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The present study focused on the difference between rhizosphere and non-rhizosphere soil nitrogen in the Stipa breviflora desert steppe in Inner Mongolia. The results showed that soil nitrogen contents in rhizosphere were always higher than those in non-rhizosphere in S. breviflora under every treatment. With the increase of soil depth, the contents of total nitrogen, ammonium nitrogen and nitrate nitrogen in both rhizosphere and non-rhizosphere soil decreased. For 0-10 and 20-30 cm soil depth under different grazing rates, total nitrogen contents in rhizosphere soil and non-rhizosphere soil had similar change. The ammonium nitrogen and nitrate nitrogen contents increased in rhizosphere soil of same depth with light grazing rate which suggested that optimal grazing was positive for nitrogen accumulation. In vertical direction under different grazing rate, the total nitrogen contents in soil 0-10 cm was higher than those in 20-30 cm soil.
The nest-style method was used to investigate the response of plant community characteristics to grazing pressure to analyze the position and function of wapiti in the grazing system in the winter pasture of Gansu wapiti in Sunan Yugu National Autonomous County where wapiti has an important effect on protecting, restoring and reconstructing of degenerated grassland ecosystem. This study showed that the plant density, coverage and aboveground biomass increased with the increase of grazing intensity, and they were a linear positive correlation with grazing rate when plant height was below 10 cm. The plant litter biomass reached a peak in wither period (middle October), and it had a significant negative correlation with the grazing rate. The grazing made the plant miniaturization, and the species richness had a decrease trend with the increasing grazing intensity under given grazing rate. A complex interaction relationship between grazing intensity and plant miniaturization was observed in this study.
The influence of different grazing intensities on the spatial heterogeneity of Leymus chinensis and Stipa grandis steppe vegetation and soil nitrogen in Bashang area of Hebei Province was studied using analysis of variance and land statistics. The results showed that the variation function of vegetation density and soil nitrogen was mostly accordance with the spherical and exponential model. The spatial distribution of vegetation community density in light grazing and moderate grazing areas and the spatial distribution of soil nitrogen in heavy grazing area were mostly influenced by random factors, while the spatial distribution of vegetation community density in non-grazing and heavy grazing areas were mostly influenced by space structural factors. Grazing reduced the spatial heterogeneity of vegetation density which resulted in that in non-grazing area (sill=0.116 8) was larger than that in the grazing area (average of sill=0.019 5). With the increase of grazing intensities, the spatial heterogeneity of soil ammonium nitrogen and nitrate nitrogen firstly decreased and then increased. Spatial heterogeneity of soil ammonium nitrogen, nitrate nitrogen significantly increased in the heavy grazing area with the sill values of 5.642 0 and 2.681 0, respectively, which were greater than the other three treatments. In conclusion, the spatial distribution of vegetation density had similar variation with the spatial distribution of soil nitrate nitrogen under the same grazing treatment.
A study was conducted in fenced grassland (F, fenced for 7 years) and grazed grassland (G) on the Loess Plateau to investigate the seasonal variation of the contents of soil ammonium nitrogen(N-N) and nitrate nitrogen (N-N). Redundancy analysis was also used to study the effects of soil water content, above-ground green biomass and microbial biomass carbon on N-N and N-N contents. The results showed that N-N was the main component of soil available nitrogen in both fenced and grazed grasslands. In the 0-10 cm soil layers of the two sites, soil N-N and nitrate nitrogen were mainly controlled by above-ground green biomass. In the 10-20 cm soil layers, soil N-N and nitrate nitrogen were mainly controlled by both of soil water content and above-ground green biomass in fenced grassland, while soil N-N and N-N were mainly controlled by above-ground green biomass in grazed grassland. There was significantly positive correlations (P<0.05) between N-N and N-N in the two sites. The results indicated that the higher above-ground biomass after fencing for 7 years increased litter inputs and soil organic matter, thus increased substrate for nitrogen mineralization. In addition, soil water content significantly increased in most seasons (P<0.05) and all of these factors promoted the nitrogen mineralization in the soil.
