黄土区灌木柠条锦鸡儿根-土间摩擦力学机制试验研究

为系统研究灌木植物根系的拉拔摩擦力学机制,该项研究在西宁盆地黄土区的自建试验区内选取生长期为2 a的柠条锦鸡儿作为供试种进行根系拉拔摩擦试验。试验结果表明:柠条锦鸡儿主根的作用主要为提供根-土间静摩擦力,侧根的作用则主要表现为增大根-土间最大静摩擦力、根-土间最大摩擦力及根-土间最大摩擦力对应的根系位移;柠条锦鸡儿根-土间最大摩擦力随着根系总表面积、根系总体积、根系总长、根系总干质量、侧根数5个根系形态学指标的增加而增大,根-土间最大摩擦力与5个根系形态学指标之间可建立幂函数关系,且通过相关性分析可知,根系总表面积是与柠条锦鸡儿根-土间最大摩擦力相关程度相对较为显著的根系形态学指标;在本试验条件下(土体质量含水率15.1%,密度1.65g/cm3)由单根(不含侧根的主根)拉拔摩擦试验所得到的柠条锦鸡儿主根与土体间静摩擦系数为0.738 9±0.04,该值显著大于区内不含根系土体内摩擦系数0.504 0±0.03,表明柠条锦鸡儿根-土界面间的摩擦力值及抵抗变形的能力大于不含根系土体。该项研究结果对于进一步探讨研究区灌木根系的拉拔摩擦力学机制,以及科学有效地防治坡面水土流失、浅层滑坡等地质灾害具有指导意义和实际应用价值。     

种基盘苗与营养钵苗根系生长和形态的差异

为了探明苗木培育方式与根系发育的关系,以侧柏、刺槐、白榆的幼苗为对象,研究种基盘苗与营养钵苗对幼苗根系形态的影响。结果表明：由于空气断根效应,种基盘苗抑制了侧柏和白榆主根的生长,促进了刺槐主根的生长,但种基盘能有效促进3个树种的主根沿着重力方向生长,使主根发达而且通直,侧根粗壮且分布比较均匀,营养钵苗的根系主根不明显,根系盘绕现象严重;侧柏和白榆2树种种基盘苗的一级侧根条数分别比其营养钵苗增加181.8%和128.6%,并能显著增加白榆种基盘苗的一级侧根直径;侧柏、刺槐和白榆种基盘苗的一级侧根均匀分布在1-2、2-3、3-4和4-5 cm 4个区间,而营养钵苗则集中分布在1-2和2-3 cm 2个区间;种基盘可以促进苗木一级侧根条数增加和均匀分布,对提高苗木吸收水肥能力和保土固土能力有着积极的作用。     

青藏高原东北部4种灌木主根和侧根抗拉力学特性比较

[目的]开展青藏高原东北部黄土区4种灌木植物主根和侧根抗拉力学强度试验,探讨主根和侧根抗拉力学特性关系,为深入研究植物根系固土护坡力学机理提供参考。[方法]选取西宁盆地长岭沟流域作为研究区,对生长期为3 a的柠条锦鸡儿(Caragana korshinskii)、中宁枸杞(Lycium chinense)、白刺(Nitraria tangutorum)和霸王(Sarcozygium xanthoxylon)4种优势灌木主根和侧根进行室内单根拉伸试验,确定其主根和侧根抗拉力、抗拉强度和杨氏模量及其与根径之间的关系;在此基础上,进一步分析了4种灌木主根和侧根根径、抗拉力、抗拉强度和杨氏模量之间的关系。[结果]柠条锦鸡儿、中宁枸杞、白刺和霸王主根抗拉力分别为侧根的28.45,13.21,11.01,7.35倍,主根抗拉强度分别为侧根的0.67,1.17,0.68,1.22倍,主根杨氏模量分别为侧根的2.00,2.39,2.82,2.48倍。[结论] 4种灌木植物主根抗拉力均显著大于侧根;柠条锦鸡儿和白刺主根抗拉强度小于侧根,而中宁枸杞和霸王主根抗拉强度大于侧根;4种灌木植物主根杨氏模量显著大于侧根,说明其主根相对于侧根不易发生形变,对边坡浅层稳定性贡献亦显著于侧根。     

