US specificity of occasion setting: Hierarchical or configural learning?

Four experiments in rats examined whether occasion setters and target CSs play qualitatively different roles in occasion-setting discriminations. Two visual occasion setters, A and B, signalled reinforcement of two auditory target CSs, x and y, with sucrose and oil (A…x→suc, B…y→oil, A-, B-, x-, y-); in addition two transfer CSs w and z were paired with sucrose and oil (w→suc, z→oil). When w and z were substituted for x and y (A…w, B…w, A…z, B…z) more responding was observed when both stimuli had been paired with the same outcome (Experiments 1 and 3a). No effect was observed when two visual "pseudo-occasion setters", C and D (paired with sucrose and oil in a trace relation to the US:C…→suc, D…→oil), were substituted for the occasion setters A and B (C…x, D…x, C…y, D…y; Experiments 2, 3b and 4). These results could not be explained in terms of Pavlovian summation: responding to combinations of Pavlovian CSs paired with same or different outcomes was either the same, or lower when both stimuli had been paired with the same outcome (Experiment 4). Implications of these results for theories of occasion setting and configural learning are discussed.     

Changes in duration of developmental phases of durum wheat caused by breeding in Spain and Italy during the 20th century and its impact on yield

Background and Aims

Although the apical development of wheat has been widely described, studies analysing how genetic breeding over the 20th century influenced the developmental phases and its consequences on yield generation are lacking, especially for durum wheat under field conditions in Mediterranean environments. The aims of this study were to analyse the effects of breeding in Spain and Italy on crop development during the last century, to determine whether or not breeding significantly altered the developmental phases between sowing and maturity, and to evaluate the importance of each phase in determining the number of grains per spike of durum wheat (Triticum durum) cultivars representing the germplasm grown throughout the 20th century in Spain and Italy.

Methods

Eight field experiments were carried out during 4 years in two contrasting latitudes (Lleida and Granada, Spain). Plant material consisted of 24 durum wheat cultivars (12 Italian and 12 Spanish) grown throughout the 20th century in Spain and Italy.

Key Results

In Spanish materials, breeding reduced the duration of the period from sowing to anthesis, placing the grain-filling period in better conditions. In those cultivars, the sub-phase sowing–terminal spikelet formation was reduced while the duration of the period from booting to anthesis was increased. The number of grains per spike increased by 23 % from old to modern cultivars, by changes in the number of grains per spikelet in both Spanish and Italian cultivars. Floral abortion from booting to anthesis diminished by 24 % from old to modern cultivars, and grain setting increased by 13 %.

Conclusions

The results suggest that breeding reduced not only plant height, but also the time to anthesis. By extending the duration of the phase from booting to anthesis, which was associated with an increase in spike dry weight and grains per spike, it suggests that future increases in spike fertility could be achieved by enlarging that phase.     

目标设定：促进糖尿病患者行为改变的方法

目标设定是将患者的自我管理和行为改变意图转换为目标的过程,是一种常见的、行之有效的行为干预策略。本文介绍了目标的种类、目标设定的原则、方法及利用目标设定的方法进行糖尿病教育的效果,分析了目标设定在实际应用中存在的问题,为以后更好地利用目标设定的方法进行糖尿病教育,从而达到改变患者行为的目的提供了理论依据。     

不同脱水处理对桔梗花粉离体萌发及贮藏性能的影响

对桔梗花粉离体萌发条件进行了筛选,并采用花粉离体萌发法测定了不同干燥方式和贮藏时间处理对桔梗花粉生活力的影响;同时采用人工授粉的方法研究了不同处理后桔梗花粉授粉结实能力的变化。结果表明：（1）30℃培养1.5h是桔梗花粉离体萌发和花粉管生长的最佳培养条件。（2）不同干燥方式、不同干燥时间处理后桔梗花粉萌发率和花粉管长度均有所下降,但下降幅度不同,其中以干燥箱45℃烘干处理1.5h~2h下降最少,其花粉耐藏性也有明显提高。（3）不同干燥方式处理桔梗花粉后其授粉结籽率的变化明显不同,阴置2h处理的花粉结籽率最低,而干燥器内放置6h、日晒2h和烘干1.5h处理后花粉结籽率略有变化;干燥处理后随贮藏时间的增加,其授粉结籽率均呈下降趋势,但45℃烘干1.5h处理的花粉结籽率下降速度最慢,其授粉结籽能力可保持5d左右。     

