D. F. Cutler

Classification and terminology of plant epicuticular waxes

Plant cuticles are covered by waxes with considerable ultrastructural and chemical diversity. Many of them are of great systematic significance. Waxes are an essential structural element of the surface and of fundamental functional and ecological importance for the interaction between plants and their environment. An extensive literature has been published since the introduction of scanning electron microscopy (SEM). Hitherto, the area has lacked a complete classification and terminology necessary as a standard for comparative descriptions. A refined classification and terminology of epicuticular waxes is therefore proposed based on high-resolution SEM analysis of at least 13 000 species, representing all major groups of seed plants. In total 23 wax types are classified. Thin wax films appear to be ubiquitous, while thicker layers or crusts are rare. The most prominent structures are local wax projections, which most probably result from self-assembly of wax molecules. These projections are supposed to be mainly of a crystalline nature and are termed crystalloids here. Among these, platelets and tubules are the most prominent types, while platelets arranged in parallel rows and stomatal wax chimneys are the most striking orientation and aggregation patterns. In addition, a comprehensive overview on the correlation between wax ultrastructure and chemical composition is given.

THE SECRETORY TISSUE OF ALOES AND THEIR ALLIES

ABSTRACT The presence of thin-walled parenchymatous cells in the inner bundle sheath of species of the liliaceous genera Aloe, Chamaealoe, Astroloba, Lomatophyllum, Gasteria, Haworthia, Asphodeline, Asphodelus, Bulbine, Eremurus and Trachyandra was observed and described. Some species, however, have lignified sclerenchymatous cells in this position and this is general in Kniphofia. Cells in this region produce a secretion in the form of a copious exudate in many species of Aloe, or much sparser contents in the case of related genera. The leaves of most species contain small amounts of anthraquinones, while the related anthrone-C-glycosides accumulate in others. A wide range of other phenolic substances occurs, recognized as distinct zones on thin layer chromatograms, but mainly consisting of unidentified compounds. It is not certain if synthesis occurs in the thin-walled bundle sheath cells or if these have only a storage function. Another layer of rather smaller parenchymatous cells in the outer bundle s...

Anatomia e densidade básica da madeira de Caesalpinia pyramidalis Tul. (Fabaceae), espécie endêmica da caatinga do Nordeste do Brasil

This work aimed to study the anatomy and basic density of Caesalpinia pyramidalis wood, used by local populations in the municipalities of Serra Talhada and Sertânia (Pernambuco), to assess the percentage of wood elements in the trunk and branches in both localities, and in the tree itself, in order to establish total wood potential for energy production. Samples of the trunk (dbh) and of branches from six trees of the species were collected in 2002. Sample analysis followed the usual methods of wood anatomy studies. Based on the anatomical parameters of the trunk and the high basic density (>0.84 g/cm3), we conclude that Caesalpinia pyramidalis wood contains an enormous amount of cellulose and lignin. Due to these features, this species showed good perspectives for the production of alcohol and charcoal. The trunk and branches can be used for fuel even at the immature stage because of high fiber concentration, low vessel concentration and low amount of parenchyma at this stage in both municipalities.

The effects of different environments on diameter growth increments of Colophospermum mopane and Combretum apiculatum

Abstract Radial cross-sections of 46 wood samples of Colophospermum mopane and Combretum apiculatum trees from four sites were examined for growth increments. Increments were small and sometimes difficult to discern, so measurements were made to the nearest 0.1 mm. The results suggest that rainfall is of little significance in explaining variability in ring size. Combretum apiculatum consistently produced wider rings than Colophospermum mopane (an average of 1.1 mm vs. 0.9 mm, respectively). Significant regressions of total green woody biomass on tree size were found for both species. Significant interactions of species × tree size suggested separate regression equations for each species across sites, whereas the significant site × species interactions would signify different intercepts, which are a measure of site quality. Maximum increments are obtainable on potentially fertile soils but reasonable increments were also achievable on lithosols and halomorphic soils for Combretum apiculatum and Colophospermum mopane, respectively, as these species are well adapted to such abiotic conditions.

CAN WE LIVE WITH TREES IN OUR TOWNS AND CITIES

Summary There is increasing concern that data on tree root spread in ‘Tree Roots and Buildings’ (CUTLER and RICHARDSON, 1989) are open to misinterpretation by insurers, home owners and arboriculturists. Insurers have tended to use maximum root spread figures, which we believe to be statistically and biologically unsound. This paper briefly examines the evidence and interprets this to show that with sensible use of the available data, there should be little conflict between trees and buildings in urban areas.

