Genome-wide identification and expression pattern analysis of the MATE gene family in carmine radish (Raphanus sativus L.).

Carmine radish (Raphanus sativus L.) is famousforcontaininganaturalredpigment(redradishpigment) that grown in Fuling, Chongqing City, China. MATE (multidrug and toxic compound extrusion), as an integral member of the multidrug efflux transporter family, has various functions in plants. However, noinformationhasbeenavailableaboutcharacteristicsoftheMATEgenefamily in carmine radish. In this study, total of 85 candidate MATE gene family members classifiedinto 4 groups were identified and foundtobewidelyandrandomlydistributedindifferent genome. Synteny analysis revealed that twenty-one segmental and ten tandem duplications acted as important regulators for the expansion of RsMATE genes. The Ka/Ks ratios of RsMATE indicated that RsMATE may have undergone intense purification in the radish genome. Cis-acting element analysis of RsMATE in the promoter region indicated that RsMATE were mainly related to the abiotic stress response and phytohormone. Quantitative real-time polymerase chain reaction (qRT-PCR) showed that RsMATE40-b, RsMATE16-b and RsMATE13-a genes were significantly expressed under ABA (abscisic acid) and NaCl stress treatments respectively. In addition, the expression patterns of fifteen key RsMATE genes were investigated in 'XCB' (Xichangbai) and 'HX' (Hongxin) roots under Cadmium (Cd) stress for different treatment times using qRT-PCR, of those, RsMATE49-b, RsMATE33 and RsMATE26 transcripts were strongly altered at different time points in XCB responsive to Cd stress,compared to HX. This study will provide valuable insights for studying the functional characterization of the MATE gene in carmine radish and other plants.

Wood-inspired elastic and conductive cellulose aerogel with anisotropic tubular and multilayered structure for wearable pressure sensors and supercapacitors.

Cellulose nanofiber (CNF) aerogels hold considerable potential in wearable devices as pressure sensors and flexible electrochemical energy storage. However, the undirectional assembly of CNFs results in poor mechanical performance, which limits their application in structural engineering. In this study, we propose an anisotropic aerogel with both elastic and conductive properties inspired by the micro-nanostructure of natural wood. One-dimensional TEMPO cellulose nanofibers (TOCNF) were utilized as structural building blocks, while two-dimensional reduced graphene oxide (rGO) served as the electron transfer platform, owing to their high mechanical strength. The directionally aligned tubular structure composed of multilayered sheets was formed through rapid unidirectional freezing and subsequent steam heating reduction. These structures efficiently transferred stress throughout the porous skeleton, resulting in TOCNF-rGO aerogels with high compressibility and excellent fatigue resistance (2000 cycles at 60 % strain). The aerogel also exhibited high sensitivity, wide detection range, relatively fast response, and excellent compression cycle stability, making it suitable for accurately detecting various human biological and motion signals. Additionally, TOCNF-rGO can be assembled into a flexible all-solid-state symmetric supercapacitor that delivers excellent electrochemical performance. It is expected that this biomass-derived aerogel will be a versatile material for flexible electronic devices for energy conversion and storage.

Seed coating with micronutrients improves germination, growth, yield and microelement nutrients of maize (Zea mays L.).

Soil and foliar application are the most widely used methods for adding micronutrients to maize. High quality micronutrient fertilizers, however, are difficult to obtain in developing countries; micronutrient seed coatings are an attractive and practical alternative. We applied this approach to maize (Zea mays L.) to demonstrate the effects of boron (B), iron (Fe), manganese (Mn), molybdenum (Mo) and zinc (Zn) sulfates on maize germination, vigor, seedling growth, seed yield and seed quality as well as on seed microelement concentration. Seed coating was tested on three representative Chinese soil types (sandy, purple and lime soils). Compared to untreated controls, coating maize seeds with micronutrients significantly increased the seed emergence rate, seedling height, leaf length, leaf width, leaf area, main root length, root number, above ground fresh biomass, above ground dry biomass, underground fresh biomass, underground dry biomass, ear thickness and yield in sandy, purple and lime soils. Coating maize seeds with micronutrients also significantly increased the yield and quality of maize seed compared to untreated controls including ear barren tip, ear length, ear thickness, grains/row, hundred seed weigh, and rows/ear. Also, B, Zn, Fe, Mn and Mo microelements accumulated in maize seed after coating the seed with micronutrients. Our findings indicate that micronutrient seed coating may improve nutrient uptake and production of maize hybrids.

