Toxicity of Artemisia annua (Asteraceae) essential oil on the tea mealy bug,Pseudococcus viburni Sigornet (Hemiptera: Pseudococcidae)

A combination of bioassay and biochemical approaches were used to determine toxicity of Artemisia annua essential oil (AaEO) Pseudococcus viburni. AaEO via leaf dipping bioassay showed LC₅₀ values of 0.693 and 0.419% after two time exposures. Different concentrations of AaEO caused deterrence index between 28.58 to 86.26% by the calculated ED₅₀ of 0.4%. Although, α-esterase activity using α-naphtyl acetate increased in the treated nymphs by AaEO after 24 hours but it showed the lower activity in the treated nymphs using β-naphtyl acetate. Glutathione S-transferase assayed by CDNB showed the higher activity in the treated nymphs than control after 24 hours while the adverse results gained not only after 48 hours but also after 24 hours by using DCNB. No significant differences were found in the activity of alanine aminotransferase versus control, but aspartate aminotransferase and γ-glutamyl transferase showed the statistically higher activities in the treated nymphs in comparison with control. Activities of aldolase and lactate dehydrogenase were significantly lower than those of control. Only acid phosphatase showed the significantly altered activity in the treated nymphs in comparison with control after 24 hours. Results of our study indicated significant toxicity, deterrence and physiological effects of AaEO on P. viburni.     

<Emphasis Type="Italic">Artemisia lerchiana</Emphasis> as a producer of essential oil

Abstrac  The composition of essential oil of Artemisia lerchiana Web. plants growing in Volgograd oblast was studied. Sampling was performed from plots contrasting in climatic and soil characteristics. Essential oil was obtained by hydrodistillation. The content of essential oil in shoot biomass increased gradually during shoot formation, flower bud formation, and flowering beginning and then decreased. The highest content of essential oil varied from 1.1 to 1.5% of plant dry weight at the stage of flower bud formation. More than thirty compounds were identified by gas chromatography-mass spectrometry. The following major components were found: camphor, borneol, bornylacetate, camphene, and 1,8-cineole. Some of compounds (sesquiterpenes and sesquiterpenoids) were identified for the first time. The time-course of accumulation of essential oil components strongly depended on habitat edaphic factors and climatic conditions during the year of sampling. The results permit a conclusion that A. lerchiana is a valuable producer of essential oils. Original Russian Text ? E.B. Kirichenko, Yu.V. Orlova, D.V. Kurilov, 2008, published in Fiziologiya Rastenii, 2008, Vol. 55, No. 6, pp. 934–941.     

Effects of sheep urine on growth characteristics of different life form plants in a Chinese steppe grassland

The effects of sheep urine deposition volume (0, 1, 2 or 4 L/m²) and deposition stage of plant growth (vegetative or reproductive) on the number and size of tillers/branches and the biomass of Stipa bungeana, Artemisia capillaries and Lespedeza davurica in a Chinese steppe grassland were determined. The results indicate that the response of the three plant species to sheep urine deposition differs, and is influenced by both urine deposition volume and deposition stage of plant growth. Urine deposition had a short-term scorch effect on grassland plants, which mainly occurred in the inner zone of urine patches. Urine application had a long-term positive effect on S. bungeana and a long-term negative effect on A. capillaries and L. davurica, which lasted at least two years and decreased with decrease in urine deposition volume. All species growing in the inner zone of urine patches were scorched by sheep urine deposition, some species in the marginal zone of patches were also scorched, while no species were scorched in the outer zones. The reproductive and vegetative stages of A. capillaries and the reproductive stages of S. bungeana and L. davurica were sensitive to sheep urine deposition.     

放牧对鄂尔多斯高原油蒿草场生物量及植被-土壤碳密度的影响

以围封保护和自由放牧油蒿草场为研究对象,通过野外调查与室内分析,研究了围封和放牧条件下沙地草场生物量和植被-土壤碳密度。结果表明:(1)自由放牧使油蒿群落中植物种类增加,但降低了植物群落盖度。自由放牧不仅导致油蒿草场地上、地下总生物量降低,也使得油蒿地上、地下生物量占群落地上、地下总生物量的比例减小。生长季自由放牧样地凋落物生物量显著大于围封保护样地(P0.05);(2)围封保护样地植被碳密度大于自由放牧样地,土壤碳密度却小于自由放牧样地,但两个样地间差异不显著(P0.05);(3)油蒿草场90%以上的碳储存于土壤中,围封保护样地和自由放牧样地油蒿草场土壤碳密度占植被-土壤系统碳密度的91%、93%;(4)围封保护油蒿草场碳密度为2.29 kg/m2,自由放牧油蒿草场碳密度为2.68 kg/m2,两个样地间差异不显著,自由放牧对油蒿草场碳密度影响不大。     