Five different types of cultivated lands, which were mainly planted for barley (Avena nuda), potato (Solanum tuberosum), alfalfa (Medicago sativa), sickle alfalfa (Medicago falcata) and rape (Brassica campestris) mixed with pea (Pisum sativum), respectively, were selected in Longzi County, Tibet and the nitrogen status of various forms, phosphorus content, soil organic matter (SOM) content and soil pH were analyzed in the present study. The results showed that the average soil nutrient contents in different types of cultivated lands were different and SOM and total N contents in potato land were significantly higher (P<0.05) than the other four cultivated lands. In general, the average contents of SOM and total N for all five cultivated lands were 2.59% and 0.18%, respectively, which indicated that the soil fertility was high in all cultivated lands. There was little variations for ammonium contents in different cultivated lands, however, there was strong variations for nitrate contents in different cultivated lands with the highest nitrate content in sickle alfalfa farmland. The C/N ratio of SOM was low which attributed to accelerate the mineralization of soil organic nitrogen. Phosphorus content was rich in all the five types of cultivated lands with the average content of 0.13% although it was a little bit lower in the two types alfalfa lands. The mean pH of all the lands changed from 8.12 to 8.48, which suggested that it was all alkalescence in Longzi. Different crops had different effects on soil pH and barley land had significantly higher pH than that of other lands. There were complicated correlations between soil nutrient properties in the soils of cultivated lands. Both SOM and total N had very positively significantly correlation (P<0.01) with total P, ammonium and nitrate N. There was no correlations between each other of total N, ammonium and nitrate N. Soil pH had very negatively significantly correlation (P<0.01) with nitrate N.
Grassland degradation had characteristic of vegetation and soil degradation synchronization. In order to study the relationships between community biomass and soil nutrient during degradation processes in the northern Tibet grassland, alpine grassland in Nagqu, northern Tibet with different degraded degrees were selected to study the variations of soil nutrients and above ground biomass. The results showed that with increasing of grassland degradation, aboveground biomass and soil organic matter significantly decreased. Total nitrogen, total phosphorus and total potassium had significant positive correlation with soil organic matter (P<0.05) whereas soil pH had significant negative correlation with soil organic matter content (P<0.05). Aboveground biomass had significant positive correlation with soil organic matter content (P<0.05) but had no correlation with total nitrogen, total phosphorus, total potassium and pH (P>0.05).
In order to explore the effects of nitrogen (N) deposition on grassland plant metabolism function,this study conducted N fertilization addition on the Loess Plateau natural grassland by simulating nitrogen deposition and analyzed leaves N content, net photosynthetic rate(Pn), stomata conductance(Gs), transpiration rate(Tr), water use efficiency(WUE) and Chlorophyll content of Stipa bungeana on different N addition levels to explore the effects of nitrogen addition on photosynthetic characteristics and leaf senescence of S. bungeana. The results showed the N content, chlorophyll content, net photosynthetic rate and water use efficiency increased significantly with N addition. However, the stomata conductance and transpiration rate did not response to N addition remarkably. In addition, the chlorophyll degradation rate of S. bungeana was delayed by N addition. This paper revealed that nitrogen fertililization played primary roles in regulating photosynthetic characteristics and leaf senescence of S. bungeana, also appropriate nitrogen deposition could improve photosynthetic performance and delay leaf senescence of S. bungeana.
