Phenological features in relation to growth forms and biomass accumulation in an alpine meadow of the Central Himalaya

Phenological records of 50 plant species were made during 1988–89 in an alpine meadow (30° 10-30° 13 N lat. and 79° 39-79°-41 E long.) of Central Himalaya located between 3100–3750 m elevation. The growth initiation occurred when temperature began to rise continuously and the resulting in snowmelt. The peaks of the various phenophases succeeded one after another in time, within a period of about four months (from May to September) which is longer than the period reported for the alpine sites of higher latitudes. The period of growth initiation appeared to be related to growth form, the species showing earlier growth initiation (when temperatures were lower) deployed leaves to lower heights, close to the ground. A majority of forbs completed growth cycle earlier than the grasses. For example, one group represented by Trachydium roylei reached peak growth a few weeks before did another group of species, represented by Danthonia cachemyriana, which is indicative of niche separation of the respective group of species. Activities of accumulation of live and dead shoot biomass were clearly separated in time in most communities, the former occurring from May to August, and the latter mainly in September. Nomenclature: Osmaston (1926).     

Diffusion of lactose in kappa-carrageenan/locust bean gum gel beads with or without entrapped growing lactic acid bacteria

Effective diffusion coefficients (De) of lactose in kappa-carrageenan (2.75% wt/wt)/locust bean gum (0.25% wt/wt) (LBG) gel beads (1.5-2.0-mm diameter)with or without entrapped lactic acid bacteria (LAB) were determined at 40 degrees C. The effects of lactose concentration, bacteria strain (Streptococcus salivarius subsp. thermophilus and Lactobacillus casei subsp. casei) and cell content at various steps of the fermentation process (after immobilization, pre-incubation of the beads and successive fermentations) were measured on De as a first step for process modelling. Results were obtained from transiend concentration changes n well-stirred lactose solutions in which the beads were suspended. A mathematical model of unsteady-state diffusion in a sphere was used, and De was obtained from the best fit of the experimental data. Diffusivity of lactose in cell-tree beads was significantly lower than in pure water mainly because of the obstruction effect of the polymer chains and the hydration region. Furthermore, effective diffusivity and equilibrium partition factor were independent of lactose concentration in the range from 12.5 to 50 g/L. No significant difference was found for De (effective diffusivity) and Kp (partition) coefficients between beads entrapping S. thermophilus (approximately 5 x 10(9) CFU/mL) and cell-free beads. On the other hand higher cell counts obtained with L. casei (close to 1.8 x 10(11) CFU/mL) increased mass transfer resistance resulting in lower effective diffusivities and Kp. Finally, the effects of the type of bacteria and their distribution in the beads on the diffusivity were also discussed.     

New insights on plant phenological response to temperature revealed from long‐term widespread observations in China

Constraints of temperature on spring plant phenology are closely related to plant growth, vegetation dynamics, and ecosystem carbon cycle. However, the effects of temperature on leaf onset, especially for winter chilling, are still not well understood. Using long‐term, widespread in situ phenology observations collected over China for multiple plant species, this study analyzes the quantitative response of leaf onset to temperature, and compares empirical findings with existing theories and modeling approaches, as implemented in 18 phenology algorithms. Results show that the growing degree days (GDD) required for leaf onset vary distinctly among plant species and geographical locations as well as at organizational levels (species and community), pointing to diverse adaptation strategies. Chilling durations (CHD) needed for releasing bud dormancy decline monotonously from cold to warm areas with very limited interspecies variations. Results also reveal that winter chilling is a crucial component of phenology models, and its effect is better captured with an index that accounts for the inhomogeneous effectiveness of low temperature to chilling rate than with the conventional CHD index. The impact of spring warming on leaf onset is nonlinear, better represented by a logistical function of temperature than by the linear function currently implemented in biosphere models. The optimized base temperatures for thermal accumulation and the optimal chilling temperatures are species‐dependent and average at 6.9 and 0.2°C, respectively. Overall, plants’ chilling requirement is not a constant, and more chilling generally results in less requirement of thermal accumulation for leaf onset. Our results clearly demonstrate multiple deficiencies of the parameters (e.g., base temperature) and algorithms (e.g., method for calculating GDD) in conventional phenology models to represent leaf onset. Therefore, this study not only advances our mechanistic and quantitative understanding of temperature controls on leaf onset but also provides critical information for improving existing phenology models.     

富士苹果萌芽至新梢旺长期肥料氮去向和土壤氮库盈亏

运用¹⁵N同位素示踪技术,以5年生‘烟富3’/SH6/平邑甜茶苹果为试材,研究了萌芽至新梢旺长期不同施氮水平(0、50、100、150、200、250 kg·hm^-2)下肥料氮的吸收利用、土壤残留和土壤氮库盈亏特点.结果表明:早春施氮后,15N均优先分配到根系中,然后转运用于地上部新生器官(果实、新生枝叶)的形态建造.新梢旺长期结束后(施氮2个月后),5.9%~9.9%的肥料氮被树体吸收,29.8%~33.4%的肥料氮残留在0~60 cm土体中,56.7%~64.4%的肥料氮通过其他途径损失.随施氮水平的提高,树体吸收的肥料氮量和土壤残留氮量逐渐增加,但肥料氮利用率和土壤残留率却不断降低,同时损失量和损失率不断增加.随施氮水平的提高,土壤氮素总平衡由亏缺转为盈余,且盈余量随施氮水平的提高而显著提高.表明施氮不足将会造成土壤氮肥力的下降;而过量施氮则会加剧土壤氮素累积,增加氮素污染风险.施氮水平与土壤氮素总平衡呈显著线性相关关系,拟合方程为:y=0.3511x-20.808(R^2=0.9927),当施氮量为59.27 kg·hm^-2时,由萌芽至新梢旺长期的土壤氮库达到平衡.     

