Frontiers of Agriculture in China

ISSN 1673-7334

ISSN 1673-744X(Online)

CN 11-5729/S

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Current progress on genetic interactions of rice with rice blast and sheath blight fungi
Yulin JIA, Guangjie LIU, Stefano COSTANZO, Seonghee LEE, Yuntao DAI
Front Agric Chin. 2009, 3 (3): 231-239.

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Analysis of genetic interactions between rice and its pathogenic fungi Magnaporthe oryzae and Rhizoctonia solani should lead to a better understanding of molecular mechanisms of host resistance, and the improvement of strategies to manage rice blast and sheath blight diseases. Currently, dozens of rice resistance (R) genes against specific races of the blast fungus have been described. Among them, ten were molecularly characterized and some were widely used for breeding for genetic resistance. The Pi-ta gene was one of the best characterized rice R genes. Following the elucidation of its molecular structure, interaction, distribution, and evolution, user friendly DNA markers were developed from portions of the cloned genes to facilitate the incorporations of the Pi-ta mediated resistance into improved rice varieties using marker assisted selection (MAS). However, rice blast is still a major threat for stable rice production because of race change mutations occurring in rice fields, which often overcome added resistance based on single R genes, and these virulent races of M. oryzae pose a continued challenge for blast control. For sheath blight, progress has been made on the exploration of novel sources of resistance from wild rice relatives and indica rice cultivars. A major quantitative trait locus (QTL), named qSB9-2, was recently verified in several mapping populations with different phenotyping methods, including greenhouse methods. The ability to identify qSB9-2 using greenhouse methods should accelerate the efforts on the qSB9-2 fine mapping and positional cloning.

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Cloning and structure analysis of an NBS-LRR disease-resistant gene from Setaria italica Beauv
Qiaoyun WENG, Zhiyong LI, Jihong XING, Zhiping DONG, Jingao DONG
Front Agric Chin. 2009, 3 (3): 240-246.

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Degenerate PCR primers targeting conserved motifs of most NBS-LRR disease-resistant genes in plants were tested in Setaria italica Beauv. cultivar Shilixiang, which is resistant to Uromyces setariae-italicae. A sequence with a length of 2673 bp has been obtained by using Genomic Walking technology. The nucleotide sequence contained an open reading frame that encoded 891 amino acid residues with a calculated molecular mass of 101.44 kDa. It was named RUS1 (Resistance against Uromyces setariae-italicae, GenBank No. FJ467296). It contained an NB-ARC domain and three conserved motifs P-loop, kinase 2, and kinase 3, which had the characteristics of NBS-LRR type resistant gene of plant. Phylogenetic analysis indicated that it was similar to RPM1 and might belong to LZ-NBS-LRR type disease resistance gene. Southern blotting result displayed that there were at least three copies of RUS1 in the foxtail millet genome.

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Isolation and characterization of Bacillus subtilis EB-28, an endophytic bacterium strain displaying biocontrol activity against Botrytis cinerea Pers.
Shutong WANG, Tongle HU, Yanling JIAO, Jianjian WEI, Keqiang CAO
Front Agric Chin. 2009, 3 (3): 247-252.

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The fungal pathogen Botrytis cinerea Pers. causes severe rotting on tomato fruits during storage and shelf life. As a biological control agent, endophytic bacterium was regarded as an effective alternative to chemical control. Out of 238 endophytic bacterial isolates, three strains (EB-15, EB-28, and EB-122) isolated from Lycopersicum esculentum Mill., Speranskia tuberculata (Bge.) Baill, and Dictamnus dasycarpus Turcz. respectively were found to be strongly antagonistic to the pathogen in vitro and were selected for further in vivo tests. One endophytic bacterium strain, encoded EB-28, was selected from the three in vivo tested isolates. The inhibitive rate of EB-28 reached 71.1% in vitro and 52.4% in vivo. EB-28 was identified as Bacillus subtilis according to its morphological, physiological, and biochemical characteristics and 16S rDNA sequence analysis.

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Studies on induction of chlorophyll mutations in soybean, Glycine max (L.) Merrill
Mudasir Hafiz KHAN, Sunil Dutt TYAGI
Front Agric Chin. 2009, 3 (3): 253-258.

