Ricinus communis L. plants due to different volumes of containers and substrates

Abstract: The objective of this study was to evaluate the production of castor bean seedlings due to different volumes of containers and substrates. The work was conducted from May to June 2014, in the nursery of the State University of Paraiba, Campus IV, Catole do Rocha, PB. The experimental design was a completely randomized design, adopting the 4 x 2 factorial scheme, with 6 replicates, with four container volumes: (polyethylene plastic bags with capacity 1000 dm³; polyethylene plastic bags with a capacity of 500 dm³; tubes with a capacity of 300 dm³ and disposable cups with a capacity of 270 dm³) and two types of substrates (S1 = 50% soil + 50% earthworm humus and S2 = 40% soil + 30% earthworm humus + 30% sand). The variables studied were: (LN) leaf number; (ULA) unitary leaf area; (RD) root diameter; (RL) root length; (SB) shoot biomass; (TPB) total plant biomass. All variables had a significant effect on cantainer volumes. Probably the largest container provided larger area of substrate to be explored. Castor bean seedlings of the BRS Gabriela variety respond well to larger container volumes. The substrate V1 (50% soil and 50% humus) influenced the initial growth of BRS Gabriela seedlings.

Arbuscular mycorrhizal fungi improve plant growth of Ricinus communis by altering photosynthetic properties and increasing pigments under drought and salt stress

Castor bean (Ricinus communis) is one of the most important candidate crops that can be used to increase the land cover and crop yield in the arid and saline region of China. To evaluate the effects of arbuscular mycorrhizal (AM) fungi on the growth of castor bean under drought and salt stresses, a pot experiment was carried out to examine how AM fungi improve the plant growth of castor bean by affecting the leaf gas exchange, pigments, and metabolites accumulation of castor bean seedlings. The results showed that AM fungi stimulated plant growth and increased the castor bean aboveground biomass. AM fungi significantly increased the net photosynthetic rate (A), stomatal conductance (gs) and transpiration rate (E) of castor bean and decreased the intercellular CO2 concentration (Ci) under drought and salt stress. The contents of chlorophyll a, chlorophyll b, chlorophyll a + b and carotenoids in leaves treated by AM fungi were higher than in those without the AM fungi treatment. AM fungi notably increased the soluble protein and proline contents and decreased the malondialdehyde (MDA) content of castor bean. The results indicated that AM fungi could protect castor bean against drought and salt stresses by improving its leaf gas exchanges and photosynthetic capacity and altering its concentrations of metabolites. Our results highlight that AM fungi might be a promising bio-approach that can be used to plant castor beans in northeast and northwest China.

English

Castor bean (Ricinus communis L.) is an oleaginous of high economic value because its oil has numerous applications in the industry, such as in the manufacture of enamels and paints. Presently, its production is aimed at being used as a biodiesel. The main obstacle to a high production is the survival of the young plants in field in a no-tillage system. An alternative would be the production of seedlings. The objective of this research was to evaluate the initial growth of BRS Gabriela (R. communis L.) castor bean seedlings in function of different substrates and container volumes. The work was conducted at the nursery of the State University of Paraíba (UEPB), Catolé do Rocha, PB, Brazil. The experimental design was completely randomized (CRB) in a 4 × 2 factorial design with 6 replications. The factors consisted of 4 container volumes: 1, 0.5, 0.3, and 0.27 dm-3 and 2 substrates (S1 = 50% soil and 50% earthworm humus, and S2 = 40% soil, 30% earthworm humus and 30% sand). The analyzed variables were stem dry matter (SDM), root dry matter (RDM), plant leaf area (PLA), leaf biomass (LPM), stem biomass (SPM), water content (WC), plant height and stem diameter ratio (PHe/SD), root dry matter and dry shoot dry matter ratio (RDM/SDM), Dickson quality index (DQI) and succulence. The morphological characteristics were influenced by container volume and substrate. The largest container volume, together with the substrate S1 (50% soil and 50% earthworm humus), provided viable seedlings ready to be transplanted to the field.     Key words: Ricinus communis L., Initial growth, greenhouse, earthworm humus. &nbsp

Morphophysiological and biochemical alterations in Ricinus communis L. seeds submitted to cobalt60 gamma radiation.

