A wound-inducible gene fromSalix viminalis coding for a trypsin inhibitor

A gene designatedswin1.1 has been isolated by screening aSalix viminalis genomic library with a heterologous probe,win3 fromPopulus. The region sequenced included the entire coding sequence for a protein with 199 amino acids plus the promoter and terminator. At the 5 end of the coding region is a sequence that encodes a hydrophobic region of 25–30 amino acids, that could form a signal peptide. A putative TATAA box and polyadenylator sequence were identified. Introns were absent. The gene product showed similarities with serine protease inhibitors from the Kunitz family and especially withwin3 from wounded leaves ofPopulus. Southern blot analysis indicated thatswin1.1 is a member of a clustered gene family,swin1. An oligonucleotide corresponding to the putative hypervariable region to-wards the carboxyl end when used as a probe in Southern hybridization showed high specificity forswin1.1. Expression of theswin1.1 gene was enhanced in wounded leaves. Theswin1.1 coding region without the signal sequence was highly expressed inEscherichia coli and the protein showed inhibitory activity against trypsin but at most slight activity against the other proteases tested. A systemically induced protein, SVTI, with inhibitor activity against trypsin, was isolated fromSalix leaves by affinity chromatography on a column of trypsin-Sepharose 4B and N-terminal sequenced. It corresponded with the translatedswin1.1 gene at 16 of the 19 amino acid sites, suggesting that SVTI is encoded by another member of theswin1 gene family.     

阿尼玛卿山八种柳属植物叶片的形态结构特征研究

对阿尼玛卿山柳属八种植物的叶片进行了形态和解剖研究。观察结果表明：除旱柳外,其余７种均为异面叶;栅栏组织２－３层,细胞排列紧密;有些种的叶上表皮有光滑的角质膜,下表皮为复表皮。表面多有灰白色的粉粒蜡质,气孔不下陷;此外,在叶表皮、叶肉及维管束鞘中皆存在有含单宁或胶质的异细胞。这些特征与高山地区严酷的自然环境条件是相适应的。     

Preference and performance linkage in aPhyllocolpa sawfly on the willow,Salix miyabeana,on Hokkaido

A leaf-folding sawfly in the genusPhyllocolpa (Hymenoptera: Tenthredinidae) attackingSalix miyabeana (Salicaceae) was studied near Sapporo, Hokkaido, along the Ishikari River in 1993. Host plant individuals were young trees 4–7 years old which were growing rapidly, producing some long shoots with large leaves. On a gradient of shoot length classes from 0–5 cm long to over 80 cm long, shoots were much more abundant in the shorter shoot length classes. However, attacks by ovipositing females increased as shoot length increase from 0 attacks on the shortest shoots to 5.17 attacks per shoot on the longest shoots. The frequency of attack per leaf increased from 0 to 0.13 over the same range of shoot lengths. This pattern of attack resulted in a high frequency of larval establishment in feeding sites, between 0.96 and 1.00, in all attacked shoot length categories. However, probability of survival to a late instar larva increased with shoot length and corresponded to the attack pattern, indicating a preference-performance linkage between female ovipositional decisions and larval survival. The patterns found for thisPhyllocolpa species are similar for galling sawflies in North America and Europe, especially in the genusEuura, members of which make stem, bud and leaf midrib galls. Extending the pattern to aPhyllocolpa species broadens identification of pattern and ultimately the generality of the emerging theory on populations of galling sawflies.     

GENETICS OF RESISTANCE OF SALIX SERICEA TO A DIVERSE COMMUNITY OF HERBIVORES

We measured resistance of Salix sericea, the silky willow, to a diverse assemblage of 12 herbivores. We investigated the potential for multispecies coevolution among these herbivores by measuring genetic correlations between pairs of herbivores interacting within the component community. After measuring herbivore attack on half-sib families of potted S. sericea during three years, we found significant narrow-sense heritabilities of resistance to Phyllonorycter salicifoliella and Phyllocnistis sp. in 1991. Thus, there is the potential for selection on resistance to these two herbivores. Despite the many significant phenotypic correlations between herbivore abundances within a year, most genetic correlations between herbivore abundances within a year were not significant. The genetic and phenotypic correlation structure varied from year to year in this three-year study. Thus, it appears that there is the potential for evolution of resistance to the two herbivores for which we found significant heritabilities, but multispecies coevolution seems unlikely.     

农田防护林木材材质物理特性研究

对早柳和小青杨的年轮宽度、年轮密度、木材纤维长度和干缩率及其径向变异进行了研究．结果表明,木材物理特性受年轮年龄的影响显著,而纤维长度不受年轮宽度影响．综合材质物理特性的径向变异规律,可将旱柳和小青杨整个生长期划分为４个时期：幼林期、速生期、成熟期和更新期,确定了各生长期的年龄值．     

柳苗对盐激的快速反应

采用电子称重法检测了柳(Salix babylonica L.)苗蒸腾对盐激(NaCl)的快速反应。结果表明,100～500mmol/L的NaCl处理柳苗根系时,均能引起根系中产生一个负水压信号,并以极快的速度传递至冠部叶片,引起植物体液向下流动,在1～2s内使柳苗蒸腾速率增加至原来的8～15倍,然后逐渐下降,8～12min后,蒸腾速率保持在原来的水平(或略低)。另外,在蒸腾速率变化约2min后,在叶片区柳茎表面记录到电波的快速传递(速度变化范围在28～120mm·s~(-1)),这可能是主动调节冠部水分消耗的一个信号。     

