青春期雌性根田鼠初次择偶行为与雄性优势等级

在实验室条件下，研究了性刚成熟的雌性根田鼠对一对互为同胎同胞的以体重划分为优势和从势的雄性个体的择偶行为，目的在于检验雄性社会等级是否影响其配偶选择。结果发现：(1)根田鼠存在显著的偏雄性二型，而雄性动物优势度与体重大小成正比；(2)在Y字型迷宫中，初次发情雌鼠对优势雄鼠的访问时间、社会探究频次和友好频次等显著大于从属雄鼠；(3)在随后24h的一雌二雄共居中，优势雄优先交配；从属雄的干扰不能中断优势雄鼠的交配。这些结果说明，体重差异可以作为划分雄性优势的指标，社会等级可以作为择偶行为的一个依据。优势雄鼠与处于从属地位的同胞相比，能获得优先交配机会。同胎同胞虽具有遗传相似性，但雄性竞争的结果表现在体重和社会等级上具有显著差异，表明配偶选择在发挥着作用。根田鼠是一雄多雌制，而且具有较大的偏雄性二型，提示社会等级、雌性选择和婚配制度有密切关联[动物学报49(3)：303—309，2003]。     

Seasonal changes of root hydraulic conductance (KRL) in four forest trees: an ecological interpretation

This paper deals with the possibility of relating root hydraulic parameters to an ecological index describing the continentality/oceanicity of four forest trees. Root hydraulic conductance ($K_R$) of seedlings of Fagus sylvatica L., Quercus ilex L., Quercus suber L. and Quercus pubescens Willd. was measured in May, August and November 1996. $K_R$ was calculated in terms of the relation of the water flow through intact root systems in situ measured with the pressure chamber, and the pressure driving the flow. The sufficiency of the root system to supply the foliage was estimated by dividing $K_R$ by the seedlings leaf surface area ($A_L$) thus obtaining $K_RL$. In the spring, $K_RL$ was largest in F. sylvatica and smallest in Q. pubescens with intermediate values recorded in Q. ilex and Q. suber. All the species studied showed a large decline in $K_RL$ just prior to the winter rest except for Q. suber which mantained $K_RL$ approximately constant through the period of study. In most cases, $K_RL$ changed in accordance with analogous changes in the flow. When the total seedlings' leaf surface area ($A_L$) was plotted versus $K_RL$, it appeared that $K_RL$ of Q. pubescens increased with $A_L$, proportionally, while $K_RL$ of F. sylvatica was inversely related to $A_L$. This, together with the largest $K_RL$ recorded in the summer in Q. pubescens, was interpreted as advantageous to this species (which is adapted to semi-arid environments) in that: (a) roots could supply water to foliage efficiently even during the adverse season and (b) the foliage growth could be sustained even in summer.No statistically significant relation of $K_RL$ to the continentality index calculated for the four species studied on the basis of their European distribution, was found to exist. Nonetheless, our data appear to be encouraging for future research aimed at better interpreting the typical distribution areas of plant species.     

Nuclear magnetic resonance in environmental engineering: Principles and applications

This paper gives an introduction to nuclear magnetic resonance spectroscopy (NMR) and magnetic resonance imaging (MRI) in relation to applications in the field of environmental science and engineering. The underlying principles of high resolution solution and solid state NMR, relaxation time measurements and imaging are presented. Then, the use of NMR is illustrated and reviewed in studies of biodegradation and biotransformation of soluble and solid organic matter, removal of nutrients and xenobiotics, fate of heavy metal ions, and transport processes in bioreactor systems.     

Timing of root dormancy and tolerance to root waterlogging in clonal Sitka spruce

 Actively growing root tips of Picea sitchensis (Bong.) Carr. plants are highly susceptible to damage if waterlogged, but they are known to have some tolerance after they stop growing in the autumn. This paper describes the selection of clones on the basis of root dormancy timing and the corresponding responses of their roots to over-winter waterlogging. Sitka spruce transplants of Alaska, Queen Charlotte Islands (QCI), and Washington provenances were screened for early or late root dormancy over 2 successive years. Cuttings were propagated from the selected plants and after growing on for 2 years, they were planted in transparent acrylic tubes within outdoor ‘root observation chambers’. Extension of main roots and the timing of onset of root dormancy was recorded on the clonal plants. The tubes were flooded in November and maintained with a water table 280 mm below the soil surface until March of the next year. Waterlogging caused most main root tips to die back, but within 2 months of draining regeneration occurred on the main roots below the waterlogging level. This regeneration was most commonly the growth of existing lateral tips or production of new lateral roots. Roots of early-dormant Washington plants died back on average 129 mm less than late-dormant Washington plants, and early-dormant Alaska plants had 173 mm less dieback than late-dormant Alaska plants. Differences between the clones of the QCI provenance were not significant. The 40% and 52% increases in survival depth of roots in early-dormant Washington and Alaska clones respectively indicates a potential for improving the rooting depth of Sitka spruce on seasonally waterlogged soils by planting clones selected on the basis of root dormancy. Received: 14 July 1997 / Accepted: 15 September 1997     

Vertical distribution of arbuscular mycorrhizal fungi under corn (Zea mays L.) in no-till and conventional tillage systems

