17 morphological characteristic indexes and 11 nutritive elements of five different parts of Amorpha fruiticosa firstly planted in the Qinghai-Tibet Plateau（Lhasa,Maqu） were investigated to understand the response of phenotypic plasticity and plant resource allocation of Amorpha fruiticosa to alpine habitat.The results of this study showed that phenotypic differences of A.fruiticosa was found in the two investigation regions,especially,the root morphological indexes were greatly different.The biomass proportion and nutritive element concentrations of different parts of A.fruiticosa was different between Lhasa region and Maqu region,which was caused by the response of plant resource allocation to alpine habitat.The correlation relationship between morphological indexes and nutrient element concentrations of A.fruiticosa was complex among two regions.

△12 fatty acid desaturases(fad2) are key enzymes which catalyze the introduction of double bonds at the delta 12 position in the hydrocarbon chain and thereby convert oleic acid to linoleic acid.They control the synthesis of oleic acid,linoleic acid and other polyunsaturated lipids in plant cells.△12 fatty acid desaturases are categorized into fad2 and fad6 type according to their different electron donors.fad2 type can be further categorized into housekeeping-type and seed-type fad2.fad2 and fad6 types have the same functionality but different genetic relationship.In this article,recent research advances on △12 fatty acid desaturases in terms of their structure and function,classification,evolutionary system,physiological function,gene cloning,gene structure and copy number in plants are reviewed.The directions of the relative research field are also discussed.

For decades, arid desert ecosystems in northwest China, covering one-fourth the country’s land surface, have experienced a rapid decline in plant species diversity, productivity and soil carbon stock owing to degradation by overgrazing. In this study, plant community composition, diversity and productivity, as well as soil carbon (C) and nitrogen (N) stocks, were monitored over 26 years from 1981 to 2006 in a severely degraded Haloxylon ammodendron-dominated shrubland where livestock densities were reduced from 4–5 to 1–2 dry sheep equivalent ha-1. The objective was to assess long-term grazing effects on vegetation and soil C and N accumulation dynamics. Results showed that the reduction of grazing pressure significantly increased vegetation cover, plant diversity and productivity, resulting primarily from an increase in livestock-preferred species. Controlled grazing also led to marked increases in soil C and N stocks in the top 30 cm of soil. This increase was strongly associated with increased plant species richness, vegetation cover and biomass production. Averaged over 26 years, soil C and N accumulated at rates of 89.9 g C and 8.4 g N m-2 year-1, respectively, but rates of C and N accumulation varied greatly at different time periods. The greatest species regeneration occurred in the first 8 years, but the largest C and N accumulation took place during years 9–18, with a time-lag in response to changes in vegetation. Our results provide insights into the long-term recovery patterns of different ecosystem components from the influence of prolonged overgrazing disturbance that cannot be inferred from a short-term study. The findings are important for assessing the resilience of these livestock-disturbed desert ecosystems and developing a more effective strategy for the management of this important biome from a long-term perspective.

为了解氮素沉降对草地群落的影响,通过人工氮肥添加模拟试验,研究了黄土高原天然草地优势植物长芒草（Stipa bungeana）在不同施氮水平下叶片和立枯物碳（C）、氮（N）、磷（P）元素含量的变化特征,探讨了N素增加对N、P重吸收率和C:N:P化学计量比的影响及其内在联系。结果表明:氮素添加显著增加了长芒草叶片的C、N和立枯物的N、P含量,对叶片P和立枯物C含量无显著影响;氮素添加显著降低了长芒草的N、P重吸收率,对照处理的N、P重吸收率最高,分别为60.35%和71.75%,并且,在相同氮素处理条件下P的重吸收率显著大于N重吸收率;随着氮素添加量的增大,叶片的C:N降低,N:P和C:P增加,N:P为18.25–29.01。研究表明,黄土高原天然草地群落主要受P限制,随氮素沉降增加,P限制进一步加剧;长芒草较高的N、P重吸收率是保证其在贫瘠的土壤中生存的重要机制。

Cutting is one of the main ways to utilize grassland plants,moderate cutting could promote tillering and regrowth,and thus increase above-ground biomass and nutritional element NPK.According to the growth characteristics of Amorpha fruticosa,the effect of cutting frequency on growth height,above-ground biomass and NPK content of stem and leaf were studied in this study.The results showed that,during rapid growth period which was from April to September,the above-ground biomass ranged as cutting twice treatmentoncethree times.A similar trend was also observed in terms of NPK content.These results implied the optimal cutting frequency for A.fruticosa was twice at least in present study.