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The phenotypic response of two soybean cultivars to a chemical mutagen (ethyl methane sulphonate, EMS), physical mutagen (gamma rays) and their combinations were studied in M1 and M2 generations and the frequency and spectrum of chlorophyll mutations were worked out. Combined treatment was found to be more effective in inducing chlorophyll mutations compared to individual treatments of gamma rays and EMS in both the cultivars. As far as the spectrum of chlorophyll mutations is concerned, a wider spectrum in both the cultivars was observed in 45 kR + 0.2% EMS combined treatment.

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Improvement of organic phosphate acquisition in transgenic tobacco plants by overexpression of a soybean phytase gene Sphy1
Li GUO, Yuxin ZHAO, Shuhua ZHANG, Haina ZHANG, Kai XIAO
Front Agric Chin. 2009, 3 (3): 259-265.

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Due to the huge amount in the soil, phytate is an important potential source for providing the plants with available phosphorus (Pi) by the involved catalytic reaction of phytase. In this study, a construct fusing the open reading frame (ORF) of Sphy1 into corresponding positions in the fragment of binary expression vector pBI121 was created and used to transform tobacco. Molecular identification by PCR and RT-PCR indicated the target gene Sphy1 in the transgenic tobacco plants was transcribed under the regulation of an upstream promoter. Compared with the control plants, the phytase activities in all the transgenic plants were increased, with the increased range consistent with the expression levels in the transgenic plants. Under the growth conditions with phytate as the sole phosphorus source, the transgenic line 1 plants displayed a high expression level of Sphy1 and shows notable improved growth performance, such as higher fresh weight and dry weight, as well as higher total P content and more accumulative P amount per plant than CK. This clearly indicated that overexpression of Sphy1 could improve the phosphorus acquisition by the extruded Sphy1 phytase in the rhizosphere, where this enzyme could catalyze the degradation of the phytate and release the available Pi for plants. The Sphy1 gene seemed to have a potential value in the creation of new crop cultivars with high phosphorus use efficiency.

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Effects of mannitol induced osmotic stress on proline accumulation, pigment degradation, photosynthetic abilities and growth characters in C3 rice and C4 sorghum
Suriyan CHA-UM, Souvanh THADAVONG, Chalermpol KIRDMANEE
Front Agric Chin. 2009, 3 (3): 266-273.

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Osmotic stress is one of the most important abiotic factors which inhibit growth and development in both the vegetative and reproductive stages of many plant species. The aim of this investigation was to compare the biochemical and physiological responses in C3 rice and C4 sorghum to water deficit. Chlorophyll a (Chla), chlorophyll b (Chlb), total chlorophyll (TC) and total carotenoid (Cx+c) contents in both rice and sorghum seedlings under osmotic stress were adversely affected, related to increasing osmotic pressure in the culture media. In addition, the chlorophyll’s fluorescence parameters and net photosynthetic rate (Pn) decreased, leading to growth reduction. Also, a positive correlation was found between physiological and biochemical data, while proline accumulation showed a negative relationship. The Chlb, Pn and fresh weight were maintained better in osmotic-stressed (-1.205 MPa) C4 sorghum seedlings than those in C3 rice seedlings. The growth and physiological responses of C3 rice and C4 sorghum decreased depending on the plant species, the osmotic pressure in the media and their interactions. Pigment content and Pn ability in C4 sorghum grown under mannitol-induced osmotic stress increased to a greater degree than in C3 rice, resulting in maintenance of growth.

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Accumulation of lipoproteins in Chinese winter wheat cultivars and their impact on dough mixing characteristics
Zhiying DENG, Jichun TIAN, Yongxiang ZHANG, Cailing SUN, Jiansheng CHEN
Front Agric Chin. 2009, 3 (3): 274-278.

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The changes in the accumulation of lipoproteins, the relationship between lipoproteins and the dough mixing characteristics of Chinese winter wheat (Triticum aestivum L.) were investigated for six cultivars that differ in quality characteristics and was classified into three groups according to their gluten index. All cultivars were grown under the same experimental field conditions, with three replicates. The lipoproteins were found to accumulate during the early stages of grain development. The rate of lipoproteins’ accumulation appeared to follow a similar pattern of marked increase during the time from 5 DAA (days after anthesis) to 15 DAA, with a peak at 15 DAA, then quickly decreased for the same group of cultivars. Different patterns appeared from 20 DAA until maturity, but those cultivars with medium quality gluten showed a significant decrease during this period. Significant differences were found in lipoproteins for the six cultivars during grain development on the same days after anthesis. Correlation analysis indicated that lipoproteins from 25 DAA to 30 DAA were positively correlated with dough mixing parameters. However, the correlation coefficients were not statistically significant.