红花岩黄蓍

<正> 红花岩黄蓍(Hedysarum multijugum),又名豆花牛脖筋,俗名羊柴。豆科岩黄蓍属多年生半灌木。主要分布于甘肃、陕西、内蒙、宁夏等地。 形态特征及生物学特性 红花岩黄蓍主根粗壮深长,入土深度可达3～5m,根上有丰富的根瘤,根皮棕红色,侧根发达多与地面平行生长,主根基部密生根状茎。茎直立,株高50～80cm,茎白色具柔毛。奇数羽状复叶,具     

丛枝菌根真菌与根瘤菌接种对大豆根瘤分布及磷素吸收的影响

在温室条件下,采用石英砂盆栽试验研究了大豆(冀豆6号)接种丛枝菌根真菌（Glomous mosseae）与根瘤菌 （Bradyrhizobium japonicum）对根瘤的形成、分布以及磷素吸收效率的影响。结果表明,大豆生长至开花期（接种后56 d）,与单接种根瘤菌处理相比,双接种AM真菌和根瘤菌显著增加大豆生物量、氮、磷含量、根系上的总根瘤数。单接种根瘤菌条件下,总根瘤数的48.4%分布在主根上,51.6%分布在侧根上;根瘤菌与AM真菌双接种时,总根瘤数的32.5%分布在主根上,67.5%分布在侧根上。双接种处理的侧根根瘤的固氮酶活性显著高于单接种处理的。双接种条件下大豆侧根中AMF侵染增强,尤其是结根瘤侧根上的AM真菌的侵染率高于未结瘤的侧根的菌根侵染率。接种后28 d单接种菌根真菌处理显著高于双接种处理的植株磷的吸收效率;而56 d 时趋势相反。以上结果表明,AM真菌侵染改变根瘤在大豆根系上的分布,根瘤数量、分布与结根瘤侧根上AM真菌的侵染强度存在正相关关系。     

不同处理方法对芒果实生苗生长效果的试验初报

为了研究不同的育苗方法对芒果实生苗生长效果的影响,为规模快速繁育优质芒果苗木提供参考依据,采用剥壳催芽法、剥壳法和直播法3种方法对广西百色市土芒种子进行育苗对比试验,测定和比较苗木的出苗率、株高、地径和根系。结果表明,剥壳催芽法的出苗率、平均株高、平均地径、正常根率、侧根数量、主根和侧根长度等各项指标均最优,直播法的出苗率、平均株高、平均地径、正常根率、侧根数量、主根和侧根长度等各项指标均最差,剥壳苗法的出苗率、平均株高、平均地径和根系等指标介于两者之间。说明剥壳催芽法的苗木质量明显高于剥壳法和直播法,有利于芒果苗木的出苗、地径生长和根系生长。     

运用ET-100根系生态监测系统进行紫花苜蓿根系特征研究

运用引进设备ET-100根系生态监测系统,对两种紫花苜蓿(15°缓坡1年生、35°陡坡5年生)根系进行定时观测,分析不同条件下紫花苜蓿的根系生长状况。结果表明:缓坡当年生紫花苜蓿侧根发生的主要部位在距地面12—36 cm之间,0—12 cm之间仅有少量侧根发生,43 cm以下几乎没有侧根发生,根系生物量、主根直径整体上表现为从土壤表层到深层逐渐递减;当年生紫花苜蓿根系监测前期(9月15日—10月15日)在距地面18—33 cm之间生长最快,后期(10月16日—11月15日)在距地面43—53 cm之间生长最快,根系总长度增加量前期较后期大,但根系表面积、体积增加量则是后期比前期大;陡坡5年生紫花苜蓿根系发达、形状分散、分布均匀,在距地面30—70 cm之间生长相对较快,根系平均直径前期为4.3 cm,后期为5.4 cm。     