The best experiment conditions,accuracy and precision for determining the microamounts of lead content in plant by microwave-heating GF-AAS approach were studied.Results indicated that the best acid system is 5 mL HNO3-3 mL H2O2-2 mL HF,the best microwave-heating condition is under the state of power 600 W、temperature 180 ℃ and microwave-heating 15 min.The optimal working condition of Graphite Furnace is the dried 45 s under 90 ℃,cineration 20 s under 900 ℃,atomized temperature 1 400 ℃ and cleaned temperature 2 500 ℃.The limit of detection of this method was found to be 0.068 4 mg/kg,the relative standard deviation error were in the range of 1.2%-5.6%,and recoveries were in the range of 95.81%-100.09%.

The amount of available silicon in soil was determined by flow injection analysis approach in this paper.The determination coefficient(R2) of this standardized work curve was found to be above 0.9999.The detection limit of this method was 0.012 μg/mL,the relative standard deviation was in the range of 0.04%-0.06%,and the spike recoveries ranged from 97.89% to 99.93%.The experimentation has proved that this approach is characterized by simple operation and pretty good linear correlation,the precision,accuracy and sensitivity could meet the analytical requirements.

The effects of uniconazole(S3307) on the drought resistance of Perennial ryegrass were investigated by pot experiment under different concentration treatments of SS3307(0-80 mg/L).Perennial ryegrass was subjected to soil drought stress by withholding watering at the fifteen days after spraying SS3307.The results showed that S3307 increased the relative water content of Perennial ryegrass and therefore increased the drought resistance.When the soil water content decreased to 14%,the leaves of non-spraying control withered greatly,however,the leaves in uniconazole treatment had normal leaf color,the contents of chlorophyll,the leaf water content and free-proline,and also the ratio of the root to crown of Perennial ryegrass were significantly increased,the treatment with 40 mg/L concentration were better than others.When the concentration increased to 80 mg/L,it restrained the growth of underground part,and decreased the range and depth of imbibing ability,then reduced the resistance of the Perennial ryegrass.This suggested that spraying 40 mg/L uniconazole could effectively increase the drought resistance of the Perennial ryegrass.

The characteristics of total amino acids,essential amino acids,sulfur amino acids,limited amino acids and essential amino acid index(EAAI)of 38 forages in the Alxa desert grassland were studied.The total amino acid content ranged from 2.47% to 22.50% and declined in the order: LiliaceaeLeguminosaeZygophyllaceaeAsteraceaeGramineaeChenopodiaceaeRosaceaeTamaricaceaePolygonaceae.The essential amino acid content ranged from 0.97% to 8.92%.There were 23 forages with EAA/NEAA60% and EAA/TAA40%.The content ratio of essential amino acid to total amino acid declined in the order: RosaceaeAsteraceaeChenopodiaceaeLeguminosaePolygonaceaeGramineaeLiliaceaeTamaricaceaeZygophyllaceae.The sulfur amino acid content ranged from 0.28% to 1.40%,the content ratio of sulfur amino acid to total amino acid followed the order: TamaricaceaeChenopodiaceaePolygonaceaeLeguminosaeRosaceaeZygophyllaceaeGramineaeAsteraceaeLiliaceae.The total content of limited amino acids in Inner Mongolian White Cashmere Goats ranged from 0.70% to 3.22%.The EAAI value of 38 forages to mutton,cashmere and hair ranged from 0.914-1.010,0.976-1.250 and 0.951-1.219 respectively.Forages in the Alxa desert grasslands play an important role in yield and quality of cashmere and hair.They are an excellent feed resource for local Cashmere Goats and sheep.

通过向培养基中添加Fe2+(Fe-EDTA),以探讨Fe2+对葡萄试管苗生长发育的影响.结果表明:随Fe2+浓度的升高,根萌动时间提前,芽萌动时间推迟,根冠比和叶绿素含量增加;Fe2+浓度为13.9 mg/L时,株高、节间数、叶片数以及地上部干鲜重均达到最大.Fe2+浓度低于13.9 mg/L时,根系活力随Fe2+浓度升高而增强,而Fe2+浓度高于13.9 mg/L时,根系活力随Fe2+浓度升高而减弱.