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Somatic embryogenesis and plant regeneration in glandless upland cotton (Gossypium hirsutum L.)
Jingyan SUN, Weiming LI, Hanshuang ZHANG, Junli ZHAO, Xiaolin YIN, Li’an WANG
Front Agric Chin. 2009, 3 (3): 279-283.

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Glandless upland cotton has an important economic value. Embryogenic calli and regenerated plants were obtained from the hypocotyl explants of glandless upland cotton seedlings, cultivar Jisheng1. The results indicated that somatic embryogenesis was significantly influenced by the types of auxin and cytokinin. 2, 4-D was advantageous to induce cotton callus, but embryogenic callus could not be obtained on the 2, 4-D medium. Embryogenic calli were also not obtained on the MSB sold medium with the combination of IBA and BA. However, embryogenic calli were induced when the hypocotyl explants were cultured on the IBA and KT medium. More than 31% of the hypocotyl segments produced embryogenic calli when the MSB medium was supplemented with 1.0 mg·L-1 IBA and 0.5 mg·L-1 KT. Embryogenic calli with somatic embryos could be observed within three months. Somatic embryo germination and maturation occurred on the hormone-free MSB medium with 1.0 g·L-1 Gln and 0.5 g·L-1 Asn. A number of regenerated plants could be obtained in six months. In the present study, a simple and efficient system was established to induce a number of embryogenic calli and regenerate plantlets from hypocotyl explants.

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Ecological effect analysis of pumpkin and oil sunflower intercropping in arid area of northwest Hebei Province: I. moisture analysis
Junhua ZHANG, Wei HUANG, Fenglu ZHANG, Lifeng ZHANG
Front Agric Chin. 2009, 3 (3): 284-290.

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Experiments were conducted during 2007-2008 at the Zhangbei Agricultural Resource and Ecological Environment Key Field Research Station, Hebei Province, China to study water-efficient pumpkin planting patterns in this area. Four treatments of pumpkin and oil sunflower intercropping were used to study the problem of water resource scarcity and inefficient water use in the plateau of northern Hebei Province. The four treatments were: pumpkin sole cropping (Sp), oil-sunflower sole cropping (So), intercropping one row oil sunflower (IC1) or two rows (IC2) between pumpkin rows. The results showed that oil sunflower competed for soil water with pumpkin during late growth stage of pumpkin in IC2, but there was no water competition in IC1. Total rainfall during the growing season was 201.6 mm and the soil water balance differed between treatments. In all cases the water percolation was low and soil moisture storage always negative. Nearly all water loss was through evapotranspiration, which varied by treatment. The seasonal evapotranspiration of IC1 was less than SO, Sp and IC2, 46.57%, 41.22% and 46.73%, respectively. Economic yield of pumpkin decreased from 30.00% (IC1) to 71.42% (IC2). However, yield per plant of intercropping oil sunflower increased from 190.71% to 241.26%, as compared with So, because oil sunflower showed remarkably partial advantage. The Land Equivalent Ratio (LER) of pumpkin-oil sunflower was 1.08-1.22, and the Water Equivalent Ratio (WER) of pumpkin-oil sunflower was 1.07-1.26. Economic value of sole pumpkin was greatest but did not differ from treatment IC1. Other treatments had significantly less economic value. In this region of rain-fed dry land farming, a sparse planting of sole pumpkin with high efficiency production could realize water resources most effectively in the Plateau of northern Hebei Province.

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Effects of grading on the main quality attributes of peanut kernels
Jiancheng ZHANG, Chuantang WANG, Yueyi TANG, Xiuzhen WANG
Front Agric Chin. 2009, 3 (3): 291-293.

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Near infrared reflectance spectroscopy (NIRS) analysis of peanut kernels of different grades by mainly using advanced breeding lines derived from intersectional crosses in 2 experiments gave similar results, showing remarkable inter-grade variation in oil content of a specific entry. The effects of genotype on qualitative attributes proved to be predominant. No significant differences in protein content, oleic acid/linoleic acid content in total fatty acids, and oleic acid/linoleic acid ratio were detected among the No. 1, No. 2 and No. 3 grade peanut kernels of a given peanut genotype.

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Determination of ultratrace cadmium in food and environmental samples by ETAAS after vapor generation and in situ preconcentration
Ran SUO, Weijuan AN, Na LI
Front Agric Chin. 2009, 3 (3): 294-299.

