不同ES细胞系体定量神经分化的比较

利用视黄酸（RA）诱导小鼠胚胎干细胞通过悬浮类胚培养体外定量分化为神经样细胞,结果显示能够进行种系嵌合的MESPU22细胞系与不能进行种系统嵌合的MESPU13细胞系的体外神经分化比例在统计学上没有明显差异,此结果对于人的胚胎干细胞全能性的鉴定和检测有重要启示。     

小叶龙竹（Dendrocalamus barbatus）愈伤组织诱导及植株再生

以小叶龙竹种子为外植体,通过研究MS培养基中不同植物生长调节剂浓度组合对外植体愈伤组织诱导和不定芽分化的影响以及不同配比对生根的作用,建立了稳定的繁殖再生体系。试验结果表明愈伤组织诱导的最适培养基为MS＋2,4-D5．0mg·L-1;不定芽分化的最适培养基为MS＋2,4-D0．5mg·L-1＋6．BA1．0mg·L-1＋KT0．25mg·L-1;小苗的最适生根培养基为1／2MS＋6-BA0．5mg·L-1＋NAA1．0mg·L-1＋IBA0．4mg·L-1,建立的繁殖再生体系将为进一步利用分子生物学技术对竹类植物进行遗传改良奠定基础。     

施钾对甘薯氮素转移分配及氮代谢酶活性的影响

利用¹⁵N示踪技术,研究了施钾对甘薯发根结薯期、薯块膨大期地上和地下部氮素转移分配、光合特性及氮代谢酶活性的影响.结果表明: 在发根结薯期,施钾显著提高¹⁵N向地上部的转移分配,其中K₃(K₂O, 300 mg·kg^-1)处理与对照相比¹⁵N向叶片转移速率提高了76.2%,¹⁵N积累量提高了92.1%.在薯块膨大期,随施钾量增加地上部叶片¹⁵N总分配率由33.7%降低至24.4%,块根¹⁵N分配率由5.8%升高至17%,其中K₃处理块根¹⁵N积累量是对照的3倍.两个关键生长期硝酸还原酶、谷氨酸脱氢酶、谷氨酰胺合酶、谷氨酸合酶和净光合速率(P_n)均随施钾量的增加而提高.逐步回归分析表明,氮代谢酶活性和P_n是影响甘薯¹⁵N转移和分配的主要因素(R分别为0.965和0.942),通径分析表明,在发根结薯期主要通过促进硝酸还原酶和谷氨酸脱氢酶介导的氮素催化能力促进氮素向地上部分配;在薯块膨大期主要通过提高谷氨酰胺合酶/谷氨酸合酶循环介导的氮素同化能力促进氮素向地下部分配.     

Faster returns on ‘leaf economics’ and different biogeochemical niche in invasive compared with native plant species

Plant‐invasive success is one of the most important current global changes in the biosphere. To understand which factors explain such success, we compared the foliar traits of 41 native and 47 alien‐invasive plant species in Oahu Island (Hawaii), a location with a highly endemic flora that has evolved in isolation and is currently vulnerable to invasions by exotic plant species. Foliar traits, which in most cases presented significant phylogenetic signal, i.e. closely related species tended to resemble each other due to shared ancestry, separated invasive from native species. Invasive species had lower leaf mass per area and enhanced capacities in terms of productivity (photosynthetic capacity) and nutrient capture both of macro‐ (N, P, K) and microelements (Fe, Ni, Cu and Zn). All these differences remain highly significant after removing the effects of phylogenetic history. Alien‐invasive species did not show higher efficiency at using limiting nutrient resources, but they got faster leaf economics returns and occupied a different biogeochemical niche, which helps to explain the success of invasive plants and suggests that potential increases in soil nutrient availability might favor further invasive plant success.     

Curvature in models of the photosynthesis‐irradiance response

An equation for the rate of photosynthesis as a function of irradiance introduced by T. T. Bannister included an empirical parameter b to account for observed variations in curvature between the initial slope and the maximum rate of photosynthesis. Yet researchers have generally favored equations with fixed curvature, possibly because b was viewed as having no physiological meaning. We developed an analytic photosynthesis‐irradiance equation relating variations in curvature to changes in the degree of connectivity between photosystems, and also considered a recently published alternative, based on changes in the size of the plastoquinone pool. When fitted to a set of 185 observed photosynthesis‐irradiance curves, it was found that the Bannister equation provided the best fit more frequently compared to either of the analytic equations. While Bannister's curvature parameter engendered negligible improvement in the statistical fit to the study data, we argued that the parameter is nevertheless quite useful because it allows for consistent estimates of initial slope and saturation irradiance for observations exhibiting a range of curvatures, which would otherwise have to be fitted to different fixed‐curvature equations. Using theoretical models, we also found that intra‐ and intercellular self‐shading can result in biased estimates of both curvature and the saturation irradiance parameter. We concluded that Bannister's is the best currently available equation accounting for variations in curvature precisely because it does not assign inappropriate physiological meaning to its curvature parameter, and we proposed that b should be thought of as the expression of the integration of all factors impacting curvature.     