The ribosomal ITS region as a marker to detect hybridization in pines

Amplified fragment length polymorphism (AFLP) analysis of 26 trees of three Salix taxa: Salix alba L. (White Willow), S. fragilis L. (Crack Willow) and their hybrid S. x rubens Schrank, across an example of their habitat range in south-west Germany, supported the distribution previously determined using morphological characterization. UPGMA and principal coordinates analysis of the AFLP data revealed three distinct clusters corresponding to the three taxa. In addition, AFLP analysis on individuals which were difficult to identify morphologically revealed that they were either the hybrid S. x rubens or S. fragilis. Four specimens of S. fragilis were indistinguishable with three primer combinations suggesting they are members of one clone.     

Phytoremediation of groundwater contaminated with pesticides using short-rotation willow crops: A case study of an apple orchard

The occurrence of pesticides in groundwater represents an important health issue, notably for population whose drinking water supply source is located in agricultural areas. However, few solutions have been considered with regard to this issue. We tested the efficacy of a vegetal filtering system made of shrub willows planted at a high density (16,000 plants ha^?1) to filter or degrade pesticides found in the groundwater flowing out of an apple orchard. Ethylene urea (EU), ethylene thiourea (ETU), tetrahydrophthalimide (THPI), atrazine, and desethylatrazine were monitored in the soil solution in willow and control plots over one growing season. ETU and atrazine concentrations were lower in the willow plots relative to the control plots, whereas desethylatrazine concentration was higher in the willow plots. No significant difference was detected for EU and THPI. Furthermore, pesticide concentrations displayed complex temporal patterns. These results suggest that willow filter systems can filter or degrade pesticides, notably ETU and atrazine, and could be used for phytoremediation purposes. Yet, this potential remains to be quantified with further studies using experimental settings allowing more estimation in time and space.     

Livestock grazing limits beaver restoration in northern New Mexico

The North American beaver (Castor canadensis) builds dams that pond water on streams, which provide crucial ecological services to aquatic and riparian ecosystems and enhance biodiversity. Consequently, there is increasing interest in restoring beavers to locations where they historically occurred, particularly in the arid western United States. However, despite often intensive efforts to reintroduce beavers into areas where they were severely reduced in numbers or eliminated due to overharvesting in the eighteenth and nineteenth centuries, beavers remain sparse or missing from many stream reaches. Reasons for this failure have not been well studied. Our goal was to evaluate certain biotic factors that may limit the occurrence of dam‐building beavers in northern New Mexico, including competitors and availability of summer and winter forage. We compared these factors at primary active dams and at control sites located in stream reaches that were physically suitable for dam‐building beavers but where none occurred. Beaver dams mostly occurred at sites that were not grazed or where there was some alternative grazing management, but were mostly absent at sites within Forest Service cattle allotments. Results indicated that cattle grazing influenced the relation between vegetation variables and beaver presence. The availability of willows (Salix spp.) was the most important plant variable for the presence of beaver dams. We conclude that grazing by cattle as currently practiced on Forest Service allotments disrupts the beaver‐willow mutualism, rendering stream reaches unsuitable for dam‐building beavers. We recommend that beaver restoration will require changes to current livestock management practices.     

Growth responses of selected clones of birch (Betula pendula roth.,B. pubescens Ehrh.) and willow (Salix caprea L.,S. cinerea L.) to nitrogen in solution culture

Summary Growth of selected clones of birch and willow obtained from nitrogen deficient soils was compared with that of unselected controls in pot experiments using three levels of nitrogen. Unselected controls of both genera continued shoot growth, albeit very slowly, with a very low level of nitrogen (5 ppm), while selected clones of birch grew significantly more than the controls. Selected clones of willow, on the other hand, ceased shoot growth after 10 weeks with this low nitrogen treatment. Nevertheless, they remained healthy, their leaves containing similar concentrations of nitrogen to those of the plants which continued stem growth throughout the experiment. Furthermore, they had very high root: shoot ratios compared with those of control willows and both selected and unselected birch. The two genera may have developed different mechanisms for tolerating low nitrogen, birch producing a small, relatively efficient root system; willow a larger but less efficient one. Both appear equally effective in ensuring survival on low-nitrogen sites in the field since all the selected clones were obtained from such sites and have survived well in field trials on similar sites. Both birch and willow responded toincreased nitrogen availability with increasing shoot growth and a relative decline in root growth. However, whereas in willow the unselected plants responded significantly more than selected clones, a similar but less markeddifference was found in birch. It appears that in both genera, as in herbaceous plants originating from nitrogen deficient sites, selected clones are less able to respond to increasing nitrogen supply than control plants from more fertile habitats. Attempts to correlate the response of the selected clones to nitrogen in this experiment with that to added nitrogen fertilizer in field trials has been unsuccessful. Further work is required to determine the importance of the many interacting factors which influence the response of young trees to nitrogen under the unusual field conditions associated with restored mineral workings.