The experiment studied hydraulic lift of Astragalus adsurgens Pall.planted for three years by using the split-root apparatus.We investigated the relationships between the hydraulic lift and the soil water potential,the water potential of plant tissues and the osmotic adjusting materials.The results showed that when the soil volumetric water content and the soil water potential in upper pot reached 14.9% and -1.28 MPa,and in lower pot reached 19% and -0.6 MPa respectively.The soil water potential in lower potthe root water potential in lower potthe root water potential in upper potthe soil water potential in upper potthe leaf water potential.At the same time,the phenomenon of hydraulic lift would occur.In sunny days,the soil volumetric water content and the soil water potential in upper pot declined from 7 AM to 16 PM and increased from 16 PM to 22 PM,reached maximum at 22 PM,and declined subsequently.In cloudy days,the soil volumetric water content and the soil water potential in upper pot declined gradually.The concentrations of the osmotic adjusting materials(including proline,soluble sugar,K+ and Na+) in the leaves and the roots in upper pot at 16 PM were higher than that at 22 PM,which could result in the variations of leaf water potential and root water potential in upper pot to some extent,and finally promoted the occurrence of hydraulic lift of A.adsurgens.

The effects of fertilization on root hydraulic lift and nutrition activity in Astragalus adsurgens was investigated through root dividing methods by supplying different quantity of fertilizer to down parts of roots.The results indicated that the water volume of hydraulic lift increased with the increase of fertilizer supplying.Poa pratensis planted in upper basin without irrigation grew better than control because of hydraulic lift of A.adsurgens in the treatment group with more fertilizer.Furthermore,soil respiration rate in upper basin increased to the highest value and the active N,P and K in the soil of upper basin was also up to the best.In conclusion,fertilization promoted the root growth of A.adsurgens;the water which absorbed by the roots in down basin was released by the roots in upper basin.Therefore,drought stress was alleviated effectively,the activity of soil microbe was enhanced,the decomposition of soil organic matter was accelerated,the release of efficient nutrition was facilitated.

The leaf water potential and biomass of Z.xanthoxylum were investigated by pot experiment under different soil water stress.The results are as follows: the leaf water potential of Z.xanthoxylum during the seeding stage dropped following the decrease of soil water content,its biomass was not restrained under the light and medial water stress but was remarkably reduced under the severe water stress(P0.05).Distributive proportion of biomass in the individuals varied regularly with the decrease of soil water content.It has alse been revealed that the ratio of the root to crown of Z.xanthoxylum increased in the whole individuals,the proportion of the stems by contrast with the leaves on the overground,the proportion of the yellow leaves by contrast with the green leaves decreased,and the ratio of the roots with diameter2 mm to the roots with diameter2 mm in underground increased.These results showed the adaptive ability of Z.xanthoxylum to aridity by the adjustment of itself.

In this study, we examined the pedoe co logical effects of three shrub species that occur generally in shifting, semi-s hifting and semi-fixed sand lands in the Horqin Sandy Land. Several important conclusions were drawn from this study. (1) There were significant differences in the interception and retention of sand and aeolian dust among three shrub spe cies. Of the three shrubs, the mean amount of the interception and retention of sand and aeolian dust perplant was the greatest (0.49 m~3) in Caragana microphylla, followed by Artemisia halodendrom (0.16 m~3) and Salix gordejvii (0.03 m~3). Regression analyses showed that the sediment a mount of sand and aeolian dust perplant was positively and significantly correl ated with its average canopy (accounting for 18-58% of the variance), branching number (accounting for 16-31% of the variance) and shoot diameter (accounting for 14-17% of the variance). (2) All three shrubs exhibited significant effects of of fertility, i.e. the soils under shrub canopies were significa ntly higher in nutrient availability than those beyond shrub canopies. Such effects may create a nutrient-rich substrate, thus providing a better environment for further invasion and establishment of other plant species on bare sandy land . The effects of inland of fertility varied markedly with the type of shrubs pecies. Of the three shrubs examined, Caragana microphylla had the greatest fertile island effect, followed by Artemisia halodendrom and Salix gord ejvii, largely because of significantly higher levels of organic matter, total N and available P in soils (0-20 cm) under the Caragana microphylla canopies than those under Artemisia halodendrom and Salix gordejvii canopies. Shrubs differed appreciably in accumulation efficiency of different nutrients. For example, the accumulation efficiencies of organic matter, total P, available P and total N in soils under shrub canopies averaged 1.20-1.44, 1.08-1.2 3, 1.11-1.36 and 1.17-1.40. (3) Wind direction appeared not to influence the spatial distribution of soil physical properties, but showed an effect on the spatial distribution of organic matter content. Organic matter contents in soils at the SE and NE directions of the shrubs were somewhat higher than the other directions.