Effects of elevated CO₂, warming and drought episodes on plant carbon uptake in a temperate heath ecosystem are controlled by soil water status

The impact of elevated CO₂, periodic drought and warming on photosynthesis and leaf characteristics of the evergreen dwarf shrub Calluna vulgaris in a temperate heath ecosystem was investigated. Photosynthesis was reduced by drought in midsummer and increased by elevated CO₂ throughout the growing season, whereas warming only stimulated photosynthesis early in the year. At the beginning and end of the growing season, a T × CO₂ interaction synergistically stimulated plant carbon uptake in the combination of warming and elevated CO₂. At peak drought, the D × CO₂ interaction antagonistically down‐regulated photosynthesis, suggesting a limited ability of elevated CO₂ to counteract the negative effect of drought. The response of photosynthesis in the full factorial combination (TDCO₂) could be explained by the main effect of experimental treatments (T, D, CO₂) and the two‐factor interactions (D × CO₂, T × CO₂). The interactive responses in the experimental treatments including elevated CO₂ seemed to be linked to the realized range of treatment variability, for example with negative effects following experimental drought or positive effects following the relatively higher impact of night‐time warming during cold periods early and late in the year. Longer‐term experiments are needed to evaluate whether photosynthetic down‐regulation will dampen the stimulation of photosynthesis under prolonged exposure to elevated CO₂.     

固沙树种梭梭在不同水分梯度下的光合生理特征

对不同水分梯度下梭梭光合作用的研究发现,地下水位、土壤含水量、灌水量对梭梭的光合具有明显的影响。在1．4m、2．4m、3．4m地下水位下,梭梭的光合速率、呼吸作用、量子效率随水位的降低而降低,光补偿点随水位的降低而增大;在滴灌供水时,梭梭的光合速率较对照明显提高,且灌水量越大,梭梭的光合速率越高;半流动沙丘、丘间低地、粘土沙障固定沙丘退化梭梭的光合作用的强弱同其林地土壤水分的高低基本一致。7月,不同水分梯度下的梭梭光合作用均表现出午休现象,9月只有立地条件较差的梭梭发生光合午休,而且9月光合作用要强于7月,说明9月环境条件更有利于梭梭生长。     

诱导紫云英根瘤菌nod基因表达的一些植物因子

利用柱层析、薄层层析（TLC）和高压液相色谱（HPLC）从紫云英种子中分离并纯化对紫云英根瘤菌nd基因表达有诱导活性的成分,质谱（MS）鉴定为抽皮素（naringenin）。19种类黄酮或非类黄酮化合物对紫云英根瘤菌结瘤基因表达的诱导活性实验表明,紫云英根瘤菌的结瘤基因可以应答多种诱导咸分,除抽皮素外,还有类黄酮物质毛地黄黄酮（luteolin）、大豆素（daidzein）以及非类黄酮化合物7-羟基香豆素（umbelliferone）和葫芦巴碱（trigonelline）。     

不同剂量^137Cs-γ辐射对毛竹幼苗叶片叶绿素荧光参数的影响

利用不同剂量的137Cs-γ射线对毛竹（Phyllostachys heterocycla ‘Pubescens’）种子进行辐射, 测定实生苗叶片中的光合色素含量和叶绿素荧光参数等指标, 探讨辐射对毛竹幼苗生长的影响, 为筛选有利的突变单株奠定良好基础。结果表明：30或60 Gy的137Cs-γ射线辐射后, 毛竹幼苗的光合色素含量以及最大荧光强度（Fm）、可变荧光强度（Fv）、PSII最大光化学效率（Fv/Fm）、PSII的潜在活性（Fv/Fo）、PSII实际光化学效率（Yield）和表观光合电子传递速率（ETR）等荧光参数值均高于90 Gy辐射处理, 说明较低剂量辐射后PSII反应中心的能量捕获效率高, 且具有较强的光合能力; 而90 Gy的137Cs-γ射线辐射对毛竹的影响则与之相反。不同处理剂量之间叶片光能耗散程度以及表观光合电子传递速率-光合有效辐射（ETR-PAR）响应曲线的分析结果也进一步证实了以上结论。     

石臼湖原生动物种群分布及其同质化

石臼湖地处长江中下游,是国内为数不多的通江淡水湖。为探讨湖泊与入湖支流不同生境中原生动物种群结构及其相似性,于2012年平水期和枯水期分别对石臼湖及其周边入湖支流进行原生动物调查,研究河流和湖泊区域原生动物的种类组成及其季节变化,同时与同一地区的相邻湖泊固城湖作对比,通过计算相似性指数,探讨原生动物对生境同质化的响应。结果表明:调查共采集到原生动物57种,平水期种类多于枯水期;石臼湖河流区各站点原生动物相似性指数在Ⅰ~Ⅲ级之间,为完全不同-轻度相似;湖区站点相似性指数在Ⅱ~Ⅳ之间,为极不相似-中度相似;河流区种类季节之间的相似度极低(0.050~0.267),而湖泊区种类季节之间处于中等相似水平(0.250~0.375),说明河流区原生动物种类的季节变化较湖泊区明显,生物组成的异质性也高于湖泊;原生动物分布对水质有很好的响应关系,氮磷元素在影响原生动物种类组成和分布中起了主要作用;通过石臼湖与固城湖及长江中下游其他湖泊的对比分析,表明在一定范围内,随着生境尺度的增加,生境的同质化会提高生物同质化水平,但超过景观尺度,原生动物地域性特征逐渐显现,即使生境同质,其生物也未必同质;且随着距离的增加,不同区域的生物相似性呈降低的趋势。