NH4 : NO3 nutrition influence on biomass productivity and root respiration of poplar and willow clones

Nitrogen fertilization often improves the yield of intensively managed, short‐rotation coppices. However, information of N nutrition form on the growth of common species and clones used for biomass production is limited. Thus, this study aims at evaluating N form effects on the growth of two Salicaceae clones. Cuttings of the poplar clone Max 4 (Populus maximovizcii × P. nigra) and the willow clone Inger (Salix triandra × S. viminialis) were fertilized in a pot experiment with four ratios of nitrate (NO₃^?) to ammonium (50%, 62.5%, 75% and 87.5% NO₃^? balanced with ammonium (NH₄⁺) to constant total N) for one growing season and under stable soil pH. Plants were harvested for analysis of biomass and morphology of leaves, stem and roots. Respiration of fine and coarse roots (RR) was determined and related to biomass growth. Salix cv. Inger accumulated more total dry matter than Populus cv. Max 4. In both Salicaceae clones, the total biomass was significantly influenced by the nitrate ratio and greatest in plants fertilized with 50% NO₃^? of the total N supply. Both clones possess a different leaf and root morphology, but no significant influence of the NO₃^? ratio on the morphology was found. Fine RR rates differed significantly between clones, with significantly greater fine RR in Max 4; 87.5% NO₃^? fertilization increased the fine RR. Fine RR and total accumulated plant biomass were closely related. Our study is the first to show the tremendous influence of fine root respiration, especially including the carbon‐intensive reduction of NO₃^? to NH₄⁺, on the aboveground growth of Salicaceae clones. Ways to improve yield in SRC are thus to lower the assimilate consumption by fine roots and to match fertilization regimes to the used clones or vice versa.     

Do holly leaf spines really deter herbivory?

Summary Although spinose teeth of holly leaves have been widely cited as an example of a physical defense against herbivores, this assumption is based largely on circumstantial evidence and on general misinterpretation of a single, earlier experiment. We studied the response of third and fifth instar larvae of the fall webworm, Hyphantria cunea Drury, a generalist, edge-feeding caterpillar, to intact American holly leaves and to leaves that had been modified by blunting the spines, by removing sections of leaf margin between the spines, or by removing the entire leaf margin. The results suggest that the thick glabrous cuticle and tough leaf margin of Ilex opaca are more important than the spinose teeth in deterring edge-feeding caterpillars. Microscopic examination of mature leaves revealed that the epidermis is thickened at the leaf margin, and that the leaf is cirucumscribed by a pair of fibrous veins. In simple choice tests neither domesticated rabbits nor captive whitetailed deer discriminated between spinescent holly foliage and foliage from which spines were removed. Nevertheless, we found little evidence of herbivory by mammals in the field, either on small experimental trees or in the forest understory. While it is possible that spinose teeth contribute to defense by reducing acceptibility of holly relative to other palatable plant species, we suggest that the high concentrations of saponins and poor nutritional quality of holly foliage may be more important than spines in deterring vertebrate herbivores. The degree of leaf spinescence and herbivory was compared at different heights with the tree canopy to test the prediction that lower leaves should be more spinescent as a deterrent to browsers. Leaves on lower branches of mature forest trees were slightly more spinescent than were upper leaves, and juvenile trees were slightly more spinescent than were mature trees. However, there was no relationship between degree of spinescence and feeding damage. The greater spinescence of holly leaves low in the canopy is probably an ontogenetic phenomenon rather than a facultative defense against browsers.The investigation reported in this paper (No. 87-7-8-77) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Dirctor     

Accommodation of powdery mildew fungi in intact plant cells

Parasitic powdery mildew fungi have to overcome basic resistance and manipulate host cells to establish a haustorium as a functional feeding organ in a host epidermal cell. Currently, it is of central interest how plant factors negatively regulate basal defense or whether they even support fungal development in compatible interactions. Additionally, creation of a metabolic sink in infected cells may involve host activity. Here, we review the current progress in understanding potential fungal targets for host reprogramming and nutrient acquisition.     

棉花根际亲和性高效促生细菌的分离筛选

为了从棉花根际土壤筛选能与棉花凝集素具有亲和作用的高效促生细菌,以选择性培养基从棉花根部初步筛选具有固氮能力、解磷能力及解钾能力的促生细菌,再以异硫氰酸磺(FITC)标记的棉花凝集素为复筛工具,从棉花根际促生细菌中筛选能与棉花凝集素结合的亲和性菌株,分别挑选2株固氮菌、2株解磷细菌和2株解钾细菌作为微生物肥料接种到棉花根部进行盆栽试验.观察其在根部定殖情况.结果是在选择性平板上有20%～30%的菌株具有凝集素染色阳性.盆栽试验显示,接种的6株亲和性菌株能在棉花根部成功定殖,根际细菌数量约是灭活对照的`0倍.通过初步鉴定,固氮菌株N1111为固氮菌属(Azotobacter),N2121属于德克斯氏菌属(Derxia);解磷菌株P2126属于黄单胞菌属(Xanthomonas),P1108菌株为假单胞菌属(Pseudomonas);解钾菌株K2204和K2116属于芽孢杆菌属(Bacillus).     