Grass brick is a frequently used material of urban ground surface. The maintenance of the grass is a big problem after establishment. Whether the degenerated grass brick has different thermal contribution to surrounding environment or not is the key point of the study. Based on the observedone year’ data of 3 frequently-used surface materials including grass brick, degenerated grass brick and concrete brick’s, the annual temperature variations, relevant level of meteorology factors and influence factors of the land surfaces were analyzed; The general linear model was established based on three surface materials and the monthly temperature of the year. The results are as follows: 1)The difference of thermal effects on surrounding environment between grass brick material and degenerated grass brick material is not significant; 2)Both the grass brick and the degeneratedgrass brick material have significant differences with the concrete brick material. 3)The general linear model passed the check and the match accuracy between the surface and the air temperature is high. The surface temperature can be calculated through the model. The coefficient represent the surface temperature’s rising range with the increase of solar radiation.The rank of rising range is as follows: grass brick<degenerated grass brick<concrete brick.
In order to comprehensively evaluate the drought resistance of four light green roof plants including Alternanthera bettzickiana, Kalanchoe fedtschenkoi ‘Rosy Dawn’, Sedum polytrichoides and Callisia sp., their drought resistance was comprehensively evaluated using the method of membership function which combined their physiological indices under water stress in pots experiment, including the permanent wilting rate, leaf water losing rate, foliage relative water content, chlorophyll fluorescence parameters (Fv/Fm, Fv’/Fm’, ETR, ΦPSⅡ, NPQ) with their morphological changes during stress and rehydration. The results showed that K. fedtschenkoi ‘Rosy Dawn’ and Callisia sp. had relative low permanent wilting rate and leaf water losing rate which had strong drought resistance. With the extension of drought stress period, the leaf water losing rate of these 4 species decreased and the parameters of Fv/Fm, Fv’/Fm’, ETR, ΦPSⅡ, NPQ decreased in varied degree whereas NPQ increased. The drought resistance of these 4 species decreased in the following order Callisia sp.> K. fedtschenkoi ‘Rosy Dawn’ >S. polytrichoides>A. bettzickiana which consistent with the actual performance in pots. Callisia sp., K. fedtschenkoir ‘Rosy Dawn’ and S. polytrichoides can tolerated 12 days persistent naishdrought under high temperature conditions in summer in South China which suggested that these three species were suitable for light roof greening in this area.
With a purpose for strategies of Poa crymophila to adapt to environmental interference, we studiedthe growth of P. crymophila subject to varying moving frequencies and time using factorial design and in field conditions. Mowing frequencies are divided into one time, two times, and three times; and the mowing time is divided into early mowing and late mowing. The results showed that overcompensation effects occurred with all the P. crymophila in all cases, and the occurrence of overcompensation was irrelevant to moving frequencies and time. Above-ground biomass and tiller number had a significant positive correlation, P. crymophila resisted environmental interference by growing more tillers, and the resources required to produce tillers were mainly supplied by the roots. The mowing treatments of P. crymophila at different time were evaluated in respect of life history strategy. In case of early moving treatment, plants produced seeds as soon as possible to ensure their capability of production of the seeds; in case of late mowing, plants reduced the production of seeds to ensure the survival of individual plants in the coming year and taking root. Redistribution and balancing of resources in plants was the major strategy of P. crymophila to respond to interference of external environment.
The normalized difference vegetation index (NDVI) can characterize the vegetation growth status. The temporal and spatial changes of Ganan vegetation and of its response to climatic factors and human activities are analyzed using EOS/MODIS NDVI data,precipitation, temperature and stock capacity data during 2000-2014.The results show that: 1) The overall stability of vegetation takes on an increasing trend in recent 15 years. The stability of forest is higher than that of grassland. The spatial variability of vegetation is mainly caused by the grassland. 2) The vegetation tends to be improved and accounting 70% of the studying area. The decreasing trend (P0.05) happens only in a local place occupying 21% of total studying area. The decreasing is mainly owing to grassland degradation which contributes to 75% of the total degraded area. The degraded regions are primarily distributed in Maqu, Luqu and Diebu County. 3) Temperature tends to increase mainly in degraded regions (Maqu, Luqu and Diebu). The stock capacities show an extremely significant increasing trend (P0.01) except Zhouqu County, which has a decreased trend (P0.05). The increasing stock capacity and overgrazing are the primary reasons caused the vegetation degradation, discrete, and nonuniform distribution.