Transcriptome profiles reveal the protective role of seed coating with zinc against boron toxicity in maize (Zea mays L.).

Despite its low abundance during biological growth, excessive boron (B) is potentially toxic to both plants and humans. Cultivation of maize (Zea mays L.), one of the most important crops worldwide, has been severely affected by B toxicity, thereby threatening human and animal food security. The effects of coating maize seed with B, zinc (Zn), and B+Zn were evaluated using transcriptome analysis. It was found that Zn coating significantly reduce B accumulation and toxicity in maize. Compared to the uncoated control, expression of 10871, 2844, and 1347 genes demonstrated alterations in response to coating with B, Zn, and B+Zn, respectively. Of the differentially expressed genes (DEGs), the expression of 7529, 1056, and 357 DEGs was found to be specific for coating with B, Zn, and B+Zn, respectively. Additionally, 132 co-modulated DEGs were found to primarily encode stress resistance- and membrane-related proteins. These genes were primarily involved in plant hormone signal transduction, ribosome assembly, carbon metabolism, phenylpropanoid biosynthesis, and oxidative phosphorylation pathways. Overall, our results suggested that seed coating with Zn significantly alleviates B accumulation and toxicity in maize by changing the expression of selected genes and constitutes a simple and effective strategy for alleviating B toxicity in high-B soils.

Identification and functional characterization of RsGST1, an anthocyanin-related glutathione S-transferase gene in radish.

Anthocyanins not only affect the quality of horticultural crops but are also vital for human health. Glutathione transferase family members (GSTs) are enzymes that help to control plant development and stress responses, and are also involved in anthocyanin accumulation. In this study, we targeted a phi (F) class glutathione S-transferase gene RsGST1 (RSG01330.t1) as a crucial gene in the accumulation of anthocyanins in radish. RsGST1 expression was closely associated with anthocyanin content in the skin and flesh of taproot from different color type radish cultivars. Furthermore, RsGST1 was able to restore anthocyanin accumulation in Arabidopsis tt19 mutants, indicating that RsGST1 has a similar function as AtTT19, a gene responsible for the transport of anthocyanins in Arabidopsis. Transient overexpression of RsGST1 together with the key anthocyanin biosynthesis regulator RsMYB1a in radish leaves significantly enhanced anthocyanin biosynthesis compared with in plants that overexpressed RsMYB1a alone. Dual-luciferase and yeast one-hybrid assays revealed that RsMYB1a binds to promotor and activates the expression of RsGST1. Altogether, these results provide molecular evidence indicating that RsGST1 and RsMYB1a coordinate radish anthocyanin accumulation.

Development and application of two novel functional molecular markers of BADH2 in rice

BACKGROUND: Fragrance is one of the most important quality traits in rice, and the phenotype is attributed to the loss-of-function betaine aldehyde dehydrogenase (BADH2) gene. At least 12 allelic variations of BADH2 have been identified, and some of these have been applied to rice fragrance breeding using traditional molecular markers and Sanger sequencing techniques. However, these traditional methods have several limitations, such as being very expensive, imprecise, inefficient, and having security issues. Thus, a new molecular marker technology must be developed to improve rice fragrance breeding. RESULTS: In this study, more than 95% of the cultivated fragrant rice varieties belonged to a 7-bp deletion in exon 2 (badh2-E2) or an 8-bp deletion and 3-bp variation in exon 7 (badh2-E7). Both allelic variations resulted in the loss of function of the badh2 gene. We developed two novel SNP molecular markers, SNP_badh2-E2 and SNP_badh2- E7, related to the alleles. Their genotype and phenotype were highly cosegregated in the natural variation of rice accessions, with 160 of the 164 fragrant rice varieties detected with the two markers. These markers cosegregated with the fragrance phenotype in the F2 population. CONCLUSIONS: Two functional SNP molecular markers of badh2-E2 and badh2-E7 allelic variations were developed. These functional SNP molecular markers can be used for genotype and genetic improvement of rice fragrance through marker-assisted selection and will significantly improve the efficiency of fragrant rice breeding and promote commercial molecular breeding of rice in the future.

Genome-wide identification and functional analysis of ARF transcription factors in Brassica juncea var. tumida.