Variações sazonais na sobrevivência e produção de biomassa de Caesalpinia pyramidalis Tul. após o corte raso e implicações para o manejo da espécie

A demanda de uso energetico da vegetacao da Caatinga tem gerado modificacoes nas paisagens e perda de diversidade biologica por insuficiencia de informacoes sobre o manejo das especies. Considerando o fato da estacionalidade climatica ser um fator de influencia na sobrevivencia, ritmo biologico, rebrota e produtividade das plantas, neste estudo objetivou-se avaliar a influencia da sazonalidade climatica sobre a sobrevivencia e a producao de biomassa de Caesalpinia pyramidalis Tul. (Caesalpiniaceae). Para tal, foram selecionados aleatoriamente 180 individuos de C. pyramidalis, sendo estes distribuidos em tres blocos de 1ha de caatinga (60 individuos por bloco). O delineamento experimental foi de blocos ao acaso com 6 tratamentos (sendo duas estacoes climaticas e tres anos consecutivos de avaliacao) para a avaliacao da sobrevivencia e com 4 tratamentos (duas estacoes climaticas e dois anos de medicao) para a avaliacao da biomassa aerea. As avaliacoes foram realizadas em duas estacoes: seca e chuvosa, sendo metade dos individuos de cada bloco (n = 30) submetidos a corte raso em cada uma das estacoes. Apos o corte, a quantificacao do peso fresco foi determinada em tres componentes previamente definidos como lenha, estaca e graveto. As plantas foram monitoradas por 3 anos, sendo a sobrevivencia anual registrada e a producao de biomassa da rebrota medida no ultimo ano. A sobrevivencia das plantas foi similar e elevada nos tres anos, independente da estacao climatica. As plantas recem cortadas apresentaram elevado percentual de lenha e as rebrotas apresentaram elevado percentual de graveto. O tamanho inicial das plantas nao esta relacionado a variacao do peso fresco da rebrota. O estudo mostra que, apesar de ocorrer regeneracao das plantas apos corte raso, o tempo de tres anos nao e suficiente para recuperacao da producao dos produtos madeireiros em C. pyramidalis, sendo necessario um tempo de repouso maior para um novo ciclo de corte, visando manter a producao da especie para atender a demanda energetica da populacao rural.

INTERACTIONS BETWEEN TREE ROOTS AND CONSTRUCTION WORK

Summary The roots of trees perform two major functions (i) anchorage and (ii) water extraction from the soil. In addition roots function as a storage system for starch, reserves of which may be used for flowering and fruiting. The indiscriminate nature of the process of mineral uptake in many tree species has a bearing on the possible harmful effect of soil contamination within the area of root spread during construction work. The effective functioning of roots is examined in the light of the authors tree root survey following the 1987 and 1990 storms. There is now a greater understanding of the extent of tree root systems, but there is still great scope for further detailed investigations. The possible direction of this research is examined and discussed in relation to root spread and different soil textures and the effect of structures on roots and of roots on structures. The provisions of BS 5837 1991 are examined and their adequacy discussed.

Leaf anatomy of the genusPsoralea sensu stricto(Psoraleeae, Papilionoideae, Leguminosae)☆

Abstract Leaf anatomy is described from 17 species of Psoralea sensu stricto which includes four species of the genus Hallia Thunberg. Species of the two genera share many characters including the presence of rod-shaped crystals, similar stipule structure and a possible continuum in secretory cavity anatomy ranging from a small and non-trabeculate to a large and trabeculate form. Hallia species are distinguished by the presence of large tannin cells in the bundle sheaths and a narrow length:width ratio of palisade cells. In the light of other floral evidence this is considered insufficient to separate the two genera, a view confirmed by cluster analysis. Thus, Salters proposal of 1939 for their amalgamation is supported. Leaf anatomy of herbaceous species is compared with that of seedlings of Psoralea sp. to assess the possibility that the herbaceous species may have arisen through neoteny from species that are trees or shrubs. Comparative venation studies between stipules and scale leaves suggest that the scale leaf form arose from pinnate-leaved ancestors by leaf reduction.