Effect of NH_4^+-N/NO_3^--N Ratios on Growth and Some Physiological Parameters of Chinese Cabbage Cultivars

The responses of three cultivars of Chinese cabbage (Brassica chmensis L.), one of the main vegetable crops in China, to different ratios of NH4+-N/NO3--N was investigated to find the optimal ratio of ammonium to nitrate for maximal growth and to explore ways of decreasing the nitrate content, increasing nitrogen use efficiency of Chinese cabbage, and determining distributions of nitrogen and carbon. Three cultivars of Chinese cabbage were hydroponically grown with three different NH4+-N/NO3--N ratios (0:100, 25:75 and 50:50). The optimal ratio of NH4+-N/NO3- -N for maximal growth of Chinese cabbage was 25:75. The increase in the ratio of NH4+-N/NO3--N significantly decreased nitrate content in various tissues of Chinese cabbage in the order of petiole > leaf blade > root. The highest total nitrogen (N) content was found when the ratio of NH4+-N/NO3--N was 25:75, and N contents in plant tissues were significantly different, mostly being in the order of leaf blade > petiole > root. At the NH4+-N/NO4+-N ratio of 25:75, the biomasses of Chinese cabbage cultivars ’Shanghaiqing’, ’Liangbaiye 1’ and ’Kangre 605’ increased by 47%, 14% and 27%, respectively. The biomass, SPAD chlorophyll meter readings and carbon content of ’Shanghaiqing’ were all higher than those of ’Liangbaiye 1’, while nitrate and total nitrogen contents were lower. Thus, partial replacement of nitrate by ammonium could improve vegetable production by both increasing yields and decreasing nitrate content of the plants.

Tomato Growth and Organic Acid Changes in Response to Partial Replacement of NO_3^--N by NH_4^+-N

A hydroponic experiment was conducted to study the effect of partial replacement of NO-3-N by NH4+-N on the seedling growth and organic acid content of tomato (Lycopersicon esculentum Mill.). A completely randomized design was established with three replications and five treatments, i.e., NO-3-N/NH4+-N of 100/0, 75/25, 50/50, 25/75 and 0/100. Results showed that 25% replacement of NO3--N by NH4+-N significantly (P = 0.05) improved fresh and dry weight, revealing that a proper percentage of NH4+-N was important for tomato nitrogen nutrition. This could increase the plant growth even though tomato was a crop that preferred nitrate nutrition. Also an increase in the proportion of NH4+-N in the nutrient solution led to a significant decrease (P = 0.05) in malate, citrate and fumarate. However, the 25% NH4+-N plus 75% NO3--N treatment had no significant effect (P = 0.05) on the 2-ketoglutarate, succinate or oxalic acid content, showing that only some organic acids in tomato plants were affected. Only pyruvate increased significantly (P = 0.05), and it only increased for 25% and 50% replacement of NO3--N by NH4+-N. Metabolism of these organic acids, especially malate, citrate and fumarate, should be further studied at the molecular level in vegetables applied with different nitrogen forms.

Effect of Incorporation of Wheat Straw and Urea into Soil on Biomass Nitrogen and Nitrogen-Supplying Characteristics of Paddy Soil

Pot experiments were carried out to study the effect of incorporation of wheat straw and/ or urea into soil on biomass nitrogen and mineral nitrogen and its relation to the growth and yield of rice.The combined appliation of wheat straw and urea increased much more biomass nitrogen in soil than the application of wheat straw or urea alone and consequently increased the immobilization of urea nitrogen added and reduced the loss of urea nitrogen.An adequate nitrogen-supplying process to rice plant could be obtained if C/ N ratio of the material added was about 20.The three yield components of rice were affected significantly by the status of nitrogen supplying.More than 30mg N/ kg soil of mineral nitrogen at effective tillering stage,panicle initiation stage and filling stage should be maintained in order to get high rice yield,though the criteria varied with the different experimental conditions.