The justification for providing dietary guidance for the nutritional intake of boron

Because a biochemical function has not been defined for boron (B), its nutritional essentiality has not been firmly established. Nonetheless, dietary guidance should be formulated for B, because it has demonstrated beneficial, if not essential, effects in both animals and humans. Intakes of B commonly found with diets abundant in fruits, vegetables, legumes, pulses, and nuts have effects construed to be beneficial in macromineral, energy, nitrogen, and reactive oxygen metabolism, in addition to enhancing the response to estrogen therapy and improving psychomotor skills and cognitive processes of attention and memory. Perhaps the best-documented beneficial effect of B is on calcium (Ca) metabolism or utilization, and thus, bone calcification and maintenance. The paradigm emerging for the provision of dietary guidance that includes consideration of the total health effects of a nutrient, not just the prevention of a deficiency disease, has resulted in dietary guidance for chromium (Cr) and fluoride; both of these elements have beneficial effects in humans, but neither has a defined biochemical function. Knowledge of B nutritional effects in humans equals or is superior to that of Cr and fluoride; thus, establishing a dietary reference intake for B is justified. An analysis of both human and animal data suggests that an acceptable safe range of population mean intakes of B for adults could well be 1–13 mg/d. Recent findings indicate that a significant number of people do not consistently consume more than 1 mg B/d; this suggests that B could be a practical nutritional or clinical concern.     

微管的冷稳定性与植物抗寒性关系的研究

利用间接免疫荧光的细胞化学技术对番茄、黄瓜、菠菜、甜菜及小麦等不同抗寒性植物微管的冷稳性进行了比较研究。结果指出,不抗寒的喜温性植物番茄和黄瓜的气孔保卫细胞的微管在0℃—1℃冷处理3小时即解聚;属于中等抗寒性植物的菠菜和甜菜幼苗经秋季低温锻炼后,其气孔保卫细胞的微管在0℃和—5℃低温处理3小时,均不发生解聚;具有较强抗寒性的冬小麦品种农大139幼苗在2—3℃低温锻炼期间,微管结构保持完整,经过15天低温锻炼的幼苗在-8℃冰冻处理3小时,微管也不受破坏。这些结果表明,微管的冷稳性与植物的抗寒性成正相关。     

Regeneration of plants from alginate-encapsulated shoot tips of Withania somnifera (L.) Dunal, a medicinally important plant species

A protocol was developed for plant regeneration from encapsulated shoot tips collected from in vitro proliferated shoots of Withania somnifera. The best gel composition was achieved using 3% sodium alginate and 75 mM CaCl2.2H2O. The maximum percentage response (87%) for conversion of encapsulated shoot tips into plantlets was achieved on MS medium supplemented with 0.5 mg/l IBA after 5 weeks of culture. The conversion of encapsulated shoot tips into plantlets also occurred when calcium alginate beads having entrapped propagules were directly sown in autoclaved soilrite moistened with 14-MS salts.     

松材线虫入侵后不同伐倒干扰强度对马尾松林植物多样性的影响

以松材线虫入侵马尾松林后经过不同伐倒干扰强度经营形成的不同群落类型作为研究对象,对9个群落类型的物种多样性进行了研究.结果表明,乔木层物种多样性指数大小排列顺序为: 马尾松纯林受害皆伐后形成的阔叶林(富阳)＞轻度受害的马尾松 木荷混交林(富阳)＞对照＞轻度受害的马尾松 纯林(富阳)＞马尾松 栓皮栎混交林受害择伐后形成的栓皮栎林(舟山)＞马尾松纯林受害皆伐后形成的马尾松幼龄林(富阳)＞马尾松纯林受害择伐后形成的枫香林(舟山)＞受害的黑松 马尾松混交林(舟山)＞受害的马尾松纯林(舟山).灌木层舟山马尾松纯林的3种多样性指数均最低,其余各地相差不大.草本层马尾松幼树纯林、栓皮栎林和枫香林的3个指数较高.不同地理位置和不同受害程度的马尾松林植物多样性差异显著;不同干扰程度、不同恢复方式下马尾松林内的植物多样性差异也显著.建立了伐倒干扰强度指数,发现物种多样性指数随伐倒干扰强度指数的变化规律符合“中间高度膨胀”理论.协方差分析结果表明,所建的指数能有效地反映松材线虫入侵及病木伐除后马尾松林植物多样性的变化.     

Cell wall proteomics of sugarcane cell suspension cultures

The use of cell walls to produce cellulosic ethanol from sugarcane bagasse is a new challenge. A better knowledge of proteins involved in cell wall remodelling is essential to improve the saccharification processes. Cell suspension cultures were used for this first cell wall proteomics study of sugarcane. Proteins extracted from cell walls were identified using an adapted protocol. They were extracted using 0.2 M CaCl₂ and 2 M LiCl after purification of cell walls. The proteins were then identified by the innovative nanoACQUITY UPLC MS/MS technology and bioinformatics using the translated SUCEST EST cluster database of sugarcane. The experiments were reproduced three times. Since Sorghum bicolor is the closest plant with a fully sequenced genome, homologous proteins were searched for to complete the annotation of proteins, that is, prediction of subcellular localization and functional domains. Altogether, 69 different proteins predicted to be secreted were identified among 377 proteins. The reproducibility of the experiments is discussed. These proteins were distributed into eight functional classes. Oxidoreductases such as peroxidases were well represented, whereas glycoside hydrolases were scarce. This work provides information about the proteins that could be manipulated through genetic transformation, to increase second‐generation ethanol production.