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A method is described for the determination of ultratrace cadmium by coupling a continuous flow vapor generation system with in situ preconcentration technique and electrothermal atomic absorption spectrometry (ETAAS). A graphite tube coated with Ir as permanent chemical modifier was used for trapping cadmium vapor species. The effects of the flow rates of carrier gas and sample injection in vapor generation systems on the trapping measurement for cadmium were respectively investigated. Graphite tubes with different characteristic surfaces were comparatively studied for trapping cadmium vapor. The experimental results showed that the permanent chemical modifier of Ir is an alternative to the thermolabile modifier of Pd for simplifying the trapping measurement. The trapping efficiency of cadmium on the graphite tube coated with Ir was estimated. The trapping temperature and time were also investigated. A detection limit (3σ) of 0.005 μg·L-1 was obtained for this proposed method. The relative standard deviation (RSD) was 1.4% for 0.5 μg·L-1 of Cd (n=11). This method can be applied to the determination of ultratrace cadmium in food and environmental samples with good agreement between the certified and found values.

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Behavioral patterns of captive alpine musk deer: sex-specific behavior comparisons
Lin LU, Peishi YAN, Xiuxiang MENG, Jinchao FENG, Hongfa XU, Qisen YANG, Zuojian FENG
Front Agric Chin. 2009, 3 (3): 300-303.

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The aim of this study was to document the behavior of captive alpine musk deer and to determine if daily behavior patterns varied between females and males. From August 2002 to January 2003, focal sampling was used to observe 32 adult captive alpine musk deer (13 female and 19 male) at Xinglongshan Musk Deer Farm (XMDF), Xinglongshan National Nature Reserve, Gansu Province. Results indicated similar behavior patterns for males and females, with only two out of 12 recorded behaviors showing significant sex differences. In comparison to females, males rested for a longer duration and exhibited tail pasting more frequently. This study also provided the first recording of tail pasting by female musk deer.

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The identification of MacSe in Streptococcus equi ssp. equi
Jiande YANG, Yanfei LIU, Jun XU, Jifei MA
Front Agric Chin. 2009, 3 (3): 304-310.

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Streptococcus equi subsp. equi (S. equi ssp. equi) causes equine strangles, a highly contagious and widespread purulent lymphadenitis of the head and neck. We have identified MacSe, a novel protein of S. equi, by screening a phage library of 3-8 kb random DNA fragments of S. equi CF32. MacSe shares 62% and 67.5% amino acid homology with Mac5005 and Mac8345 of S. pyogenes respectively. Expression during infection was shown by strong reactivity of the protein with convalescent sera and mucosal wash IgA of ponies infected by commingling exposure. Release into the culture medium was detected during the log phase of growth. Dose dependent anti-phagocytic activity for equine neutrophils involved interaction of MacSe with C3 and neutrophils.

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Effect of oilseeds rich in linoleic and linolenic acids on milk production and milk fatty acid composition in dairy cows
Yanxia GAO, Tao SUN, Jianguo LI
Front Agric Chin. 2009, 3 (3): 311-318.

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Nine multiparous cows averaging 93±13 days in milk production (DIM) were used in a triple 3×3 Latin square design to determine the effects of feeding them whole roasted flaxseed, cracked roasted soybean and fresh alfalfa in the diet on milk production, milk fatty acid profiles and the digestibility of nutrients. Each experimental period lasted 30 d and a sample collection was performed during the last 7 d. The cows were fed on the control basal diet (CON) or diets containing whole roasted flaxseed (FLA) or cracked roasted soybean (SOY). All diets were fed as a total mixed ration (TMR) and had similar concentrations of crude protein (CP), Net Energy Lactation (NEL), acid detergent fibre (ADF) and neutral detergent fibre (NDF). The dry matter intake (DMI) was not significantly different (P>0.05), but tended to increase in FLA and SOY diets compared with the control (P>0.05). Cows in all treatments had a similar milk yield, although 4% fat corrected milk (FCM) yield was higher on the FLA and SOY diets than on the CON diet. Milk fat percentage (3.45%) increased in the FLA diet compared with the control (3.31%) and SOY diets (3.39%). Milk protein percentages were similar among the diets (P>0.05). There were similar digestibilities of DM, CP and ADF among the treatments and lower digestibilities of NDF and ether extract in the SOY diet compared with the CON diet. Feeding various oilseeds significantly increased the concentrations of C18∶1, C18∶3 and conjugated linoleic acid (CLA). The FLA diet decreased the ratio of omega-6 to omega-3 fatty-acids in the milk, which would improve the nutritive value of the milk.