氮肥施用量对高产甜菜纤维根系分布及活力的影响

为了解施N肥对甜菜生长的影响规律。在田间条件下,研究了不同施N量（0、90、180、270、360 kg/hm2）对甜菜（KWS2409）纤维根系生长、分布和活力变化的影响。结果表明,施N比对照增加浅层侧根数、外层和深层纤维根干重及100 cm土层纤维根总干重,并提高各生育期侧根和主根活力。其中,100 cm土层最大纤维根干重施N 比对照增加了60.4%～168.4%,最大侧根数增加了22.7%～75.1%,且以0—20 cm和40—60 cm深的外土层及80—100 cm深的内土层纤维根系增加较大,分别比对照增加了129.6%～266.8%、71.0%～234.0%和101.5%～202.8%。主根伤流液量和侧根的活力分别比对照增加了56.2%～89.9%、23.7%～63.4%。N 180 kg/hm2处理0—100 cm土层中纤维根总量、各土层中根量最大,各生育时期主根和侧根活力最强,块根产量（82609.63 kg/hm2）和产糖量（13892.64 kg/hm2）均最高,而含糖率（16.83%）较N0处理（18.34%）略降。说明合理施N量有利于甜菜纤维根系生长和提高产糖量。     

不同耕作方式棉花根系发育能力的研究

研究了不同耕作方式棉花根系的发育能力。结果表明,根系生物量、根系体积、侧根数在不同耕作方式间差异明显,在土壤中表现为从表层到深层逐渐递减。免耕方式根系分布较浅,主要集中在0~10 cm土层,而翻耕方式根系主要分布在10~20 cm土层。侧根的发生部位受不同深度土壤含水量的影响,侧根发生的主要部位在0~20 cm的主根段,40 cm以下没有侧根发生。     

丁香酸对不同品种烟草苗期根系生长的影响

为探究最新发现的植物源生物硝化抑制剂丁香酸对烟草品种K326和云烟85苗期根系生长的影响,通过基质培养试验,设置0、10、25、50、100、200 μmol/L 6个丁香酸浓度,研究了不同浓度丁香酸在不同时间(3 d和5 d)对K326和云烟85主根伸长量和一级侧根发育的影响。结果表明:与对照(0 μmol/L)相比,25～100 μmol/L丁香酸能促进K326主根伸长,在3 d时促进率为13.33%～30.67%,在5 d时促进率降为8.54%～22.55%,最适浓度为50 μmol/L;10～50 μmol/L丁香酸促进云烟85主根伸长,在3 d时促进率为7.81%～18.75%,在5 d时促进率维持在4.10%～10.66%,最佳促进浓度25 μmol/L;丁香酸对两个烟草品种主根伸长的促进效果均为3 d优于5 d。在侧根发育方面,低浓度丁香酸能显著促进K326和云烟85一级侧根数,两个品种促进侧根发育的最适浓度均为25 μmol/L。相关性分析表明,丁香酸处理下两个烟草品种苗期的主根伸长变化率与侧根数变化率呈显著正相关。可见,适宜浓度的丁香酸对两个典型烟草品种苗期主根增长和...     

Agricultural potential of Mediterranean grain and forage legumes: Key differences between and within Vicia species in terms of phenology, yield, and agronomy give insight into plant adaptation to semi-arid environments

