黄土高原不同封育年限草地土壤与植物根系的生态化学计量特征

黄土高原特别是干草原地区植被演替的研究比较薄弱。当前植物生态化学计量学的研究主要集中在植物叶片方面,对根系的研究较少。选取宁夏云雾山草原植被不同封育年限的土壤和植物样品,以生态化学计量学原理为基础,测定并分析了土壤与根系的碳(C)、氮(N)、磷(P)及其生态化学计量比与相互关系。结果表明:(1)随着封育年限的增加,土壤容重逐渐减小,土壤有机碳和全氮变异性较大,全磷变异性较小,且封育初期土壤有机碳和全氮含量先降后升,至封育20、30年,保持相对平稳。0~20 cm土层土壤的碳氮比(C∶N)、碳磷比(C∶P)、氮磷比(N∶P)分别为9.04~9.63、19.62~32.27、2.14~3.37,20~40 cm土层土壤的分别为8.68~9.22、15.74~26.32、1.80~3.03。土壤有机碳与全氮、全磷之间存在极显著的正相关。(2)植物根系C、N、P含量变化范围分别为357.6~381.4 g kg-1、7.35~8.18 g kg-1、0.54~0.70 g kg-1;根系中的C元素含量随封育年限的增加逐渐升高,N、P元素含量均小于全球平均值。根系C∶N随着封育年限的增加变异性较大,C∶P、N∶P随着封育年限的增加变异性较小。(3)植物根系的C∶N∶P化学计量特征受土壤的影响调控大于其自身,且土壤磷含量对植物根系C∶N∶P生态化学计量特征影响的显著性(p0.01)大于土壤氮含量(p0.05)。此外,该地区封禁后,草地生产力易受到土壤N含量的限制。     

Is PLOS ONE Attracting Highly Cited Papers in the Food Sciences? Comparing Authors' Most Cited Work to Their PLOS ONE Articles Published 2006–2016

Since 2007, the Open Access journal PLOS ONE has published 194,622 expert-reviewed scientific papers, including 85 related to the human food sciences such as food safety, general food science, and nutrition. Seventy-five of their corresponding authors had previously published. Their most cited articles in other journals were identified and citation counts compared against those earned by their PLOS ONE papers. No PLOS ONE food sciences paper has yet been cited more than an author's best effort in the field in other journals. More than half (38) of the 75 PLOS ONE papers studied remain uncited even by their own authors.     

典型自然带土壤氮磷化学计量空间分异特征及其驱动因素研究

植物生活型、地形及区域气候特征等对土壤养分的空间分布有着重要的影响。通过对我国典型自然带土壤氮磷化学计量与植物生活型、地形及气候因素间相互关系的研究,探讨了我国土壤氮磷的空间变异与分布特征及其主要控制因素。结果发现,5个自然带的土壤全氮(TN)和氮磷比(N/P)存在显著差异(p0.01);除温带荒漠带较低(0.47 mg g~(-1))外,土壤全磷(TP)均值总体变化不明显(p0.05)。在不同自然带区域内,TN、TP及N/P变化与海拔、温度及降水呈现出显著的线性和非线性二次相关,即表现出线性与单峰模式。暖温带落叶阔叶林带、温带草原带、温带荒漠带森林土壤中TN,以及青藏高原高寒植被带草本土壤中TP、温带荒漠带森林土壤的N/P主要受海拔因素的影响,而温带草原带草本植物的土壤TP则主要受降水的影响。同时,研究还发现,在多要素共同作用时,其影响程度也略有差异,温度和海拔作为控制因素影响亚热带常绿阔叶林带森林和温带草原带草本土壤TN变化,但前者受温度控制更为明显,后者则以海拔为主要驱动因素,而温带荒漠带草本土壤和森林土壤的TN主要受海拔和降水作用的影响,但以降水影响为主;亚热带常绿阔叶林带森林土壤TP,温带草原带、温带荒漠带和青藏高原高寒植被带草本土壤的N/P受植物生活型、地形及气候的共同影响,但程度略有不同,其中TP表现为降水温度海拔,而N/P为温度海拔降水。因此,在自然带和植物生活型的主控背景下,海拔、温度和降水的主控或交互作用直接驱动土壤氮磷及其化学计量特征的空间分异。     

Nitrogen effects on cantaloupes

Abstract

The NO₃ levels in cantaloupe (Cucumis melo L.) petioles relate closely to N treatment and reflect the N status of the cantaloupe plant. Suggested levels of petiole NO₃ in cantaloupes grown in Arizona are presented. Nitrogen treatment had little effect on melon size, earliness, or most storage quality factors that were evaluated except that deficiencies resulted in lower netting, poor general appearance and an increase in cull melons.     