Auxin signalling is vital for plant growth and development, from embryogenesis to senescence. Recent studies have shown that auxin regulates biological processes by mediating gene expression through a family of functionally original DNA-binding auxin response factors, which exist in a large multi-gene family in plants. However, to date, no information has been available about characteristics of the ARF gene family in Brassica juncea var. tumida. In this study, 65 B. juncea genes that encode ARF proteins were identified in the B. juncea whole-genome, classified into three phylogenetical groups and found to be widely and randomly distributed in the A-and B-genome. Highly conserved proteins were also found within each ortholog based on gene structure and conserved motifs, as well as clustering level. Furthermore, promoter cis-element analysis of BjARFs demonstrated that these genes affect the levels of plant hormones, such as auxin, salicylic, gibberellin acid, MeJA, abscisic acid, and ethylene. Expression analysis showed that differentially expressed BjARF genes were detected during the seedling stage, tumor stem development and the flowering period of B. juncea. Interestingly, we found that BjARF2b_A, BjARF3b_A, BjARF6b_A, and BjARF17a_B were significantly expressed in tumor stem, and an exogenous auxin assay indicated that these genes were sensitive to auxin and IAA signaling. Moreover, eight of the nine BjARF10/16/17 genes and all of the BjARF6/8 genes were involved in post-transcriptional regulation, targeted by Bj-miR160 and Bj-miR167c, respectively. This analysis provides deeper insight of diversification for ARFs and will facilitate further dissection of ARF gene function in B. juncea.

Identification of differential expression genes related to anthocyanin biosynthesis in carmine radish (Raphanus sativus L.) fleshy roots using comparative RNA-Seq method.

Radish (Raphanus sativus L.), is an important root vegetable crop grown worldwide, and it contains phyto-anthocyanins. However, only limited studies have been conducted to elucidate the molecular mechanisms underlying anthocyanin biosynthesis in the different color variants of the radish fleshy root. In this study, Illumina paired-end RNA-sequencing was employed to characterize the transcriptomic changes in seven different types of radish fleshy roots. Approximately, 126 co-modulated differentially expressed genes were obtained, and most DEGs were more likely to participate in anthocyanin biosynthesis, including two transcription factors RsMYB_9 and RsERF070, and four functional genes RsBRICK1, RsBRI1-like2, RsCOX1, and RsCRK10. In addition, some related genes such as RsCHS, RsCHI, RsANS, RsMT2-4, RsUF3GT, glutathione S-transferase F12, RsUFGT78D2-like and RsUDGT-75C1-like significantly contributed to the regulatory mechanism of anthocyanin biosynthesis in the radish cultivars. Furthermore, gene ontology analysis revealed that the anthocyanin-containing compound biosynthetic process, anthocyanin-containing compound metabolic process, and significantly enriched pathways of the co-modulated DEGs were overrepresented in these cultivars. These results will expand our understanding of the complex molecular mechanism underlying anthocyanin synthesis-related genes in radish.

Identification and characterization of the glutathione S-Transferase (GST) family in radish reveals a likely role in anthocyanin biosynthesis and heavy metal stress tolerance.

Glutathione S-transferases (GSTs) are a large complex family of enzymes (EC 2.5.1.18) that play vital roles in flavonoid metabolism and plant growth and development and are responsive to heavy metal stress. However, knowledge about GST genes in radish (a vegetable crop with an extraordinary capacity to adapt to heavy metal stresses) is limited. Therefore, it is critical to identify putative candidate GST genes responsible for heavy metal stress tolerance and anthocyanin biosynthesis. In this study, we first identified 82 R. sativus GST (RsGST) genes using various bioinformatic approaches, and their expression profiles were characterized from RNAseq data. These RsGST genes could be grouped into 7 major subclasses: tau (43 members), phi (21 members), tetrachlorohydroquinone dehalogenase (7 members), dehydroascorbat reductase (5 members), zeta (3 members), lambda (2 members) and theta (1 member). In addition, most of the RsGST genes showed organ-specific expression in our study. Moreover, the transcripts of RsGSTF12-1 and RsGSTF12-2, belonging to the phi class, might be candidates encoding anthocyanin transporters in carmine radish, whereas the tau class, consisting of RsGSTU13-1, RsGSTU19, RsGSTU24-1, and RsGSTU3, and theta class, consisting of RsGSTT1-1, might be defend radish against adverse heavy metal stresses. These results will aid in understanding the functions of the GST family related to heavy metal stress and anthocyanin biosynthesis, thereby potentially improving radish breeding programs for high-pigment-content material as well as HM-tolerant material.

