Genome-Wide Analysis of Cation/Proton Antiporter Family in Soybean (Glycine max) and Functional Analysis of GmCHX20a on Salt Response.

Monovalent cation proton antiporters (CPAs) play crucial roles in ion and pH homeostasis, which is essential for plant development and environmental adaptation, including salt tolerance. Here, 68 CPA genes were identified in soybean, phylogenetically dividing into 11 Na+/H+ exchangers (NHXs), 12 K+ efflux antiporters (KEAs), and 45 cation/H+ exchangers (CHXs). The GmCPA genes are unevenly distributed across the 20 chromosomes and might expand largely due to segmental duplication in soybean. The GmCPA family underwent purifying selection rather than neutral or positive selections. The cis-element analysis and the publicly available transcriptome data indicated that GmCPAs are involved in development and various environmental adaptations, especially for salt tolerance. Based on the RNA-seq data, twelve of the chosen GmCPA genes were confirmed for their differentially expression under salt or osmotic stresses using qRT-PCR. Among them, GmCHX20a was selected due to its high induction under salt stress for the exploration of its biological function on salt responses by ectopic expressing in Arabidopsis. The results suggest that the overexpression of GmCHX20a increases the sensitivity to salt stress by altering the redox system. Overall, this study provides comprehensive insights into the CPA family in soybean and has the potential to supply new candidate genes to develop salt-tolerant soybean varieties.

The WRKY10-VQ8 module safely and effectively regulates rice thermotolerance.

WRKY transcription factors (TFs) play crucial roles in biotic and abiotic stress responses. However, their roles in thermal response are still largely elusive, especially in rice. In this study, we revealed the functions of WRKY10 TF and VQ8 protein containing VQ motif in rice thermotolerance. Overexpression of WRKY10 or loss of VQ8 function increases thermosensitivity, whereas conversely, overexpression of VQ8 or loss of WRKY10 function enhances thermotolerance. Overexpression of WRKY10 accelerates reactive oxygen species (ROS) accumulation in chloroplasts and apoplasts, and it also induces the expression of heat shock TF and protein genes. We also found that WRKY10 regulates nuclear DNA fragmentation and hypersensitive response by modulating NAC4 TF expression. The balance between destructive and protective responses in WRKY10-overexpression plant is more fragile and more easily broken by heat stress compared with wild type. In vitro and in vivo assays revealed that VQ8 interacts with WRKY10 and inhibits the transcription activity via repressing its DNA-binding activity. Our study demonstrates that WRKY10 negatively regulates thermotolerance by modulating the ROS balance and the hypersensitive response and that VQ8 functions antagonistically to positively regulate thermotolerance. The functional module of WRKY10-VQ8 provides safe and effective regulatory mechanisms in the heat stress response.

Integration of transcriptomic and proteomic analyses reveals several levels of metabolic regulation in the excess starch and early senescent leaf mutant lses1 in rice.

BACKGROUND: The normal metabolism of transitory starch in leaves plays an important role in ensuring photosynthesis, delaying senescence and maintaining high yield in crops. OsCKI1 (casein kinase I1) plays crucial regulatory roles in multiple important physiological processes, including root development, hormonal signaling and low temperature-treatment adaptive growth in rice; however, its potential role in regulating temporary starch metabolism or premature leaf senescence remains unclear. To reveal the molecular regulatory mechanism of OsCKI1 in rice leaves, physiological, transcriptomic and proteomic analyses of leaves of osckI1 allele mutant lses1 (leaf starch excess and senescence 1) and its wild-type varieties (WT) were performed. RESULTS: Phenotypic identification and physiological measurements showed that the lses1 mutant exhibited starch excess in the leaves and an obvious leaf tip withering phenotype as well as high ROS and MDA contents, low chlorophyll content and protective enzyme activities compared to WT. The correlation analyses between protein and mRNA abundance are weak or limited. However, the changes of several important genes related to carbohydrate metabolism and apoptosis at the mRNA and protein levels were consistent. The protein-protein interaction (PPI) network might play accessory roles in promoting premature senescence of lses1 leaves. Comprehensive transcriptomic and proteomic analysis indicated that multiple key genes/proteins related to starch and sugar metabolism, apoptosis and ABA signaling exhibited significant differential expression. Abnormal increase in temporary starch was highly correlated with the expression of starch biosynthesis-related genes, which might be the main factor that causes premature leaf senescence and changes in multiple metabolic levels in leaves of lses1. In addition, four proteins associated with ABA accumulation and signaling, and three CKI potential target proteins related to starch biosynthesis were up-regulated in the lses1 mutant, suggesting that LSES1 may affect temporary starch accumulation and premature leaf senescence through phosphorylation crosstalk ABA signaling and starch anabolic pathways. CONCLUSION: The current study established the high correlation between the changes in physiological characteristics and mRNA and protein expression profiles in lses1 leaves, and emphasized the positive effect of excessive starch on accelerating premature leaf senescence. The expression patterns of genes/proteins related to starch biosynthesis and ABA signaling were analyzed via transcriptomes and proteomes, which provided a novel direction and research basis for the subsequent exploration of the regulation mechanism of temporary starch and apoptosis via LSES1/OsCKI1 in rice.

