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71.
Enzyme activities and microbial community structure in semiarid agricultural soils 总被引:15,自引:0,他引:15
Acosta-Martínez V. Zobeck T. M. Gill T. E. Kennedy A. C. 《Biology and Fertility of Soils》2003,38(4):216-227
This study investigated the effect of management on -glucosidase, -glucosaminidase, alkaline phosphatase, and arylsulfatase activities and the microbial community structure in semiarid soils from West Texas, USA. Surface samples (0–5 cm) were taken from a fine sandy loam, sandy clay loam, and loam that were under continuous cotton ( Gossypium hirsutum L.) or in cotton rotated with peanut ( Arachis hypogaea L.), sorghum ( Sorghum bicolor L.), rye ( Secale cereale) or wheat ( Triticum aestivum L.), and had different water management (irrigated or dryland), and tillage (conservation or conventional). The enzyme activities were higher in the loam and sandy clay loam than in the fine sandy loam. Soil pH was not affected by management, but the soil organic C and total N contents were generally affected by the different crop rotations and tillage practices studied. The trends of the enzyme activities as affected by management depended on the soil, but in general crop rotations and conservation tillage increased the enzyme activities in comparison to continuous cotton and conventional tillage. The soil enzyme activities were significantly correlated with the soil organic C ( r -values up to 0.90, P< 0.001), and were correlated among each other ( r -values up to 0.90, P <0.001). There were differences in the fatty acid methyl ester profiles between the fine sandy loam and the sandy clay loam and loam, and they reflected the differences in the enzyme activities found among the soils. For example, a 15:0 ranged from 1.61±0.25% in cotton-peanut/irrigated/no-till in the fine sandy loam to 3.86±0.48% in cotton-sorghum/dryland/conservation tillage in the sandy clay loam. There were no differences due to management within the same soil.Trade names and company names are included for the benefit of the reader and do not infer any endorsement or preferential treatment of the product by USDA-ARS 相似文献
72.
Yelena V. Lyubun Paul V. Kosterin Elena A. Zakharova Alexander A. Shcherbakov Evgenii E. Fedorov 《Journal of Soils and Sediments》2002,2(3):143-147
Background, Aim and Scope Environmental pollution caused by arsenic (As) is a major ecological problem. There has been intense worldwide effort to find
As-hyperaccumulating plants that can be used in phytoremediation—the green-plant-assisted removal of chemical pollutants from
soils. For phytoremediation, it is natural to prefer cultivated rather than wild plants, because their agriculture is well
known. This study was conducted to evaluate the tolerance of common sunflower(Helianthus annuus L.) and sugar sorghum(Sorghum saccharatum Pers.) for soil-As contents of 10–100 mg As kg-1 soil, with sodium arsenite as a model contaminant.
Methods Plants were grown in a growth chamber for 30 days. Microfield experiments were conducted on experimental plots. To study the
phytoremediation effect of the auxins indole-3-acetic acid (IAA) and 2,4-dichlorophenoxyacetic acid (2,4-D), we treated 1-
and 3-day-old plant seedlings with water solutions of the auxins (concentrations 10-5, 10-7, and 10-9 g l-1). The soil and plant-biomass samples were analyzed for total As by using the color reaction of ammonium molybdate with As.
Results and Discussion Phytotoxicity studies showed that 100 mg As kg-1 soil poisoned sunflower and sorghum growth by 50%. There was a linear correlation between soil-As content and As accumulation
in the plants. Laboratory experiments showed that the soil-As content was reduced two- to threefold after sunflower had been
grown with 10–100 mg As kg-1 soil for 30 days. Treatment of sunflower and sorghum seedlings with IAA and 2,4-D at a concentration of 10-5 g l-1 in microfield experiments enhanced the phytoremediation two- to fivefold as compared with untreated control plants. The best
results were obtained with 3-day-old seedlings.
Conclusion, Recommendation and Outlook (a) Sunflower and sorghum are good candidates to remediate As-polluted soils. (b) Phytoremediation can be improved with IAA or 2,4-D. (c) Mixed cropping of sorghum and sunflower may be another way of improving phytoremediation. 相似文献
73.
The objective of this study was to determine the effect of foliar salicylic acid (SA) applications on growth, chlorophyll, and mineral content of cucumber grown under salt stress. The study was conducted in pot experiments under greenhouse conditions. Cucumber seedlings were treated with foliar SA applications at different concentrations (0.0, 0.25, 0.50, and 1.00 mM). Salinity treatments were established by adding 0, 60, and 120 mM of sodium chloride (NaCl) to a base complete nutrient solution. The SA was applied with spraying two times as before and after transplanting. Salt stress negatively affected the growth, chlorophyll content and mineral uptake of cucumber plants. However, foliar applications of SA resulted in greater shoot fresh weight, shoot dry weight, root fresh weight, and root dry weight as well as higher plants under salt stress. Shoot diameter and leaf number per plant increased with SA treatments under salt stress. The greatest chlorophyll content was obtained with 1.00 mM SA treatment in both saline and non-saline conditions. Leaf water relative content (LWRC) reduced in response to salt stress while SA raised LWRC of salt stressed cucumber plants. Salinity treatments induced significant increases in electrolyte leakage. Plants treated with foliar SA had lower values of electrolyte leakage than non-treated ones. In regard to nutrient content, it can be interfered that foliar SA applications increased almost all nutrient content in leaves and roots of cucumber plants under salt stress. Generally, the greatest values were obtained from 1.00 mM SA application. Based on these findings, the SA treatments may help alleviate the negative effect of salinity on the growth of cucumber. 相似文献
74.
