Australian Journal of Botany

The grasslands of temperate Australia seem to require disturbance to maintain species diversity. Grasslands in semiarid environments do not seem to have the same requirement. This short-term study suggests that subtropical grasslands on the Darling Downs do not have a requirement for disturbance to maintain species diversity. Drought in the subtropical environment may maintain grasslands in a sufficiently open structure to overcome the requirement for disturbance to maintain diversity of the intertussock flora.

Four small Australian desert succulents respond to drought by switching from CO₂ uptake in the light to CO₂ uptake in the dark. Uptake of CO₂ in the dark enables plants to persist at low water-cost, thereby potentially aiding reproduction. The ability to switch between photosynthetic pathways is a trait that may be more common within Australia’s flora than considered previously.

In arid Australia, the survival of a white cypress-pine seedling to maturity is rare. We found that fencing, particularly rabbit-proof fencing, resulted in increased numbers of white cypress-pine seedlings – but not at all sites. While protection from grazing is important for seedling survival, the potential for other factors to intervene means that rabbit-proof fencing does not guarantee the next generation of white cypress-pines.

Genome multiplication (polyploidy) is an important phenomenon in plant evolution and has significant implications for conservation and ecological restoration. We studied genome multiplication in a group of rare sedges (the Lepidosperma costale species complex) in south-west Western Australia. Four ploidy levels were discovered, suggesting that polyploidy may be an important driver of diversification in these sedges.

Gahnia radula is an important species of sedge needed for vegetation restoration. To understand the extent and source of genetic variation in this species in southern Australia, variation within different populations of the species was investigated. Knowledge gained from the study indicates a prevalence of asexual reproduction and supports recommendations for areas suitable for sourcing material for revegetation.

Population genetics is a key element for the conservation of endangered plant species. The comparison of two congeneric species of Scaevola in New Caledonia, one widespread and one narrow endemic, indicates high differentiation between populations, especially for the narrow endemic species on very small geographical scale. These results demonstrated the importance of conserving multiple populations of narrow endemic species even when they co-occur in close proximity.

Competition from neighbours can simultaneously favour increased dispersal and increased offspring provisioning (seed size), however, these functions trade-off with each other. We demonstrate a non-linear relationship between how fast seeds of wind dispersed Asteraceae species fall, and seed architecture (the size of the parachute like pappus versus the size of the ‘seed’). This non-linear relationship can be used to predict when plants allocate more to dispersal or provisioning when faced with intense competition.

Bark constitutes plant tissue that transports photosynthates and protects plants against pathogen attack, herbivore damage and high temperatures caused by Cerrado fires. Bark traits are directly related to fire protection in a fire-prone habitat and efficient photosynthate transport in a non-fire-prone habitat, with thicker rhytidome and wider sieve tubes respectively. Our study demonstrated that although bark anatomy is little studied, it offers rich diagnostic and adaptive information.

Eucalyptus plantations are replacing natural grasslands in South Brazil, and under these plantations few plants establish, but processes shaping this pattern have been scarcely investigated. We showed that Eucalyptus saligna releases chemical substances in leaf litter that inhibit germination and seedling growth of grassland species. Therefore, suppression of grassland vegetation under E. saligna plantations may be potentially related to effects of allelochemicals.

This work analysed the vegetation of gallery and savanna forest distributed in the lower Uruguay River basin. Plant associations of this vegetation type have been poorly studied. Plant communities are related to tropical forests of southern Brazil, but are present into a warmer climate zone because of the north–south corridor generated by the Uruguay River. Two new associations and a new alliance are described to add to the syntaxonomical scheme of Argentina, with the aim to improve the knowledge of the diversity of its plant communities.

This study is the first embryological report on male structures in the genus Cephalanthus. It includes the analysis of anther development, both the study of the processes leading to the formation of pollen and the histology of the wall of the anther, describing how dehiscence occurs. The results contribute to future studies in other genera of the tribe Naucleeae in the Rubiaceae family.

Germination of fire-prone plant species can be complex. Understanding this key component of the regeneration niche can help elucidate mechanisms for persistence and inform conservation. Like many threatened species in fire-prone south-eastern Australia, Asterolasia buxifolia is restricted to riparian habitats. Germination ecology of this physiologically dormant family (Rutaceae) is not well understood. We found that seeds germinated only with smoke at winter temperatures. Darkness inhibited germination. These results help us understand why such species may be limited to riparian habitat.

Gleditsia triacanthos is a woody exotic species that colonises different ecosystems in several countries around the world. In this work we review numerous studies about its invasion to show its importance as an invasive species in Argentina. Since the end of the 18th century, G. triacanthos has spread across different ecoregions in Argentina affecting flora, fauna and ecosystem processes. Our review highlights the need to develop monitoring and control strategies for this invasive species.

Eucalyptus camaldulensis is the most widely distributed Eucalyptus species both globally and in its native range. In the present study, we explored the natural variation in foliar terpene composition across its natural distribution in Australia and how elevated CO₂ can affect the accumulation of terpenes. We found four chemical varieties dominated by different monoterpenes across the natural range. In addition, plants growing under elevated CO₂ accumulated a lower concentration of monoterpenes, suggesting that climate change can affect terpene accumulation in natural populations and plantations.

Physical dormancy prevents immediate germination of seed and allows species to maintain a persistent soil seed bank providing the resource for post-fire recovery of plant populations. Temperature is a key driver for dormancy release but hot summer temperatures can result in rupture of the seed coat in the inter-fire period. Gradual leakage of seed from the seed bank under a warming climate may compromise the risk-spreading ability afforded by hardseededness potentially reducing species capacity to recover from disturbance.

In this paper we report on studies of the reproduction biology of an Amazonian orchid pollinated by Centridini bees that search for nectar on flowers. To our knowledge, this is the first report of reward production in Encyclia. This discovery provides new insights on the function of the cuniculus in Laeliinae, and sheds light on the evolution of floral rewards and pollination mechanisms within this diverse group of Neotropical orchids.

The incidence of snow was largely constant between 1983 and 2013 at Mt Field and on other high mountains in Tasmania, but decreased on lower elevation alpine mountains, trends apparently caused by changes in atmospheric instability. At Mt Field, obligate snow patch species persisted during the same period and cushion plants and shrubs increased.