不同纬度高蔊菜的交配系统和繁殖保障

高山植物的繁殖适应策略一直是进化生态学研究的热点, 但是目前仍缺乏对繁殖适应性状的量化研究。本研究以横断山特有十字花科植物高蔊菜(Rorippa elata)为研究材料, 结合野外同质园控制实验, 在居群水平探讨了其繁殖适应策略。结果表明, 高蔊菜的繁殖能力与纬度呈负相关, 而越冬存活率与纬度呈正相关。不同交配方式结实率的显著性差异分析表明, 高蔊菜具有混合交配系统, 其中自交为主型和中间型的株系各占45.5%和39.4%; 不同株系具有不同程度的繁殖保障现象, 自交为主型最高(0.163), 中间型最低(0.011)。本研究表明高蔊菜在居群水平的繁殖和存活之间存在沿纬度梯度的权衡变化, 以自交为主的混合交配系统为其提供不同程度的繁殖保障。     

A meta‐analysis of the effects of nutrient enrichment on litter decomposition in streams

The trophic state of many streams is likely to deteriorate in the future due to the continuing increase in human‐induced nutrient availability. Therefore, it is of fundamental importance to understand how nutrient enrichment affects plant litter decomposition, a key ecosystem‐level process in forest streams. Here, we present a meta‐analysis of 99 studies published between 1970 and 2012 that reported the effects of nutrient enrichment on litter decomposition in running waters. When considering the entire database, which consisted of 840 case studies, nutrient enrichment stimulated litter decomposition rate by approximately 50%. The stimulation was higher when the background nutrient concentrations were low and the magnitude of the nutrient enrichment was high, suggesting that oligotrophic streams are most vulnerable to nutrient enrichment. The magnitude of the nutrient‐enrichment effect on litter decomposition was higher in the laboratory than in the field experiments, suggesting that laboratory experiments overestimate the effect and their results should be interpreted with caution. Among field experiments, effects of nutrient enrichment were smaller in the correlative than in the manipulative experiments since in the former the effects of nutrient enrichment on litter decomposition were likely confounded by other environmental factors, e.g. pollutants other than nutrients commonly found in streams impacted by human activity. However, primary studies addressing the effect of multiple stressors on litter decomposition are still few and thus it was not possible to consider the interaction between factors in this review. In field manipulative experiments, the effect of nutrient enrichment on litter decomposition depended on the scale at which the nutrients were added: stream reach > streamside channel > litter bag. This may have resulted from a more uniform and continuous exposure of microbes and detritivores to nutrient enrichment at the stream‐reach scale. By contrast, nutrient enrichment at the litter‐bag scale, often by using diffusing substrates, does not provide uniform controllable nutrient release at either temporal or spatial scales, suggesting that this approach should be abandoned. In field manipulative experiments, the addition of both nitrogen (N) and phosphorus (P) resulted in stronger stimulation of litter decomposition than the addition of N or P alone, suggesting that there might be nutrient co‐limitation of decomposition in streams. The magnitude of the nutrient‐enrichment effect on litter decomposition was higher for wood than for leaves, and for low‐quality than for high‐quality leaves. The effect of nutrient enrichment on litter decomposition may also depend on climate. The tendency for larger effect size in colder regions suggests that patterns of biogeography of invertebrate decomposers may be modulating the effect of nutrient enrichment on litter decomposition. Although studies in temperate environments were overrepresented in our database, our meta‐analysis suggests that the effect of nutrient enrichment might be strongest in cold oligotrophic streams that depend on low‐quality plant litter inputs.     

