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排序方式: 共有1422条查询结果,搜索用时 15 毫秒
1.
Formation of a Tree having a Low Lignin Content 总被引:2,自引:0,他引:2
Received 30 September 2001/ Accepted in revised form 26 October 2001 相似文献
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Abstract: The leaf extracts of Populus nigra were collected and identified by steam distillation, air entrainment and gas chromatographic–mass spectrometric analysis. Electroantennograms were recorded from Helicoverpa armigera adults in response to the chemicals identified. Both aromatic compounds and green-leaf volatiles elicited strong responses. Field experiments revealed that the active compounds responsible for attracting H. armigera moths are mainly short-side-chain aromatic alcohols and aldehydes. We, for the first time, used agaropectin as the controlled-release matrix of insect attractants. A five-component lure containing all the aromatics without phenolics, mixed in the proportions as found in the steam distillate of the leaves collected in August, produced the best trap catch. The results showed that the volatiles of wilted leaves of P. nigra can attract H. armigera adults by feeding attraction. 相似文献
4.
Summary The root systems ofEucalyptus grandis W. Hill ex Maiden, irrigated with recycled municipal effluent at two sites in north-western Victoria, Australia, were studied
by excavation and coring. Trees at Robinvale were four years-old and were irrigated using micro-sprays that covered only 70%
of the ground surface area, whereas at Mildura, effuent was uniformly was uniformly applied to six years-old trees by flood
and sprinkler irrigation.
At Mildura where roots were excavated from a 2.80×2.80×1.20 m block of soil, a total root length of 1193 m.m−2 and a total root weight of 3.1 kg m−2 were estimated in the top metre. For roots >1 mm diameter, 77% of intercepts were at 0–30 cm, whereas only 50% were in the
50–100 cm soil horizon.
At both sites where roots in the top 30 cm were studied by coring, the vertical distributions of root intercepts, length and
weight were similar. Root length was greatest in the 0–10 cm soil horizon at both sites, and intercepts of roots <1 mm diameter
comprised 73% and 81% of all roots at Mildura and Robinvale respectively. Roots <1 mm diameter contributed 85% of total length
at both sites, but only 19% and 21% of total weight at Mildura and Robinvale respectively. The horizontal distribution of
roots differed at the two sites. With uniform application of effuent at Mildura, root intercepts and length were concentrated
in the centre of the irrigation bay, but at Robinvale, the concentration occurred closer to the tree row due mainly to the
different method of irrigation. Root weight at both sites was highest within 50 cm of the tree row.
Root densities of 0.11 to 0.57 cm cm−3 were estimated in the two plantations; these were similar to root densities measured inPinus radiata D. Don plantations up to 46 months old, but were considerably lower than those estimated for pastures. The implications of
the results for the management of irrigated plantations of eucalypts are discussed. 相似文献
5.
初期采脂对马尾松木材构造的影响 总被引:1,自引:0,他引:1
广东省韶关林场采用标准的采脂工艺,在其马尾松人工林进行了两年的初期采脂试验。 在这些马尾松的采脂树的采脂盘上,主要呈现泌脂和木材增生,而在其下方距离0.5m的影响盘上。仅有一些创伤轴向树脂道和树脂囊。创伤树脂道使其邻近的轴向管胞的形状不规则,又与树轴倾斜近45°。 从山中试验区不同的松树林分,在其对照盘(对照树的)、影响盘上,自髓向外每隔一个生长轮的离析材料;另在采脂盘上密切邻近采脂面两侧,自圆盘周围向内各选4轮材料;分别测定轴向管胞的长度,得知这些30(20)年生的马尾松树仍在幼态期间,其管胞长度一般是增加的;至于采脂面两侧的管胞却显出不同程度的减短,其中一些管胞呈现种种不规则形状。 相似文献
6.