 We compared the vertical distribution (0–25 cm) of arbuscular mycorrhizae, extraradical hyphae, and glomalean spores at grain-filling of corn under conventional tillage versus no tillage. Root colonization, total hyphae density, and spore density were correlated, and were highest at a depth of 0–15 cm in soil. Tillage significantly reduced total hypha density and spore density at 0–5 cm depth, but did not affect root colonization. Plowing below 15 cm is likely to diminish AM fungus inocula in the rooting zone of establishing seedlings. Accepted: 19 April 1998     

Ca2+对小麦种根及其根毛生长发育的影响

低浓度的ＣａＣｌ２对小麦种根生长、根毛发生和生长无明显影响,高浓度的ＣａＣｌ２（０．１ｍｏｌ／Ｌ）对种根和根毛生长有抑制作用,但不影响根毛的发生。Ｃａ２＋专一性螯合剂ＥＧＴＡ抑制种根生长和根毛的发生及生长,添加一定浓度的外源ＣａＣｌ２,这种抑制作用可被消除。ＣａＭ抑制剂ＴＦＰ（三氟拉嗪）和ＣＰＺ（氯丙嗪）对种根生长、根毛发生和生长均有抑制作用,添加外源ＣａＭ可减弱或消除这种抑制作用。     

Water stress and indol-3yl-acetic acid content of maize roots

Water-stress conditions were applied to the apical 12 mm of intact or excised roots ofZea mays L. (cv. LG 11) using mannitol solutions (0 to 0.66 M) and changes in weight, water content, growth and IAA level of these roots were investigated. With increasing stress a decrease in growth, correlated with an increased IAA level, was observed. The largest increase in IAA (about 2.7-fold) was found in the apical 5 mm of the root and was obtained under a stress corresponding to an osmotic potential of −1.39 MPa in the solution. This stress led to an isotonic state in the cells after 1 h. When the duration of water stress (−1.09 MPa) was increased to 2 or 3 h, no further increase in the IAA content was observed in the root segments. This indicated that there was no correlation between a hypothetical passive penetration of mannitol in the cells and IAA content. Indol-3yl-acetic acid rose to the same level in excised as in intact roots. In both cases, IAA accumulation was apparently independent of the hydrolysis of the conjugated form. The caryopsis and shoot seem not to be necessary to induce the increase of the IAA level in the roots during water stress (−1.09 MPa). Therefore, there seems to be a high rate of IAA biosynthesis in excised maize roots under water-stress conditions. Exodiffusion of IAA was observed during an immersion in either buffer or stress (−1.09 MPa) solution. In both cases, this IAA efflux into the medium represented about 50% of the endogenous level. Considering the present results, IAA appears to play an important part in the regulation of maize root metabolism and growth under water deficiency.     

The action of gravity in agravitropic Zea primary roots: Effect of gravistimulation on the extracellular free-Ca2+ content in the 1-mm apical root tip in the dark

The action of gravity stimulation in darkness was examined in agravitropic primary roots of Zea mays L. (cv. Golden Cross Bantam 70). Contents of diffusible and nitric-acid-extractable Ca²⁺ in 1-mm apical tips of roots gravistimulated in the dark were measured by flowinjection analysis as free Ca²⁺ and bound Ca²⁺, respectively. The free-Ca²⁺ content increased transiently, reaching a maximum 0.5 h after gravistimulation. This transient increase was also observed when gravistimulation was applied by changing the orientation of the roots back from horizontal to vertical again. On the other hand, the bound-Ca²⁺ content decreased transiently following gravistimulation. Furthermore, when the root caps were treated with 10 mM 2-(N-morpholino) ethanesulfonic acid buffer, the elevation of free Ca²⁺ following gravistimulation was prevented. These results indicate that gravity perception and the initial transduction steps proceed in the dark, and moreover that the elevation of free Ca²⁺ brought about by the interaction of Ca²⁺/H ⁺ in the apoplast of root tips may be involved in transmission of the gravity signal.Abbreviations FIA flow-injection analysis - Mes 2-(N-morpholino) ethanesulfonic acid - Pipes 1,4-piperazinediethanesulfonic acid - Quin 2 2-[(2-bis-[carboxymethyl]amino-5-methylphenoxy)methyl]-6-methoxy-8-bis(carboxymethyl) aminoquinoline     

反硝化聚磷菌及其脱氮除磷机理研究进展

水体富营养化是当前水环境保护工作的重点关注问题,微生物修复富营养化水体具有高效、低耗且不产生二次污染等特点,已经成为富营养化水体生态修复的一种重要方式。近年来,对反硝化聚磷菌的研究及其在污水处理工艺中的应用越来越广泛。不同于传统的反硝化细菌联合聚磷菌去除氮磷工艺,反硝化聚磷菌在交替厌氧、缺氧/好氧条件下能同时进行脱氮除磷而被广泛关注与研究。值得注意的是,近几年报道的部分微生物仅在好氧条件下就可进行同时脱氮除磷,但是其脱氮除磷机理仍未理清。基于此,文中总结了目前发现的反硝化聚磷菌和同时硝化反硝化聚磷微生物的种类及特点,并对其脱氮与除磷的关系及其机理进行了系统性分析,对目前反硝化除磷存在的问题进行了梳理,最后对今后的研究方向进行了展望,以期为完善反硝化聚磷菌的脱氮除磷机理及工艺改进提供参考。