ORIENTATION AND LOCUS OF TROPIC PHOTORECEPTOR MOLECULES IN SPORES OF BOTRYTIS AND OSMUNDA

Study of the tropic responses of Botrytis cinerea and Osmunda cinnamomea spores to blue light shows the photoreceptor molecules to be highly dichroic and oriented: in Botrytis their axes of maximum absorption lie perpendicular to the nearby cell surface; in Osmunda, parallel. The chief evidence lies in a comparison of their responses to plane polarized light—both germinate parallel to the vibration planes (defined by the axis of vibration of the electric vector and the axis of light propagation)—with those to partial illumination with unpolarized light: Botrytis grows from its brighter part; Osmunda, from its darker. The degree of orientation produced by polarized light corresponds, at high intensities, to that produced by the imposition of such large (about 100 per cent) intensity differences across a cell as to preclude all alternatives to oriented dichroic receptors. The photoreceptors of the Botrytis spore lie within the cell wall's inner half. The chief evidence lies in the component of its tropic responses to polarized light within the vibration plane: germination peaks about 10° off the vibration axis. This deviation arises from focusing which is effective only in the wall's inner half. At high intensities, anomalies appear in Botrytis which are interpreted as "centering," i.e., a tendency toward growth from the center of two or more equally illuminated points of a cell rather than from one of them.     

An acetylenic epoxide and a ferulate from Coreopsis longula

The aerial parts of Coreopsis longula gave, in addition to known compounds, a new acetylenic epoxide, hepta-deca-1,9E,15E-trien-11,13-diyn-7,8-epoxide, while the roots afforded a new ferulate, coniferyl ferulate.     

Guaianolide α-arabinopyranosides from Helenium amarum

The aerial parts of Helenium amarum afforded, in addition to compounds reported previously, several known sesquiterpene lactones as well as some new ones, two pseudoguaianolides and a complex mixture of guaianolide α-arabinopyranosides, which differed in the position of the double bond, the configuration at C-8 and the position of an acetate group in the sugar moiety. Furthermore seco-caryophyllenes and phenylpropane derivatives were isolated. The structures were elucidated by spectroscopic methods and few chemical transformations.     

Bisabolene derivatives and acetylenic compounds from peruvian Coreopsis species

The investigation of three Peruvian Coreopsis species afforded, in addition to compounds isolated previously from this genus, two new tetraynenes and five sesquiterpenes all related to perezone, including a tricyclic ketone with a cedrane skeleton closely related to pipitzol. The structure were elucidated by spectroscopic methods.     

Further cadinene derivatives from Heterotheca latifolia

A reinvestigation of the aerial parts of Heterotheca latifolia afforded four new cadinene derivatives.     

A rearranged eudesmane and further verbesindiol derivatives from Verbesina eggersii

A reinvestigation of Verbesina eggersii gave in addition to compounds isolated previously two further verbesindiol derivatives, a rearranged eudesmane and a benzofuran related to tremetone.     

A global distribution of biodiversity inferred from climatic constraints: results from a process‐based modelling study