This study aimed to evaluate the radiosensitivity of castor bean seeds after applications of different doses of Cobalt60 gamma radiation. Seeds were pre-soaked for 24 hours in distilled water and then irradiated with 50, 100, 150, and 200 Gy, except the control. Sowing was performed in trays, which contained soil as substrate and were maintained in a greenhouse. The electrical conductivity, emergence, emergence speed index, growth parameters and activities of antioxidant enzymes (superoxide dismutase, ascorbate peroxidase, and catalase) were evaluated in the leaves and roots of castor bean seedlings. Gamma radiation did not affect the electrical conductivity of the seeds; however, at a dose of 200 Gy, the emergence and emergence speed index of the seedlings was negatively affected. An analysis of the morphophysiological parameters revealed a reduction in seedling size as the radiation dose increased. There was a significant increase in superoxide dismutase and ascorbate peroxidase activities at higher radiation doses in the leaves, but not in roots. Thus, the analysis of all the variables suggests a response pattern as to the morphophysiological and biochemical changes of castor bean seedlings due to the increase of gamma radiation, which may serve as a tool for generating greater genetic variability.

Responses of Ricinus communis L. (castor bean, phytoremediation crop) seedlings to lead (Pb) toxicity in hydroponics

Lead is not essential for metabolism of organisms. Lead toxicity to nervous system in human is well established. It is released into the environment through various technogenic and geogenic sources. Soils are often co-contaminated with potentially toxic metals like lead, cadmium etc. and petroleum and chlorinated hydrocarbons etc. Organics can be degraded to less toxic forms by bioremediation strategies, while inorganics such as Pb, cannot be degraded. Phytormediation is one of the effective strategies to achieve natural attenuation. Ricinus communis L. (Castor bean, Euphorbiaceae) is a potential cadidate for environmental cleanup and revegetation of contaminated lands. Published literature acknowledges its outstanding remediation functions. Additionally, its environmental sustainable aspects and circular economics are attracting researchers in the field of agriculture and environmental sciences. Thispresent paper investigates the responses of castor bean seedlings to Pb-toxicity in hydroponics, which offers unique clues for understanding toxicity and tolerance manifestatins.

A novel fluorescent conjugate applicable to visualize the translocation of glucose-fipronil.

The ability to visualize the movement of glycosyl insecticides contributes to learning their translocation and distribution in plants. In our present work, a novel fluorescent glucose-fipronil conjugate N-[3-cyano-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-[(trifluoromethyl)sulfinyl]-1H-pyrazol-5-yl]-1-(2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxy-β-D-glucopyranosyl)-1H-1,2,3-triazole-4-methanamine (2-NBDGTF), was obtained via click chemistry. Disk uptake experiments showed that an active carrier-mediated system was involved in the 2-NBDGTF uptake process. Meanwhile, 2-NBDGTF exhibited comparable phloem mobility with GTF in castor bean seedlings. Visualization of 2-NBDGTF uptake and transport experiment showed that this fluorescent glucose-fipronil conjugate could be loaded into sieve tubes after transiting through epidermal cells and mesophyll cells and then translocate from cotyledon to hypocotyl via phloem in castor bean seedlings. The results above determined that it is a promising fluorescence tagging approach for revealing the activities of glycosyl insecticides and 2-NBDGTF is a reasonable and feasible fluorescent surrogate of GTF for tracing the distribution of glucose-fipronil conjugates.

Seeds' physicochemical traits and mucilage protection against aluminum effect during germination and root elongation as important factors in a biofuel seed crop (Ricinus communis).

We determined the length, volume, dry biomass, and density in seeds of five castor bean cultivars and verified notable physicochemical trait differences. Seeds were then subjected to different toxic aluminum (Al) concentrations to evaluate germination, relative root elongation, and the role of root apices' rhizosphere mucilage layer. Seeds' physicochemical traits were associated with Al toxicity responses, and the absence of Al in cotyledons near to the embryo was revealed by Al-hematoxylin staining, indicating that Al did not induce significant germination reduction rates between cultivars. However, in the more sensitive cultivar, Al was found around the embryo, contributing to subsequent growth inhibition. After this, to investigate the role of mucilage in Al tolerance, an assay was conducted using NH4Cl to remove root mucilage before or after exposure to different Al concentrations. Sequentially, the roots were stained with hematoxylin and a quantitative analysis of staining intensity was obtained. These results revealed the significant contribution of the mucilage layer to Al toxicity responses in castor bean seedlings. Root growth elongation under Al toxicity confirmed the role of the mucilage layer, which jointly indicated the differential Al tolerance between cultivars and an efficient Al-exclusion mechanism in the tolerant cultivar.