Quantifying Responses of Winter Wheat Physiological Processes to Soil Water Stress for Use in Growth Simulation Modeling

A deep understanding of crop-water eco-physiological relations is the basis for quantifying plant physiological responses to soil water stress. Pot experiments were conducted to investigate the winter wheat crop-water relations under both drought and waterlogging conditions in two sequential growing seasons from 2000 to 2002, and then the data were used to develop and validate models simulating the responses of winter wheat growth to drought and waterlogging stress. The experiment consisted of four treatments, waterlogging (keep 1 to 2 cm water layer depth above soil surface), control (70%-80% field capacity), light drought (40%-50% field capacity) and severe drought (30%-40% field capacity) with six replicates at five stages in the 2000-2001 growth season. Three soil water content treatments (waterlogging, control and drought) with two replicates were designed in the 2001-2002 growth season. Waterlogging and control treatments are the same as in the 2000-2001 growth season. For the drought treatment, no water was supplied and the soil moisture decreased from field capacity to wilting point. Leaf net photosynthetic rate, transpiration rate, predawn leaf water potential, soil water potential, soil water content and dry matter weight of individual organs were measured. Based on crop-water eco-physiological relations, drought and waterlogging stress factors for winter wheat growth simulation model were put forward. Drought stress factors integrated soil water availability, the sensitivity of different development stages and the difference between physiological processes (such as photosynthesis, transpiration and partitioning). The quantification of waterlogging stress factor considered different crop species, soil water status, waterlogging days and sensitivity at different growth stages. Data sets from the pot experiments revealed favorable performance reliability for the simulation sub-models with the drought and waterlogging stress factors.

高等植物体内γ—氨基丁酸合成、代谢及其生理作用

对γ-氨基丁酸(GABA)在植物体内的合成、代谢和与之有关的谷氨酸脱羧酶、γ-氨基丁酸转氨酶和琥珀酸半醛脱氢酶的特性,H+、Ca2+、CaM等因素对GABA合成代谢的影响和GABA在高等植物体内可能的生理作用作了介绍.

Organic carbon stock in topsoil of Jiangsu Province, China, and the recent trend of carbon sequestration

Data collection of soil organic carbon(SOC) of 154 soil series of Jiangsu, China from the second provincial soil survey and of recent changes in SOC from a number of field pilot experiments across the province were collected. Statistical analysis of SOC contents and soil properties related to organic carbon storage were performed. The provincial total topsoil SOC stock was estimated to be 0 1 Pg with an extended pool of 0 4 Pg taking soil depth of 1 m, being relatively small compared to its total land area of 101700 km 2 One quarter of this topsoil stock was found in the soils of the Taihu Lake region that occupied 1/6 of the provincial arable area. Paddy soils accounted for over 50% of this stock in terms of SOC distribution among the soil types in the province. Experimental data from experimental farms widely distributed in the province showed that SOC storage increased consistently over the last 20 years despite a previously reported decreasing tendency during the period between 1950—1970 The evidence indicated that agricultural management practices such as irrigation, straw return and rotation of upland crops with rice or wheat crops contributed significantly to the increase in SOC storage. The annual carbon sequestration rate in the soils was in the range of 0 3—3 5 tC/(hm 2·a), depending on cropping systems and other agricultural practices. Thus, the agricultural production in the province, despite the high input, could serve as one of the practical methods to mitigate the increasing air CO 2

Dynamics of Soil Erosion in Xingguo County, China, Determined Using Remote Sensing and GIS

The spatial and temporal dynamics of soil erosion in Xingguo County, Jiangxi Province, China were studied using multi-period remote sensing images and GIS. The results indicated that the soil erosion status of the region has been improving, particularly since the 1980s, with the erosion rate showing an evident decline over the past 30 years. The improvement showed not only in the decline of eroded soil area, but also with the reduction in the extent of erosion. The extent of erosion mainly changed by one level, and the change primarily occurred with the severely or moderately eroded soil types. However, in general, soil erosion was still an overriding problem in the region with some areas becoming more serious, especially those with large quantities of granite.

Sorption of dissolved organic matter and its effects on the atrazine sorption on soils