We investigated the connection between plant species diversity and climate by using a process‐based, generic plant model. Different ‘species' were simulated by different values for certain growth‐related model parameters. Subsequently, a wide range of values were tested in the framework of a ‘Monte Carlo' simulation for success; that is, the capability of each plant with these parameter combinations to reproduce itself during its lifetime. The range of successful parameter combinations approximated species diversity. This method was applied to a global grid, using daily atmospheric forcing from a climate model simulation. The computed distribution of plant ‘species' diversity compares very well with the observed, global‐scale distribution of species diversity, reproducing the majority of ‘hot spot' areas of biodiversity. A sensitivity analysis revealed that the predicted pattern is very robust against changes of fixed model parameters. Analysis of the climatic forcing and of two additional sensitivity simulations demonstrated that the crucial factor leading to this distribution of diversity is the early stage of a plant's life when water availability is highly coupled to the variability in precipitation because in this stage root‐zone storage of water is small. We used cluster analysis in order to extract common sets of species parameters, mean plant properties and biogeographic regions (biomes) from the model output. The successful ‘species' cannot be grouped into typical parameter combinations, which define the plant's functioning. However, the mean simulated plant properties, such as lifetime and growth, can be grouped into a few characteristic plant ‘prototypes', ranging from short‐lived, fast growing plants, similar to grasses, to long‐lived, slow growing plants, similar to trees. The classification of regions with respect to similar combinations of successful ‘species' yields a distribution of biomes similar to the observed distribution. Each biome has typical levels of climatic constraints, expressed for instance by the number of ‘rainy days' and ‘warm days'. The less the number of days favourable for growth, the greater the level of constraints and the less the ‘species' diversity. These results suggest that climate as a fundamental constraint can explain much of the global scale, observed distribution of plant species diversity.     

Post‐Hurricane Regeneration of Pioneer Plant Species in South Florida Subtropical Hardwood Hammocks1

After Hurricane Andrew crossed southern Florida (U.S.A.) on 24 August 1992, native and exotic pioneer species in subtropical hardwood forests (hammocks) regenerated from seed banks. Regeneration occurred in hammocks of metropolitan Dade County and the Long Pine Key region of Everglades National Park. The density of the native pioneer Trema micrantha was significantly higher in hammocks of Long Pine Key than in those of metropolitan Dade County. In contrast, the basal area of the exotic pioneer Carica papaya was greater in Dade County hammocks than Long Pine Key hammocks. Although T. micrantha tended to be restricted to areas of soil disturbance (tip‐up pits) formed by trees uprooted during Hurricane Andrew, especially in Long Pine Key, C. papaya was located throughout hammocks. These results suggest differences in the regeneration niches in which the native T. micrantha required more specific disruptions (i.e., both canopy and soil) than C. papaya (only removal of canopy) for establishment. A broad regeneration niche could in part account for the capability of an exotic species with a dormant seed bank to invade native subtropical forests following natural large‐scale disturbances.     

Sequential Reductive Dechlorination of meta-Chlorinated Polychlorinated Biphenyl Congeners in Sediment Microcosms by Two Different Chloroflexi Phylotypes

Three species within a deeply branching cluster of the Chloroflexi are the only microorganisms currently known to anaerobically transform polychlorinated biphenyls (PCBs) by the mechanism of reductive dechlorination. A selective PCR primer set was designed that amplifies the 16S rRNA genes of a monophyletic group within the Chloroflexi including Dehalococcoides spp. and the o-17/DF-1 group. Assays for both qualitative and quantitative analyses by denaturing gradient gel electrophoresis and most probable number-PCR, respectively, were developed to assess sediment microcosm enrichments that reductively dechlorinated PCBs 101 (2,2′,4,5,5′-CB) and 132 (2,2′,3,3′,4,6′-CB). PCB 101 was reductively dechlorinated at the para-flanked meta position to PCB 49 (2,2′,4,5′-CB) by phylotype DEH10, which belongs to the Dehalococcoides group. This same species reductively dechlorinated the para- and ortho-flanked meta-chlorine of PCB 132 to PCB 91 (2,2′,3′,4,6′-CB). However, another phylotype designated SF1, which is more closely related to the o-17/DF-1 group, was responsible for the subsequent dechlorination of PCB 91 to PCB 51 (2,2′,4,6′-CB). Using the selective primer set, an increase in 16S rRNA gene copies was observed only with actively dechlorinating cultures, indicating that PCB-dechlorinating activities by both phylotype DEH10 and SF1 were linked to growth. The results suggest that individual species within the Chloroflexi exhibit a limited range of congener specificities and that a relatively diverse community of species within a deeply branching group of Chloroflexi with complementary congener specificities is likely required for the reductive dechlorination of different PCBs congeners in the environment.