Development and application of an optimized drop-slide technique for metaphase chromosome spreads in maize.

Chromosome spreads are important for complex molecular cytogenetic studies. An adequate chromosome spreading method for identification and isolation of the maize B chromosome, however, has not been reported. We used the maize inbred lines, B73 and Mo17, the hybrid YD08 line and the landrace DP76 to develop an optimized chromosome spreading method. We investigated the effects of four treatment factors on the quality of metaphase chromosome spreads using a factorial analysis of variance. Optimal conditions for metaphase spreading were identified using regression analysis based on multifactor orthogonal design of four treatment factors with five levels for each factor. We developed optimal conditions for metaphase spreading as follows: nitrous oxide treatment for 2 h, glacial acetic acid fixation for 2 h, enzyme hydrolysis for 6.0 h, and a drop height of 35 cm for cell suspension. We obtained high quality metaphase chromosome spreads with large metaphase areas, large numbers of chromosomes, few chromosome overlaps and high frequency of intact metaphases. Our optimized drop-slide procedure was markedly better than the traditional flame smear technique. We identified 487 B chromosomes in three forms from maize landraces from Southwest China. We found no relation between the C-band number and B chromosome. Single B chromosomes also were isolated directly from a metaphase chromosome drop-slide using a micromanipulator. Our optimized method provides a simple, efficient and reproducible procedure for preparing high quality plant chromosome spreads.

Differential anthocyanin accumulation in radish taproot: importance of RsMYB1 gene structure.

KEY MESSAGE: RsMYB1a was the crucial MYB, and RsbHLH4 is the essential partner in regulating the anthocyanin biosynthesis in radish. There are four color types of radish according to whether or not the anthocyanin accumulates in the skin and flesh of taproot. Red radishes accumulate a substantial amount of anthocyanins in both the skin and flesh. It is well known that the MYB-bHLH-WD40 transcription factor(s) complex regulates the biosynthesis of anthocyanin in plants. Here in, four candidate MYB and bHLH genes, RsMYB1a, RsMYB1b, RsbHLH2 and RsbHLH4, were isolated from red radish 'Hongxin 1'. The expression of RsbHLH4 and the two structural genes RsANS and RsUFGT was significantly positively correlated with anthocyanin contents. The expression of RsMYB1a was also highly correlated with anthocyanin accumulation, particularly when the white flesh sample of 'Hongxin 1-1' was excluded. The transient expression of RsMYB1a in the radish cotyledon and leaf induced anthocyanin accumulation with even stronger promoting role when expression in combination with RsbHLH4. These results suggested that RsMYB1a was the crucial MYB, and that RsbHLH4 is an essential partner in regulating the biosynthesis of anthocyanins in radish. The low or undetectable RsbHLH4 expression paralleled the lack of anthocyanin accumulation in the white flesh of 'Hongxin 1-1' and 'Shaguan 1'. Assays demonstrated that RsMYB1a interacted with RsbHLH4 and activated the expression of RsbHLH4. Notably, all the dark red radish cultivars have a longer RsMYB1a genomic DNA sequence, while the short and nonfunctional RsMYB1a is present in non-red cultivars. The length of the first intron and the presence of an early stop codon of RsMYB1 might underlie the differential anthocyanin accumulation in the radish taproot.

Genome-wide analysis of transcription factors related to anthocyanin biosynthesis in carmine radish (Raphanus sativus L.) fleshy roots.

