The measurement of O2 flux in two woodland soils

Summary Pitfalls in the use of the platinum micro-electrode method of determining soil oxygen flux are described, together with an example of its use. Interpretation of current measurements as oxygen fluxes is possible only if, a) an oxygen limitation to current has been demonstrated, and then b) a suitable applied potential is used. Oxygen flux values in a well drained soil can be as low as those in a seasonally waterlogged soil. However such low flux values are usually of short duration.     

报春花属植物组织培养研究进展(综述)

对国内外报春花属植物组织培养技术研究进行概述,重点分析了外植体类型、基本培养基、植物生长调节剂、试管苗移栽等方面的进展,并对今后的工作重点进行展望。     

Genetic diversity within and among populations of the endangered and endemic species Primula merrilliana in China

Primula merrilliana Schltr. is an endangered and narrowly-distributed endemic species of southern Anhui Province in China. In this study, the level of genetic variation and the pattern of genetic structure in six natural populations of P. merrilliana were assessed by using ISSR (inter-simple sequence repeats) markers. Based on ten primers, 137 clear and reproducible DNA fragments were generated, of which 109 were polymorphic. The statistical results indicated that there was a relatively low genetic diversity within populations, and a high genetic differentiation among populations (G_ST = 0.53, Φ_ST = 0.49). The level of population genetic diversity was correlated to habitat type and the gene flow (N_m) was low with only 0.45. The unexpected genetic structure of P. merrilliana may be explained by limited gene flow that was caused by habitat fragmentation and limited seeds and pollen dispersal ability, self-compatible breeding system and biennial life form.     

中国特有濒危种川东灯台报春(报春花科)的重新发现

2006年6月份和9月份,作者在对重庆市城口县大巴山地区进行考察时,采集到了中国特有种川东灯台报春（Primula mallophylla）的标本,这是近百年来对该种除模式标本外的再度发现。根据在大巴山观察及采集到的材料,作者对过去该种的特征描述中存在的一些疑问进行了澄清,更正和补充了其形态描述;对历史上混淆的几个种列出了检索表;报道了该种的染色体数目及核型;根据国际通用的“红色名录等级及标准”对其濒危等级进行了评估。     

Morph-specific differences in reproductive success in the distylous Primula veris in a context of habitat fragmentation

Heterostylous self-incompatible plant species are particularly sensitive to habitat fragmentation and to disruption of pollination processes because of the need of intermorph cross-pollination for producing seeds. Heterostyly is characterized by sexual polymorphism through the occurrence of two (distyly) or three (tristyly) morph types that differ in floral traits (style length and anther position). We examined whether the long-styled (pin) and short-styled (thrum) morph types show differences in reproductive components and responses to habitat fragmentation in the distylous, self-incompatible perennial herb Primula veris. We documented reproductive components for pin and thrum individuals and their relationships with population size, plant density and morph ratio (pin frequency), in nine populations from Flanders (northern Belgium) located in fragmented habitats of the intensively used agricultural landscape. Seed abortion increased in small populations as a result of inbreeding depression. Fruit set increased with plant density. Seed set was positively related to pin proportion. Seed set was higher for pin than thrum in small populations, but lower in large populations. Two hypotheses can be considered to explain these morph-specific differences: a pollen transfer asymmetry, and a reproductive advantage for the partially self-compatible pin morph. Morph types appear to respond differently to habitat fragmentation constraints. A floral morph type showing partial self-compatibility may be favored in populations under pollination failure, because it can increase reproductive success and mating opportunities through intramorph crosses.     

Genetic diversity in Primula obconica (Primulaceae) from central and south-west China as revealed by ISSR markers

Genetic diversity was investigated in 60 individuals of Primula obconica from four natural populations (from Hubei, central China, and Sichuan, south-west China) and from cultivated material. Inter-simple sequence repeat (ISSR) techniques produced 249 polymorphic bands and identified 60 ISSR genotypes. Based on Shannon's index and Nei's genetic diversity, the genetic diversity detected in all natural populations of P. obconica was much higher than that in the cultivated plants, and that in the three Dalaoling (Hubei) populations was higher than that in the Wawushan (Sichuan) population. UPGMA cluster analysis showed that there was no distinct genetic differentiation between populations from the Mt Dalaoling area and the Mt Wawushan area. This study provides a population-level genetic profile of P. obconica, which was previously poorly known but which is important for Primula breeding and cultivation.     