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Variation of 184C→T of goat callipyge gene in different populations and its effect on body weight
Xianglong LI, Hailiang WANG, Rongyan ZHOU, Guiru ZHENG, Lanhui LI, Zunan SHEN
Front Agric Chin. 2009, 3 (3): 319-324.

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In order to investigate its distribution in different goat populations, one SNP (184C→T, corresponding to AY850925) of goat callipyge (CLPG) gene recognized by Fork I was identified after sequencing 23 individuals from 10 breeds. PCR-RFLP was carried out according to the variation site in 584 goats of 14 populations from 11 provinces and autonomous regions in China. An interesting result was found that the Boer goat having the characteristics of double muscle had significantly higher T allele (0.2465) frequency and lower C allele (0.7535) frequency compared to other breeds. It could be inferred that the 184C→T mutation might be related to the double muscle characteristics of the Boer goat. The general linear model analysis showed that parental genotype had significant effect on the body weight of their offspring at different ages. It could be inferred that transition of 184C→T might be a paternal imprinting form, a polar over-dominance, in which only individuals that received the allele from their mother expressed the callipyge phenotype. The double muscle characteristics of the Boer goat might be related to its maternal genotype. More data with detailed information need to be investigated in order to confirm this assumption.

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Chemical composition and antimicrobial activity of the essential oil of Syzygium aromaticum flower bud (Clove) against fish systemic bacteria isolated from aquaculture sites
Seongwei LEE, Musa NAJIAH, Wee WENDY, Musa NADIRAH
Front Agric Chin. 2009, 3 (3): 332-336.

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This paper describes the chemical composition and antimicrobial activity of the essential oil of Syzygium aromaticum against Vibrio spp. (n=6), Edwardsiella spp. (n=21), Aeromonas spp. (n=2), Escherichia coli (n=2), Flavobacterium spp. (n=1), Salmonella spp. (n=2), Streptococcus spp. (n=1) and Pseudomonas spp. (n=1) isolated from aquaculture sites as well as seven reference strains of bacteria, namely, Escherichia coli (ATCC 25922), Citrobacter freundii (ATCC 8090), Aeromonas hydrophila (ATCC 49140), Pseudomonas aeruginosa (ATCC 35032), Streptococcus agalactiae (ATCC13813), Edwardsiella tarda (ATCC 15947) and Yersinia enterocolitica (ATCC 23715). Nowadays, most antibiotics are no longer effective in controlling diseases in aquaculture, especially fish systemic bacterial diseases, due to increasing incidences of antibiotic resistance among pathogenic bacteria. Furthermore, many countries have banned antibiotics in aquaculture use due to public health concerns and environmental hazards. Therefore, this study was carried out to evaluate the potential of the essential oil of S. aromaticum as an alternate commercial antibiotic to antimicrobial agents against fish systemic bacteria in aquaculture. The essential oil of S. aromaticum was prepared using a steam distillation method, and the chemical composition was analysed using Gas chromatography–mass spectroscopy (GC–MS). Minimum inhibitory concentration (MIC) values of the essential oils against the tested bacteria were determined using the broth two fold micro dilution method, with kanamycin and eugenol as positive controls. The MIC values of the essential oil of S. aromaticum ranged from 0.015 μg·mL-1 to 0.062 μg·mL-1 against the tested bacterial isolates. A total of nine chemical compounds were detected in the essential oil, with eugenol (49.0%) and caryophyllene (7.5%) being the major compounds. The results of the present study indicate that the essential oil of S. aromaticum shows a huge potential to substitute commercial antibiotics as antimicrobial agents for aquaculture use.

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Genetic diversity of Robinia pseudoacacia populations in China detected by AFLP markers
Xuemei HUO, Hongwei HAN, Jun ZHANG, Minsheng YANG
Front Agric Chin. 2009, 3 (3): 337-345.

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The genetic diversity of ten Robinia pseudoacacia L. populations collected from China was analyzed by amplified fragment length polymorphism (AFLP) technique using ten primer combinations. A total of 752 amplified bands were obtained, among which 352 (46.8%) were polymorphic. At species level, the percentage of polymorphic loci (P) was 49.87%, the Shannon’s information index (I) was 0.2160, and the mean Nei’s gene diversity index (H) was 0.1403. At population level, P=25.47%, I=0.1381, and H=0.0927. The genetic diversity within populations was higher than that among populations. The coefficient of gene differentiation among populations within species (Gst) was 0.390, which indicated that gene differentiation was mainly within the population, and between populations, it accounted for 33.90% of the total variation. Gene flow (Nm) between the populations was 0.975, suggesting that the gene exchange between populations was small. The UPGMA cluster analysis showed that the ten populations were divided into three major groups, and most individuals from the same population were clustered together. There was no significant correlation between the genetic diversity parameters (D, IN, P, Ne, H, and I) and geographic and climatic factors (longitude, latitude, annual mean temperature, and annual mean precipitation). The results provide useful information about the level of genetic diversity, and it has a wide application prospect in Robinia pseudoacacia L. utilization and breeding in China.