Carmine radish produced in Chongqing is famous for containing a natural red pigment (red radish pigment). However, the anthocyanin biosynthesis transcriptome and the expression of anthocyanin biosynthesis-related genes in carmine radish have not been fully investigated. Uncovering the mechanism of anthocyanin biosynthesis in the 'Hongxin 1' carmine radish cultivar has become a dominant research topic in this field. In this study, a local carmine radish cultivar named 'Hongxin 1' containing a highly natural red pigment was used to analyze transcription factors (TFs) related to anthocyanin biosynthesis during the dynamic development of fleshy roots. Based on RNA sequencing data, a total of 1,747 TFs in 64 TF families were identified according to their DNA-binding domains. Of those, approximately 71 differentially expressed transcription factors (DETFs) were commonly detected in any one stage compared with roots in the seedling stage (SS_root). Moreover, 26 transcripts of DETFs targeted by 74 miRNAs belonging to 25 miRNA families were identified, including MYB, WRKY, bHLH, ERF, GRAS, NF-YA, C2H2-Dof, and HD-ZIP. Finally, eight DETF transcripts belonging to the C2C2-Dof, bHLH and ERF families and their eight corresponding miRNAs were selected for qRT-PCR to verify their functions related to anthocyanin biosynthesis during the development of carmine radish fleshy roots. Finally, we propose a putative miRNA-target regulatory model associated with anthocyanin biosynthesis in carmine radish. Our findings suggest that sucrose synthase might act as an important regulator to modulate anthocyanin biosynthesis in carmine radish by inducing several miRNAs (miR165a-5p, miR172b, miR827a, miR166g and miR1432-5p) targeting different ERFs than candidate miRNAs in the traditional WMBW complex in biological processes.

Genome-wide identification and characterization, phylogenetic comparison and expression profiles of SPL transcription factor family in B. juncea (Cruciferae).

SQUAMOSA promoter-binding protein-like (SPL), as plant specific transcription factors, is involved in many plant growth and development processes. However, there is less systematical study for SPL transcription factor in B. juncea (Cruciferae). Here, a total of 59 SPL genes classified into eight phylogenetic groups were identified in B. juncea, highly conserved within each ortholog were also found based on gene structure, conserved motif, as well as clustering level. In addition, clustering of SPL domain showed that two zinc finger-like structures and NLS segments were identified in almost of BjuSPLs. Analyzed of putative cis-elements for BjuSPLs demonstrated that SPL transcription factors were involved in adverse environmental changes, such as light, plant stresses and phytohormones response. Expression analysis showed that differentially expressed SPL genes were identified in flower and stem development of Cruciferae; such as BjuSPL3a-B, BjuSPL2b_B and BjuSPL2c_A were significantly expressed in flower; BjuSPL 3b_B and BjuSPL10a_A were significantly expressed in stem node (VP: vegetative period). Moreover, 28 of the 59 BjuSPLs were found involved in their posttranscriptional regulation targeted by miR156. We demonstrated that miR156 negatively regulated BjuSPL10a_A and BjuSPL3b_B to act for stem development in B. juncea.

De novo transcriptome sequencing of radish (Raphanus sativus L.) fleshy roots: analysis of major genes involved in the anthocyanin synthesis pathway.

BACKGROUND: The HongXin radish (Raphanus sativus L.), which contains the natural red pigment (red radish pigment), is grown in the Fuling district of Chongqing City. However, the molecular mechanisms underlying anthocyanin synthesis for the formation of natural red pigment in the fleshy roots of HongXin radish are not well studied. RESULTS: De novo transcriptome of HX-1 radish, as well as that of the advanced inbred lines HX-2 and HX-3 were characterized using next generation sequencing (NGS) technology. In total, approximately 66.22 million paired-end reads comprising 34, 927 unigenes (N50 = 1, 621 bp) were obtained. Based on sequence similarity search with known proteins, total of 30, 127 (about 86.26%) unigenes were identified. Additionally, functional annotation and classification of these unigenes indicated that most of the unigenes were predominantly enriched in the metabolic process-related terms, especially for the biosynthetic pathways of secondary metabolites. Moreover, majority of the anthocyanin biosynthesis-related genes (ABRGs) involved in the regulation of anthocyanin biosynthesis were identified by targeted search for their annotation. Subsequently, the expression of 15 putative ABRGs involved in the anthocyanin synthesis-related pathways were validated using quantitative real-time polymerase chain reaction (qRT-PCR). Of those, RsPAL2, RsCHS-B2, RsDFR1, RsDFR2, RsFLS, RsMT3 and RsUFGT73B2-like were identified significantly associated with anthocyanin biosynthesis. Especially for RsDFR1, RsDFR2 and RsFLS, of those, RsDFR1 and RsDFR2 were highest enriched in the HX-3 and WG-3, but RsFLS were down-regulated in HX-3 and WG-3. We proposed that the transcripts of RsDFR1, RsDFR2 and RsFLS might be act as key regulators in anthocyanin biosynthesis pathway. CONCLUSIONS: The assembled radish transcript sequences were analysed to identify the key ABRGs involved in the regulation of anthocyanin biosynthesis. Additionally, the expression patterns of candidate ABRGs involved in the anthocyanin biosynthetic pathway were validated by qRT-PCR. We proposed that the transcripts of RsDFR1, RsDFR2 and RsFLS might be acted as key regulators in anthocyanin biosynthesis pathway. This study will enhance our understanding of the biosynthesis and metabolism of anthocyanin in radish.

