多环芳烃污染土壤的微生物与植物联合修复研究进展

通过对江西省余江县洪湖乡历史资料的分析,结合农户经济行为调查,阐述了典型红壤丘陵区农作系统的演变过程及其特征,并且针对农业生产中存在的问题,提出解决对策。分析结果表明,20世纪50年代以前,长江中下游流域农作系统的演变过程可以分为丘陵和河谷砂性水稻土的游垦系统-雨季水稻耕作系统-水旱轮作系统3个阶段。20世纪50年代以后,江西省余江县洪湖乡农作系统的演变分为农业革命和现有系统2个阶段,粮食安全驱动和生存型经济福利驱动是其演变的主要驱动力。80年代以来,随着经济的发展,一部分农作系统演变为可持续再生产型,但需要较高的劳力和资金投入,并且有物价和农业政策等方面的风险。目前发展区域可持续农业需要解决的关键问题是优化农林牧副渔结构、扩大土地经营规模、增加种粮比较效益、促进信贷资金使用、提高劳力素质。     

Effects of Cu, Ni and Zn on Lettuce Grown in Metal-Enriched Vermicompost Amended Soil

A study has been conducted in a salt marsh, located in the coast of the Mar Menor lagoon (SE Spain), in which three watercourses overflow. Water samples were regularly collected over a one-year period from two transects established through the salt marsh towards the lagoon. All the samples were analysed for electrical conductivity, pH, sulphides, chlorides, nitrate, ammonium and dissolved phosphorus. The quality of the water flowing from the watercourses to the salt marsh showed a seasonal pattern, with higher contents of nitrates (> 200 mg NO^? ₃ L^?1) in periods of maximum agricultural activities in the nearby areas, as well as a higher content of ammonium (> 30 mg NH⁺ ₄ L^?1) and phosphorus (> 10 mg PO^3? ₄?P L^?1) when the human population increased in the zone as a result of tourism. The general spatial pattern of nutrient retention in the salt marsh, indicated by a reduction in the nutrient concentrations in the water closer to the lagoon, was modulated depending on the season. In the driest months, the marsh was 100% effective in reducing nutrient concentrations, but in the rainy periods the effectiveness was reduced. This reduction was more evident for phosphorus in autumn, whose concentration increased in the lower part of the salt marsh closer to the lagoon until it reached that of the inflow. This could mainly be explained by the accumulation of water in some sites near the lagoon, which can act as sinks of pollutants. Our data support the existence of polluted water in the surface watercourses of the area, and the associated risk can include soil salinization and the eutrophication of aquatic systems. Based on our data, the Mar Menor coastal marshes have an important role as filters to reduce pollution in this lagoon.     

Index for potato nitrogen status diagnosis in a three-phase hydroponic system

Abstract

Up to now, there has not been any research that has tried to establish nitrogen (N) status diagnosis in basic seed potatoes, propagated by sprout in a three-phase hydroponic system. The objective of this study was to develop a potential index to be used in the diagnosis of N status in potato, using a three-phase hydroponic system, with the potato cultivar Agata. The treatments consisted of four N concentrations: 0, 7.8, 13 and 26?mmol L^?1. The experiment was conducted in a randomized block design with 12 replications in a non-acclimatized greenhouse. It was evaluated in a destructive and non-destructive way, and in real-time or space–time, 18 biometric characteristics of the reference leaf and of plant organs besides other variables related to the fourth leaf green color. Among the non-destructive characteristics measured, length, and diameter of the internodes and thickness of the fourth leaf showed the highest correlation coefficient (p?相似文献   

Critical phosphorus concentrations in potato plant parts at two growth stages

Adequately evaluating the phosphorus (P) nutritional status of a potato crop is dependent upon sampling the appropriate plant part at a defined growth stage. To establish P critical concentration levels in various potato plant parts (leaves, stems, tubers, leaflets, and petioles) at two growth stages [20 and 50 days after plant emergence (DAE)], an experiment under Brazilian climatic and soil conditions was conducted using seven P treatment levels (0, 40, 80, 160, 320, 640, and 1,280 kg P₂O₅ ha^‐1) applied in a randomized complete block design with four replications. ‘Baraka’ potato tubers were seeded at a spacing of 0.80 x 0.30 m following agronomic cultural practices recommended for this crop. Phosphorus concentrations in all the potato plant parts were significantly affected by the P fertilizer rates applied. The highest correlation between the P concentration in the various plant parts and marketable yield and optimum profit yield was obtained for the petiole taken 20 days DAE. Critical P levels associated with optimum profit yield were lower than those for maximum marketable tuber yield, and they were, 0.41, 0.39,0.39,0.57, and 0.57 g P 100 mg^‐1 DM in the leaf, stem, tuber, petiole, and leaflet, respectively.     

Growth of Brazilian Cotton Cultivars in Response to Soil Applied Boron

ABSTRACT

The growth of cotton (Gossypium hirsutum L.) was evaluated in a 6 × 5 factorial experiment with 6 boron (B) levels (0.0, 0.5, 1.0, 1.5, 2.0, and 3.0 mg dm^?3), 5 cultivars (‘CNPA 8H’, ‘BRS Aroeira’, ‘BRS Antares’, ‘BRS Sucupira’, ‘BRS Ipe’), and 3 replications. As B increased in the soil, leaf B concentrations increased linearly in ‘BRS Aroeira’ and ‘CNPA 8H’, and quadratically in ‘BRS Ipe’ and ‘BRS Sucupira’. The concentrations of B in the leaves and in the soil increased with the B increasing in the soil. The agronomic characteristics evaluated showed ‘BRS Aroeira’ and ‘BRS Sucupira’ responding more and BRS responding less to the B doses applied. The variation in the effFiciency of B utilization was: ‘BRS Aroeira’ > ‘CNPA 8H’ = ‘BRS Antares’ > ‘BRS Sucupira’ > ‘BRS Ipe’. Cultivar ‘BRS Aroeira’ had the greatest potential to respond positively to the addition of B to the soil.     