利用组织培养技术提取甘草黄酮

本研究筛选了两种能快速诱导甘草疯长型愈伤组织的培养基MS5和MS7,用微波法提取甘草愈伤组织和野生甘草根中总黄酮。测定结果显示：三年生野生型胀果甘草根中总黄酮的含量约为6.02%,培养3~4周的胀果甘草愈伤组织中总黄酮的含量约为1.1%。结果表明：组织培养生产黄酮在生产效率、工厂化生产、避免季节限制、保护野生甘草资源及实际应用中更具优势。本研究可为从甘草中提取总黄酮提供一条可借鉴的途径。     

Prediction of grain protein content in winter wheat through leaf color measurements using a chlorophyll meter

A field trial was conducted over a 3-year period at the Hokkaido Kitami Agricultural Experiment Station to examine whether the grain protein content (GPC) of a winter wheat cultivar (Triticum aestivum L. cv. Chihokukomugi) suitable for Japanese noodle-making could be predicted before harvest. The prediction of the GPC was accurate based on the color of the second leaf (just below the flag leaf) at the end of the emergence of the inflorescence, when nitrogen application was graded. In order to evaluate the reliability of this test, a survey of 95 wheat fields in the eastern part of Hokkaido was also carried out during a 3-year period. The prediction of the GPC for this cultivar based on the color of the second leaf was less accurate across many sites. The results of this survey, however, suggested that the leaf color could be used as an index for ranking the GPC as low or high in relation to processing requirements. When the leaf color value of the second leaf measured with a chlorophyll meter at the end of the emergence of the inflorescence was less than 40, it was predicted that the GPC would be lower than the processing requirement. This index could be applied to the cultivars grown in the eastern part of Hokkaido, except for those grown on peat soils.     

氮磷钾互作效应对甘草黄酮含量影响的初步研究

研究结果表明,宁夏红寺堡扬黄新灌区沙壤灰钙土氮、磷、钾对甘草总黄酮含量影响大小为:施磷(负效应)大于施氮(正效应)大于施钾(负效应);因子互作效应对甘草总黄酮含量影响大小顺序为P×K>N×P>N×K;红寺堡扬黄新灌区沙壤灰钙土人工栽培甘草总黄酮含量≥5.0%以上的农艺措施为:施纯N 119.6~138.8kghm-2、施纯P2O5153.2~178.5 kghm-2、施纯K2O 90.9~105.6 kghm-2。     

Species composition of arbuscular mycorrhizal fungi in two mountain meadows with differing management types and levels of plant biodiversity

Species composition of arbuscular mycorrhizal fungi (AMF) was analysed in two differently managed mountain grasslands in Thuringia (Germany). Arbuscular mycorrhizal fungi were studied in the roots of 18 dominant plant species from a total of 56 (32%). Additionally, spores of AMF were isolated from soil samples. Arbuscular mycorrhizal fungi species composition was analysed based on 96 sequences of the internal transcribed spacer of the nuclear ribosomal DNA, 72 originated from mycorrhizal roots, and 24 originated from AMF spores. Phylogenetic analyses revealed a total of 19 AMF species representing all genera of the Glomeromycota except Scutellospora and Pacispora. Despite a different farming intensity, resulting in remarkable differences concerning their plant species diversity (27 against 43 plant species), the diversity of AMF was found to be similar with 11 species on the intensively farmed meadow and ten species on the extensively farmed one. Nevertheless, species composition between both sites was clearly different. It thus seems likely that the AMF species composition, but not necessarily the species number, is related to above ground plant biodiversity in the system under study.     

Correlation between earthworms and plant litter decomposition in a tropical wet forest of Puerto Rico

Earthworms are recognized to play an important role in the decomposition of organic materials. To test the use of earthworms as an indicator of plant litter decomposition, we examined the abundance and biomass of earthworms in relation to plant litter decomposition in a tropical wet forest of Puerto Rico. We collected earthworms at 0–0.1 m and 0.1–0.25 m soil depths from upland and riparian sites that represent the natural variation in soils and decomposition rates within the forest. Earthworms were hand-sorted and weighed for both fresh and dry biomass. Earthworms were dominated by the exotic endogeic species Pontoscolex corethrurus Müller; they were more abundant, and had higher biomasses in the upland than in riparian sites of the forest. Plant leaf litter decomposed faster in the upland than riparian sites. We found that earthworm abundance in the upper 0.1 m of the soil profile positively correlated with decomposition rate of plant leaf litter. Ground litter removal had no effect on the abundance or biomass of endogeic earthworms. Our data suggest that earthworms can be used to predict decomposition rates of plant litter in the tropical wet forest, and that the decomposition of aboveground plant litter has little influence on the abundance and biomass of endogeic earthworms.     

果糖的利用现状及其与现代流行病的关系研究进展

果糖作为一种大多数水果中普遍存在的成分,长时间被人们所食用。20世纪70年代果糖生产技术瓶颈获得突破,被商品化应用于饮料、焙烤食品、蜜饯类等诸多食品当中,直至20世纪末期果糖因其甜度高、口感醇、代谢途径不同于蔗糖,而一直被认为是一种可取代蔗糖的具有保健功能的糖类,并推荐作为糖尿病患者的食用糖。近年来,随着研究手段的提高、研究人员对果糖营养学问题的更加关注,很多新的研究发现,果糖的大量食用可导致一些现代常见流行病的发生,如心脏病、心血管疾病、高血压、血液指标异常、增加代谢综合征的出现几率,甚至增加癌症的发病几率。通过对近年来果糖相关的营养学问题、食用安全性问题,以及果糖与现代流行病的关系进行阐述,为合理利用果糖提供一定的参考依据。