不同砧木嫁接番茄光合特性的研究

采用LI-6400便携式光合作用系统对田间条件下嫁接番茄(珍红/砧木1号,珍红/桂砧1号)以及接穗(珍红)的光合作用特性进行了系统研究。结果表明:自根苗的光饱和点显著高于嫁接苗;自根苗和嫁接苗的光补偿点差异不显著,以珍红/桂砧1号最高(31.8μmolphotons·m-2·s-1),珍红/砧木1号最低(17.6μmolphotons·m-2·s-1);嫁接苗的CO2补偿点显著低于自根苗,且珍红/桂砧1号与自根苗的差异达极显著水平;表观量子效率变化范围为0.062~0.073;CO2饱和点在844~971μmolCO2·mol-1左右,CO2羧化效率变化范围为0.055~0.086molCO2·m-2·S-1;光合作用CO2补偿点珍红、珍红/砧木1号和珍红/桂砧1号分别为74.0、60.8和50μmolCO2·mol-1。嫁接苗的日平均光合速率和蒸腾速率高于自根苗,但两者的日进程曲线均为“单峰型”,其光合作用不存在“午休现象”。     

Body Mass Index Cutoffs for Underweight,Overweight, and Obesity in South Korean Schoolgirls

Objectives: To establish BMI percentiles and cutoffs for underweight, overweight, and obesity in South Korean schoolgirls. Research Methods and Procedures: A total of 1229 South Korean schoolgirls aged 8 to 18 years were randomly selected to complete a self‐administered questionnaire. BMI charts and cutoffs were constructed after analyzing data from 1107 subjects. Percentile curves were established by the modified LMS method. Results: The percentiles for underweight, overweight, and obesity corresponding to BMI of 18.5, 23.0, and 25.0 kg/m² at age 18 were the 13.0th percentile, the 77.8th percentile, and the 91.2nd percentile, respectively. The corresponding prevalences of underweight, overweight, and obesity were 12.1, 12.5, and 9.8%, respectively. Discussion: We established for the first time, to our knowledge, new BMI cutoffs for ages 8 to 18 that corresponded to BMIs of 18.5, 23.0, and 25.0 kg/m² for Asian adults designated by the International Obesity Task Force. These newly established BMI cutoffs might help to estimate the prevalence of overweight and obesity in Asian children.     

不同降水条件下沙鞭种群非生殖株丛空间格局分析

植物空间分布格局是物种自身生物学特性与环境因素共同作用的结果,非生殖株丛空间分布格局能够揭示物种无性繁殖与种群扩张过程对异质生境的生态学适应机制。利用基于完全随机、泊松聚块和嵌套双聚块模型的点格局方法和群落学调查,分析了沙鞭(Psammochloa villosa)种群非生殖株丛空间分布格局,探讨了空间格局对降水梯度的响应和适应过程。结果表明：(1)聚集分布是沙鞭种群非生殖株丛的主要类型。在89 mm/a、107.8 mm/a、117.4 mm/a、186 mm/a、191.1 mm/a、363 mm/a降水梯度上聚集尺度分别为3—126 cm、9—200 cm、9—129 cm、6—77 cm、2—95 cm、2—96 cm;(2)基于完全随机模型的空间分布格局对降水的响应规律显著,整体表现为随干旱程度加剧,沙鞭种群非生殖株丛聚集尺度从2—96 cm下降至6—77 cm;(3)在107.8 mm/a、117.4 mm/a、191.1 mm/a、363 mm/a降水梯度上,基于泊松聚块模型的空间分布格局分别在15—19 cm、2—6 cm、2—4 cm、9—25 cm尺度正向偏离泊松聚...     

随机区块法在空间点格局分析中的应用

利用一种以随机模拟技术为基础的空间点格局分析方法--随机区块法对长白山阔叶红松林中5个主要树种的空间格局及空间关系进行了分析.随机区块法利用ICS(t)=s2(t)/x(t)-1来衡量不同尺度t上空间点的分布格局,并通过随机模拟技术构建零假设的95%或99%置信区间,以确定空间点格局偏离零假设的显著性程度.结果表明,除蒙古栎、山荆子、怀槐为随机分布外,其它树种均在局部空间尺度上呈聚集分布;并且绝大多数种对或种组在局部空间尺度上呈正相关关系.随机区块法克服了小样方统计法研究尺度单一的问题,也避免了以空间点距离为基础的点格局分析过程中边缘效应带来的影响和误差,尤其是在多变量点格局分析中具有明显的优势.     