The dissolved organic matter(DOM), water soluble organic matter derived from sewage sludge was separated into hydrophobic fraction(Ho) and hydrophilic fraction(Hi). The sorption of DOM and its fractions on soils and the effects of DOM sorption on a nonionic pesticide(atrazine(2-chloro-4-ethylamino-6-isopropylamino-1,3,5-trazine)) distribution between soil and water were investigated using a batch equilibrium technique. The total DOM sorption on soils described by the Langmuir equation reached saturation as the DOM concentration increased. The sorption of Ho fit the Freundlich model. In contrast, a negative retention evidently occurred as adding Hi at higher level in tested soils. The sorption of Ho dominated the total DOM sorption and the release of soil organic matter(SOM). Effects of DOM on the atrazine sorption by soils were DOM-concentration dependent and dominated by the interaction of atrazine, DOM, and soil solids. Generally, the presence of DOM with lower concentration promoted atrazine sorption on soils, namely the apparent partitioning constant(K*_d) for atrazine sorption in the presence of DOM was larger than the distribution constant(K_d) without DOM; whereas the presence of DOM with higher concentration inhibited atrazine sorption(i.e., K*_d<K_d). The overall effects of DOM on atrazine sorption in soils might be related to the DOM sorption and the release of soil intrinsic organic matter into aqueous solution. The sorption of Ho on soils promoted the atrazine sorption on soil, while the release of SOM by Hi and the competitive sorption between Hi and atrazine on soil surface led to a decrease of atrazine sorption. Information provided in this work may contribute to a better understanding of the DOM sorption and its impacts on the contaminant soil-water distribution.

Effect of Bacterial-Feeding Nematode Inoculation on Wheat Growth and N and P Uptake

A 40-day gnotobiotic microcosm experiment was carried out to quantify the effect of hastenal-feeding nematode on plant growth and nutrient absorption. The results showed that inoculation of bacterial-feeding nematode Protorhabditis sp. stimulated the growth of wheat (Triticum aestivum) and the uptake of N. By the end of the 40-day incubation wheat biomass and N uptake in the treatment with nematode and bacteria (Pseudomonas sp.) increased by 6.5% and 5.9%, respectively, compared with bacteria alone treatment. The presence of nematode mainly accelerated the growth of aboveground of wheat, while it slightly inhibited the root development. There was little difference in plant tissue N concentration between treatments. P concentration and uptake of wheat, however, were generally reduced by nematode. It appears that the enhancement of plant growth and nitrogen uptake is attributed to the enhancement of nitrogen mineralization induced by nematode feeding on bacteria, and the reduction of phosphorous uptake is the result of weak root status and competition by bacteria immobilization.

Differences in Soil Microbial Biomass and Activity for Six Agroecosystems with a Management Disturbance Gradient

Different management practices in six agroecosystems located near Goldsboro, NC, USA were conducted including a successional field (SU), a plantation woodlot (WO), an integrated cropping system with animals (IN), an organic farming system (OR), and two cash-grain cropping systems employing either tillage (CT) or no-tillage (NT) to examine if and how microbial biomass and activity differ in response to alterations in disturbance intensity from six land management strategies. Results showed that soil microbial biomass and activity differed, with microbial activity in intermediately disturbed ecosystems (NT, OR, IN) being significantly higher (P ＜ 0.01) than systems with either high or low disturbance intensities. There was also a significant and a highly significant ecosystem effect from the treatments on microbial biomass C (MBC) (P ＜ 0.05) and on microbial activity (respiration) (P ＜ 0.01), respectively. Multiple comparisons of mean respiration rates distinctly separated the six ecosystem types into three groups: CT ＜ NT, SU and WO ＜ OR and IN.Thus, for detecting microbial response to disturbance changes these results indicated that the active component of the soil microbial community was a better indicator than total biomass.

Size of Microbial Biomass in Soils of China

The microbial biomass C,N and P of soils all over China were determined in this study to study their affecting factors.The results,about 100-417 mg C kg^-1 soil,18-51 mg Nkg^-1 soil and 4.4-27.3mg P kg^-1 soil,showed the biomass C,N and P in linear relationship with the soil total organic C,toal N and soil organic P.The ratios of C:Nand C:P,ranging from 5.6 to 9.6 and from 11.2 to 48.4 respectively,were affected by soil pH.texture,crop rotation,macroclimate etc.The ratio of C:N in soil biomass increases gradually from the north to the south in China.

Effects of salinity on activities of H^+-ATPase, H^+-PPase and membrane lipid composition in plasma membrane and tonoplast vesicles isolated from soybean(Glycine max L.) seedlings

The effects of NaCl stress on the H +-ATPase, H +-PPase activity and lipid composition of plasma membrane(PM) and tonoplast(TP) vesicles isolated from roots and leaves of two soybean cultivars(Glycine max L.) differing in salt tolerance(Wenfeng7, salt-tolerant; Union, salt-sensitive) were investigated. When Wenfeng7 was treated with 0.3%(W/V) NaCl for 3 d, the H +-ATPase activities in PM and TP from roots and leaves exhibited a reduction and an enhancement, respectively. The H +-PPase activity in TP from roots also increased. Similar effects were not observed in roots of Union. In addition, the increases of phospholipid content and ratios of phospholipid to galactolipid in PM and TP from roots and leaves of Wenfeng7 may also change membrane permeability and hence affect salt tolerance.