Kin recognition affects plant communication and defence

The ability of many animals to recognize kin has allowed them to evolve diverse cooperative behaviours; such ability is less well studied for plants. Many plants, including Artemisia tridentata, have been found to respond to volatile cues emitted by experimentally wounded neighbours to increase levels of resistance to herbivory. We report that this communication was more effective among A. tridentata plants that were more closely related based on microsatellite markers. Plants in the field that received cues from experimentally clipped close relatives experienced less leaf herbivory over the growing season than those that received cues from clipped neighbours that were more distantly related. These results indicate that plants can respond differently to cues from kin, making it less likely that emitters will aid strangers and making it more likely that receivers will respond to cues from relatives. More effective defence adds to a growing list of favourable consequences of kin recognition for plants.     

Compartmentation and fluxes of carbon in leaf blades and leaf sheaths of Poa annua L. and Poa x jemtlandica (Almq.) Richt

Abstract The allocation of photosynthetically fixed carbon in the leaf blades and sheaths of Poa annua (a ruderal grass) and Poa x jemtlandica (a sub-arctic grass) was followed over a light-dark cycle. Labelling with ¹⁴Carbon and gas exchange measurements provide data for an eight-compartment model describing the partitioning of carbon between spatially and chemically separated pools and their rates of turnover. Soluble sugars and fructans were turned over rapidly in the leaf blades of both species. The flux of carbon through pools of storage carbohydrates was higher in the leaves of P. x jemtlandica than in P. annua. The exchange of carbon between pools was slower in the sheath than the blade. Carbohydrates stored in the sheath appeared to have no significant role in metabolism over the light-dark cycle studied here.     

Ludalbin,a new lactone from Artemisia ludoviciana

Artemisia ludoviciana Nutt. ssp. albula (Woot.) Keck, a member of the vulgaris complex, contains a sesquiterpene lactone, ludalbin, which is 8-α-acetoxydouglanine.     

Comparison of phosphorus distribution and cycling between adjacent native semidesert shrub and cultivated grass-dominated ecosystems

Summary P concentrations at several soil profile depths and for various plant parts were monitored over most of one year in adjacent native semidesert shrub and cultivated crested wheatgrass ecosystems. When multiplied by appropriate soil bulk densities and phytomass values, it was possible to calculate P mineralomasses in these two ecotessera. Knowledge of new to old growth ratios allowed estimation of P turnover. Although there was greater P in the vegetation of the native stand, the tissues lived longer and decomposed less rapidly than those in the grass stand that has been established in a portion of the original shrub dominated semidesert. The grass stand showed higher net primary productivity and had a much higher fraction of phytomass that is consumable by livestock. There was thus, at least a five-fold greater turnover of P in the tilled and seeded system. The introduced grasses are also withdrewing more P from the soil reserves. Whether nutrient export from the systems could lead to long-term declines in productivity will require further monitoring and experimental effort.     

差巴嘎蒿灌丛土壤和根系含水量对降雨的响应

以科尔沁沙地半固定沙丘灌木差巴嘎蒿(Artemisia halodendron)为对象,用土钻取样法和壕沟法研究了2006年生长季降雨后差巴嘎蒿周围土壤和根系含水量的时空分布特征及其相互关系,并计算了该灌丛的水量平衡.结果表明:该灌丛在降雨后对水分有暂时存储作用;降雨结束后,灌丛主干的茎流作用使得灌丛中心位置的土壤含水量高于灌丛丛幅垂直投影1/4和3/4处的土壤含水量;雨后6 h灌丛根系含水量与灌丛中心位置的土壤含水量呈极显著的负相关(r=-0.89,P＜0.01);灌丛根系含水量在雨后126 h内出现胁迫脉冲间歇反应.水量平衡计算表明,灌丛边缘外1 m处土壤蒸散量高于灌丛覆盖区的蒸散量,灌丛覆盖可降低土壤水分蒸散速率.