N-酰基高丝氨酸内酯酶的分子改造及酶学特性

革兰氏阴性细菌的群体感应系统利用N-酰基高丝氨酸内酯（N-acyl-homoserine lactone, AHL）作为主要信号分子诱导致病因子表达,造成细菌性病害. N-酰基高丝氨酸内酯酶（N-acyl-homoserine lactonase, AHLase）能水解AHL分子的内酯键,减弱致病菌的危害.本研究利用从苏云金芽孢杆菌克隆的N-酰基高丝氨酸内酯酶基因（auto inducer inactivation A, aiiA）,根据Swiss-model模拟aiiA所编码的AiiA蛋白三维结构,预测可能形成的分子内盐桥、活性中心位点等,利用环状诱变方法对AiiA进行定点突变,以期提高其酶活力和热稳定性等酶学性能.对AiiA及其突变蛋白酶学特性分析结果发现,突变体AiiA-N65K-A206E酶活力要比野生型AiiA-wild提高87.4%,并表现出良好的热稳定性和储存稳定性;37 ℃温浴30 min后酶活力剩余73;9%,比AiiA-wild有了大幅提高;4 ℃储存120 h后酶活力剩余12.9%,而AiiA-wild丧失酶活力.酶动力学分析表明,AiiA-N65K-A206E酶促反应的米氏常数Km为1.23 mmol/L,与野生型相当;最大反应速率Vmax为32.36 μmol/L/min,比野生型有较大提高.本研究表明,利用定点突变技术改造AiiA的分子结构,可有效提升AiiA酶活力、热稳定性和储存稳定性.本研究结果为进一步阐明AiiA结构与功能的关系,促进AiiA在植物病害生物防治上的应用,提供了有益的参考和新的思路.     

Photoperiodic and Thermal Regulation of Development and Cold Hardiness in Larvae of the Clover Leaf Weevil, Hypera punctata

Effects of photoperiod and temperature on the development and cold hardiness were investigated in larvae of Hypera punctata. At a relatively low temperature (15°C), the larvae fed less and developed more slowly under a 12L:12D (SD) photoperiod than under a 16L:8D photoperiod (LD). SD larvae had lower gut weight against the whole body weight and lower supercooling point (SCP) than the LD counterparts for the same instar and same body weight. This was because the larval SCP is markedly affected by the quantity of the gut content. Laboratory experiments indicated that the low temperature mortality of this larvae occurred mainly due to freezing irrespective of the photoperiod and temperature, suggesting that the lower lethal temperature (LLT) depends on the supercooling ability of larvae. The SD larvae tended to have a lower SCP and hence a lower LLT than the LD counterparts at 15 or 10°C, unlike at 20°C. Thus, the slower larval development under SD conditions at relatively low temperatures may prevent larvae from reaching the later instar, which have a higher SCP and thus less cold tolerance, during the coldest season. The suppressed feeding activity under SD conditions would lower the SCP, thereby reducing the possibility of lethal tissue freezing. Such a photoperiodic and thermal regulation of the larval development and the supercooling ability appear to represent adaptive mechanisms for winter survival in this beetle.     

太白山巴山冷杉林主要树种与开花秦岭箭竹的空间点格局分析

采用单变量和双变量O-ring函数对太白山大熊猫栖息地巴山冷杉林主要树种的空间分布格局、种间关联性及其与林下开花箭竹的空间关联性进行了多尺度分析.结果表明: 巴山冷杉林中,巴山冷杉数量最多,但种群结构衰退,白桦种群相对年轻,种群结构稳定,红桦种群也呈衰退趋势;3个主要树种在小尺度上呈聚集分布,随尺度增加,逐渐表现为随机分布.3个树种的空间关联性主要表现在小尺度范围内,随尺度增加,空间分布格局逐渐表现为不关联;巴山冷杉和白桦与开花秦岭箭竹在大、中尺度内呈现正相关,而红桦与开花秦岭箭竹在大、中尺度上表现出负相关.大熊猫栖息地内乔木和林下秦岭箭竹共同推动森林的动态演替和发展,进而影响秦岭大熊猫栖息地的环境变化.     

Associating somatic mutation with clinical outcomes through kernel regression and optimal transport

Somatic mutations in cancer patients are inherently sparse and potentially high dimensional. Cancer patients may share the same set of deregulated biological processes perturbed by different sets of somatically mutated genes. Therefore, when assessing the associations between somatic mutations and clinical outcomes, gene-by-gene analysis is often under-powered because it does not capture the complex disease mechanisms shared across cancer patients. Rather than testing genes one by one, an intuitive approach is to aggregate somatic mutation data of multiple genes to assess their joint association with clinical outcomes. The challenge is how to aggregate such information. Building on the optimal transport method, we propose a principled approach to estimate the similarity of somatic mutation profiles of multiple genes between tumor samples, while accounting for gene–gene similarities defined by gene annotations or empirical mutational patterns. Using such similarities, we can assess the associations between somatic mutations and clinical outcomes by kernel regression. We have applied our method to analyze somatic mutation data of 17 cancer types and identified at least five cancer types, where somatic mutations are associated with overall survival, progression-free interval, or cytolytic activity.     

A periodicity result for a nonlinear functional integral equation

In this paper, we study the effect of introducing a delay in a model of cell proliferation considered originally by O. Arino and M. Kimmel (J. Math. Biol. 27, 341–354 (1989)). We prove that slow oscillations take place and periodic oscillations appear for appropriate values of a parameter.