Community structure of arbuscular mycorrhizal fungi in a primary successional volcanic desert on the southeast slope of Mount Fuji

Community structure of arbuscular mycorrhizal fungi (AMF), evaluated as spore samples and mycorrhizal roots of four herbaceous plant species, was investigated at different altitudes in a primary successional volcanic desert on Mount Fuji using molecular methods (fragment and sequence analysis of the large ribosomal subunit RNA gene). In total, 17 different AMF clades were identified, and most were members of the Glomaceae, Acaulosporaceae, and Gigasporaceae. The AMF community structures detected by spore sampling were inconsistent with those from plant roots. Of all AMF clades, six (35.3%) were detected only on the basis of spores, six (35.3%) only in roots, and five corresponded to both spores and roots (29.4%). Although an Acaulospora species was the most dominant among spores (67.1%), it accounted for only 6.8% in root samples. A species analysis of AMF communities at different altitudes demonstrated that AMF species diversity increased as altitude decreased and that the species enrichment at lower altitudes resulted from the addition of new species rather than species replacement. The inconsistencies in the species composition of spore communities with those in roots and the change in species diversity with altitude are discussed.     

大花蕙兰组培快繁技术研究

选用大花蕙兰杂交新品种1053为外植体,采用1/2MS为基本培养基进行大花蕙兰组培快繁技术研究,结果表明：类原球茎诱导的最佳外植体为大花蕙兰鳞茎,培养基最佳激素浓度配比为0.5 mg/L 6-BA＋0.2 mg/L NAA;类原球茎增殖与分化芽最佳激素浓度配比为1.0 mg/L 6-BA＋0.3 mg/L NAA;幼芽增殖的最佳激素浓度配比为2.0 mg/L 6-BA＋0.5 mg/L NAA,最佳有机添加物为150 ml/L椰汁,幼芽增殖正交试验得出影响因素主次顺序：6-BA〉椰汁添加物〉NAA,优组合为2 mg/L 6-BA、0.5 mg/L NAA、添加物椰汁150 ml/L;诱导生根的最佳激素浓度配比为0.3 mg/L IBA＋0.2 mg/L NAA,添加香蕉泥100 g/L对幼苗根生长有显著的促进作用。优化后的大花蕙兰组培快繁技术参数,可为大规模工厂化生产提供参考。     

Adaptive significance of sprouting ofEuptelea polyandra,a deciduous tree growing on steep slopes with shallow soil

We investigated growth characteristics ofEuptelea polyandra Sieb. et Zucc. (Eupteleaceae), a Japanese endemic deciduous tree species growing on unstable ground such as that of very steep slopes with thin soil.Euptelea polyandra began to sprout at the juvenile stage and had a multiple-stemmed tree form. There was a positive correlation between diameter of the maximumsized stem within a stool (DMS) and the number of stems within the stool. Many stools had suffered from disturbances as shown by the fact that uprooting scars were found on 31.4% and 42.4%, respectively, of the stools of the two populations studied. Sprouting played a significance role in repairing damaged stems and stools, and at least 15.5% and 18.2% of the stools of the two populations, respectively, had apparently avoided death by sprouting. Sprouted stems gradually inclined with the increase in their relative sizes within each stool, and this seemed to facilitate the establishment of younger sprouted stems. The small younger sprouted stems had their own roots. There were dormant buds on stems which originated from axillary buds, and secondary dormant buds occurred by branching. The total number of dormant buds in a stool increased with DMS. It is concluded thatE. polyandra accumulates dormant buds for sprouting in order to respond to disturbances quickly.     

Relations between cytokinin level, bud development and apical control in Norway spruce, Picea abies

In conifers such as Norway spruce, the extent of shoot growth is predetermined by the size and number of embryonal organs of the buds laid down the previous year. As it is known that cytokinins have a key role in bud development a possible hypothesis is that the level of cytokinin in the buds during their formation determines their size and complexity. As a first step to test this hypothesis we compared cytokinin levels in buds of different size of annual shoots from 15- to 20-year-old trees of Picea abies (L.) Karst. Apical buds from the leaders, and from branches in lower parts of the trees, were collected in April, July and August. The difference in size of the buds and the shoots growing from them was considerable in these three positions. Extracts were purified by immunoaffinity columns, and the retained compounds were separated by high-performance liquid chromatography (HPLC). Quantification was made by enzyme-linked immunosorbent assay (ELISA), and the accuracy of this method was checked by measurements with liquid chromatography-mass spectrometry (LC-MS) and UV absorption. Zeatin riboside (ZR) was the most abundant cytokinin, but isopentenyladenosine (iPA) was also present in all samples. The large apical bud of the leader contained much higher cytokinin concentrations than the considerably smaller buds from lower positions, and during the period of secondary growth in July, similar relationships were found for annual stem tissue from different positions. The possible role of ZR as a controlling factor in bud development and apical control is discussed. Our conclusion is that the level of zeatin-type cytokinins appears to play an important role in the establishment of differences in bud size and, thereby, the architecture of the tree crown.     