Rice OsCASP1 orchestrates Casparian strip formation and suberin deposition in small lateral roots to maintain nutrient homeostasis.

Arabidopsis Casparian strip membrane domain proteins (CASPs) form a transmembrane scaffold to recruit lignin biosynthetic enzymes for Casparian strip (CS) formation. Rice is a semi-aquatic plant with a more complex root structure than Arabidopsis to adapt its growing conditions, where the different deposition of lignin and suberin is crucial for adaptive responses. Here, we observed the structure of rice primary and small lateral roots (SLRs), particularly the deposition patterns of lignin and suberin in wild type and Oscasp1 mutants. We found that the appearance time and structure of CS in the roots of rice are different from those of Arabidopsis and observed suberin deposition in the sclerenchyma in wild type roots. Rice CASP1 is highly similar to AtCASPs, but its expression is concentrated in SLR tips and can be induced by salt stress especially in the steles. The loss of OsCASP1 function alters the expression of the genes involved in suberin biosynthesis and the deposition of suberin in the endodermis and sclerenchyma and leads to delayed CS formation and uneven lignin deposition in SLRs. These different depositions may alter nutrient uptake, resulting in ion imbalance in plant, withered leaves, fewer tillers, and reduced tolerance to salt stress. Our findings suggest that OsCASP1 could play an important role in nutrient homeostasis and adaptation to the growth environment.

The soybean plasma membrane-localized cation/H+ exchanger GmCHX20a plays a negative role under salt stress.

Cation/H+ -exchanger (CHX) perform diverse functions in plants, including being a part of the protective mechanisms to cope with salt stress. GmCHX1 has been previously identified as the causal gene in a major salt-tolerance quantitative trait locus (QTL) in soybean, but little is known about another close paralog, GmCHX20a, found in the same QTL. In this study, GmCHX20a was characterized along with GmCHX1. The expression patterns of the two genes and the direction of Na+ flux directed by overexpression of these two transporters are different, suggesting that they are functionally distinct. The ectopic expression of GmCHX20a led to an increase in salt sensitivity and osmotic tolerance, which was consistent with its role in increasing Na+ uptake into the root. Although this seems counter-intuitive, it may in fact be part of the mechanism by which soybean could counter act the effects of osmotic stress, which is commonly manifested in the initial stage of salinity stress. On the other hand, GmCHX1 from salt-tolerant soybean was shown to protect plants via Na+ exclusion under salt stress. Taken together these results suggest that GmCHX20a and GmCHX1 might work complementally through a concerted effort to address both osmotic stress and ionic stress as a result of elevated salinity.

In-Frame and Frame-Shift Editing of the Ehd1 Gene to Develop Japonica Rice With Prolonged Basic Vegetative Growth Periods.

Japonica rice has become increasingly popular in China owing to its superior grain quality. Over the past decades, "indica to japonica" projects have been proposed to promote cultivation of japonica rice in low latitudes in China. Traditionally, japonica varieties were planted mainly in mid latitudes in the northeast plain and Yangtze River region. The key obstacle for introducing elite mid-latitude japonica varieties to low latitudes is the severe shortening of growth period of the japonica varieties due to their sensitivity to low-latitude short photoperiod and high temperature. Here we report development of new japonica rice with prolonged basic vegetative growth (BVG) periods for low latitudes by targeted editing the Early heading date 1 (Ehd1) gene. Using CRISPR/Cas9 system, we generated both frame-shift and/or in-frame deletion mutants in four japonica varieties, Nipponbare, Longdao16, Longdao24, and Xiushui134. When planting at low-latitude stations, the frame-shift homozygous lines exhibited significantly longer BVG periods compared with wild-types. Interestingly, we observed that minor deletion of the first few residues within the receiver domain could quantitatively impair the function of Ehd1 on activation of Hd3a and RFT1, resulting in an intermediate-long BVG period phenotype in the homozygous in-frame deletion ehd1 lines. Field investigation further showed that, both the in-frame and frame-shift lines exhibited significantly improved yield potential compared with wild-types. Our study demonstrates an effective approach to rapid breeding of elite japonica varieties with intermediate-long and long BVG periods for flexible cropping systems in diverse areas or under different seasons in southern China, and other low-latitude regions.