Characterization of cadmium-responsive MicroRNAs and their target genes in maize (Zea mays) roots.

BACKGROUND: Current research has shown that microRNAs (miRNAs) play vital roles in plant response to stress caused by heavy metals such as aluminum, arsenic, cadmium (Cd), and mercury. Cd has become one of the most hazardous pollutants in the environment. Maize can be a potential model to study phytoremediation of Cd-contaminated soil owing to its large biomass production. However, little is known about miRNAs as a response to Cd stress in maize. RESULTS: To investigate the role of miRNAs in response to Cd stress, roots of seedlings of the inbred maize lines B73 and Mo17 were collected and treated with 200 mg/L CdCl2·2.5 H2O over different exposure times. Enzyme activities of superoxide dismutase and peroxidase were measured to confirm Cd stress. The expression of six candidate miRNAs and their targets were validated using quantitative real-time PCR (qRT-PCR) technology. In addition, the expression of Zma-miR171b was assessed using in situ hybridization. CONCLUSIONS: Our results showed that miRNAs and their respective target genes were differentially expressed in maize seedling roots exposed to Cd stress. This research produced new insights into the molecular mechanism of miRNAs responsive to Cd stress in plants and sheds light on the latent roles of miRNAs in plants exposed to heavy metal stresses.

Effects of mutual intercropping on cadmium accumulation by the accumulator plants Conyza canadensis, Cardamine hirsuta, and Cerastium glomeratum.

In this study, three cadmium (Cd) accumulator species (Conyza canadensis, Cardamine hirsuta, and Cerastium glomeratum) were co-cultured in Cd-contaminated soil in pots to study the effects of intercropping on co-remediation. Only C. canadensis intercropped with C. glomeratum, C. hirsuta intercropped with C. glomeratum, and three-species intercropping increased plant biomass compared with their respective monocultures. The treatments of C. canadensis intercropped with C. glomeratum and three-species intercropping increased the Cd contents in roots and shoots of C. canadensis, whereas the other intercropping treatments decreased or had no significant impact on Cd contents. As for Cd accumulation, the treatments of C. canadensis intercropped with C. glomeratum, C. hirsuta intercropped with C. glomeratum, and three-species intercropping increased Cd accumulation in a single plant compared with that of their respective monocultures, whereas other intercropping treatments decreased Cd accumulation in individual plants. Only the treatments of C. canadensis intercropped with C. glomeratum and C. hirsuta intercropped with C. glomeratum increased Cd accumulation in shoots of a single pot compared with that of their respective monocultures. Therefore, C. canadensis intercropped with C. glomeratum and C. hirsuta intercropped with C. glomeratum may improve the phytoremediation efficiency for Cd-contaminated soil.

Effects of living hyperaccumulator plants and their straws on the growth and cadmium accumulation of Cyphomandra betacea seedlings.

To determine whether the living hyperaccumulator plants and their straws have the same effects on the growth and heavy metal accumulation of common plants, two pot experiments (intercropping experiment and straw mulch experiment) were conducted to study the effects of living hyperaccumulator plants (Solanum photeinocarpum, Tagetes erecta, Galinsoga parviflora and Bidens pilosa) and their straws on the growth and cadmium (Cd) accumulation of common plant Cyphomandra betacea seedlings. Intercropping with T. erecta or B. pilosa promoted the growth of C. betacea seedlings compared with the monoculture, while intercropping with S. photeinocarpum or G. parviflora inhibited that. Intercropping with S. photeinocarpum decreased the Cd contents in the roots and shoots of C. betacea seedlings compared with the monoculture, but intercropping with the other plants did not. In the straw mulch experiment, the straw of S. photeinocarpum or T. erecta promoted the growth of C. betacea seedlings compared with the control, while the straw of G. parviflora or B. pilosa did not. The straw of S. photeinocarpum or T. erecta decreased the Cd contents in the shoots of C. betacea seedlings, and the straw of G. parviflora or B. pilosa increased the shoot Cd contents. Thus, intercropping with S. photeinocarpum and applying S. photeinocarpum or T. erecta straw can reduce the Cd uptake of C. betacea.

