成体干细胞的研究现状与展望

近年来，干细胞特有的生物学特性及其潜在的生物医学应用价值使之成为生命科学领域最热点、最前沿的课题之一。随着对干细胞研究的不断深入，人们发现成体干细胞除了具有较强的自我更新、高度增殖和多向分化潜能外还具有分化方向的可塑性。作者根据国内外研究成果，综述了成体干细胞的“可塑性”研究的最新进展，以及成体干细胞可塑性研究的前景及存在的主要问题。     

Root architecture of sorghum genotypes differing in root angles under different water regimes

Plant root architecture offers the potential for increasing soil water accessibility, particularly under water-limited conditions. The objectives of this study were to evaluate the root architecture in two genotypes of sorghum (Sorghum bicolor (L.) Moench) differing in root angles and to assess the influence of different deficit irrigation regimes on root architecture. The response of two sorghum genotypes, ‘Early Hegari-Sart’ (EH; steep root angle) and ‘Bk7’ (shallow root angle) to four irrigation treatments was investigated in two replicated outdoor studies using large pots. The results indicated that EH possessed steeper brace and crown root angles, fewer brace roots, greater root biomass, and root length density than Bk7 at deeper soil depths (i.e., 15–30 and 30–45 cm) compared with a shallower depth (i.e., 0–15 cm). Across the soil profile, EH had greater root length density and length of roots of small diameter (<1 mm) than Bk7. Accordingly, EH showed more rapid soil-water capture than Bk7. Different levels of irrigation input greatly affected root architecture. Severe deficit irrigation (25% of full crop transpiration throughout the season) increased the angle and number of crown roots, root biomass, and root length density compared with 75 and 100% of full crop transpiration treatments. Consequently, root system architecture can be effectively manipulated through both genotypic selection and irrigation management to ensure optimal performance under different levels of soil available water.     

Living on the edge: morphological and behavioral adaptations to a marginal high-elevation habitat in an arboreal mammal

Habitats are characterized by different local environmental conditions that influence both behavior and morphology of species, which can result in habitat-dependent phenotypic differences among animals living in heterogeneous environments. We studied 3 alpine populations of Eurasian red squirrels (Sciurus vulgaris), 1 living in a marginal high-elevation habitat at the edge of the species’ altitudinal distribution, and 2 occurring in higher-quality habitats. Here, we investigated whether squirrels living in the marginal area differed in 2 morphological parameters (body size and body mass) and/or in the expression of 4 personality traits estimated with an open field test and a mirror image stimulation test (activity, exploration, activity-exploration, and social tendency). Furthermore, we tested whether within-individual variance of the traits (behavioral plasticity) was higher in the edge habitat. Male squirrels in the edge habitat were smaller and weighed less than in the other study areas, while among females, size–habitat relationships were less marked. These sex-specific patterns were explained by a strong association between body mass and reproductive success in female squirrels. Squirrels in the marginal habitat were more active, explorative, and had a more social personality than in the other habitats. However, in contrast to our predictions, behavioral plasticity was smaller in the marginal habitat, but only for the trait exploration. Our results suggest that animals choose the habitat that best fits their personality, and that habitat-related differences in selective pressures may shape animals’ morphology.     

Root Plasticity Not Evident in N-Enriched Soil Volumes for Wheat (Triticum aestivum L.) and Barley (Hordeum vulgare L.) Varieties

Root plasticity is a unique characteristic of root systems that may enhance the nutrient foraging capacity of plants. Here we investigated the effect of localized high nitrogen (N) concentration on plasticity of wheat and barley roots in soil. We conducted a series of experiments to maintain localized high concentration of N in soil and to evaluate any root morphological variation in the enriched N zone. Wheat and barley seedlings were grown in N responsive Red Ferrosol with an enriched subsurface N band for 12 days. Wheat and barley roots did not proliferate in N-enriched soil volumes. Rather, higher root length density (~1.6 times) was observed in low N surface soil. Shoot dry matter and shoot N uptake of banded N treatment was statistically similar between uniform and low N treatments. Results indicated the absence of plastic root response of the wheat and barley seedlings in subsurface N band.     