湿地松(Pinus elliottii)是阳性乔木,茶树(Camellia sinensis)是阴性灌木。这两种树种间作,形成针阔、乔灌两层树冠结构的茶园复合生态系统,可以改善茶树生态条件,提高茶叶的产量和品质。但间作存在胁地现象。一般认为这是上层树木的过度遮荫和根系间的竞争造成的。为了解这两种树种根系的分布状况和相互关系,并为间作茶园的合理配置和加强这种茶园的耕作管理提供依据,我们进行了湿地松与茶树间作根系分布状况的研究。 相似文献
7.
Claire Lurin Lise Jouanin 《Molecular breeding : new strategies in plant improvement》1995,1(4):411-417
A novel method for studying differential expression of multigene family members based on the high sensitivity of RT-PCR completed by restriction site polymorphism of DNA is described. This method allows the identification of specific patterns of expression of fourchalcone synthase genes in a Hunnegem poplar clone (Populus trichocarpa ×Populus deltoides). 相似文献
8.
Involvement of putrescine in the inductive rooting phase of poplar shoots raised in vitro 总被引:1,自引:0,他引:1
Micropropagated poplar shoots rooted 100% on a rooting medium (A) containing NAA, but they did not root in the absence of auxin (NA). Putrescine, but not spermidine and spermine, promoted rooting up to 42% when added to the NA medium. Cyclohexylamine (CHA), an inhibitor of spermine synthase, also promoted (up to 36%) rooting in the absence of auxin. The inhibitors of polyamine biosynthesis DFMA (α-difluoromethylarginine) and DFMO (α-difluoromethylomithine), aminoguanidine (AG) and methylglyoxal-bis-guanylhydrazone (MGBG), inhibited rooting when applied in the presence of auxin and had no effect in its absence.
The rooting inductive phase (in the presence of auxin) was determined by periodical transfer of shoots from A to NA medium, and by changes in peroxidase activity, to be 7 h. Putrescine (not spermidine and spermine) accumulated to a maximum during the inductive phase. Both putrescine and CHA promoted rooting on NA medium when applied during the first 7 h. In contrast DFMA and AG inhibited rooting during this period. The results point to the involvement of putrescine and its Δ1 -pyrroline pathway, in the inductive phase of rooting in poplar shoots. 相似文献
The rooting inductive phase (in the presence of auxin) was determined by periodical transfer of shoots from A to NA medium, and by changes in peroxidase activity, to be 7 h. Putrescine (not spermidine and spermine) accumulated to a maximum during the inductive phase. Both putrescine and CHA promoted rooting on NA medium when applied during the first 7 h. In contrast DFMA and AG inhibited rooting during this period. The results point to the involvement of putrescine and its Δ
9.
DOCA—Salt高血压大鼠模型的一种简易制备方法:DOCA硅胶管皮下埋入法 总被引:4,自引:0,他引:4
用外径4mm,内径2.50mm的硅胶管制成长25mm,管内填入DOCA100mg,管壁钻有10一14个直径约300μm微孔的药管,埋入雄性SD大鼠(140±9g)右下腹皮下,摘除一侧肾脏,术后喂1%盐水。埋管后3周即可形成高血压,埋管后8周大鼠的收缩压达23.3±0.37kPa。而DOCA皮下注射组大鼠(10mg/周)术后5周形成高血压,术后13周大鼠的收缩压达23.3±0.66kPa。两组升压曲线回归系数(1.295和0.692)之间的差异有极显著性意义(P<0.001)。对照鼠的收缩压一直保持在正常水平(16±0.16kPa)。与DOCA皮下注射法相比,皮下埋管法具有两个显著优点:(1)升压速率较快,升压幅度较大;(2)方法简便可靠,重复性好。 相似文献
10.
田林老山中山两类森林凋落物研究 总被引:15,自引:2,他引:13
田林老山中山两类森林凋落物研究梁宏温(广西农学院林学分院,南宁530001)StudiesontheLitterfallofTwoForestTypcsinMid—AltitudeofLaoshanMountaininTianlinCounty.¥L... 相似文献