Topographic mediation of growth in high elevation foxtail pine (Pinus balfouriana Grev. et Balf.) forests in the Sierra Nevada, USA

Aim Climate variability is an important mediating agent of ecosystem dynamics in cold, semi‐arid regions such as the mountains of western North America. Climatically sensitive tree‐ring chronologies offer a means of assessing the impact of climate variability on tree growth across temporal scales of years to centuries and spatial scales of metres to subcontinents. Our goal was to bring practices from landscape ecology that highlight the impact of landscape heterogeneity on ecological pattern and processes into a dendroclimatic study that shows that the biophysical setting of target trees affects ring‐width patterns. Location This study was conducted at two sites near alpine treeline in the Sequoia National Park, USA (36°30′ 00′ N, 118°30′ 00′ W). Methods We collected stand information and increment cores from foxtail pines (Pinus balfouriana Grev. et Balf.) for eight tree‐ring chronologies in four extreme biophysical settings at two sites using proxies for soil moisture and radiation derived from a digital elevation model. Results Biophysical setting affected forest age–class structure, with wet and bright plots showing high recruitment after 1900 ad , but had no obvious effect on immature stem density (e.g. seedlings). Biophysical setting strongly affected ring‐width patterns, with wet plots having higher correlation with instrumental temperature records while dry plots correlated better with instrumental precipitation records. Ring‐width chronologies from the wet plots showed strong low‐frequency variability (i.e. hundreds of years) while ring‐width chronologies from the dry plots showed strong variability on multidecadal scales. Main conclusions There was a strong association between biophysical setting and age‐class structure, and with ring‐width patterns in foxtail pine. The mediation of ring widths by biophysical setting has the potential to further the understanding of the expression of synoptic‐scale climate across rugged terrain. When combined with remotely sensed imagery, a priori GIS modelling of tree growth offers a viable means to devise first‐order predictions of climatic impacts in subalpine forest dynamics and to develop flexible and powerful monitoring schemes.     

应用DOS批处理文件配置新版NCRE考试服务器

根据全国计算机等级考试(NCRE)考试服务器设置的需要,介绍了相关DOS命令的使用,并编写了设置NCRE考试服务器的DOS批处理文件。一方面充分展示了DOS命令及DOS批处理文件的强大功能,而且在NCRE考试服务器的设置等需要进行大量重复操作的场合,相对使用Windows操作可以显著地提高工作效率、减轻劳动强度。     

春化处理控制冬小麦的小穗发育

春化作用是决定冬性及二年草本植物成花和穗化的一个关键生理过程,通过用不同时间的前期低温处理,观察对冬小麦（Triticum aestivum L.)后期形态建成中穗分化启动,小花发育及结实率的影响,发现前期低温处理对穗启动分化的早晚具有决定作用,春化时间越长,穗分化启动越早,较长时间低温有利于促进穗分化,在实验室低温处理条件下,促进小花分化和提高结实率的最佳春化处理时间是45d左右,实验观察表明,春化处理促进小麦生长锥分化启动时间和分化速率,减少小穗退化,这一结果表明了春化处理不仅是冬小麦开花启动过程所必需的,而且是花序正常发育过程和顶部与基部小穗完全结实所不可缺少的。     

化学调控四季花龙眼成花座果的初步研究

不同化学试剂组合对四季花龙眼枝梢生长和成花座果研究表明,不同时期成熟的枝梢对四季花龙眼成花座果无重大的影响;乙烯利、多效唑和赤霉素三者共同作用可促进成花座果;当枝梢充分成熟时,树冠喷施乙烯利250mg·L-1+多效唑450mg·L-1,谢花3/4时再喷施赤霉素50mg·L-1,可以有效抑制四季花龙眼植株新梢的萌发,促使植株100%成花,并且花穗和果穗性状的综合表现最好。