两种野生灌木幼苗对干旱和盐交叉胁迫的生理响应

长枝木蓼(Ateaphaxis viegata)和刺叶锦鸡儿(Caragana acanthophulla)是乌鲁木齐周边植被组成的重要种,在植被恢复中具有潜在价值。该文通过盆栽控水控盐法研究两种野生灌木幼苗在不同程度的干旱和盐交叉胁迫下的生理反应。结果表明,干旱和盐交叉胁迫下,长枝木蓼可溶性糖增幅较刺叶锦鸡儿大;轻度交叉胁迫时,两种灌木的可溶性糖含量高于仅干旱胁迫或盐胁迫下的。中度和重度交叉胁迫下,长枝木蓼叶片丙二醛含量增幅高于刺叶锦鸡儿。交叉胁迫下,两种灌木叶片叶绿素含量下降,且长枝木蓼叶片的叶绿素含量降幅大于刺叶锦鸡儿。因膜系统的过氧化作用,使MDA含量升高。轻度干旱胁迫提高了两种野生灌木对盐胁迫的耐受能力。两种灌木能很好地适应中度交叉胁迫,重度交叉胁迫对两种灌木的伤害很大,但也能生存。综合比较各参数发现,刺叶锦鸡儿更耐早,而长枝木蓼更耐盐;综合比较各生理参数发现,刺叶锦鸡儿对干旱和盐胁迫的耐受能力较长枝木蓼强。     

中国鳞伞属拟火菇亚属新记录种

报道了中国鳞伞属Pholiota拟火菇亚属Subgen. Flammuloides的3个新记录种：暗红褐鳞伞P. decorata、黄盘鳞伞P. fulvodisca和杂纹鳞伞P. virgata,并提供详尽的形态描述和线条图。研究标本存放于吉林农业大学菌物标本馆（HMJAU）。     

Distribution of Insect Attacks in Biological Control of Weeds: Infestation of Centaurea virgata Flowerheads by a Gall Fly

The success of biological control efforts to reduce weed density through release of insects may depend as much on the distribution of insect attacks among individual plants or plant parts as on the mean level of infestation. We used an index of dispersion to describe the distribution of Urophora quadrifasciata (Diptera: Tephritidae) galls among squarrose knapweed (Centaurea virgata) flowerheads at 18 west central Utah sites in the first 5 years following introduction of the biological control agent. Two thirds of the samples showed a significantly aggregated distribution of galls among flowerheads. Statistical analysis showed that site and year accounted for relatively small proportions of the variance in the index of dispersion. The degree of gall aggregation among flowerheads was positively correlated with the mean flowerhead quality (mean number of seeds per flowerhead; P = 0.013) and tended to be negatively correlated with the mean fly density per flowerhead at a site in a given year (P = 0.097). Our data suggest that higher quality flowerheads, and possibly higher quality plants, are preferentially attacked by U. quadrifasciata and therefore are more heavily subject to reduced reproductive potential through biological control. However, an aggregated distribution of fly attacks may undercut the potential of the fly to reduce seed production by the weed population as a whole. Understanding both the distribution of insect attacks among individual plants and the behavioral mechanisms producing such distribution patterns is important to the biological control of weeds.     

松嫩平原羊草、虎尾草群落钙元素时空分布的比较研究

本文分析了松嫩平原羊草（Ｌｅｙｍｕｓｃｈｉｎｅｎｓｉｓ）群落和虎尾草（Ｃｈｌｏｒｉｓｖｉｒｇａｔａ）群落钙元素在土壤中和植物体中的分布特征及季节动态,以及土壤中钠钙含量的关系。结果表明,两种群落的土壤水溶性和交换性钙含量均为春秋两季较高,夏季较低,优势种植物体中钙的含量为羊草明显高于虎尾草,根部均高于其它部位。两种群落土壤中交换性钙的垂直分布均以表层最低,并随着土层深度而逐渐增加,其中羊草群落各土层的含量均高于虎尾草群落。     

Evaluation of Herbicides for Restoring Native Grasses in Buffelgrass-Dominated Grasslands