In order to identify key adaptive traits which affect productivity in Mediterranean grain and forage legumes and simultaneously determine the agricultural potential of a wide range of Vicia species, germplasm collected from the wild throughout the eastern Mediterranean was grown under semi-arid conditions in Tel Hadya, Syria (313 mm growing season rainfall). These included species currently in use in Mediterranean agriculture, such as V. sativa L., as well as those more widely used in the past-such as V. ervilia L., but also a broad selection from Section Narbonensis (B. Fedtsch. ex Radzhi) Maxted, including V. narbonensis L, V. johannis Tamamsch., V. hyaeniscyamus Mout., V. serratifolia Jacq., and V. kalakhensis Khattab et al. V. faba, a near relative of the taxa in Section Narbonensis, was included as a domesticated control. Where applicable, a representative range of subspecies was used. Accessions were chosen from a wide range of habitats in terms of latitude (31.02–40.72 decimal^o), longitude (27.1–43.17 decimal^o), altitude (20–1510 m), rainfall (180–1700 mm/yr) and soil depth (5–50 cm) in order to maximise diversity within species. Agricultural potential was determined by measuring seed, hay and biological yield, as well as agronomic traits such as harvest index, standing crop height, and seed size. The comparative influence of phenology and key agronomic traits such as plant habit and seed size on productivity varied tremendously between species, depending on their reproductive strategies. In V. sativa and V. ervilia, the smaller seed species which rely on long vegetative phases and growing seasons to accumulate sufficient biomass to set seed, and in which there was comparatively little agronomic variation, phenology had a large impact on yield. In early emerging taxa such as V. ervilia and V. s. subsp. sativa, with built-in long vegetative phases and growing seasons, seed yield was negatively correlated with flower ing (r = –0.86 to –0.88), whereas the opposite was the case for later emerging taxa such as V. s. subsp. nigra (L.) Ehrh. (r = 0.95). Within V. narbonensis and relatives, the larger seeded Vicia species which rely on more conservative reproductive strategies where high seedling vigour associated with large seeds enables the species to enter reproductive phases relatively early, phenology had a much smaller impact on yield than did variation of key traits such as seed weight, plant habit and pod shattering. Among the undomesticated germplasm harvest indices ranged from 0.09–0.31, hay yields from 0.1–3.4 t/ha, seed yield from 0–2.0 t/ha, and dry matter at maturity from 1.6–6.5 t/ha. Sub-specific taxonomy was crucial in determining agronomic potential. V. narbonensis var. aegyptiaca Kornhuber ex Asch. et Schweinf. showed the most potential, combining an upright habit, large seeds (212 mg) and tendency to retain intact pods after maturity, with the highest yield, harvest index and crop height of all the wild Vicia species. V. sativa subsp. sativa, V. ervilia and V. narbonensis var. narbonensis were less productive, but still showed agricultural potential. The smaller seeded V. narbonensis, var. affinis, var. jordanica H. Schäf. and var. salmonea (Mout.) H. Schäf., and their close relatives V. johannis, V. hyaeniscyamus, V. serratifolia and V. kalakhensis have little to offer Mediterranean agriculture on the basis of poor agronomy.     

On the Taxonomy of the Members of ‘Saccharum Complex’

The difficulty and problems encountered in the study of cultivated plants, in general and sugarcane, in particular has been indicated. In order to understand these problems, a brief review on the taxonomy of Saccharum and closely related taxa, namely, Erianthus, Sclerostachya, Narenga and Miscanthus (generally known as ‘Saccharum complex’) has been given. A short account on the important morphological features that are specific to sugarcane has also been stated as classification is commonly based on such morphological characters. A note has been added on the chromosome number, origin, and distribution of the species of ‘Saccharum complex’ members. Taxonomic keys have been devised for identification of the genera of Saccharinae and for the species of Saccharum and Erianthus occurring in India. A new combination, Sclerostachya fallax (Balansa) Amalraj et Balasundaram, has also been proposed.     

Effect of agroforestry woody species on earthworm activity and physicochemical properties of worm casts