Abscisic acid,abscisic acid-esters and phaseic acid in vegetative terminal buds of Acer pseudoplatanus during emergence from winter dormancy

Levels of free-abscisic acid and boundabscisic acid (alkaline hydrolyzable abscisic acidesters) in replicated samples of terminal vegetative buds of sycamore trees were measured during natural emergence from winter dormancy by gas chromatographic methods together with isotope dilution estimation of recovery rates. Not until after the buds had been released from true dormancy in January by winter chilling did any clear change occur in either abscisic acid (ABA) fraction, or in total ABA, on any basis of comparison. The percentage of total ABA present as the free acid declined at the end of true dormancy to approximately two-thirds of its value in the earlier winter months. It is concluded that glucosylation of ABA is unlikely to play a major part in the mechanism of release from dormancy in vegetative sycamore buds. At the end of true dormancy there was a large transient increase in what appeared to be phaseic acid, but this was not accompanied by any marked decrease in either free- or bound-ABA.Abbreviations ABA abscisic acid - TLC thin layer chromatography - GLC gas chromatography     

鳜早期味蕾发育的组织学特征

采用石蜡切片、H.E染色研究了3 ~ 28日龄鳜（Siniperca chuatsi）味蕾发育的组织学特征,并通过扫描电镜观察28日龄鳜口咽腔组织味蕾类型与数目。结果表明,未开口期（3日龄）,鳜口裂未张开,味蕾尚未分化;开口期（7日龄）,鳜口裂张开明显,味蕾呈椭圆形,突起高度平缓,主要分布在上下颌上皮上,舌、咽、鳃弓上皮上有少量分布;稚鱼期（14日龄）,味蕾呈圆锥形,突起高度上升,舌和咽上味蕾数目增加;21日龄,味蕾呈近梯形,突起高度不变,下颌、舌、咽上味蕾数增加,鳃弓上味蕾数目显著增加;28日龄,味蕾发育完全,口咽腔味蕾数继续增加。扫描电镜观察表明,鳜味蕾主要有3种类型：Ⅰ型味蕾近球形,含有大量微绒毛,突起高于上皮,味孔向外突起;Ⅱ型味蕾含有少量微绒毛,突起略高于黏膜上皮,味孔向内凹陷;Ⅲ型味蕾微绒毛含量最少,突起几乎与黏膜上皮共面,味孔平坦或凹陷。上下颌、咽、鳃中以Ⅰ型味蕾数量最多,Ⅱ型味蕾最少,舌上主要分布Ⅰ型味蕾,无Ⅲ型味蕾。结果表明,鳜早期味蕾结构发育与其摄食关联,推测其主要通过Ⅰ型味蕾和Ⅱ型味蕾对食物的机械性和化学成分进行识别。     

毒死蜱乳油对辣椒根围土壤细菌群落结构的影响

【目的】了解有机磷杀虫剂毒死蜱对土壤细菌群落结构的作用。【方法】联合微生物平板计数法、末端限制性片段多态性分析,选择PRIMER 5进行群落结构分析,以研究不同浓度的毒死蜱对辣椒根围可培养和不可培养细菌群落结构的影响。【结果】毒死蜱施入后前30 d,3个处理组的可培养细菌较对照组具有显著差异(P0.05),但在第30天后,处理组可培养细菌数均能恢复到对照水平。采用PRIMER 5对T-RFLP数据进行多角度分析发现,HaeⅢ酶切片段中,对照组C3、处理组Y0和Z2的细菌群落结构较整体聚类较远。HhaⅠ酶切片段中,150μg/g的毒死蜱处理组(Z0)在第0天表现出最大的群落差异。ANOSIM表明,以不同浓度的毒死蜱分组,各组间细菌群落组成差异不显著(HaeⅢ:Global R=0.041,P=0.168;HhaⅠ:Global R=-0.04,P=0.842);以不同取样时间分组时,细菌群落组成差异显著(HaeⅢ:Global R=0.304,P=0.001;HhaⅠ:Global R=0.28,P=0.001)。经SIMPER分析所有TRFs可知,对群落丰度贡献最大的片段分别为TRF239、TRF240、TRF241。在线比对得到其代表菌群有芽孢杆菌属(Bacillus sp.)、梭菌属(Clostridium sp.)、葡萄球菌属(Staphylococcus sp.)、八叠球菌属(Sarcina sp.)、假单胞菌属(Pseudomonas sp.)等。【结论】高浓度的毒死蜱会对土壤细菌群落产生影响,抑制根围细菌生长,从而遏制植物的健康生长,因而有必要及时采取措施以减少大量重复使用毒死蜱所带来的危害。     

