山西煤核中辉木植物二个新种的研究--山西枝蕨和山西始莲座蕨

辉木植物是莲座蕨目在晚古生代最重要的成员，广泛分布于当时处于热带－亚热带气候条件下的晚石炭世－二叠纪欧美植物区和华夏植物区。目前欧美植物区晚石炭世的辉木植物已经研究得非常深入和全面，但相对来说二叠纪的辉木植物的研究，尤其是关于其非茎器官的研究要薄弱得多。中国山西太原西山煤田早二叠世早期太原组7号煤层煤核中产有丰富的辉木植物各种器官化石，这就为深入了解二叠纪辉木植物的形态、解剖以及辉木植物的系统发育与演化提供了重要的化石材料。本论文利用国际上研究煤核时广泛采用的揭膜法，深入研究了山西煤核中2种分散保存的辉木植物器官：羽轴－山西枝蕨（新种）和生殖羽片－山西始莲座蕨（新种）。由于目前尚无有关二叠纪具解剖构造的辉木植物羽轴的详细研究的报道，因此，山西枝蕨（新种）是国内外目前为止第一种研究得最详细的二叠纪具解剖构造的辉木植物羽轴，它与欧美植物区枝蕨属已有的几个种（均为晚石炭世）的主要区别在于：前者为背腹扁状，后者则为两侧扁状;前者具较发育的鳞片，后者一般没有;前者的表皮下方有一条含有较大的单宁质细胞的薄壁组织带，后者没有;前者的内维管束呈“C”形，较大，位于正中央，后者的内维管束一般呈“W”形，较小，位于一侧。山西始莲座蕨（新种）是目前为止国内第一种（世界第二种）详细研究的二叠纪具解剖构造的两侧对称形的辉木植物聚合囊，同时也是目前国内发现的时代最早的华夏植物区两侧对称形的莲座蕨目聚合囊（包括印痕－压型化石和具解剖构造的矿化化石），它与欧美植物区始莲座蕨属已有的2个种（均为晚石炭世）的主要区别在于：前者的聚合囊囊托维管化，后者的囊托中无维管组织存在;前者的孢子囊侧壁细胞在近顶端呈明显的径向伸长状，后者的孢子囊侧壁细胞的形状和大小在孢子囊的上下没有很明显的变化;前者的孢子很小，数量多，纹饰简单，后者的孢子大，数量少，纹饰复杂。总的来说，本文所研究的二个新种与欧美植物区同属其它种之间的区别要大于后者彼此之间的区别，这可能是由于处于不同的植物地理区，经过长期地理隔绝和平行演化的结果。本研究成果不仅丰富了我们对二叠纪辉木植物非茎器官解剖构造的认识，而且对今后开展华夏植物区二叠纪辉木植物的分类、系统发育和演化以及整体植物的研究，都具有重要的作用和意义。

Sexual selection in a tropical fruit fly : role of a plant derived chemical in mate choice

The specific mechanisms by which selective pressures affect individuals are often difficult to resolve. In tephritid fruit flies, males respond strongly and positively to certain plant derived chemicals. Sexual selection by female choice has been hypothesized as the mechanism driving this behaviour in certain species, as females preferentially mate with males that have fed on these chemicals. This hypothesis is, to date, based on studies of only very few species and its generality is largely untested. We tested the hypothesis on different spatial scales (small cage and seminatural field-cage) using the monophagous fruit fly, Bactrocera cacuminata. This species is known to respond to methyl eugenol (ME), a chemical found in many plant species and one upon which previous studies have focused. Contrary to expectation, no obvious female choice was apparent in selecting ME-fed males over unfed males as measured by the number of matings achieved over time, copulation duration, or time of copulation initiation. However, the number of matings achieved by ME-fed males was significantly greater than unfed males 16 and 32 days after exposure to ME in small cages (but not in a field-cage). This delayed advantage suggests that ME may not influence the pheromone system of B. cacuminata but may have other consequences, acting on some other fitness consequence (e.g., enhancement of physiology or survival) of male exposure to these chemicals. We discuss the ecological and evolutionary implications of our findings to explore alternate hypotheses to explain the patterns of response of dacine fruit flies to specific plant-derived chemicals.