The effects of five agroforestry woody species (Dactyladenia barteri, Gliricidia sepium, Leucaena leucocephala, Senna siamea andTreculia africana) on the surface aasting activity ofHyperiodrilus africanus were studied in an Alfisol (Oxic Paleustalf) in southwestern Nigeria. Casting activity under the woody species decreased in the following order:Dactyladenia sp. (26.4 Mg ha^-1 year^-1)>Gliricidia sp. (24.4 Mg ha^-1 year^-1)>Treculia sp. (22.9 Mg ha^-1 year^-1)>Leucaena sp. (18.6 Mg ha^-1 year^-1)>Senna sp. (18.3 Mg ha^-1 year^-1). These differences in casting activity were partly explained by microclimatic effects. Irrespective of the woody species, the worm casts were higher in clay and silt contents, bulk density, water-stable aggregates, pH, organic C, exchangeable cations, effective cation exchange capacity, and extractable P levels than the corresponding surface soils. The woody species did affect the physicochemical properties and P sorption of the worm casts. The content of water-stable aggregates of worm casts decreased in the following order:Dactyladenia sp.>Treculia sp.>Senna sp.>Leucaena sp.>Gliricidia sp. Large differences in extractable P levels were observed.Senna sp. was associated with the highest extractable P level (11.5 mg kg^-1) andTreculia sp. the lowest (4.9 mg kg^-1). P sorption was highest on worm casts underDactyladenia sp. and lowest on those underTreculia sp. Without fertilizer application, there were no significant differences in the dry weight of maize grown in the different worm casts. With NPK applications, the dry weight of maize grown in worm casts associated withTreculia sp. was significantly lower than that of maize grown in the other worm casts, mainly due to the low extractable P level. Despite a high organic C and exchangeable K status, maize grown in the worm casts still responded significantly to N and K applications. The N uptake by maize grown in worm casts associated withTreculia sp. was lower than that in the other treatments.     

Genetic diversity of rhizobia associated with indigenous legumes in different regions of Flanders (Belgium)

We investigated the diversity of rhizobia isolated from different indigenous legumes in Flanders (Belgium). A total of 3810 bacterial strains were analysed originating from 43 plant species. Based on rep-PCR clustering, 16S rRNA gene and recA gene sequence analysis, these isolates belonged to Bradyrhizobium, Ensifer (Sinorhizobium), Mesorhizobium and Rhizobium. Of the genera encountered, Rhizobium was the most abundant (62%) and especially the species Rhizobiumleguminosarum, followed by Ensifer (19%), Bradyrhizobium (14%) and finally Mesorhizobium (5%). For two rep-clusters only low similarity values with other genera were found for both the 16S rRNA and recA genes, suggesting that these may represent a new genus with close relationship to Rhodopseudomonas and Bradyrhizobium. Primers for the symbiotic genes nodC and nifH were optimized and a phylogenetic sequence analysis revealed the presence of different symbiovars including genistearum, glycinearum, loti, meliloti, officinalis, trifolii and viciae. Moreover, three new nodC types were assigned to strains originating from Ononis, Robinia and Wisteria, respectively. Discriminant and MANOVA analysis confirmed the correlation of symbiosis genes with certain bacterial genera and less with the host plant. Multiple symbiovars can be present within the same host plant, suggesting the promiscuity of these plants. Moreover, the ecoregion did not contribute to the separation of the bacterial endosymbionts. Our results reveal a large diversity of rhizobia associated with indigenous legumes in Flanders. Most of the legumes harboured more than one rhizobial endosymbiont in their root nodules indicating the importance of including sufficient isolates per plant in diversity studies.     

Diversity of native rice (Oryza Poaceae:) species of Costa Rica

We found several populations of wild Oryza species in the lowlands of Costa Rica. The plants showed extensive morphological variation, suggesting the presence of several species. In the morphologic study, 33 traits were scored for plants of all the species. A principal component analysis revealed the significant morphological separation of the different species. The analyses indicated that there are three species, O. grandi­glumis, O. latifolia and O. glumaepatula. Two putative hybrid types were found, both significantly differing in their morphology from the known species and intermediate at several traits. O. grandi­glumis is a new record for Costa Rican flora. Its main population is located in Caño Negro Wildlife Refuge, Los Chiles, Alajuela. O. latifolia is distributed throughout the lowlands of the country and the plants of the Atlantic slope are significantly bigger in general habit than those of the Guanacaste area. During this study a population of O. glumaepatula of hundreds of thousands of plants was discovered in the Medio Queso River wetland, Los Chiles, Alajuela. This population is the most important source of genes for cultivar's improvement from the primary gene pool of rice in Costa Rica. The small ligule and the wide flag leaf characteristic of the two CCDD species separated them from the AA diploid O. glumaepatula. Seed size, ligule size, number of branches in the panicle, plant height and sterile lemma length are all bigger in O. grandi­glumis, and influenced the second factor that separated the CCDD species in two discrete clusters. The species found offer great possibilities for the improvement of rice cultivars and they should be thoroughly studied and appropriately protected.     

