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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. University of California Press and American Institute of Biological Sciences are collaborating with JSTOR to digitize, preserve and extend access to BioScience. Morphological and anatomical features of plant leaves are commonly associated with metabolic type (e.g., Kranz anatomy of C4 species), amount of sun exposure (e.g., sun and shade leaves), or water stress (e.g., xeromorphism). However, although the primary function of the leaf is to absorb and process sunlight and carbon dioxide for photosynthesis, few structural features of leaves have been related mechanistically to these tasks. For example, it has been known for over a century that the internal anatomy of leaves is characterized by different cell layers (e.g., the palisade and spongy mesophyll) and that stomatal pores can be located on one or both sides of a leaf. Yet, only recently has any functional relationship between leaf form and photosynthetic performance been suggested.A variety of ecological studies have correlated numerous leaf structural parameters with photosynthetic performance (e.g., Abrams and Kubiske 1990, 1994, Hinckley et al. 1989, William K. Smith (e-mail: wksmith@uwyo. edu) and Thomas C. Vogelmann (e-mail: tvogel@uwyo.edu) are professors in the

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Australian species germinate under the combination of environmental conditions where the potential for survival is enhanced. Most species also have dormancy mechanisms that prevent all seeds from germinating in any particular rainfall event. Immaturity of the embryo prevents some species from germinating until environmental parameters change to more favourable conditions. Seed-coat inhibitors may also delay germination, with some seed requiring ingestion and dispersal by animals or a series of rainfall cycles to facilitate germination. Adaptations to fire include germination mechanisms facilitated by impervious seed coats, seed-coat inhibitors and biochemical sensing of water-soluble components of smoke and the high soil nitrate levels found following the burning of vegetation. Germination is generally limited under saline soil conditions until rainfall dilutes concentrations to near-zero water potentials. Australian species tend to germinate under temperatures that approximate the rainfall season in their native habitat. Light sensing by Australian species ensures germination takes place only near the surface for some species or only under complete burial conditions in others. More recent research has emphasised the interaction of multiple and sequential cues to relieve dormancy and initiate germination. Knowledge of germination mechanisms provides a basis for better land management, enriched conservation, improved rehabilitation and advanced horticulture, forestry and farming practices.

Abstract. Species native to the southwest of Western Australia, representing a range of plant families, life‐history strategies, fire‐response syndromes, seed‐store types and seed weights, were tested for viability using tetrazolium chloride and for germination under combinations of constant temperatures of 15 °C or 23 °C, constantly dark or 12 h diurnal whitelight conditions, and with, or without, addition of gibberellic acid (GA3, 50 mg/l). Species previously known to require a heat‐shock treatment to overcome dormancy due to an impervious testa were pre‐treated prior to imposition of temperature, light and GA3 conditions. The test environmental conditions related to differences between winter and autumn temperatures and surface and buried seed germination positions of post‐fire habitats. The viability of the selection of native Western Australian species ranged from 0 to 100 %, averaging 71 %. For all taxa, no combination of temperature, light and gibberellic acid treatment induced all viable seeds to germinate. The greatest percentage germination achieved in any combination of treatments averaged 71 % of all viable seeds for all species. Larger seeds (> 10 mg seed weight) tended to have greater viability percentages, but no overall patterns of viability or germinability were attributable to seed storage syndrome, strategy of fire recovery response or life‐form type. Germination of most of the dominant tree representatives (Eucalyptus calophylla, E. diversicolor, E. erythrocorys, E. gomphocephala, and E. patens) was indifferent to the trial conditions of temperature, light and GA3. However, Eucalyptus marginata showed reduced germination in the light, which was overcome with GA3. GA3 also overcame the inhibition resulting from exposure to light in some understorey species (e.g. Allocasuarina campestris, Regelia ciliata, Xanthorrhoea gracilis and X. preissii). Germination of many hard‐seeded, understorey shrub and herbaceous perennial species, especially those with small (< 10 mg) seeds (e.g. Bossiaea ornata, B. aquifolium and Acacia drummondii ssp. candolleana) was greater at the lower trial temperature and in the dark. Some large (> 10 mg) seeded, understorey species (e.g. Acacia extensa, Kennedia coccinea, K. prostrata, Hovea trisperma and Hardenbergia comptoniana) germinated in high percentages in both temperatures, but maximum germination percentages still tended to be at 15 °C. Large‐seeded species were less sensitive to exposure to light compared to the smaller seeded species. The largest seeded species tested, Paraserianthes lophantha, germinated best in the warmer incubation temperature and in the light. The ecological significance of the tests would be that species which have seed dormancy mechanisms capable of delaying germination until the cool temperature, winter rainy period of this mediterranean‐type climate would be more likely to survive than if germination followed summer rain showers or the first, intermittent rains of autumn. Burial of seeds becomes more important if germination occurs when...

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The effects of herbicide management of genetically modified herbicide-tolerant (GMHT) beet, maize and spring oilseed rape on the abundance and diversity of soil-surface-active invertebrates were assessed. Most effects did not differ between years, environmental zones or initial seedbanks or between sugar and fodder beet. This suggests that the results may be treated as generally applicable to agricultural situations throughout the UK for these crops. The direction of the effects was evenly balanced between increases and decreases in counts in the GMHT compared with the conventional treatment. Most effects involving a greater capture in the GMHT treatments occurred in maize, whereas most effects involving a smaller capture were in beet and spring oilseed rape. Differences between GMHT and conventional crop herbicide management had a significant effect on the capture of most surface-active invertebrate species and higher taxa tested in at least one crop, and these differences reflected the phenology and ecology of the invertebrates. Counts of carabids that feed on weed seeds were smaller in GMHT beet and spring oilseed rape but larger in GMHT maize. In contrast, collembolan detritivore counts were significantly larger under GMHT crop management.