This study analyzed the total soil nitrogen content(TSN) of grasslands at different elevations on the west-slope of Helan Mountain in Alxa, Inner Mongolia.Factors which affect nitrogen distribution such as annual precipitation,temperature,plant coverage and productivity,soil water content,0.05 mm particle content,soil organic carbon,and soil PH,were measured.The results indicated that TSN content declined with decreasing altitude in the following order: alpine meadow classical steppe desert steppe steppe desert.In the classical steppe,TSN content showed a decline along the vertical soil profile.In the alpine meadow,desert steppe and steppe desert,TSN content showed no difference between the 0-20 and 20-40 cm soil layers,however TSN was higher in these layers than in the 40-60 cm layers.In the five steppe desert(elevation 1 360-1 380 m),because of different grazing degree and plant type,TSN content in the 0-20 cm layer changed from 0.022 8 % to 0.034 7 %.Total soil nitrogen in the 0-20,20-40 and 40-60 cm soil layers were positively correlated with annual precipitation,plant coverage,plant productivity,soil water content,SOC,and 0.05 mm particle content(P0.001),and negatively correlated with average temperature and soil pH value(P0.001).The most important factors affecting TSN in the 0-20 cm soil layers were plant coverage and annual precipitation,with the relationship described as: TN%=0.002 040 C+0.000 585 AP-0.076 800.In the 20-40 cm soil layers,TSN was mostly affected by productivity with the relationship given as: TN%=0.001 6 B+0.024 7.Among the environmental factors,both soil organic carbon and annual precipitation were the most important factors affecting TSN in the 0-20 cm layers.In the 20-40 cm soil layer,TSN was most affected by soil organic carbon.

Sewage sludge from Qilihe Sewage Treatment Factory,Lanzhou, China, were applied to lawn sown by Lolium perenne  and effects on the soil environment were measured by using different quantity of sewage sludge in comparison with chemical fertilizer. The results showed that the physical and chemical characters of the soil were improved while the application quantity of sewage sludge was in the range of 0.5~8.0 kg/m2, the contents of total and available N, total and available P, organic matter were increased, bulk density was decreased. While the application quantity of sewage sludge was in the range of 4.0~8.0 kg/m2, the contents of Fe, Cu and Zn were increased, and the contents of Ni, Pb, Cr, As and Hg in soil of 0~20 cm depth had no significant difference compared with that of the control treatment. Heavy metal elements did not move down to the deep layer of soil and cause pollution on the soil.

Sewage sludge from Qilihe sewage treatment factory,Lanzhou China,was applied for the study of the growth and element content of Lolium perenne L.by use of different quantity level in comparison with chemical fertilizer.The results showed that when the application quantity of sewage sludge was in the range of 0.5～8kg/m 2,the coverage,density,biomass of aboveground and underground of Lolium perenne L.were increased,and the chlorophyll content was increased significantly with the increase of application quantity of sewage sludge.The contents of N, P,Mg,K,Fe,Zn and Cu were increased,but Mn content was decreased,and the contents of Ca and heavy metal elements of Hg,Ni,Pb,As in aboveground biomass of that grass were no significant difference when compared with that of the control treatment.The heavy metal elements contents in he aboveground biomass were not more than the average concentration in whole plant,so the application of sewage sludge did not cause the injury on Lolium perenne L.

Sewage sludge collected from Qilihe Sewage Treatment Factory, Lanzhou, China, was applied to artificial grassland sown with Medicago sativa L. cv. Xingjiang Daye, and effects of sewage sludge on the soil environment were investigated. The results showed that application of sewage sludge improved the physical and chemical characters of the soil--the contents of organic matter, total N and P were increased; unit weight was decreased. While the application dosage of sewage sludge was in the range of 4~8 kg/m2, the contents of Fe, Ca, Cu and Zn were increased significantly, and the contents of K, Mn and heavy metal element of Ni, Pb, As and Hg in soils of 0~20 cm depth were no significant difference compared with that of the control. Also, the above elements had not moved into the lower layer of the soil and the application of sewage sludge did not cause the pollution of the soil environment.