Effects of indole-3-butytric acid on lead and zinc accumulations in Pseudostellaria maximowicziana.

Plant hormones can improve the phytoremediation capabilities of heavy metal hyperaccumulator plants. In this study, different doses of indole-3-butytric acid (IBA) were sprayed on the leaves of the lead (Pb) and zinc (Zn) accumulator plant Pseudostellaria maximowicziana, which was planted in Pb-Zn contaminated soil, and the effects of IBA on Pb and Zn accumulation levels in P. maximowicziana were studied. Spraying 25- and 50-mg/L IBA doses increased the stem, leaf and shoot biomasses of P. maximowicziana compared with the control, while 75- and 100-mg/L IBA doses decreased them. The 50-mg/L IBA dose increased the P. maximowicziana contents of chlorophyll a, total chlorophyll and carotenoid of compared with the control, and other doses had no significant effects or decreased these values. Spraying IBA reduced the superoxide dismutase activity of P. maximowicziana compared with the control, but improved the peroxidase and catalase activities. The 50-, 75-, and 100-mg/L IBA doses increased the Pb and Zn contents in P. maximowicziana compared with the control and also increased the amounts of Pb and Zn extracted by P. maximowicziana. Thus, 50 mg/L of IBA could promote the growth and the Pb and Zn phytoremediation capabilities of P. maximowicziana.

Effects of melatonin on the growth and cadmium characteristics of Cyphomandra betacea seedlings.

To determine whether the melatonin (MT) could reduce cadmium (Cd) accumulation in Cyphomandra betacea seedlings, different concentrations of MT were added to the nutrient solution and soil to study its effects on the growth and Cd characteristics of C. betacea seedlings. Fifty micromoles per liter (µmol/kg) of MT increased the biomass of C. betacea seedlings, but 100-200 µmol/L (µmol/kg) MT decreased seedling biomass in both the nutrient solution and soil cultivation experiments. The photosynthetic pigment contents showed no significant changes compared with the control when the MT dose was 150 µmol/L (µmol/kg) or less, while 200 µmol/L (µmol/kg) MT decreased the photosynthetic pigment contents. Low levels of MT improved the antioxidant enzyme activities of C. betacea seedlings, whereas high MT levels reduced them. MT increased the Cd contents in different organs of C. betacea seedlings in the nutrient solution cultivation experiment, but only 50 µmol/kg MT increased the Cd contents in stems, leaves, and shoots of C. betacea seedlings in the soil cultivation experiment. Therefore, only low levels of MT can promote the growth of C. betacea seedlings, and MT is not suitable for reducing Cd accumulation in C. betacea seedlings.

Effects of mutual intercropping on the cadmium accumulation in accumulator plants Stellaria media, Malachium aquaticum, and Galium aparine.

Intercropping affects heavy-metal uptake in plants. In this study, three cadmium (Cd)-accumulator species (Stellaria media, Malachium aquaticum, and Galium aparine) were intercropped together in Cd-contaminated soil to study the effects of intercropping on co-remediation. Mutual intercropping significantly increased the biomasses of S. media, M. aquaticum, and G. aparine compared with their respective monocultures. The photosynthetic pigment contents of three species were not significantly affected by mutual intercropping. Mutual intercropping did not increase the Cd contents in roots and shoots of G. aparine, but it increased the Cd contents in roots of S. media and M. aquaticum. It also decreased the Cd contents in shoots of S. media and M. aquaticum. Only G. aparine intercropped with M. aquaticum and three-species intercropping increased Cd-accumulation levels in whole plants of each species. Only S. media intercropped with M. aquaticum and three-species intercropping increased the Cd accumulation at the whole plant level in every plant in a single pot, with S. media intercropped with M. aquaticum showing the greatest increase. Therefore, S. media intercropped with M. aquaticum and three-species intercropping may improve the efficiency of phytoremediation of Cd-contaminated soil, with S. media intercropped with M. aquaticum representing the best combination.