Ectopic Expression of Gs5PTase8, a Soybean Inositol Polyphosphate 5-Phosphatase, Enhances Salt Tolerance in Plants.

Inositol polyphosphate 5-phosphatases (5PTases) function in inositol signaling by regulating the catabolism of phosphoinositol derivatives. Previous reports showed that 5PTases play a critical role in plant development and stress responses. In this study, we identified a novel 5PTase gene, Gs5PTase8, from the salt-tolerance locus of chromosome 3 in wild soybean (Glycine soja). Gs5PTase8 is highly up-regulated under salt treatment. It is localized in the nucleus and plasma membrane with a strong signal in the apoplast. Ectopic expression of Gs5PTase8 significantly increased salt tolerance in transgenic BY-2 cells, soybean hairy roots and Arabidopsis, suggesting Gs5PTase8 could increase salt tolerance in plants. The overexpression of Gs5PTase8 significantly enhanced the activities of catalase and ascorbate peroxidase under salt stress. The seeds of Gs5PTase8-transgenic Arabidopsis germinated earlier than the wild type under abscisic acid treatment, indicating Gs5PTase8 would alter ABA sensitivity. Besides, transcriptional analyses showed that the stress-responsive genes, AtRD22, AtRD29A and AtRD29B, were induced with a higher level in the Gs5PTase8-transgenic Arabidopsis plants than in the wild type under salt stress. These results reveal that Gs5PTase8 play a positive role in salt tolerance and might be a candidate gene for improving soybean adaptation to salt stress.

The Function of Inositol Phosphatases in Plant Tolerance to Abiotic Stress.

Inositol signaling is believed to play a crucial role in various aspects of plant growth and adaptation. As an important component in biosynthesis and degradation of myo-inositol and its derivatives, inositol phosphatases could hydrolyze the phosphate of the inositol ring, thus affecting inositol signaling. Until now, more than 30 members of inositol phosphatases have been identified in plants, which are classified intofive families, including inositol polyphosphate 5-phosphatases (5PTases), suppressor of actin (SAC) phosphatases, SAL1 phosphatases, inositol monophosphatase (IMP), and phosphatase and tensin homologue deleted on chromosome 10 (PTEN)-related phosphatases. The current knowledge was revised here in relation to their substrates and function in response to abiotic stress. The potential mechanisms were also concluded with the focus on their activities of inositol phosphatases. The general working model might be that inositol phosphatases would degrade the Ins(1,4,5)P3 or phosphoinositides, subsequently resulting in altering Ca2+ release, abscisic acid (ABA) signaling, vesicle trafficking or other cellular processes.

Differential Expression Proteins Contribute to Race-Specific Resistant Ability in Rice (Oryza sativa L.).

Rice blast, caused by the fungus, Magnaporthe grisea (M. grisea), lead to the decrease of rice yields widely and destructively, threatening global food security. Although many resistant genes had been isolated and identified in various rice varieties, it is still not enough to clearly understand the mechanism of race-specific resistant ability in rice, especially on the protein level. In this research, proteomic methods were employed to analyze the differentially expressed proteins (DEPs) in susceptible rice variety CO39 and its two near isogenic lines (NILs), CN-4a and CN-4b, in response to the infection of two isolates with different pathogenicity, GUY11 and 81278ZB15. A total of 50 DEPs with more than 1.5-fold reproducible change were identified. At 24 and 48 hpi of GUY11, 32 and 16 proteins in CN-4b were up-regulated, among which 16 and five were paralleled with the expression of their corresponding RNAs. Moreover, 13 of 50 DEPs were reported to be induced by M. grisea in previous publications. Considering the phenotypes of the three tested rice varieties, we found that 21 and 23 up-regulated proteins were responsible for the rice resistant ability to the two different blast isolates, 81278ZB15 and GUY11, respectively. Two distinct branches corresponding to GUY11 and 81278ZB15 were observed in the expression and function of the module cluster of DEPs, illuminating that the DEPs could be responsible for race-specific resistant ability in rice. In other words, DEPs in rice are involved in different patterns and functional modules' response to different pathogenic race infection, inducing race-specific resistant ability in rice.