Effect of Nitrogen and Trinexapac-Ethyl Rates on the SPAD Index of Wheat Leaves

ABSTRACT

The objective of this study was to evaluate the effect of nitrogen (N) and trinexapac-ethyl (TE) rates on the SPAD index in wheat flag leaf. The treatments were five N rates (30, 60, 90, 120, 150 kg ha^?1) combined with four TE rates (0, 63, 125, 188 g ha^?1). The experiment was carried out in a randomized block design with four repetitions. SPAD index, leaf N content and grain yield showed quadratic response to the increase in N rates, whereas area, wet and dry weight of flag leaf presented linear increase. TE caused linear increase in SPAD index, linear decrease in leaf area, reduction in grain yield with smaller N rates and increase with larger N rates. The N content, and the wet and dry weight of flag leaf were not affected by TE. SPAD calibration to estimate N status in wheat should be specific for each TE rate.     

Carbon, nitrogen, organic phosphorus, microbial biomass and N mineralization in soils under cacao agroforestry systems in Bahia, Brazil

Large amounts of plant litter deposited in cacao agroforestry systems play a key role in nutrient cycling. Organic matter, nitrogen and phosphorus cycling and microbial biomass were investigated in cacao agroforestry systems on Latosols and Cambisols in Bahia, Brazil. The objective of this study was to characterize the microbial C and N, mineralizable N and organic P in two soil orders under three types of cacao agroforestry systems and an adjacent natural forest in Bahia, Brazil and also to evaluate the relationship between P fractions, microbial biomass and mineralized N with other soil attributes. Overall, the average stocks of organic C, total N and total organic P across all systems for 0?C50?cm soil depth were 89,072, 8,838 and 790?kg?ha^?1, respectively. At this soil depth the average stock of labile organic P was 55.5?kg?ha^?1. For 0?C10?cm soil depth, there were large amounts of microbial biomass C (mean of 286?kg?ha^?1), microbial biomass N (mean of 168?kg?ha^?1) and mineralizable N (mean of 79?kg?ha^?1). Organic P (total and labile) was negatively related to organic C, reflecting that the dynamics of organic P in these cacao agroforestry systems are not directly associated with organic C dynamics in soils, in contrast to the dynamics of N. Furthermore, the amounts of soil microbial biomass, mineralizable N, and organic P could be relevant for cacao nutrition, considering the low amount of N and P exported in cacao seeds.     

Interaction of Tritrichomonas foetus and the bovine oviduct in an organ culture model

Tritrichomonas foetus is an extracellular parasite of the reproductive tract in cattle. The mechanism by which T. foetus causes abortion in cattle is largely unknown. There are no studies of infection in the cow oviducts, almost all published papers are related to vagina infection and few articles focusing on the uterus. The aim of the present study was to establish a working model of bovine oviduct epithelial cells and submit these cells to Tritrichomonas foetus interaction. Twenty bovine oviducts were obtained from cows at a commercial abattoir and T. foetus was injected through the isthmus into the oviduct lumen. The whole oviduct was analyzed by scanning and transmission electron microscopy. The results reported here demonstrate that: (1) fresh whole oviducts can be used as a good model to study parasite-host cell interaction; (2) cow oviduct epithelium has been shown to consist of two cell types: ciliated and nonciliated secretory cells, and T. foetus displayed great specificity for the nonciliated cells localized in the deeper oviduct folds; (3) T. foetus adheres as single separate cells, and maintains the flagella externalized; (4) differently from T. vaginalis, T. foetus does not change its shape during the adhesion process; and (5) oviduct cells exhibited morphological characteristics of apoptosis after trichomonadal interaction.     

Biological and molecular properties of Tomato rugose mosaic virus (ToRMV), a new tomato-infecting begomovirus from Brazil

A viral complex causing golden mosaic and leaf distortion (rugosity) in tomato plants was obtained from viruliferous whiteflies, and named TGV-Ub1. This complex was sap-transmitted from tomato to Nicotiana benthamiana . PCR amplification using universal begomovirus primers yielded two distinct fragments for DNA-A, suggesting that the TGV-Ub1 complex comprised at least two distinct viruses. Clones corresponding to full-length viral genomes were obtained from tomato plants infected with TGV-Ub1. Comparisons of the complete sequences of clones pUb1-49 (DNA-A), pUb1-62 and pUb1-81 (both DNA-B) indicated that they constitute novel western hemisphere begomoviruses. Clones pUb1-49 and pUB1-81 have identical common regions, thus representing the cognate DNA-A and -B of a novel begomovirus, named Tomato rugose mosaic virus (ToRMV). Clone pUb1-62 has a distinct common region from ToRMV and all other geminiviruses. A cognate DNA-A for pUb1-62 was not found. Clones containing 1·8 copies of the genomic components were constructed. Infectivity assays of these clones in tomato and N. benthamiana demonstrated that the clones corresponding to ToRMV systemically infected both hosts. Symptoms were analogous to those observed when using the pure isolates obtained in this study. The combination of pUb1-49 and -62 did not result in systemic infection, indicating that these components do not form a viable virus. ToRMV was sap-transmitted from N. benthamiana to N. benthamiana , and by grafting to Solanum tuberosum and Datura stramonium . ToRMV-A and ToRMV-B were detected in plants of Nicandra physaloides and Phaseolus vulgaris , respectively, growing in nearby tomato fields, in association with distinct DNA components.