Why do so many petals have conical epidermal cells?

Background

The conical epidermal cells found on the petals of most Angiosperm species are so widespread that they have been used as markers of petal identity, but their function has only been analysed in recent years. This review brings together diverse data on the role of these cells in pollination biology.

Scope

The published effects of conical cells on petal colour, petal reflexing, scent production, petal wettability and pollinator grip on the flower surface are considered. Of these factors, pollinator grip has been shown to be of most significance in the well-studied Antirrhinum majus/bumble-bee system. Published data on the relationship between epidermal cell morphology and floral temperature were limited, so an analysis of the effects of cell shape on floral temperature in Antirrhinum is presented here. Statistically significant warming by conical cells was not detected, although insignificant trends towards faster warming at dawn were found, and it was also found that flat-celled flowers could be warmer on warm days. The warming observed is less significant than that achieved by varying pigment content. However, the possibility that the effect of conical cells on temperature might be biologically significant in certain specific instances such as marginal habitats or weather conditions cannot be ruled out.

Conclusions

Conical epidermal cells can influence a diverse set of petal properties. The fitness benefits they provide to plants are likely to vary with pollinator and habitat, and models are now required to understand how these different factors interact.     

Some evolutionary trends in caligid copepods

The genera Caligus and Lepeophtheirus can be used to illustrate some evolutionary trends. The most striking example of these trends is a gradual reduction of the fourth thoracopod, now largely functionless. All stages of this reduction can be found in Caligidae. Other, apparently correlated, changes are also present. For example, reduction in the armature of the first thoracopod occurs mainly among species in which the fourth exopod has become two-segmented, though still retaining the seta associated with the original three-segmented structure.     

红木花色素的微波提取与特性研究

对红木花色素的理化性质及微波提取方法进行了研究.结果表明红木红色素可能属醇溶性黄酮类,其耐酸、耐氧化性很好,耐光氧化和耐热处理性极佳,而耐碱性和耐Fe2+、Fe3+、Cu2+、Pb2+盐离子性较差.微波提取工艺研究表明微波提取时间在设定的提取工艺三因素中居主要影响,其次是乙醇用量和浓度;只需一次微波处理便可将花瓣中红色素提完.进一步研究该色素的光照和热处理降解特性,结果表明在设定的各处理温度下,该红色素降解均很缓慢,但其降解速度随设定处理温度升高呈加快趋势.在90℃～100℃的热处理下,其降解速度与热处理时间有A(最大光吸收)～t及lnA～t线性相关关系;当低于90℃时,仅80℃的设定热处理下有lnA～t直线相关,而A～t间都不呈线性关系.连续光照处理中,随处理时间延长其降解幅度极小,降解速度与光照时间不存在A～t及lnA～t线性相关.     

Programmed Cell Death in Relation to Petal Senescence in Ornamental Plants

Cell death is a common event in all types of plant organisms. Understanding the phenomenon of programmed cell death (PCD) is an important area of research for plant scientists because of its role in senescence and the post-harvest quality of ornamentals, fruits, and vegetables. In the present paper, PCD in relation to petal senescence in ornamental plants is reviewed. Morphological, anatomical, physiological,and biochemical changes that are related to PCD in petals, such as water content, sink-source relationships,hormones, genes, and signal transduction pathways, are discussed, Several approaches to improving the quality of post-harvest ornamentals are reviewed and some prospects for future research are given.     

昆虫肢体再生的研究进展

文中就发生断肢再生的昆虫类群、出现虫态、再生的类型、再生能力、影响再生的因素、再生的生物学意义几个方面进行了综述 ,特别对猎蝽科昆虫的肢体再生有关方面做了介绍     

Towards an organismic concept of land plants: The marginal blastozone and the development of the vegetation body of selected frondose gametophytes of liverworts and ferns

An organismic concept of land plants is outlined, which is based on a synthesis of plant morphology and plant anatomy. The entire plant, the living unity, is conceived as the organism being subdivided into cells, which cannot be interpreted as organisms themselves in the sense of elementary organisms. The evolution of land plant tissue systems is discussed in the introductive chapter.To test the proposed concept, some frondose plants were selected from liverworts (Pellia epiphylla, Metzgeria furcata, Pallavicinia lyallii) and comparable fern gametophytes (Dryopteris filix mas, Vittaria lineata, Stenochlaena tenuifolia) and studied with respect to their organization and the principles of development. They all have an archetypic, two-dimensional, open construction, which is described as the repens-type of plant construction. Primary form growth occurs in the marginal blastozone, which controls cell wall integration. One of the most significant processes of form generation is blastozone fractionation. The tissues leaving the blastozone differentiate during extension growth and maturation of the vegetation body. While the plant grows continuously in the blastozone, it decays steadily in the necrozone.The implications of the two-dimensional repens-type are discussed. It appears as a perfect plant construction, fit to start plant evolution on the land surface. Growing upwards into the atmosphere, the repens-type is obscured. But is reappears in all groups of higher land plants. This demonstrates the existence of evolutionary cycles in plants. It is argued that mutation and selection do not suffice to understand cyclical evolutionary patterns. The influence of organismic construction seems to predetermine evolution because of the limited options to change an appropriately functioning construction. Via construction analysis evolutionary options can be detected and thus, evolution becomes predictable to some extent. Instead of being object of mutation and selection, living organisms should be conceived as subjects in evolution (Weingarten 1993).Dedicated to my admired teacher Professor DrWilhelm Troll on the occasion of his 100^th birthday, 3rd November, 1997.