泽鹬越冬期间机体结构表型弹性变化

［目的］评价越冬泽鹬器官表型的变化趋势。［方法］选择在上海越冬的泽鹬作样本,按迁移时间分为中转停歇期和越冬期,分析这两个阶段泽鹬体重的差异,并分析泽鹬越冬期机体结构变化及2002～2004年的环志数据,评估其器官表型弹性变化的趋势。［结果］越冬泽鹬样本平均体重为（81.760±11.217）g,比中转停歇期的增加了14.570 g。增重的最大因素是脂肪,占72.260% 其次是胸肌部分,为14.170% 腿肌随体重仅略有增加,占3.490%。在越冬早期,腿肌、剩余骨骼及肝、砂囊、心、脑、肺、肾等重量都保持稳定,不随体重增加变化。与迁徙期的研究资料比较,越冬早期泽鹬器官大小弹性变化的范围和程度均较小。［结论］越冬期的泽鹬的脂肪、胸肌和腿肌均随体重增加发生不同程度地变化,其他器官没有实质性变化。     

Evaluation on the Damage Evolution of the CRCP+AC Composite Pavement by the Concrete Dameged Plasticity Material Model

In the study on the CRCP+AC composite pavement, the form and distribution pattern of cracks are two important factors influencing the performance and the lifetime of the pavement. The concrete damaged plasticity material model incorporated in the general purpose finite element software named ABAUQS was adopted to describe the mechanical characteristics of the CRC slab. Combining with the temperature field database drawn from the three-dimensional transient heat transfer analysis, the structural damage under the condition of temperature changing is analyzed. The structural damage evolution and the crack behavior of the CRC slab subjected to the thermal-mechanical coupling condition are further analyzed, which suggests that the role of the asphalt concrete surface is not confined only to the scope of improving the performance of the road, its capacity for improving the stress state of CRCP slab is worthwhile to be affirmed. And the reasonable thickness of AC layer should be designed in consideration of the thermal contraction and damage properties of the CRC slab comprehensively.     

支持柱直径对紫萼龙吐珠形态特征和生物量分配的影响

【目的】研究支持柱直径对紫萼龙吐珠(Clerodendrum speciosum)形态特征和生物量分配的影响,为其在城市园林垂直绿化中的快速攀援提供理论依据。【方法】以紫萼龙吐珠1年生扦插苗为试验材料,采用完全随机区组设计,设置3种直径支持柱(8,16,24mm竹竿)处理,并以无支持柱为对照(CK),分析不同直径支持柱下植株的生长动态、形态特征、生物量分配及表型可塑性指数的变化规律。【结果】(1)直径8mm支持柱上植株主茎长、节间长和叶片数均增长较快;直径16mm支持柱上紫萼龙吐珠具有较高的自主螺旋缠绕能力,且植株通过增加叶片数和主茎长提高自主攀援能力;直径24mm支持柱上植株的叶柄长和分枝节间长显著大于16mm支持柱上的植株(P0.05),自主缠绕情况较差的植株通过增加分枝的比茎长和比叶柄长、伸长节间等方式进一步搜寻外界支持物。(2)无支持柱组植株的根冠比显著大于有支持柱的植株(P0.05),显示支持柱的存在使植株的生物量更多地分配到地上部分的枝和叶;当植株攀援外界支持柱的扭转率下降时,植株分配更多的生物量到地上部分的分枝茎和叶柄上。(3)紫萼龙吐珠在主茎水平上具有较强的形态可塑性;而在其分枝水平上,植株主要通过改变生物量的分配来适应不同的外界支持物条件。【结论】紫萼龙吐珠对不同直径支持柱表现出较强的形态和生物量可塑性,在园林实践中选取直径为8~16mm的支持柱供其攀援更为合适。     

须弥红豆杉的研究进展

对须弥红豆杉的栽培育种、组织与细胞培养、植物化学、种群生物学与遗传多样性、生殖生态学以及资源保护等方面的研究进展进行综述,提出今后在不同海拔及气候类型下开展须弥红豆杉幼苗形态可塑性及其他方面研究的设想.     

Comparative performance of the highly invasive Mimosa invisa and its less invasive subspecies under different nutrient and light conditions

Invasive plants may be more plastic than non‐invasive plants and maintain high fitness under various environmental conditions. Previous studies mainly focused on the comparisons between invasive and native plants, and comparisons between highly invasive and less invasive exotic species are still relatively rare, especially for comparisons at the subspecies level. This study examined the effects of nutrient addition and shading on the performance of the highly invasive Mimosa invisa and its less invasive subspecies M. invisa var. inermis under either isolated or competitive conditions. Nutrient addition increased biomass and plant height and decreased root‐to‐shoot ratio (R/S). Shading decreased biomass and R/S and increased plant height. Under isolated conditions, the two invaders did not differ in R/S, plant height and plasticity of these traits in response to nutrient addition or shading, and the two invaders also did not differ in biomass production under each of the nutrient and light treatments. When the two invaders competed with each other, M. invisa outcompeted M. invisa var. inermis under high soil nutrient conditions, and the two invaders did not differ in performance under other growth conditions. Thus, only considering competition may we find out the difference between highly invasive species and their closely related, less invasive subspecies. Management of M. invisa should focus on habitats with high soil nutrient availability, in which M. invisa is more likely to dominate.