In order to provide scientific basis for precise fertilizing for fast-growing trees, and exploring a suitable forest soil nutrient classification method, a grid soil sample method was used in Guangxi Leli Forest Farm. The soil available phosphorus in each grid was calculated and interpolated. Based on forest resources planning data, the average soil available phosphorus in fast-growing Chinese fir unit was extracted. Then we calculated average annual growth and relative annual growth where in medium available nitrogen and available potassium. The relationship between the relative annual growth and soil available phosphorus was fitted with “logarithmic” type. Soil phosphorus contents corresponding to the average annual growth of 50%, 75%, 90% and 95% were calculated. Then the area of soil available potassium critical value is divided into: 2.6, 4.0, 5.7 and 6.3, respectively, according to the results of classification.
Most of rubredoxin is concentrated from the strict anaerobic bacteria, including the bacteria, the ancient bacteria and a few micro aerobic bacteria in nature. In plants, these proteins are relatively few. It acts as a cofactor or electron donor to participate in multiple biochemical pathways. Researches show that these proteins both in plants, and in microorganisms play an important role in helped biological against oxidative stress. In this paper, we introduced the classification, structure and role of rubredoxinin microbes and plants, with aim to provide reference for further research in the future.
Seed ageing was the pivotal problem to influence their storage, which could be delayed by the non-enzymatic scavenging agents of reactive oxygen species (ROS). However, the content of non-enzymatic scavenging agents reduced during seed ageing. Therefore, it was necessary that non-enzymatic scavenging agents were applied to extend the life span in seeds by eliminating ROS during storage, which would be an inevitable development tendency in ex-situ conservation of germplasm resources. This papermainly reviewed the types and their influences of non-enzymatic scavenging agents on aged seeds, and systematically analyzed their research status, existing problems, and future prospects during seed ageing. This paper might provide a theoretical foundation to study the mechanism of non-enzymatic scavenging agents during seed ageing.
Genetic diversity and population genetic structure of seven Medicago archiducis-nicolai and three M. ruthenica populations distributed at Qinghai-Tibet plateau(QTP)or adjacent areas and Inner Mongolia were analyzed. The results showed that, 11 polymorphic sites were detected based on the alignment of 161 trnL-trnF fragments, 14 haplotypes were identified(H1~H14). Analysis of genetic diversity and distribution of haplotypes in each population showed that the southeast edge of the Qinghai-Tibet plateau might be a refugia for M. archiducis-nicolai and gene invasion could happened across M. archiducis-nicolai to M. ruthenica in this area. Both spatial analysis of molecular variance and N-J clustering of populations based on K-2P genetic distance divided the 10 populations into two groups, that is, M. archiducis-nicolai and M. ruthenica. Analysis of molecular variation suggested that most of the genetic variation existed within populations, high population differentiation was found among some populations. Both of the two species did not experience recent population expansion based on mismatch distribution and neutrality tests. These results suggested that the genetic structure of the two species might be caused by complex topography and climate oscillations during glacial periods of the QTP. The evolutionary history of these species could also play an important role.
The relationship of genetic diversity with geographical origin between 15 white clover cultivars on the popularization and application of the large area in China, which provides genetic theory support the white clover breeding. The results showed that 15 white clover cultivars were divided into two categories, the class Ⅰ has 10 cultivars of white clover, mainly comes from Denmark, Australia, New Zealand and the Netherlands; There are five white clover cultivars in the class Ⅱ, mainly comes from USA, China and Argentina. White clover cultivars clustering has certain regional distribution, the genetic diversity of white clover cultivars could be studied by using ISSR and ITS analyzing , and ISSR can be more detailed on the classification.