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Influences of leaf litter replacement on soil biochemical characteristics of main planted forests in Qinling Mountains of China
Zengwen LIU, Erjun DUAN, Wenjun GAO
Front Agric Chin. 2009, 3 (3): 346-352.

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Long-term continuous growth of the same tree species in planted pure forest will lead to soil polarization and degradation. Mixed forestation or litter replacement between different needle- and broad-leaved forests are effective measures, except fertilization, to control soil polarization according to the mutual compensation principle of different tree species. Through a two-year leaf litter replacement experiment in 4 typical planted pure forests of Larix kaempferi, Pinus tabulaeformis, Catalpa fargesii and Quercus aliena var. acuteserrata in Qinling Mountains of China, influences of leaf litter replacement on soil biochemical characteristics and their interspecific relationships were studied and main conclusions were reached as follows. (1) Annual leaf litter decomposition rate of broad-leaved forests was 33.70 % higher than those of needle-leaved forests and increased by 8.35%-12.15% when needle-leaved litter was replaced with broad-leaved forests, whereas it decreased by 5.38%-9.49% when broad-leaved litter was replaced with needle-leaved forests. (2) Leaf litter replacement between needle- and broad-leaved forests popularly raised the contents of organic C, available N, P and K in soil, whose content increments in the needle-leaved forests (8.70%-35.84%) were obviously more than those in the broad-leaved forests (3.73%-10.44%), and in the former, the content increments after replacement with the litter of Catalpa fargesii (24.63%-35.84%) were more than those after replacement with the litter of Quercus aliena var. acuteserrata (8.70%-28.15%). Furthermore, the litter replacement was found to make the soil pH of needle-leaved forests developed from light-acid to neutral. (3) Litter replacement of the needle-leaved forests with the broad-leaved litter popularly raised enzyme activities, amounts of microorganisms and contents of micro-biomass C and N in soil, the increments of which after replacement with the litter of Catalpa fargesii were also more than those after replacement with the litter of Quercus aliena var. acuteserrata; while the litter replacement of broad-leaved forests with needle-leaved litter resulted differently depending upon the tree species. Among them, the soil enzyme activities and contents of micro-biomass C and N in the forest of Quercus aliena var. acuteserrata raised while they lowered in the forest of Catalpa fargesii.

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Effect of extracts of Chinese pine on its own seed germination and seedling growth
Meiqiu ZHU, Changming MA, Ying WANG, Lili ZHANG, Hui WANG, Yuxin YUAN, Kejiu DU
Front Agric Chin. 2009, 3 (3): 353-358.

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The allelopathic potential of Chinese pine (Pinus tabulaeformis Carr.) against its own seed germination and seedling growth was tested with aqueous extracts (0.01, 0.02, 0.05, and 0.10 g·mL-1) obtained from different organs (roots and litter needles) at different individual ages (12, 52, and 110 years old). The results showed that root and litter extracts had different effects on seed germination and seedling growth, and the effects varied with the concentrations, the organs, and the tree age of extracts. The strongest stimulatory effect on seed germination of Chinese pine was exposed to 0.02 g·mL-1 root extract from the 110 years old Chinese pine trees and exposed to 0.02 g·mL-1 litter extract from the 12 years oldChinese pine trees. Meanwhile, the strongest stimulatory effect on growth of Chinese pine seedlings was exposed not only to 0.01 g·mL-1 root extracts from the 110 years old Chinese pine but also to 0.01 g·mL-1 litter extract from the 12 years old Chinese pine. The promoting effect of the extracts of root on seed germination and seedling growth increased in the order of 12, 52, and 110 years old. The promoting effect of the extracts of litter on seed germination and seedling growth increased in the order of 110, 52, and 12 years old. Our results suggested that litter leachates or root exudates of Chinese pine may influence the natural regeneration within Chinese pine stands via the release of allelochemicals into the environment.

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19 articles