Genome-Wide Analyses of the Soybean F-Box Gene Family in Response to Salt Stress.

The F-box family is one of the largest gene families in plants that regulate diverse life processes, including salt responses. However, the knowledge of the soybean F-box genes and their roles in salt tolerance remains limited. Here, we conducted a genome-wide survey of the soybean F-box family, and their expression analysis in response to salinity via in silico analysis of online RNA-sequencing (RNA-seq) data and quantitative reverse-transcription polymerase chain reaction (qRT-PCR) to predict their potential functions. A total of 725 potential F-box proteins encoded by 509 genes were identified and classified into 9 subfamilies. The gene structures, conserved domains and chromosomal distributions were characterized. There are 76 pairs of duplicate genes identified, including genome-wide segmental and tandem duplication events, which lead to the expansion of the number of F-box genes. The in silico expression analysis showed that these genes would be involved in diverse developmental functions and play an important role in salt response. Our qRT-PCR analysis confirmed 12 salt-responding F-box genes. Overall, our results provide useful information on soybean F-box genes, especially their potential roles in salt tolerance.

Recent amplification of Osr4 LTR-retrotransposon caused rice D1 gene mutation and dwarf phenotype.

A novel rice d1 mutant was identified using map-based cloning and comparative analysis of known d1 mutants. The mutant (d1-a) shows a mild dwarf trait, which differs only slightly from the wildtype in plant height at the tillering stage. The d1-a mutant is different from other d1 mutants. We found that it was interrupted by an Osr4 long terminal repeat (LTR)-retrotransposon, which resulted in the loss of exon 7 in the mutant D1 mRNA. A paralog of the D1 gene, D1-like, was revealed. D1-like is a truncated gene that might have resulted from recombination between retrotransposons. We identified 65 Osr4 LTR-retrotransposons in Nipponbare, and found more LTR variants in contrast to coding DNA sequence (CDS) in the retrotransposons. We also identified five possible regulatory motifs in LTRs which may control the expression of the retrotransposons. In addition, we predicted six putative functional Osr4 retrotransposons that contain complete CDSs and all important elements. Osr4 retrotransposons were classified into 4 groups, and this type of retrotransposon only appears to be present in monocots. Members of group I-1, which included all putative functional retrotransposons, showed a high similarity with each other. The retrotransposons were expressed in all tissues, at especially higher levels in some leaves and seeds. These findings imply that transpositions of group I-1 members might have occurred frequently and recently.

Whole-genome analysis revealed the positively selected genes during the differentiation of indica and temperate japonica rice.

To investigate the selective pressures acting on the protein-coding genes during the differentiation of indica and japonica, all of the possible orthologous genes between the Nipponbare and 93-11 genomes were identified and compared with each other. Among these genes, 8,530 pairs had identical sequences, and 27,384 pairs shared more than 90% sequence identity. Only 2,678 pairs of genes displaying a Ka/Ks ratio significantly greater than one were revealed, and most of these genes contained only nonsynonymous sites. The genes without synonymous site were further analyzed with the SNP data of 1529 O. sativa and O. rufipogon accessions, and 1068 genes were identified to be under positive selection during the differentiation of indica and temperate japonica. The positively selected genes (PSGs) are unevenly distributed on 12 chromosomes, and the proteins encoded by the PSGs are dominant with binding, transferase and hydrolase activities, and especially enriched in the plant responses to stimuli, biological regulations, and transport processes. Meanwhile, the most PSGs of the known function and/or expression were involved in the regulation of biotic/abiotic stresses. The evidence of pervasive positive selection suggested that many factors drove the differentiation of indica and japonica, which has already started in wild rice but is much lower than in cultivated rice. Lower differentiation and less PSGs revealed between the Or-It and Or-IIIt wild rice groups implied that artificial selection provides greater contribution on the differentiation than natural selection. In addition, the phylogenetic tree constructed with positively selected sites showed that the japonica varieties exhibited more diversity than indica on differentiation, and Or-III of O. rufipogon exhibited more than Or-I.

Mapping of quantitative trait loci underlying cold tolerance in rice seedlings via high-throughput sequencing of pooled extremes.