Buffelgrass ( Pennisetum ciliare ) is an exotic grass that threatens arid and semiarid ecosystems. The objective of this study was to determine effectiveness of several herbicides at reducing competition from buffelgrass to enhance establishment of planted native grasses. In Duval County, Texas, plots were delineated in two experiments in a buffelgrass-dominated pasture and mowed on 2 September 2002. On 18 September 2002 and 7 October 2002, a 41% glyphosate (N-(phosphonomethyl) glycine) herbicide was applied to all plots. A mixture of three native grasses—green sprangletop ( Leptochloa dubia ), plains bristlegrass ( Setaria leucopila ), and four-flower trichloris ( Chloris pluriflora )—was planted on 8 October 2002. On 9 October 2002, 1.12 and 2.24 kg/ha of a 80% tebuthiuron ( N -[5-(1,1-dimethyethyl)-1,3,4-thiadiazol-2-yl]- N , N '-dimethylurea) herbicide was applied preemergence to the first experiment, and all other herbicides were applied postemergence on 27 July 2003 to the second experiment. Percent canopy cover of vegetation was estimated with a 20 × 50–cm sampling frame during April, June, and October 2003 and August 2004. Postemergent herbicides had no significant effect on canopy cover of buffelgrass or planted species ( p ≥ 0.05). Canopy cover of native grasses did not exceed 8% on any treatment or sampling date, and buffelgrass cover returned to pre-treatment conditions in less than 1 year; however, the 2.24 kg/ha rate of tebuthiuron suppressed ( p < 0.05) canopy cover of buffelgrass compared with controls and increased ( p < 0.05) native grasses almost 2 years past application. Tebuthiuron may have potential value in reducing buffelgrass canopy cover and increasing cover of native grasses, particularly Chloris spp.     

Differential antioxidant enzyme and thiol responses of tolerant and non-tolerant clones of <Emphasis Type="Italic">Chloris barbata</Emphasis> to cadmium-stress

Tolerant and non-tolerant clones of Chloris barbata Sw. obtained, respectively, from an erstwhile mercury contaminated solid waste dump site near a chloralkali plant and a non-contaminated (control) site were subjected to cadmium-stress by growing the rooted cuttings in water containing CdSO₄, 13 and 130 μM. Differences between the two clones in their response to cadmium-stress were noted in root growth, and also with respect to certain biochemical parameters. Whereas catalase activity decreased and non protein-thiol levels increased in the non-tolerant clone, the level of protein-thiol alone increased significantly in the tolerant clone in response to cadmium-stress. No remarkable differences between the clones, however, were noted with respect to total soluble protein, peroxidase activity and lipid peroxidation. Remarkably the two clones responded differently to buthionine sulfoximine, an inhibitor of glutathione and/or phytochelatin synthesis, which inhibited root growth significantly in non-tolerant clone but not in the tolerant clone. Buthionine sulfoximine, nonetheless, could potentate cadmium toxicity in either of the clones, but more effectively in the tolerant clone. The high sensitivity of tolerant-clone to the combined treatment of BSO and Cd in the present study could, therefore, be attributed to the cumulative oxidative stress generated synergistically by BSO and Cd.     

Chloris gayana (Rhodes grass), a better host for the mas production ofGlomus fasciculatum inoculum

Seven different hosts,Panicum maximum, Chrysopogon fulvis, Themeda triandra, Chloris gayana, Brachiaria brizantha, Paspalum scrobiculatum andEleusine coracana were screened in order to select a better host for mass multiplication ofGlomus fasciculatum inoculum. Of these,Chloris gayana (Rhodes grass) was found to be the best host on the basis of root colonization and spore production and of the infective propagules of the potball.     

东北草原盐碱植物虎尾草的热值和能量分配特征的研究

虎尾草全株、茎和叶的热值的季节变化规律相似,从7月初至8月初出现2个峰值,然后呈逐渐下降趋势.穗的热值变化呈U字型,2个峰值分别出现在8月初和9月中旬.立枯体热值变化不规则,最大在8月初.虎尾草种群地上部能量的季节动态呈双峰曲线,峰值分别出现在8月初和9月初,最大值在9月初为7381.27kJ     

刺木蓼和长枝木蓼种子休眠的解除及萌发条件

刺木蓼（Atraphaxis spinosa）和长枝木蓼（A.virgata）为蓼科木蓼属灌木,是乌鲁木齐周边植被组成的重要种。这两种木蓼种子成熟后不萌发,处于休眠状态,对其种子进行5℃（黑暗）和野外低温层积处理,结果表明：5℃层积处理能明显提高两种木蓼种子在15/6、20/10、25/15和30/20℃（昼12 h/夜12 h）的萌发率。野外层积处理显著提高了种子在15/6℃的萌发率。刺木蓼和长枝木蓼的种子均为非深度生理休眠,分别经8、6周的低温层积处理后种子休眠得以解除。刺木蓼种子的休眠程度比长枝木蓼深,休眠解除后,种子萌发所需的最低温度降低。这两种木蓼种子经过冬天的低温层积,可以在春天较低的生境温度下萌发。