In order to screencold tolerant Elymus germplasm, the 21 days aged seedlings of three Elymus species from Tibet were used to investigate the physiological, biochemical responses and resistanceunder different low temperature treatments(18, 10, 5, 0 ℃) with 18 ℃ as check.With the increase of low temperature stress Elymus sibiricus cv. Tongde had maximum relative membrane permeability, but Baqing (E. nutans) is the minimum. The contents of chlorophyll in Baqing showed a trend of rising first then falling, but the content of Chlorophyll in Tongde and Naqu (E. nutans) increased significantly (P<0.05). The soluble protein content in Baqing had the smallest increase and it only increased 2.59 times when compared with control; The soluble protein content in Tongde and Naqu increased significantly (P<0.05), and they increased 5.31 times than the control. The soluble sugar content in Baqing and Tongde showed a trend of rising first and then falling, but the soluble sugar content in Naqu increased significantly (P<0.05) and it is 2.14 times of the control. The MDA content in Tongde had the biggest increase; the MDA content in Baqing decreased significantly at 0 ℃ when compared with that at 5 ℃(P<0.05). The free proline in all materials tested increased.Tongde had the maximum Pro content, and it increased 2.58 times when compared with control; Baqing had the minimum Pro content, it only increased 1.44 times when compared with control. The superoxide dismutase activities of Baqing showed a trend of rising first then falling. But the superoxide dismutase activities of Naqu increased significantly (P<0.05) and it is 1.65 times of control. The peroxidase activities in Naqu is the maximum and it increased 4.13 times when compared with control; The peroxidase activities in Tongde is the maximum and it is 2.19 times of control. Membership function analysis showed the order of cold resistance of three Elymus species: Baqing>Tongde>Naqu.
Tamarix ramosissima is a dominate shrub in the lower reaches of the Tarim river. Using a single factor control test with indoor potted plants, five moisture gradients were employed: groups CK, D1, D2, D4, and D5 (flooding), for which soil water contents were 75%, 55%, 35%, 15% field water capacity, and flooding treatment, respectively. For salt stress, the plant were treated with one of five salinity (CK, S1, S2, S3, S4), soil salt contents were 0.02%, 0.2%, 0.5%, 0.8%, 1.5%. We analyzed the effects of water and salt stress on T. ramosissima seedlings by measuring their growth, the roots of microstructure and ultrastructure. The results showed that: 1) under water stress, the flooded D4, promoted the seedling height, crown diameter and biomass accumulation significantly. The relative growth rate of the seedling height and crown width were 1.9 times and 0.9 times of CK, respectively. With the increase of salt concentration, relative growth rates of plant height and crown width increased, and the biomass decreased. In the treatment S3, T. ramosissima seedlings biomass decreased significantly at a rate of 83.42%. 2) Under salt stress, the vessel diameter of the root xylemdecreased, and the diameter of the S3 treatment decreased by 64.5% significantly when compared with that of the control, but vessel densities were higher than that of control group. Opposite trends of the vessel variations were observed under water stress. 3) There were swelling and deformation of starch grains in the root cells under different water and salt stresses, and accompanied by a large number of vesicles secreted. But there was a disintegration phenomenon of organelles under salt stress. Starch grains of the root cell in the leucoplast grew large, the membrane of leucoplast and nucleus disintegrated in the treatment S3. While it was not observed in the disintegration of root organelles under water stress. The results of the experiment proved that salt stress had more influence on T. ramosissima seedlings than water stress.
