The subject of phytochemistry, or plant chemistry, has developed in recent years as a distinct discipline, somewhere in between natural product organic chemistry and plant biochemistry and is closely related to both. It is concerned with the enormous variety of organic substances that are elaborated and accumulated by plants and deals with the chemical structures of these substances, their biosynthesis, turnover and metabolism, their natural distribution and their biological function.

Methods of Plant Analysis

The synopsis of my classification of the Angiospermae that was published in Aliso (Thorne, 1968) has been much modified in recent years. Increased knowledge about many of the families has resulted in a realignment of some of them and reorganization or deletion of some of the higher categories. I have published elsewhere some explanation of my classificatory modus operandi (Thorne, 1958, 1963, 1974c) and some elucidation of certain of my major groupings, such as the Araliaceae, Annoniflorae, Urti-cales, Juglandineae, Hamamelidales, Sapindineae, and Pittosporales (Thorne 1973, 1974a,b,c, 1975). I have other manuscripts near completion and have been preparing an illustrated book with full exposition of my classification of the angiosperms. Nonetheless, it seems desirable at this time to present an updated version of my synopsis of the Angiospermae with at least a brief review of my philosophy of classification, my interpretation of the probable origins of the angiosperms and their most primitive characteristics, and some elucidation of realignments that deviate considerably from other recent classifications.

A Phylogenetic Classification of the Angiospermae

Palaeoclimates in central and south America since 18,000 BP based on pollen and lake-level records

A paleoclimatic chronology for southern South America is suggested by comparison of dated pollen records from Argentina (lat 32° to 34°S, 41°S and 51° to 54°S). The paleoenvironmental phases distinguished for the last 13,000 years are interpreted as paleoclimatic phases and explained as latitudinal shifts of atmospheric circulation anomalies by using the correlation of modern precipitation patterns with atmospheric circulation anomaly patterns over Argentina and Chile. The lateglacial type environment is characterized at all sites in the high southern latitudes by pollen assemblages of grasses, composites, sedges, and heath, suggesting climates as cold and wet as the modern Magellanic Moorland uniformly throughout Tierra del Fuego and southern Patagonia. At latitude 41°S the lateglacial pollen assemblages are dominated by rainforest types west of the Andes, suggesting cold and wet conditions, while east of the Andes grasses and herb pollen dominated the assemblages, suggesting conditions colder a...

Late and postglacial vegetational and paleoclimatic changes in subantarctic, temperate and arid environments in Argentina

Summary

1
In some ecosystems there is a positive feedback between forage quality and grazing intensity. This involves three components of plant tolerance to grazing: functional traits, herbivore selectivity and response to grazing. We analysed the relationships between these components at species and community levels in Patagonian steppe grasslands.

2
We measured plant functional traits [height, specific leaf area (SLA) and foliar toughness] and estimated sheep selectivity and grazing response indices for 35 plant species. Sheep selectivity indices were obtained from microhistological and species’ availability data, and grazing response indices from species’ abundances in sites with contrasting grazing intensities. We performed correlations and multiple regressions among the three types of variables across the pool of 35 species.

3
To analyse data at the community level, we computed weighted averages of traits and sheep selectivity indices for 34 floristic samples taken from each side of 17 fence lines with contrasting grazing intensities. Correlations between mean trait values and sheep selectivity across the 34 samples, and paired comparisons of those variables between sides of the fences, were performed.

4
Taller plants had leaves with lower SLA and/or higher toughness. Short species of intermediate toughness were selected more often by sheep, while SLA was not related to sheep selectivity. Short species with high SLA increased with grazing, while toughness and sheep selectivity were unrelated to grazing response.

5
At the community level, short swards with high average SLA had high selectivity indices and were more abundant on the most intensively grazed sides of fence lines. Leaf toughness was unrelated to other traits or to sheep selectivity, and showed no significant response to grazing.

6
Synthesis and applications. Intensive grazing can increase the forage value of grasslands by the creation of lawns dominated by tolerant species. However, results from this study showed that some plant species that were avoided by grazers also increased, indicating a potential risk of a shift in composition of grazing lawns towards states of low forage value. This suggests that periodic resting of lawns could be a good management strategy to favour palatable species, thereby minimizing the risk of undesirable shifts in the overall species composition.

https://besjournals.onlinelibrary.wiley.com/doi/epdf/10.1111/j.1365-2664.2004.00978.x

David M. Moore

Papers

Post-glacial vegetation in the South Patagonian territory of the giant ground sloth, Mylodon

Morphological and palynological studies in Phlomis L., Eremostachys Bunge and Paraphlomis Prain (Labiatae)

Chemotaxonomy, variation and geographical distribution of the Empetraceae

The taxonomic significance of leaf micromorphology in the genus Eugenia L. (Myrtaceae)

Late Pleistocene and Holocene landscape evolution and environmental change in the Lake Sulivan area, Falkland Islands, South Atlantic.