Pelleting and extrusion can ameliorate negative effects of toasting of rapeseed meal on protein digestibility in growing pigs

Toasting time (TT) of rapeseed meal (RSM), the diet processing (DP) method and the interaction between both on the apparent CP digestion along the gastrointestinal tract and the apparent ileal digestibility (AID) of amino acids of growing pigs were investigated. The experiment consisted of a 3×3 factorial design of TT of RSM (0, 60 and 120 min) and DP method (mash, pelleting and extrusion). In total, 81 boars with a starting BW of 20 kg were euthanized 4 h after their last feeding. The gastrointestinal tract was dissected and the small intestine divided in three sections of similar length. Samples were collected from the stomach, 1.5 m from the ends of each of the three sections of the small intestine, and the rectum. The apparent digestibility (AD) of CP for each of the small intestine sections was used to calculate the rate of CP digestion. Increasing the TT of RSM resulted in lower protein solubility, lower lysine/reactive lysine contents and higher protein denaturation, indicative of the occurrence of protein aggregation and Maillard reactions. There were significant effects (P⩽0.01) of TT on the AD of CP in the different sections of the gastrointestinal tract. The rate of CP digestion of the 0 min toasted RSM diets was 23% and 35% higher than that of the 60 and 120 min toasted RSM diets, respectively. There was a significant interaction (P=0.04) between TT and DP for the AID of CP. Although pelleting of the 0 and 60 min toasted RSM diets did not change the AID of CP with respect to the mash diets, pelleting of the 120 min toasted RSM diet increased the AID of CP by 9.3% units. Extrusion increased the AID of CP of the 0 and 60 min toasted RSM diets by 3.4% and 4.3% units with respect to the mash diets, whereas extrusion of the 120 min toasted RSM diet increased the AID of CP by 6.9% units. Similar positive effects of pelleting and extrusion were obtained for the AID of lysine and reactive lysine, especially in the diets with higher TT. In conclusion, processing (pelleting and extrusion) of RSM containing diets can ameliorate the negative effects of RSM toasting on protein and amino acid digestibility; these effects were larger for the RSM toasted for longer times.     

利用固定化细胞连续发酵生产酸牛奶

本文报道了利用固定化技术连续发酵生产酸牛奶的方法。对单菌种与双菌种固定化、最适发酵温度和pH、发酵时间、固定化方式等进行了研究,得出了在实验室条件下,连续发酵生产酸牛奶的最佳技术条件。与传统的间歇生产工艺相比,可简化菌种制备过程,反复利用乳酸菌种,充分利用发酵酸化设备、便于自动化控制等优点。作者尚未见国内外利用固定化技术连续生产酸牛奶的报道。     

腹主动脉瘤生长过程的蠕变力学模型

基于增强对腹主动脉瘤生长过程的理解、为腹主动脉瘤临床手术提供参考的目的,本文根据腹主动脉瘤的生长物理机制,提出了以蠕变力学为基础模拟腹主动脉瘤生长过程的模型.建立了腹主动脉瘤简化模型,利用有限元方法进行模拟计算.结果显示蠕变模型能够有效模拟腹主动脉瘤生长过程中的形态变化.参数优化模型模拟结果符合临床统计数据所示的腹主动脉瘤生长过程.本文还讨论了腹主动脉材料力学参数对模型的影响.     

Standardized ileal digestibility of amino acids in eight genotypes of barley fed to growing pigs

To determine chemical composition, physical characteristics and standardized ileal digestibility (SID) of CP and amino acids (AA) in eight current hulled barley genotypes, an experiment with growing pigs has been conducted. These genotypes included Yool, Campanile, Lomerit, Travira, Anisette, Canberra, Metaxa and Fridericus. Growing barrows with an average initial BW of 30±2 kg were surgically fitted with simple T-cannulas at the distal ileum, and allotted to an 8×9 Youden square design with eight periods of 6 days each and nine pigs. Barley was the sole dietary source of CP and AA. On average, the eight genotypes contained on as-fed basis 10.7% CP, 15.2% total non-starch polysaccharides (NSP), 17.1% NDF and 4.1% β-glucan, and had a mean test weight (TW) of 72.2 kg/hl. The SID of CP in the barley genotypes varied from 69% to 74%, and was greater (P<0.01) for genotypes Travira, Anisette and Metaxa compared to Yool and Campanile. Standardized ileal digestibility of Lys, Met and Trp (P<0.05) but not of Thr differed between genotypes. Moreover, barley genotypes differed in their standardized ileal digestible content (cSID) of CP and AA. Furthermore, SID and cSID of CP and most AA linearly decreased (P<0.05) with increasing NDF and total sugar content. Standardized ileal digestibility of CP and some AA and cSID of CP and most AA decreased linearly with increasing TW (P<0.05). Additionally, SID and cSID of CP and AA of most barley genotypes were lower when compared to tabulated values. In conclusion, a comprehensive database on chemical composition and SID of CP and AA in eight current barley genotypes has been made available. However, as present SID values are lower compared to feed tables, adjustments are required to minimize the risk of overestimating the actual protein value of barley for pigs.