Influence of host plant structure and microclimate on the abundance and behaviour of Tephritid fly

Microclimate and host plant architecture significantly influence the abundance and behavior of insects. However, most research in this field has focused at the invertebrate assemblage level, with few studies at the single-species level. Using wild Solanum mauritianum plants, we evaluated the influence of plant structure (number of leaves and branches and height of plant) and microclimate (temperature, relative humidity, and light intensity) on the abundance and behavior of a single insect species, the monophagous tephritid fly Bactrocera cacuminata (Hering). Abundance and oviposition behavior were signficantly influenced by the host structure (density of foliage) and associated microclimate. Resting behavior of both sexes was influenced positively by foliage density, while temperature positively influenced the numbers of resting females. The number of ovipositing females was positively influenced by temperature and negatively by relative humidity. Feeding behavior was rare on the host plant, as was mating. The relatively low explanatory power of the measured variables suggests that, in addition to host plant architecture and associated microclimate, other cues (e.g., olfactory or visual) could affect visitation and use of the larval host plant by adult fruit flies. For 12 plants observed at dusk (the time of fly mating), mating pairs were observed on only one tree. Principal component analyses of the plant and microclimate factors associated with these plants revealed that the plant on which mating was observed had specific characteristics (intermediate light intensity, greater height, and greater quantity of fruit) that may have influenced its selection as a mating site.

Somatic embryogenesis, organogenesis and plant regeneration in taro (Colocasia esculenta var. esculenta)

Callus was initiated in three different ‘‘esculenta’’ taro cultivars by culturing corm slices in the dark on half-strength MS medium supplemented with 2.0 mg/l 2,4- dichlorophenoxyacetic acid (2,4-D) for 20 days followed by subculture of all corm slices to half-strength MS medium containing 1.0 mg/l thidiazuron (TDZ). Depending on the cultivar, 20–30% of corm slices produced compact, yellow, nodular callus on media containing TDZ. Histological studies revealed the presence of typical embryogenic cells which were small, isodiametric with dense cytoplasms. Somatic embryos formed when callus was transferred to hormone-free medium and *72% of the embryos germinated into plantlets on this medium. Simultaneous formation of roots and shoots during germination, and the presence of shoot and root poles revealed by histology, confirmed that these structures were true somatic embryos. Plants derived from somatic embryos appeared phenotypically normal following 2 months growth in a glasshouse. This method is a significant advance on those previously reported for the esculenta cultivars of taro due to its efficiency and reproducibility.

Initiation of embryogenic cell suspensions of taro (Colocasia esculenta var. esculenta) and plant regeneration

Embryogenic callus was initiated by culturing in vitro taro corm slices on agar-solidified half-strength MS medium containing 2.0 mg/L 2,4-dichlorophenoxyacetic acid (2,4-D) for 20 days followed by transfer to 1.0 mg/L thidiazuron (TDZ). Callus was subsequently proliferated on solid medium containing 1.0 mg/L TDZ, 0.5 mg/L 2,4- D and 800 mg/L glutamine before transfer to liquid medium containing the same components but with reduced glutamine (100 mg/L). After 3 months in liquid culture on an orbital shaker, cytoplasmically dense cell aggregates began to form. Somatic embryogenesis was induced by plating suspension cells onto solid media containing reduced levels of hormones (0.1 mg/L TDZ, 0.05 mg/L 2,4-D), high concentrations of sucrose (40–50 g/L) and biotin (1.0 mg/L). Embryo maturation and germination was then induced on media containing 0.05 mg/L benzyladenine (BA) and 0.1 mg/L indole-3-acetic acid (IAA). Histological studies of the developing embryos revealed the presence of typical shoot and root poles suggesting that these structures were true somatic embryos. The rate of somatic embryos formation was 500–3,000 per mL settledcell volume while approximately 60% of the embryos regenerated into plants.

A cost-based optimization of a fiberboard pressing plant using Monte-Carlo simulation (a reliability program)

In this research the reliability and availability of fiberboard pressing plant is assessed and a cost-based optimization of the system using the Monte- Carlo simulation method is performed. The woodchip and pulp or engineered wood industry in Australia and around the world is a lucrative industry. One such industry is hardboard. The pressing system is the main system, as it converts the wet pulp to fiberboard. The assessment identified the pressing system has the highest downtime throughout the plant plus it represents the bottleneck in the process. A survey in the late nineties revealed there are over one thousand plants around the world, with the pressing system being a common system among these plants. No work has been done to assess or estimate the reliability of such a pressing system; therefore this assessment can be used for assessing any plant of this type.