Floral structure, breeding system and fruit-set in the threatened sub-shrub Tetratheca juncea Smith (Tremandraceae)

Tetratheca juncea Smith (Tremandraceae) has undergone a range contraction of approx. 50 km in the last 100 years and is now listed as a vulnerable sub-shrub restricted to the central and north coast regions of New South Wales, Australia. There are approx. 250 populations in a 110 km north-south distribution and populations are usually small with fewer than 50 plants/clumps. The reproductive ecology of the species was studied to determine why seed-set is reportedly rare. Flowers are bisexual, odourless and nectarless. Flowers are presented dependentally and there are eight stamens recurved around the pistil. Anthers are poricidal, contain viable pollen and basally contain a deep-red tapetal fluid that is slightly oily. Thus flowers are presented for buzz pollinators, although none were observed at flowers during our study. The species was found to be facultatively xenogamous with only one in 50 glasshouse flowers setting seed autogamously, i.e. without pollinator assistance. Field studies revealed fertile fruit in 24 populations but production varied significantly across sites from exceedingly low (0.6 fruits per plant clump) to low (17 fruits per plant clump). Fruit-set ranged from 0 to 65%, suggesting that pollen vectors exist or that autogamy levels in the field are variable and higher than glasshouse results. Fruit production did not vary with population size, although in three of the five populations in the south-west region more than twice as much fruit was produced as in populations elsewhere. A moderately strong relationship between foliage volume and fruit : flower ratios suggests that bigger plants may be more attractive than smaller plants to pollinators. A review of Tetratheca pollination ecology revealed that several species are poorly fecund and pollinators are rare. The habitat requirements for Tetratheca, a genus of many rare and threatened species, is discussed. (C) 2003 Annals of Botany Company

Floral Sturcture, Breeding System and Fruit-set in the Threatened Sub-shrub Tetratheca juncea Smith (Tremandraceae)

'Tetratheca juncea' Smith (Tremandraceae) has undergone a range contraction of approx. 50 km in the last 100 years and is now listed as a vulnerable sub-shrub restricted to the central and north coast regions of New South Wales, Australia. There are approx. 250 populations in a 110 km north±south distribution and populations are usually small with fewer than 50 plants/clumps. The reproductive ecology of the species was studied to determine why seed-set is reportedly rare. Flowers are bisexual, odourless and nectarless. Flowers are presented dependentally and there are eight stamens recurved around the pistil. Anthers are poricidal, contain viable pollen and basally contain a deep-red tapetal fluid that is slightly oily. Thus flowers are presented for buzz pollinators, although none were observed at flowers during our study. The species was found to be facultatively xenogamous with only one in 50 glasshouse flowers setting seed autogamously, i.e. without pollinator assistance. Field studies revealed fertile fruit in 24 populations but production varied significantly across sites from exceedingly low (0.6 fruits per plant clump) to low (17 fruits per plant clump). Fruit-set ranged from 0 to 65%, suggesting that pollen vectors exist or that autogamy levels in the field are variable and higher than glasshouse results. Fruit production did not vary with population size, although in three of the five populations in the south-west region more than twice as much fruit was produced as in populations elsewhere. A moderately strong relationship between foliage volume and fruit : flower ratios suggests that bigger plants may be more attractive than smaller plants to pollinators. A review of Tetratheca pollination ecology revealed that several species are poorly fecund and pollinators are rare. The habitat requirements for Tetratheca, a genus of many rare and threatened species, is discussed

Seed biology implications for the maintenance and establishment of Tetratheca juncea (Tremandraceae), a vulnerable Australian species

Tetratheca juncea Smith is an endemic and vulnerable shrub species with apparently poor recruitment from New South Wales, Australia. Lack of understanding of seed biology limits management options for promoting survival of existing populations and recruitment of new populations. This study investigated the soil seed bank, seed viability, germination and seed dormancy. The plants release seeds in January but no seeds germinated from soil collected near the plants in September 1999, irrespective of the soil being treated by smoke, heat or fire. When sampled again in February 2001, seeds were present in the soil seed bank but were not viable. Viability testing of seeds collected from the plants determined that at least a third of the seeds being produced were viable, even after storage for 6 months. Seed germination and dormancy investigations found that the seeds germinated following exposure to smoke or scarification of the seed coat. Untreated seeds did not germinate during the preliminary study, although a proportion of untreated seeds germinated from a later seed lot. Fire management is important for promoting the survival of this species and the soil seed bank cannot be relied on for re-establishment of populations as the longevity of the soil seed bank seems to be short. Many other species of Tetratheca are also rare or threatened and this study suggests that hand-collected seeds treated with fire-related stimuli may be important for re-establishing those species and that the soil seed bank requires assessment before being relied on as a source of propagules or for maintaining a population

First corrosion stages in Tournemire claystone/steel interaction: In situ experiment and modelling approach

International audienceSteels are possible materials for high-level radioactive waste containers used in long-term geological disposal in claystone environments. The French Institute for Radioprotection and Nuclear Safety (IRSN) is conducting an experimental programme on claystone/steel interactions in underground natural conditions at its Tournemire Underground Research Laboratory (URL, Aveyron, France). In this programme, several experimental conditions have been tested: i) the location in the geological formation, ii) the nature of the steel, iii) the claystone texture, and iv) the water content. This programme has investigated, after six years of experimentation, the effect of these parameters on the degree of steel corrosion, the spatial transport of iron and the claystone/steel interaction processes. Whatever the context results indicate corrosion rates of about 3 mu m/year for carbon steels and about 0.1 mu m/year for stainless steels. A detailed petrological study of the claystone/steel interface reveals a clear influence of free water content and claystone texture on the iron transport processes. All the data obtained from this study demonstrate that, during the initial oxic stage of steel corrosion, oxygen entrapped in the claystone porosity reacts with iron to form goethite/lepidocrocite minerals. Even after six years of reaction, there is no observed evidence of the anoxic corrosion of steel, irrespective of the context. The precipitation of iron hydroxide within the claystone causes intense calcite dissolution and a slight dissolution of mixed-layered illite smectite. The minimum amount of oxygen required to form goethite in our experiments is estimated by thermodynamic simulations. This amount of oxygen is nearly the same as the amount of iron corroded. Moreover, additional simulations show that siderite forms when goethite becomes unstable under anoxic condition, and that the Tournemire mineral assemblage buffers the pore-water pH at a value close to neutrality, which prevents magnetite formation. Conclusions underline the important role played by oxygen entrapped in the near-field formation on the first iron corrosion stage. The quantification of the amount of oxygen present in the near field is a critical parameter that has to be taken into account in the nuclear waste storage safety assessmen

Surgical and instrumental options for chronic rhinitis: A systematic review and PRISMA meta-analysis

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Experimental Investigations of Colloids and EU(III)/NI(II) Adsorption Properties of the Cavallova-Oxfordian Claystone from Bure (France)

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Guidelines of the French Society of ENT (SFORL): Drug-induced sleep endoscopy in adult obstructive sleep apnea syndrome

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