Low temperature is a major limiting factor in rice growth and development. Mapping of quantitative trait loci (QTLs) controlling cold tolerance is important for rice breeding. Recent studies have suggested that bulked segregant analysis (BSA) combined with next-generation sequencing (NGS) can be an efficient and cost-effective way for QTL mapping. In this study, we employed NGS-assisted BSA to map QTLs conferring cold tolerance at the seedling stage in rice. By deep sequencing of a pair of large DNA pools acquired from a very large F3 population (10,800 individuals), we obtained ∼450,000 single nucleotide polymorphisms (SNPs) after strict screening. We employed two statistical methods for QTL analysis based on these SNPs, which yielded consistent results. Six QTLs were mapped on chromosomes 1, 2, 5, 8 and 10. The three most significant QTLs on chromosomes 1, 2 and 8 were validated by comparison with previous studies. Two QTLs on chromosomes 2 and 5 were also identified previously, but at the booting stage rather than the seedling stage, suggesting that some QTLs may function at different developmental stages, which would be useful for cold tolerance breeding in rice. Compared with previously reported QTL mapping studies for cold tolerance in rice based on the traditional approaches, the results of this study demonstrated the advantages of NGS-assisted BSA in both efficiency and statistical power.

[Numerical analysis of morphological variation of germplasm resources of dioscorea].

OBJECTIVE: Botanical characters of germplasm resources of Dioscorea were observed and compared, which could to offer reference for its genetic improvement, germplasm resource identification and classification. METHOD: Based on field cultivation, twenty-four morphological traits of ninety-four Dioscorea germplasm resources were observed or determined. And the morphological differences among germplasm resources were compared by principal component analysis and cluster analysis. RESULT: There were ample morphological diversity in the twenty-four traits, in especially in leaf size and tuber characters of the ninety-four Dioscorea germplasm resources. The first seven principal components which accounted for 80. 957% of total variance were extracted from the principal component analysis. The ninety-four germplasm resources could be divided into four clusters, which belonging to Dioscorea opposite, D. persimili, D. fordii and D. alata respectively. CONCLUSION: There were large morphological variation among germplasm resources on Dioscorea. Identification of germplasm resources of Dioscorea should focus on leaf size and tuber characters.

[Differential protein analysis on the root response of rice with high phosphorous uptake efficiency to low phosphorous stress].

A comparative proteomics analysis was performed to identify the molecular response of a rice cultivar (Oryza sative cv. 'IRRI71331') with high phosphorous (P) uptake efficiency to low P stress. The hydroponically grown rice plants were provided with two levels of P (0.5 mg x L(-1) and 10 mg x L(-1)) supplied in quarter strength Kimura solution, and the root total proteins extracted on the 3rd and 6th day of treatments were separated by two-dimensional gel electrophoresis (2-DE). Comparing with the control (10 mg x L(-1) of P), a total of 29 protein spots under low P stress (0.5 mg x L(-1)) showed differences in their relative abundance, among which, 17 were higher, 11 were lower, and 1 was novel on the 3rd day, and 8 were induced, 19 were suppressed, 1 was disappeared, and 1 had no obvious change on the 6th day. Ten differentially expressed protein spots were identified by MALDI-TOF/MS, and searched in protein databases. According to the putative functions, the identified proteins were classified into four groups, i.e., signal transduction (glycine-rich RNA-binding protein, phosphate starvation response regulator-like), gene expression (putative pre-mRNA splicing factor, putative AAA-metalloprotease), metabolism (adenylosuccinate lyase, serpin, S-adenosylmethionine synthetase, MYB transcription factor-like protein), and ion transport (cation-transporting ATPase, sarcoplasmic reticulum protein). The identified proteins were involved in various physiological responses to enhance stress resistance, such as signal recognition and transduction, RNA cleavage, degradation of denatured protein, and ion transportation and cellular ion balance. The serine protease inhibitor and S-adenosylmethionine synthetase and the MYB transcription factor-like protein, which were the key proteins associated with P deficiency--tolerance of other species, were affected by the same stress for rice. The results indicated that the tolerance to low P stress was controlled by a complex signal transduction and metabolism regulation network in rice root system.

[Genetic analysis and gene mapping of cold-induced seedling chlorosis in rice].

We found that the seedlings of indica rice cultivar Dular showed chlorosis but the seedlings of japonica rice cultivar Lemont remained green under natural low temperature in early spring. Using an F2 population of Lemont Dular, we found that the difference of cold tolerance at seedling stage between Dular and Lemont is controlled by a single major gene, with the chlorosis allele being recessive. We named the gene cisc(t). With the help of SSR markers, cisc(t) was mapped in a 5.5 cM interval between SSR markers RM257 and RM242 on chromosome 9.