Synthesis of rotenone-O-monosaccharide derivatives and their phloem mobility.

Six monosaccharide derivatives of rotenone were designed and synthesized to assess whether rotenone could become phloem mobile by the addition of a monosaccharide group. Phloem mobility experiments showed that only D-glucose conjugates exhibit phloem transport properties in castor bean (Ricinus communis L.) seedlings. Two D-glucose conjugates, 2-O-β-D-glucopyranosyldemethylrotenone and 6'-O-β-D-glucopyranosyldalpanol, had significantly obtained systemicity compared with that of rotenone, and 6'-O-β-D-glucopyranosyldalpanol was more mobile than 2-O-β-D-glucopyranosyldemethylrotenone. Coupling with a monosaccharide core is a reasonable method for conferring phloem mobility on insecticides, but phloem mobility is also affected by the parent molecule and the position of the monosaccharide.

Phloem mobility and translocation of fluorescent conjugate containing glucose and NBD in castor bean (Ricinus communis)

Phloem mobility is an important factor for long-distance transport of systemic pesticides in plants. Our previous study revealed that a fluorescent glucose-insecticide conjugate, N-{3-cyano-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-iodo-1H-pyrazol-5-yl}-N-{[1-(β-D-glucopyranosyl)-1H-1,2,3-triazole-4-yl]methyl}-N-{[1-((N-(7-nitrobenz-2-oxa-1,3-diazole-4-amine))-propyl)-1H-1,2,3-triazole-4-yl]methyl}amine (IPGN), can be transported in tobacco cells. Several studies have also indicated that glucose moieties can guide the conjugates into plant cells. In this study, we investigated the phloem mobility of IPGN within castor bean seedlings. Cotyledon uptake experiment results show that IPGN could enter the phloem of the mid-veins of cotyledons. The results of further quantitative analysis show that IPGN was present in small amounts in the phloem sap despite the inconsistencies of physicochemical properties with diffusion through the plasma membrane. Its concentration in the phloem sap (about 370nM at 5h) was much lower than that in the incubation medium (100μM), which suggests that IPGN exhibited weak phloem mobility. After the leaves of Ricinus plantlets were treated with IPGN, green fluorescence could be observed in the phloem of the petioles, bud apical nodes, bud mid-veins, and mid-veins of the untreated leaves. The localization of the fluorescent conjugate at various levels of Ricinus plantlets indicates that it was translocated at a distance to sink organs via sieve tubes. The results proved that introducing a glucose group is a feasible approach to modify non-phloem-mobile pesticides and produce phloem-mobile pesticides.

Contribution of corticular photosynthesis to bud development in African baobab (Adansonia digitata L.) and Castor bean (Ricinus communis L.) seedlings

The African baobab (Adansonia digitata L.) and castor bean (Ricinus communis L.) are drought resistant green-stemmed succulent plants which grow in the arid and semi-arid regions of Africa. Photosynthesis in the stems of green-stemmed plants is known to contribute to plant carbon gain especially during leafless periods. To study the contribution of stem photosynthesis in stem succulent plants, the height and stem diameter of baobab and castor bean plants grown in the greenhouse were measured. The plants were completely defoliated and subjected to different treatments: Watered with open stems (WO), watered and stems covered with aluminium foil (WC) to achieve 100% light exclusion, drought and open (DO) and drought and covered (DC). Stem coverage with aluminium foil resulted in a higher stem height and diameter during drought for baobab with similar trends seen in castor bean. Light exclusion resulted in a significantly lower bud DW production and enrichment in 13C in bud dry matter of castor bean and in stem dry matter of baobab. These show that corticular photosynthesis contributes in carbon gain in these species.

Synthesis of a Series of Monosaccharide–Fipronil Conjugates and Their Phloem Mobility

To test the effect of adding different monosaccharide groups to a non-phloem-mobile insecticide on the phloem mobility of the insecticide, a series of conjugates of different monosaccharides and fipronil were synthesized using the trichloroacetimidate method. Phloem mobility tests in castor bean ( Ricinus communis L.) seedlings indicated that the phloem mobility of these conjugates varied markedly. L-Rhamnose-fipronil and D-fucose-fipronil displayed the highest phloem mobility among all of the tested conjugates. Conjugating hexose, pentose, or deoxysugar to fipronil through an O-glycosidic linkage can confer phloem mobility to fipronil in R. communis L. effectively, while the -OH orientation of the monosaccharide substantially affected the phloem mobility of the conjugates.