In this study, five high performing Melilotus accessions were evaluated seed germination and seedling growth under different PEG and NaCl treatment, by determination germination percentage, germination energy, the radicle and seedling length, germination index, vigor index. The analysis of Fuzzy Mathematics Based Comprehensive Evaluation method is used to investigate drought and salt tolerance differences among accessions. The results shows that: 1) High osmotic potential (≥-0.3 MPa) significantly(P<0.05)increased seed germination in all accessions compared to the control. In addition, the radicle and seedling growth of PI595335, MO-LX04, PI595388 was significantly reduced but significantly(P<0.05) increased for Ames19257 and PI593234 at high osmotic potential (≥- 0.3 MPa). At low osmotic potential(≤-0.9 MPa), all seeds germination and seedling growth were significantly(P<0.05)reduced. 2) Seedling growth was significantly influenced under different levels of NaCl treatment on all accessions. Seed germination was significantly(P<0.05)increased at low concertation of NaCl(≤100 mmol·L-1). 3) The analysis using Fuzzy Mathematics Based Comprehensive Evaluation showed that: the drought tolerance of five Melilotus accessions in seed germination period as follows: Ames19257>PI593234>MO-LX04>PI595335>PI595388, salt resistance is PI593234>Ames19257>PI595388>MO-LX04>PI595335. The performance of Ames19257 and PI593234 were significantly better than the other three Melilotus accessions in the drought and salt tolerance test, and therefore they are good genetic materials for the future breedingprograms in the northwest of China.
In order to determine the pathogen species of lucerne witches broom disease in Xinjiang, 193 lucerne samples with witches broom disease symptom were detected by nested-PCR with R16mF2/R16mR1 and R16F2/R16R2 universal primers for phytoplasma, and 23 samples had positive results with 1.2 kb specific fragment, which had detection rate of 16.8% and confirmed that the disease was witches broom. The phylogenetic tree showed that this phytoplasma strain was one member of 16SrⅤ-B subgroup which had 99.1% homology with euonymus whitening phytoplasma in Elm Yellows Group. To the best of authors knowledge, this was the first study to determine phytoplasma pathogen of lucerne witches broom disease in Xinjiang and identify taxonomic status using molecular biological techniques. These results provide theoretical basis for early diagnosis and detection of lucerne witches broom disease.
In order to collect Trichoderma asperellum strains which could promote the growth of woody plants, pot experiment was carried out with one-year-old tissue-cultured seedlings of Populus davidiana×P. alba var. pyramidalis to study the effects of three strains of T. aspereullm: ACCC32492 (Ta492), ACCC30536 (Ta536) and T4(Ta4) on the growth, the chlorophyll contents, diurnal variation of photosynthesis and light response curve characteristic parameters. The results showed that the height, basal stems diameter and biomass yields of the poplar seedlings inoculated with these T. asperellum strains were higher than those of the control (CK) at different levels. At most of the time points, the chlorophyll contents and chlorophyll a/b ratios in the leaves of the inoculated poplars were significantly higher (P<0.05) than those of CK which laid material foundation for the improvement of photosynthetic rate. The net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration rate (Tr) of the poplars inoculated with these T. asperellum strains increased compared with those of CK, but their respective time-course changing trends were the same as CK. The maximum net photosynthetic rate (Pn max), the light saturation point (LSP) and the apparent quantum efficiency (AQY) of the poplars inoculated with T. asperellum strains were higher than those of the CK. All the above results indicated that inoculation of the three T. asperellum strains could significantly improve the photosynthetic efficiency and growth of poplar seedlings. T. asperellum ACCC30536 strain had the best effects on the growth of poplar seedlings.
In order to efficiently utilize Brassica napobrassia, the genetic diversity of 28 B. napobrassica accessions were assessed by measuring 27 quantitative traits. The results showed that the B. napobrassica had significant genetic differentiation and diversity in 27 quantitative traits. Among those data, the coefficient of variation (CV) of the nutlet was maximum, reaching up to 64.1%, the second was the pair number of lobule with CV of 57%, and the minimum was weight per earthnut with CV of 2.4%. In addition, 28 B. napobrassica accessions were divided into four categories by cluster analysis. The first group included 14 accessions possessingthe characteristics of green cotyledon, small lateral bud and round blade leaf opex, the second group included 2 accessions with the characteristics of smooth leaf surface, no seta on leaf surface, less powder and semi upright leaf cluster, the third group included 6 accessions with the characteristics of medium tillering ability, light green siliqua, white fleshy root, and less fibrous root, the fourth group included 6 accessions with the characteristics of serrated and large corrugated leaf edge, leaf nodule and reddishbrown seed coat.