Sustainable Agriculture Evaluation for Red Soil Hill Region of Southeast China

Agricultural sustainability for economic development is important and a complex issue throughout the world; however,it is difficult to synthetically evaluate its use in the policy making process. The objective of this study was to evaluate sustainable agriculture in the red soil hill region of Southeast China through a newly proposed method combining four separate sub-systems: regional population (P), resource (R), environmental (E), and socio-economic (S). This new index system was proposed to appraise synthetically the agricultural sustainability of the red soil hill region from 1988 to 1996 with a two-step method assessing: a) the agricultural sustainability in each province independently and b) the relative sustainability of each province to the whole region. The first step only provided a development trend for each province based on its original situation, while the second step provided additional information on the comparative status of each province in agricultural development to the region as a whole. Higher index scores were found for the economy and resource categories denoting improvement. However, lower scores in the environment category indicated the improvement was achieved at the cost of deteriorating ecological surroundings due to an increasing population that demanded more from the agro-ecosystem and put heavier pressures on it. Results also showed that water and soil losses in this region were the major obstacles encountered in sustainable agriculture development. The assessment results were verified when compared with results from another method. This suggested that the new assessment system was reliable and credible in evaluating agricultural sustainability on a regional scale.

Responses of Different Pakchoi (Brassica chinensis L.) Cultivars to Cu Toxicity

Two pot experiments with a completely random design and 4 replications were performed in a greenhouse to examine the response difference of 17 cultivars of pakchoi (Brassica chinensis L.) grown in a Cu-spiked and a clean soil to Cu.relatively tolerant. When the 17 cultivars of pakchoi grew in clean garden soil, the Cu concentrations in the aboveground part were positively correlated (r = 0.6693) with their root Cu concentrations. However, when they grew in the Cu-spiked soil a highly negative correlation coefficient (r = -0.5376) was obtained in the Cu concentration between the aboveground part and the root. This meant that the Cu tolerant cultivars had a weak ability to transfer Cu from their root to their aboveground part, and therefore stored much more Cu in their root than the Cu sensitive cultivars.

Environmental Efficiency Analysis of China’s Vegetable Production

To analyze and estimate the environmental efficiency of China’s vegetable production. Methods The stochastic translog frontier model was used to estimate the technical efficiency of vegetable production. Based on the estimated frontier and technical inefficiency levels, we used the method developed by Reinhard, et al.[1] to estimate the environmental efficiency. Pesticide and chemical fertilizer inputs were treated as environmentally detrimental inputs. Results From estimated results, the mean environmental efficiency for pesticide input was 69.7%, indicating a great potential for reducing pesticide use in China’s vegetable production. In addition, substitution and output elasticities for vegetable farms were estimated to provide farmers with helpful information on how to reallocate input resources and improve efficiency. Conclusion There exists a great potential for reducing pesticide use in China’s vegetable production.

Mapping of a New Gene Wbph6(t) Resistant to the Whitebacked Planthopper, Sogatella furcifera, in Rice

A rice population consisting of 90 TN1/Guiyigu F3 lines was employed to analyze the linkage between DNA markers and a new gene Wbph6(t) conferring resistance to whitebacked planthopper, Sogatella furcifera By using the mapping approach of bulked extremes and recessive class, Wbph6(t) was mapped onto the short arm of chromosome 11 with a genetic distance of 21.2 cM to SSLP marker RM167.

TWISTED PRODUCTS AND SMASH PRODUCTS OVER WEAK HOPF ALGEBRAS

This paper gives a sufficient and necessary condition for twisted products to be weak Hopf algebras, moreover, gives a description for smash products to be weak Hopf algebras. It respectively generalizes R.K.Molnar's major result and I.Boca's result.