Powdery Mildew Resistance in a Collection of Chinese Barley Varieties

One hundred and forty-seven Chinese barley varieties maintained at the Gene Bank of the National Barley Improvement Centre, Zhejiang, and 84 progenies from these varieties were tested at the seedling stage for their reaction to 32 selected pathotypes of Blumeria graminis f. sp. hordei. Eighteen resistance spectra were identified comprising single or combined resistances from eight known (Ml(Bw), Ml(Ch), Mla7, Mla8, Mla9, Mla13, MlaRu4 and Mlg) and six unknown resistance genes. The most frequent gene was Ml(Bw), which was found in 69 varieties and previously detected in only a few European winter barley varieties. The genes Mla8 and Ml(Ch) were also often present, but other resistance genes were rare. After inoculation, considerably fewer pathogen colonies were observed in ‘Aiganqi’ and one line of ‘Tong5’. Twenty varieties were composed of lines with different resistance genes. China is likely to be a region of origin of the genes Ml(Bw), Mla7, as well as three unknown genes found in original landraces and perhaps another three unknown genes detected in cultivars bred in China. The resistances of varieties from the Zhejiang province and those originating from 11 other Chinese provinces were quite different. Unfortunately, none of the varieties are promising sources of resistance to powdery mildew and China does not seem to be a region suitable for identifying such sources.     

Polymorphism of high molecular weight glutenin subunits in three species of Aegilops

A collection of 136 accessions of Aegilops umbellulata (39), Ae. comosa (75) and Ae. markgrafii (22) was analysed for high-molecular-weight (HMW) glutenin subunits composition. The homogeneity of the accessions was studied and 55.1% of the collection was homogeneous for HMW glutenin subunits (29 Ae. umbellulata, 33 Ae. comosa and 14 Ae. markgrafii). The HMW glutenin subunits of Ae. umbellulata are encoded by the Glu-U1 locus; in Ae. comosa results showed that this proteins are encoded at the 1M chromosome, and the locus was named Glu-M1. In Ae. markgrafii it was assumed that HMW glutenin subunits were encoded by an homoeologous locus and it was named Glu-C1. All the accessions of Ae. umbellulata and Ae. markgrafii expressed both, x-type and y-type subunits. Among the Ae. comosa accessions, only one expressed an x-type subunit alone. All the accessions of Ae. umbellulata and some of Ae. comosa had x-type glutenins of higher molecular weights than those commonly present in bread wheat. A total of 8 alleles were detected at the Glu-U1 locus, 11 at the Glu-M1 and 4 at the Glu-C1. The new HMW glutenin variation found in this work suggests their possible utilisation in breeding for wheat quality.     

The effects of feeding by Oniscus asellus on leaf litter sulfur constituents

Summary Feeding by the isopod, Oniscus asellus, produced changes in the sulfur constituents of leaf litter substrates (Acer negundo, A. saccharum, Fagus grandifolia, Picea rubens, and Tsuga canadensis). Isopod consumption of leaf litter generally accelerated the mineralization of carbon-bonded S and increased the formation of ester sulfate in all substrates. After the isopod egestion of A. negundo leaves, fecal decomposition over 6 weeks increased total S concentration from 68 to 120 mol S/g due to the catabolism of organic carbon. During the same period sulfate decreased from 34 to 20 mol S/g and carbon-bonded S increased from 34 to 100 mol S/g. Thus the total S pool in aged feces became enriched with organic S (83% of total S). Macroinvertebrate consumption accelerated the transformation of S constituents and the carbon-bonded S concentration approached that of the Oa organic horizon of a northern hardwood forest.Dedicated to the late Prof. Dr. M.S. Ghilarov