[Allelopathic potential and physiological mechanism of Oryza sativa L. under phosphorus deficiency stress].

In this paper, allelopathic rice PI312777 (PI) and non-allelopahtic rice Lemont (Le) were grown in the nutrient solution with two levels of phosphorus (P) supply, and their allelopathic effects on Echinochloa crus-galli L. were studied. The results showed that under phosphorous deficiency stress, the inhibitory effect of PI on E. crus-galli root growth had an obvious increase. After growing in the nutrient solution with low P supply (0.5 mg x L(-1)) for 5, 10 and 15 days, the inhibitory rate of PI on E. crus-galli root dry matter increased by 5.64%, 3.89% and 12.13%, respectively, while that of Le did not show the same trend, compared with normal P supply. With low P supply for 5, 10 and 15 days, PI allelopathic effect on the leaf POD activity of E. crus-galli increased by 20.19%, 15.47% and 6.68%, IAAoase activity increased by 18.08%, 17.71% and 12.50%, while NR activity increased by 13.89%, 18.60% and 2.10%, respectively, suggesting that under P deficiency, PI enhanced its allelopathic potential through two pathways, i.e., to increase the weed POD and IAAoase activities to slow down its growth rate, and to decrease the weed NR activity to affect its N uptake.

[Kinetic developmental genetics analysis of Hibiscus cannabinus plant height and stem diameter].

By using quantitative traits additive-dominance genetics model and developmental genetics model, this paper analyzed the developmental behaviors of gene expression for Hibiscus cannabinu plant height and stem diameter at its different growth stages. The results showed that at different growth stages, the unconditional and conditional genetics effects of plant height all showed dominance, while the additive effect was weak. No additive effect was found for stem diameter, but dominance effect was significant at each growth stage. Plant height and stem diameter all had active gene expression from July 28 to August 9, and from September 2 to September 14. There was no additive correlation between plant height and stem diameter, but positive dominance correlation was significant after August 21. The unconditional and conditional genetics effects of plant height and stem diameter were not completely the same. According to practice, conditional genetic analysis could indicate the gene expression more truly in the whole growth period. The ecological and genetics variation patterns of Hibiscus cannabinus plant height and stem diameter at different space-time growth stages implied by our research was of significance in Hibiscus cannabinus genetics and breeding in both theory and practice.

[Interactive effects between allelochemical substitutes].

In order to understand the allelopathic mechanisms of rice on weed, the allelochemical substitutes salicylic acid, p-hydroxybenzonic acid, cinnamic acid, vanillic acid and ferulic acid were used in an orthogonally gyrating regression experiment to study their interactive effects on the growth of barnyardgrass. The results indicated that whether the interactive effects between two substitutes, e.g., between salicylic and cinnamic acid or between salicylic and p-hydrobanzonic acid, were synergistic or antagonistic depended on the concentrations of each substitutes in the mixture. In the mixture of salicylic acid and p-hydrobanzonic acid, the effect of salicylic acid was synergistic at < 0.14 mmol.L(-1) but antagonistic at > 0.14 mmol.L(-1), while p-hydrobanzonic acid showed an antagonistic effect at > 0.425 mmol.L(-1). Salicylic acid at all test concentrations exhibited antagonism to cinnamic acid, while cinnamic acid had a synergistic at < 0.14 mmol.L(-1), but an antagonistic effect at >0.14 mmol.L(-1) on alicylic acid. The interactive effects between cinnamic and ferulic acid were all synergistic at test concentrations.

[Corresponding analysis on rice grain heavy metal pollution in Fujian province].

By the methods of environmental statistics and corresponding analysis, this paper collected 38 early and late rice grain samples from the middle, southern, northern, western and eastern parts of Fujian Province to detect their Hg, As, Cr, Cd and Pb contents, and to search for the main factors resulting in the difference of rice cropping type in different regions, aiming at further understanding the relationships between heavy metal pollution and rice cropping type. The results showed that among the test heavy metals in grain, Pb had the highest percentage (100%) beyond the standard level, followed by Hg (78.95%), Cd (50.5%) and Cu (2.63%), while As did not surpass the standard level. It therefore could be concluded that Pb and Cd were the main factors resulting in the difference of rice cropping type in different regions. The results also showed that 38 rice grain samples could be clustered into 7 groups, indicating that different rice cropping types would significantly cause different degrees of heavy metal pollution, which suggested that the best way in controlling and preventing rice grain heavy metal pollution could be the approach of combining site-controlling with variety selection, based on the situation of different regions and rice cropping systems.