施肥措施对烤烟生长与经济性状的影响

1996-1998年研究了施肥量和施肥次数对烤烟生长、产量和品质形成的影响。结果表明，随施肥量的增加，烤烟上、中、下部的叶面积和植株干物重显著增加，但与施肥次数关系不明显。烤烟优质、高效施肥技术为每公倾施用N，P，K复合肥1500kg，分4次施用。     

First report of <Emphasis Type="Italic">Candidatus</Emphasis> Phytoplasma prunorum infecting almonds in Tunisia

Candidatus Phytoplasma prunorum was detected for the first time in almond (Prunus dulcis Mill.) cv. ‘Abiod’ in Tunisia. Infected trees showed emergence of new growth during dormancy and leafed out before flowers opened in addition to early defoliation in summer. Phytoplasma was detected by nested polymerase chain reaction (PCR) using universal phytoplasma primer pairs P1/P7 and F2n/R2. A band with expected size was observed in samples collected from five symptomatic, but not symptomless almond trees. PCR products (1.2 kbp) were used for restriction fragment length polymorphism (RFLP) analysis after digestion with endonucleases RsaI and SspI. RFLP patterns obtained were similar to those reported previously for the European stone fruit yellows (ESFY, 16SrX-B). Identification has been further confirmed by PCR using ESFY specific primer pairs (ECA1/ECA2). This is the first report of Ca. Phytoplasma prunorum infecting almonds in Tunisia.     

Metabolic resistance mechanisms to phosalone in the common pistachio psyllid, Agonoscena pistaciae (Hem.: Psyllidae)

The common pistachio psyllid, Agonoscena pistaciae, is the most damaging pest of pistachio in Iran, and is generally controlled by insecticides belonging to various classes especially, phosalone. The toxicity of phosalone in nine populations of the pest was assayed using the residual contact vial and insect-dip methods. The bioassay results showed significant discrepancy in susceptibility to phosalone among the populations. Resistance ratio of the populations to the susceptible population ranged from 3.3 to 11.3. The synergistic effects of TPP, PBO and DEM were evaluated on the susceptible and the most resistant population to determine the involvement of esterases, mixed function oxidases and glutathione S-transferases in resistance mechanisms, respectively. The level of resistance to phosalone in the resistant population was suppressed by TPP, PBO and DEM, suggesting that the resistance to phosalone is mainly caused by esterase detoxification. Biochemical enzyme assays revealed that esterase, glutathione S-transferase and cytochrome P450 monooxygenase activities in the resistant population was higher than that in the susceptible. Glutathione-S-transferases play a minor role in the resistance of the pest to phosalone.     

Enhancing habitat to help the plight of the bumblebee

Modern farming has caused considerable declines in UK bumblebee populations, and, while options exist for farmers to increase the quantity of bee-friendly habitat, uptake has been low. Robin Blake explains how existing habitats on farms could be enhanced for the benefit of bumblebees.     

塔中紫外辐射与气象要素的关系

分析2007年塔克拉玛干沙漠腹地紫外辐射特征和影响因子与气象要素的相关性,并依据有关要素拟合出紫外辐射的估算方程。结果表明：紫外辐射年总量达到305.64 MJ/（m2.a）,7月最大,12月最小,全年瞬时强度峰值在6月,为67.11 W/m2。紫外辐射的变化与总辐射变化呈显著正相关,且紫外辐射在总辐射中所占比例夏季大...     

Effect of Nano Fe-Chelate,Fe-Eddha and FeSO4 on Vegetative Growth,Physiological Parameters and Some Nutrient Elements Concentrations of Four Varieties of Lettuce (Lactuca sativa L.) In NFT System

In order to investigate the effects of different iron (Fe) sources (nano iron (Fe)-chelate, Fe- ethylenediamine-di(o-hydroxy phenyl acetic acid (EDDHA) and iron (II) sulfate (FeSO₄)) on lettuce (Lactuca sativa) growth in alkaline solutions, an experiment was arranged in hydroponic system. This study showed that leaf Fe content and overall plant growth was significantly increased by Fe-chelate application, and the highest values of leaf Fe, plant pigments and vegetative growth were recorded in plants treated with nano Fe-chelate. The lowest Fe, chlorophyll, carotenoids and soluble sugars in leaves were observed in FeSO₄ treatment. There were no difference in soluble sugars contents of plants between nano Fe-chelate and Fe-EDDHA treatments. Fertilization of lettuce plants with different Fe-chelate sources had a beneficial effect on the manganese (Mn) and zinc (Zn) uptake in plants. It is concluded that application of chelated form of Fe (especially nano Fe-chelate) must be performed in hydroponic system with alkaline water, to overcome Fe deficiencies and to make better nutritional status.     

Potentialities and soil impact analysis of rock phosphorus fertilization of perennial and annual legume crops

ABSTRACT

The objective of this study is to evaluate the impacts of the direct use of natural rock phosphates on two forage legumes, Vicia sativa, and Medicago sativa. Crops were grown in pots containing two P deficient soils and fertilized with Tunisian rock phosphate (TRP) or chemical triple superphosphate (TSP). TRP amendment significantly increased shoot dry yield (+53% to +162%), P-content, protein content, and chlorophyll content mainly at the rate of 150 kg P ha^?1. No significant effects were observed on mycorrhization and antioxidant enzyme activities. However, TSP negatively affected the frequency of root mycorrhization and stimulated antioxidant enzyme activities. TRP amendment induced an increase in fluorescein diacetate activity, alkaline phosphatase activity, and species richness. The stimulation involved mainly Actinobacteria, Proteobacteria, and Firmicutes with higher stimulation of Actinobacteria in the case of vetch. The present work indicated a better P-use efficiency of vetch. It suggested also that at least a part of the enhancement observed in plant-growth parameters following TRP fertilization is driven by changes in the structure of rhizosphere microbial communities. Nevertheless, the correlation between changes in microbial composition and phosphorus uses efficiency needs to be investigated further.     

Influence of plants and the microbial activity on the metal content in soil solutions of a soddy-podzolic soil in a model experiment

The influence of plants and microorganisms on the migration of metals in a soddy-podzolic loamy sandy soil was studied in a simulation experiment. It was shown that the biota has a great influence on the release of metal compounds into the soil and lysimetric solutions. In most cases, the metal content was reliably higher in the variants of the experiment with the presence of biota than in the control. The microorganisms maintained a high concentration of metals in the soil solution in the course of the experiment. The influence of the plants on the metal migration begins from the third week of the experiment as the biomass grows. The dose of the introduced metals also influences the concentration of the elements in the solutions and the ratios of the Me in the soil solutions: Me in the lysimetric solutions. In all the variants of the experiment, the ratios become narrower with the increase in the dose; i.e., the migration of the metals becomes more active. The dose of 7 APC (the approximate permissible concentration) has an inhibiting influence on the activity of the microorganisms and mustard plants.