濒危物种胡杨和灰叶胡杨的克隆生长特征

研究不同生态环境条件下胡杨和灰叶胡杨横走侧根的空间分布及其形态特征、不定芽及克隆分株的数量格局特征及其与土壤水分的关系。研究结果表明:(1)16团3个生境中灰叶胡杨克隆分株所在横走侧根均分布在10—20cm的土层;阿瓦提混交林内灰叶胡杨和胡杨克隆分株所在横走侧根分布在20—40cm的土层;轮台县河道边胡杨克隆分株所在横走侧根分布在10—20cm的土层,林内胡杨克隆分株所在横走侧根分布在20—40cm的土层。不定芽、克隆分株所在部位横走侧根最粗,向两端逐渐变细,且远端根始终比近端根要粗;(2)不定芽具有以前期克隆分株为中心向两端延伸发生分布的空间格局特征,横走侧根上不定芽数与出土克隆分株数呈极显著正相关,未出土克隆分株数与出土克隆分株数呈显著正相关,说明不定芽、未出土克隆分株的数量都直接影响出土克隆分株的数量。(3)不定芽、未出土克隆分株和出土克隆分株出现频率、空间分布范围在同一生境同一根段均表现为不定芽未出土克隆分株出土克隆分株,在不同研究区表现为16团(地下水位1.08m)轮台县(地下水位2.56m)阿瓦提县(地下水位3.34m);相关分析显示土壤水分含量与不定芽和出土克隆分株数量均呈极显著正相关。综合分析认为,地下水位和土壤含水量均对不定芽发生以及不定芽向克隆分株转化有显著的影响。     

Neurotensin metabolism in the rat: Contribution of the kidney

The kidney plays a key role in the metabolism of neurotensin (NT). We have examined the renal mechanisms of NT clearance by measuring plasma NT basally and after 45 min infusion of NT(1–13) in intact rats, anephric rats (no glomerular filtration, no peritubular metabolism) and ureteral ligated rats (reduced filtration). Plasma NT was measured by radioimmunoassay with both C (biologically active end) and N terminal directed antisera. In anephric and ureteral ligated rats, basal plasma NT like immunoreactivity measured with either antisera was increased 3-fold compared with unoperated rats. C terminal concentrations were higher than N indicating that a C terminal variant of NT was present in basal plasma. Infusion of NT(1–13) increased N terminal NT from 36±3 to 249±35 pmol/l (p<0.01) in unoperated rats with significantly larger increases in the renally compromised groups. This was reflected in the reduced metabolic clearance rates (measured with the N terminal directed antisera) in the anephric (16±1 ml/kg/min) and ureteral ligated (17±3 ml/kg/min) rats when compared with the control rats (26±4 ml/kg/min). The similar reductions in the anephric and ureteral ligated rats suggested that the decrease in N terminal NT metabolism was from the absence of filtration. Infusion of NT did not increase C terminal NT immunoreactivity in intact, anephric and ureteral ligated rats showing that the C terminal end was extremely labile. However when endogenous converting enzyme activity was blocked by captopril administration there was a significant increase in C terminal immunoreactivity suggesting a role for converting enzyme like proteases in the clearance of the biologically active end of NT. The results indicate that glomerular filtration is important for the clearance of N terminal NT while the C terminal part can be rapidly cleared by non-renal mechanisms. The higher concentration of C than N terminal immunoreactivity in basal plasma of intact rats and the further increase when renal function is reduced suggests that a NT variant sharing the C terminal end may be of physiological significance.     

Effect of Auxin and Cytokinin on Newly Synthesized Proteins of Cultured Douglas Fir Cytoledons

Newly synthetized cyloplasmic proteins of Douglas fir cotyledon culture capable of initiating adventitious bud formation (bud culture) were compared with those of morphologically distinct types of cultures, bud-callus culture (some adventitious buds with callus), and callus culture (no adventitious buds; only callus). SDS polyacrylamide gel electrophoretic profiles of double labeled (¹⁴C-and ³H-) proteins showed that a persistent increase of low molecular weight proteins (16,000 to 20,000 daltons) was associated with bud culture. Similar electrophoretic profiles of proteins extracted in the absence and in the presence of protease inhibitor (4-mcthylbenzene sulfonyl fluoride) or phenolic compounds absorbents (Dowex I-X8 and polyvinylpolypyrolidine) were obtained indicating that the detected low molecular weights of these proteins represented the real monomeric state of these molecules.