Development and persistence of sandsheaths of Lyginia barbata (Restionaceae): relation to root structural development and longevity.

Background And Aims: Strongly coherent sandsheaths that envelop perennial roots of many monocotyledonous species of arid environments have been described for over a century. This study, for the first time, details the roles played by the structural development of the subtending roots in the formation and persistence of the sheaths.

Methods: The structural development of root tissues associated with persistent sandsheaths was studied in Lyginia barbata, native to the Western Australian sand plains.

Seasonal water relations of Lyginia barbata (Southern rush) in relation to root xylem development and summer dormancy of root apices.

*Periods of dormancy in shallow roots allow perennial monocotyledons to establish deep root systems, but we know little about patterns of xylem maturation, water-transport capacities and associated economies in water use of growing and dormant roots. *Xylem development, anatomy, conductance and in situ cellular [K] and [Cl] were investigated in roots of field-grown Lyginia barbata (Restionaceae) in Mediterranean southwestern Australia. Parallel studies of gas exchange, culm relative water loss and soil water content were conducted.

Neoformation of clay in lateral root catchments of mallee eucalypts: a chemical perspective.

Background And Aims: A previous paper (Annals of Botany 103: 673-685) described formation of clayey pavements in lateral root catchments of eucalypts colonizing a recently formed sand dune in south-west Western Australia. Here chemical and morphological aspects of their formation at the site are studied.

Methods: Chemical and physical examinations of soil cores through pavements and sand under adjacent heath assessed build-up of salts, clay and pH changes in or below pavements.

Summer dormancy and winter growth: root survival strategy in a perennial monocotyledon.

Here, we tested the alternation of root summer dormancy and winter growth as a critical survival strategy for a long-lived monocotyledon (Restionaceae) adapted to harsh seasonal extremes of Mediterranean southwest Western Australia. Measurements of growth and the results of comparative studies of the physiology, water content, metabolites, osmotic adjustments, and proteomics of the dormant and growing perennial roots of Lyginia barbata (Restionaceae) were assessed in field-grown plants. Formation of dormant roots occurred before the onset of summer extremes.

Contemporary biogenic formation of clay pavements by eucalypts: further support for the phytotarium concept.

Background And Aims: Clayey (sodosolic) pavements were studied in lateral root catchments of eucalypts where mixed myrtaceous:proteaceous vegetation was colonizing a dune of quartzitic sand blown out from a playa lake during late Pleistocene times. The site at Chillinup in south-west Western Australia provided an opportunity to examine these signature pavements in an unequivocally recent setting, and to assess their effects on competing non-eucalypt vegetation.

Methods: Pavements were located, and their extents and depths assessed by probing with steel rods, followed by corings and pit excavations using an air spade.

Synthesis, transport and accumulation of quinolizidine alkaloids in Lupinus albus L. and L. angustifolius L.

Each of the principal quinolizidine alkaloids (QA) found in both xylem and phloem exudates together with extracts from all component organs collected from bitter (cv. Lupini) and sweet (cv. Ultra) cultivars of Lupinus albus L.

Environmental and physiological controls over oxygen and carbon isotope composition of Tasmanian blue gum, Eucalyptus globulus.

We measured oxygen isotope ratios (delta18O) of xylem sap, phloem sap, leaves, wood and bark of Eucalyptus globulus Labill. growing in southwestern Australia. Carbon isotope ratios (delta13C) were measured in the dry matter of phloem sap, leaves and wood.

Oxygen and carbon isotope composition of parasitic plants and their hosts in southwestern Australia.

We measured leaf dry matter delta(18)O and delta(13)C in parasitic plants and their hosts growing in southwestern Australia. Parasite/host pairs included two mistletoe species, three species of holoparasites, and five species of root hemiparasites. Among these parasite functional types, significant variation was observed in parasite/host isotopic differences for both delta(18)O ( P<0.

Water relations link carbon and oxygen isotope discrimination to phloem sap sugar concentration in Eucalyptus globulus.

A strong correlation was previously observed between carbon isotope discrimination (Delta(13)C) of phloem sap sugars and phloem sap sugar concentration in the phloem-bleeding tree Eucalyptus globulus Labill. (J. Pate, E.

Quantifying above- and below-ground growth responses of the western Australian oil mallee, Eucalyptus kochii subsp. plenissima, to contrasting decapitation regimes.

Resprouting in the oil mallee, Eucalyptus kochii Maiden & Blakely subsp. plenissima Gardner (Brooker), involves generation of new shoots from preformed meristematic foci on the lignotuber. Numbers of such foci escalated from 200 per lignotuber in trees aged 1 year to 3,000 on 4- to 5-year-old trees.

Seasonal water uptake and movement in root systems of Australian phraeatophytic plants of dimorphic root morphology: a stable isotope investigation.

A natural abundance hydrogen stable isotope technique was used to study seasonal changes in source water utilization and water movement in the xylem of dimorphic root systems and stem bases of several woody shrubs or trees in mediterranean-type ecosystems of south Western Australia. Samples collected from the native treeBanksia prionotes over 18 months indicated that shallow lateral roots and deeply penetrating tap (sinker) roots obtained water of different origins over the course of a winter-wet/summer-dry annual cycle. During the wet season lateral roots acquired water mostly by uptake of recent precipitation (rain water) contained within the upper soil layers, and tap roots derived water from the underlying water table.

The promotive effect of smoke derived from burnt native vegetation on seed germination of Western Australian plants.

Exposure of dormant seed to cold smoke derived from burnt native vegetation had a positive influence on germination in one or more seed provenances in 45 out of 94 species of native Western Australian plants that are normally hard to germinate. When tested under controlled conditions some species showed earlier germination in smoke treatments than controls; in others smoke-treated seeds continued to germinate for several weeks after controls had achieved full germination. In the remainder, treated and control seeds germinated to similar time schedules.

Growth, reproductive performance and resource allocation of the herbaceous obligate seeder Gompholobium marginatum R. Br. (Fabaceae).

Perennial species have evolved several strategies to survive fire, with resprouters and seeders forming two major categories. Gompholobium marginatum is a herbaceous seeder legume occurring in the Western Australian jarrah (Eucalyptus marginata) forest which since 1961 has been subjected to burns every sixth year. Such frequent fires potentially endanger the survival of seeder species like G.

Water relations of the root hemiparasite Olax phyllanthi (Labill) R.Br. (Olacaceae) and its multiple hosts.

Water relations of the root hemiparasite Olax phyllanthi were compared with those of its major species of hosts in natural habitat in coastal heath near Denmark, SW Australia. Leaf water potentials of Olax during winter were 0.4 to 1.

Water relations of the parasite: host relationship between the mistletoe Amyema linophyllum (Fenzl) Tieghem and Casuarina obesa Miq.

Seasonal and diurnal gas exchange and water relations of Amyema linophyllum and its host Casuarina obesa were studied at Gingin Western Australia. As recorded elsewhere for other species of mistletoe, stomatal conductances and transpiration rates were consistently higher in parasite than host, but assimilation rates did not differ significantly between partners, and water use efficiency was accordingly substantially lower in the parasite. Parallel responses of the species to environmental conditions suggested closely coordinated stomatal behaviour.