75.
Rashid Iqbal Khan Ishfaq Ahmad Hafiz Touqeer Ahmad Ishaq Ahmed Abdul Ahad Qureshi 《Journal of plant nutrition》2013,36(18):2309-2319
The study was set up to evaluate the efficiency of amino acids and seaweed on vegetative growth, reproductive phase, yield, and postharvest storage quality of hydroponically grown bell pepper cultivars “Sven Rz F-1” and “Red Knight.” Different concentrations of amino acid and seaweed were sprayed on bell pepper plants under hydroponic conditions. Pre-harvest foliar application of amino acids and seaweed significantly increased plant height, number of leaves, leaf area, yield per plant, number of marketable fruits per plant, average fruit diameter, fruit wall thickness, and average single fruit weight. Amino acid and seaweed significantly improved postharvest physicochemical quality of both bell pepper cultivars under extended cold storage conditions. Conclusively, amino acid as well as seaweed extract not only improved growth, development, yield, and overall quality of bell pepper cultivars but also increased storage life with reduced weight loss and decay along with better physicochemical quality. 相似文献
76.
单宁酸对不同pH茶园土壤中活性铝形态分布的影响 总被引:4,自引:0,他引:4
采集云南省普洱市和江西省南昌县两地典型的茶园土壤,通过添加HCl和Ca(OH)2调节土壤pH,研究不同pH(3.0、3.5、4.0、4.5)茶园土壤添加0.4 mmol·kg 1、2.0 mmol·kg 1、4.0 mmol·kg 1、8.0 mmol·kg 1、12.0 mmol·kg 1单宁酸后,活性铝形态交换态铝(Al3+)、单聚体羟基铝[Al(OH)2+、Al(OH)+2]、酸溶无机铝[Al(OH)03]和腐殖酸铝[Al-HA]的分布特征。结果表明:单宁酸添加量为0~0.4 mmol·kg 1和0~2.0 mmol·kg 1时,江西南昌和云南普洱茶园土壤中交换态铝随土壤pH的增加呈明显下降趋势,而羟基态铝、酸溶无机铝和腐殖酸铝呈逐渐上升趋势;当单宁酸浓度增至2.0 mmol·kg 1以上时,随土壤pH的增加,单宁酸对活性铝释放的抑制作用增强,各形态活性铝含量都较低,且不同pH处理土壤间的差异不显著。0~20 cm土层土壤与20~40 cm土层土壤变化规律大致相似,总体上看,下层土壤活性铝总量高于上层。云南普洱茶园土壤活性铝总量明显高于江西南昌的茶园土壤。相关分析表明,0~20 cm土层土壤中,pH与羟基态铝、腐殖酸铝、土壤酸碱缓冲容量(pHBC)呈正相关(r=0.796,P0.01;r=0.960,P0.01;r=0.852,P0.01);pHBC与交换态铝、羟基态铝呈负相关(r=0.904,P0.01;r=0.645,P0.05),而与腐殖酸铝呈正相关(r=0.795,P0.01)。同时,单宁酸加入浓度为0~0.4 mmol·kg 1时,土壤pH明显上升,之后随着单宁酸加入浓度的增加土壤pH持续下降,土壤pH(YpH)与单宁浓度(CDN)在此阶段基本符合方程:YpH=0.04CDN+3.82(R2=0.95,P0.01)的线性变化趋势,在单宁酸浓度达到8.0~12.0 mmol·kg 1时,土壤pH基本不再变化。 相似文献
77.
78.
79.
超高压处理对普洱生茶香味成分的影响研究 总被引:2,自引:0,他引:2
为了探讨超高压处理对普洱茶香味成分的影响,将普洱茶在400MPa压力、25℃温度条件下处理20min后,经顶空固相微萃取与毛细管气相色谱-质谱联用技术检测超高压处理前后普洱茶香气成分的变化,并用面积归一化法测定了各种成分的质量分数。经与超高压处理前普洱茶的主要香气成分分析比较发现,超高压处理后普洱茶中主要特征香气成分的质量分数明显增加,其中β-紫罗兰酮、愈创木酚、柏木醇、香叶基丙酮、2,6-甲氧基苯酚、氧化芳樟醇、2,3-二甲氧基甲苯和二氢猕猴桃内酯等物质的质量分数分别增长了92.31%、80.77%、75.00%、73.08%、63.64%、54.92%、54.54%和34.92%,并且新增加了香叶醇(0.22%)、杜松醇(0.15%)和α-大马酮(0.15%)等香气成分;从感官审评结果来看,超高压处理后普洱茶的陈香特征增强,滋味陈纯,因此对普洱茶加工来说超高压处理是一种很有前景的加工技术。 相似文献
80.
以季戊四醇和异辛酸为原料,以固体超强酸树脂为酯化催化剂合成了季戊四醇四异辛酸酯,考察了催化剂用量、醇酸摩尔比、反应温度、反应时间对酯化率反应的影响,确定了合成季戊四醇四异辛酸酯的优化工艺条件:以固体超强酸树脂为催化剂,催化剂用量1.2%,酸醇的物质的量之比为5.5,反应温度为150℃,反应时间为5.5h,季戊四醇四异辛酸酯收率可达98.5%。红外光谱表明,酯化反应较为完全。 相似文献