Seedling emergence patterns and dormancy/germination physiology of <Emphasis Type="Italic">Primula modesta</Emphasis> in a subalpine region

On the basis of the germination/dormancy responses of seeds to temperature and light, and local seed rain, we attempted to interpret the seedling emergence patterns of Primula modesta Bisset et Moore (Primulaceae) in two different types of habitats in a subalpine zone of Mt. Asama: an oligotrophic flat moor and a grassland with relatively dense herbaceous vegetation cover. The seasonal pattern of seedling emergence was well explained by the dormancy/germination physiology revealed in laboratory germination tests. The seeds were demonstrated to have a strict light requirement even after experiencing moist chilling, which might facilitate the incorporation of the seeds into the soil seed bank. Despite sufficient seed production, the seedlings emerging were far less at the grassy site than the moor site, but the number of seedlings was significantly dependent on the seed rain within previous season and on the litter cover of the microsite in both sites. Therefore, the spatiotemporal patterns of seedling emergence in the habitats could be well explained by the spatiotemporal patterns of seed rain and safe-sites for germination.     

Pollen flow in a population of Primula vulgaris Huds.

A British population of Primula vulgaris was visited four times between 1971 and 1976 for study of the nature and functioning of distyly. The stainability and production of pollen from pins exceeded those of thrums. About 20% of pin pollen and 48% of thrum pollen was removed from anthers by insect visitors. Pins and thrums were present in a 1:1 ratio in 1971 but pins outnumbered thrums in 1976. Thrums produced more seeds per flower than pins though the number of ovules produced by each was similar. Two methods for collecting stigmas from open flowers and analyzing them for pollen loans produced somewhat different results. For pin stigmas, the pollen load consisted of 2–23% thrum pollen; for thrum stigmas, the pollen load consisted of 0–71% pin pollen with most stigmas having less than 50% pin pollen. In general, intermorph pollen flow is less than would be expected if pollen flow were random. It is probable that most intramorph pollen on stigmas is a result of self- or geitonogamous pollination. The extensive literature concerning the natural pollinators of the primrose is reviewed. Although Darwin's hypothesis concerning the functional significance of distyly in promoting intermorph pollination was never quantified, the pollen flow patterns observed in P. vulgaris are unexpectedly deviant and are similar to those patterns observed in several unrelated heterostylous species in other plant families.     

Gene flow and inbreeding depression inferred from fine-scale genetic structure in an endangered heterostylous perennial, Primula sieboldii

We estimated the gene dispersal distance and the magnitude of inbreeding depression from the fine-scale genetic structure in the endangered heterostylous perennial Primula sieboldii. We indirectly estimated the neighbourhood size (Nb) and the standard deviation of gene dispersal distance (sigma(g)) from the detected genetic structure by using 10 microsatellite markers. We also estimated the fitness reduction in mating among neighbouring individuals caused by biparental inbreeding according to the genetic structure. We found clear fine-scale genetic structure (a significantly positive kinship coefficient within 42.3 m), and the indirect estimates of sigma(g) and Nb were 15.7 m and 50.9, respectively. These indirect estimates were similar to the direct estimates (18.4 m and 44.0). The slightly larger indirect estimate of Nb may reflect that inbreeding depression and genetic structure or rare long-distance dispersal that were overlooked in the direct estimate have elongated the long-term average of gene dispersal distance. P. sieboldii is also likely to suffer about 19% fitness reduction in progenies from mating among individuals 5 m apart. Our results suggest that biparental inbreeding and genetic structure can affect the range of gene dispersal and seed reproductive success in P. sieboldii.     

安徽特有植物安徽羽叶报春的繁殖生物学研究

本文分别从物候、繁育结构和传粉等方面研究了国家三级保护植物、安徽特有种--安徽羽叶报春(Primula merrilliana)的繁殖生物学特征。研究结果表明: (1) 安徽羽叶报春是典型的形态和功能意义上的花柱二型的二年生植物, 其始苗期为9月, 一直持续到第二年6月底或7月初死亡, 各居群长柱花植株比短柱花植株开花略早3–5 d; (2) 安徽羽叶报春的散孔型花粉显示其在报春花属中有重要的系统意义和进化意义。同时, 短柱花花粉量比长柱花少, 但其花粉直径是后者的1.78倍左右; (3) 长花柱的雌蕊长度是短花柱的1.64倍, 而且其柱头上的乳头状突起比短花柱上的长而稀; (4) 3个研究居群的P/O比都不相同, 我们发现花粉量比胚珠数量有更大的变异, 这可能与生境有关; (5) 安徽羽叶报春为异花授粉植物, 蓟马属(Thrips)昆虫为其重要的传粉者, 其同型花授粉可育性远比异型花授粉的高; (6) 其长、短柱型种子没有明显的形态差异, 多属不等边七面体, 少为其他多面体。据研究, 在小居群中两种花柱类型植株的比例失衡, 生境的破坏和伴生种的消失可能是导致安徽羽叶报春濒危的重要原因。