Diagnosis of Nitrogen Status in Rice Leaves with Canopy Spectral Reflectance

The investigation was made on the relationship of seasonal time-course canopy spectral reflectance and ratio index to total leaf nitrogen accumulation (leaf nitrogen content per unit ground area) in rice under different nitrogen treatments. The results showed there was a close correlation between the canopy spectral reflectance and total leaf nitrogen accumulation. Ratio of near infrared to green band (R810/R560) was linearly related with total leaf nitrogen accumulation. independent of nitrogen levels and development stages. Different datasets were used to test the linear regression equation, with average estimation accuracy of 91. 22%, RMSE of 1.09 and average relative error of 0. 026. Thus, the ratio index R810/R560 of canopy spectral reflectance should be useful for non-destructive monitoring and diagnosis of nitrogen status in rice plants.

Mapping QTL for Heat-Tolerance at Grain Filling Stage in Rice

A mapping population of 98 lines (backcross inbred lines, BILs) derived from a backcross of Nipponbare/Kasalath// Nipponbare was planted at two experimental sites, Nanjing and Nanchang, and treated with high and optimal temperature during grain filling, respectively. The grain weight heat susceptibility index [GWHSI= (grain weight at optimum temperature-grain weight at high temperature) / grain weight at optimum temperature × 100] was employed to evaluate the tolerance of rice to heat stress. A genetic linkage map with 245 RFLP markers and a mixed linear-model approach was used to detect quantitative trait loci (QTLs) and their main effects, epistatic interactions and QTL× environment interactions (Q×E). The threshold of LOD score=2.0 was used to detect the significance of association between marker and trait. A total of 3 QTLs controlling heat tolerance during grain filling were detected, on chromosomes 1, 4 and 7, with LOD scores of 8.16, 11.08 and 12.86, respectively, and they explained the phenotypic variance of 8.94, 17.25 and 13.50 %, correspondingly. The QTL located in the C1100-R1783 region of chromosome 4 showed no QTL× environment interaction and epistatic effect, suggesting that it could be stably expressed in different environments and genetic backgrounds, and thus it would be valuable in rice breeding for heat tolerance improvement. This QTL allele, derived from Kasalath reduced 3.31% of the grain weight loss under heat stress. One located between R1613-C970 on chromosome 1 and the other between C1226-R1440 on chromosome 7, with additive effect 2.38 and 2.92%, respectively. The tolerance alleles of both these QTLs were derived from Nipponbare. Both of these QTLs had significant QTL× environment interactions, and the latter was involved in epistatic interaction also. Eight pairs of epistatic effect QTLs were detected, one pair each on chromosomes 1,2,3, 5, 7, 8, 10 and 12. The results could be useful for elucidating the genetic mechanism of heat-tolerance and the development of new rice varieties with heat tolerance during grain filling phase.

Dynamics of Microbial Communities in Bulk and Developing CucumberRhizosphere Soil

The microbial population dynamics in bulk and developing cucumber rhizospheres were studiedby cultivation and cultivation-independent approach based on directly extracted DNA toprovide baseline data. Soil and rhizosphere samples were taken from tested field 2, 4, 7 and10 weeks after the seeds were planted, which was positively related to the corresponding dateof cucumber growth stages. The plate culture amount showed that total number of bacteria,fungi and actinomyces began to rise when cucumber planted and quickly reached peak at seedlingor blossom period, but decreased slightly later. Bacterial population in rhizosphere washigher by comparison with that of counterpart except for seedling and flowering stages, butthe shift trend of them were quite similar all the time. Nitrogen fixating, nitrobacter andammonifying bacteria showed the same change tendency in population as bacteria and actinomycesdid, however, cellulose-decomposing bacteria had the contrary rhizosphere effect as cucumberdeveloped. Data revealed that positive relevance existed between the dominant rhizospheremicrobe population and cucumber development. PCR was employed to amplify the V3 region of 16SrDNA, then the products were subjected to denaturing gradient gel electrophoresis(DGGE). DGGEprofile indicated that a few microbe species lived stable in farmland soil, but some wereinfluenced by population due to cucumber roots growth. Significant difference was observed inbulk and rhizosphere soils especially for the seedling and flowering samples. Few prominentbands in DGGE patterns, which displayed stronger or less illumination, means the representativebacteria had great population variation in that period. These phenomena indicated thatflowering cucumber heavily affected rhizosphere bacteria, or the bacteria, most probably theuncultured bacteria, functioned specially to cucumber blossom. Most detected bands with noillumination change in DGGE quite possibly represent the indigenous microbes that wereessential for constructing and stabilizing farmland microecological environment.