The variations of vitamin K epoxide reductase complex subunit 1 (vkorc1) gene play a key role in resistance of rodents to anticoagulant rodenticides. In this study, the transcriptomic methods were applied to analyze the sequence information of five rodents plateau zokor (Eospalax baileyi), plateau pika (Ochotona curzoniae), lesser long-tailed hamster (Cricetulus longicaudatus), Qinghai vole (Lasiopodomys fuscus), and Himalayan marmot (Marmota himalayana), which are endemic to the Qinghai-Tibet Plateau (QTP). We also sampled 54 plateau zokors from five populations and analyzed the variations within the complete vkorc1 gene (including introns). From transcriptome assemblies, we successfully obtained the complete coding sequences of vkorc1 gene of five QTP animals. Of which, the length of vkorc1 CDS in vole, hamster, and zokor was 486 bp, while it was 492 bp in marmot and pika. At the DNA sequence level, there were 143 variable sites among the five QTP animals, the sequence similarities between the five QTP animals and rat (Rattus norvegicus) were 80.1%~90.7%, while between the five QTP animals and mouse (Mus musculus) were 79.7~89.8%. At the amino acid sequence level, there were 37 variable sites among the five QTP animals, the sequence similarities between the five QTP animals and rat (Rattus norvegicus) were 84.0%~92.0%, while between the five QTP animals and mouse were 85.9%~92.0%; no amino acid residue was identical with which involved in anticoagulant resistance in Rattus and Mus. We obtained the complete vkorc1 gene (including introns) sequences of the 54 zokors, based on the 1 808 bp alignment we detected 8 variable sites (including 2 indel sites), all of them were in the intron region. This is the first vkorc1 sequence data from rodent species endemic to the QTP and these results will provide important scientific foundations for rodent control in the QTP regions.
Forage breeding is an important basis for the sustainable development of grass and animal husbandry. The status and differences of forage germplasm resources, the technology and system of forage breeding in USA and China were reviewed in this paper. Forage germplasm resources saved less and lack of utilization although a great deal of evaluation work accomplished between China than USA; conventional breeding method is still the main mode for cultivating new varieties, but there is a large gap in the investment and research degree between China and USA; the research subjects in USA are more diverse. They attach importance to the protection of intellectual property of new varieties, the effective combination of industry, learning, research and promotion, which are important to make the rapid development of forage industry in USA. The understanding about the similarities and differences between the two countries is helpful to provide some ideas for the forage breeding development of China.
The purpose of the paper is to generate a mode of industry chains of seed enterprises in Gansu Province using a case study of Gansu Dunhuang Seed Co., Ltd. Based on the mode, a system dynamics (SD) model was constructed and validated through a fitness test applying ahistorical model and a parametric sensitivity test. According to the simulation of seed industry chains under the different corporate strategies, the study led to the conclusion that the public seed enterprises in Gansu should adopt a preemptive market strategy to improve the market shares, insist on variety innovation and enforcea strict cost control strategy.
Grassland ecology is an important specialty course which focus on the research of the relationship between grassland and environment,and it is an theoretical, practical and integrated course. The rapid development of grassland ecology, broader research category, and more advanced research tools have proposed a severe challenge to the teaching reforms. The aim of the paper is to analyze the current issues existing in the undergraduates teaching procedure in Sichuan Agricultural University on the basis of the author’s teaching experiences and knowledge on grassland ecology. Suggestions on improving the teaching content, diversifying the teaching methods, and strengthening the practical teaching reform measures are shown in the paper to promote the teaching effect to enhance the democratic relationship between teaching and learning, perfect the experimental course system, and enhance the students’ interests in learning and innovation.