Acacia Baileyana Research Articles

Acizzia errabunda sp. nov. and Ctenarytaina insularis sp. nov.: Descriptions of two new species of psyllids (Hemiptera: Psylloidea) discovered on exotic host plants in New Zealand.

A recent molecular-based assessment of the psyllid fauna of New Zealand reported two genetically distinct, undescribed psyllid taxa on host plants not native to that country. Here, a morphological examination confirmed species-level variation that resulted in the description of two new psyllid species: Acizzia errabunda sp. nov. (Hemiptera: Psyllidae) from Acacia baileyana F. Muell and Ctenarytaina insularis sp. nov. (Hemiptera: Aphalaridae) from Syzygium smithii (Poir.) Nied. Furthermore, the examination of specimens from entomological collections and from observations recorded on an online database enabled a better understanding of the distribution and host plant associations of these psyllid species. The description of A. errabunda is based on material collected in both New Zealand and Australia from the same plant species, A. baileyana, whereas the psyllid C. insularis has been found to be present in Brunei and New Zealand on S. smithii and in New Caledonia on Melaleuca quinquenervia (Cav.) S. T. Blake.

Australian native flowering plants enhance the longevity of three parasitoids of brassica pests

AbstractFloral resources from native plants that are adapted to the local environment could be more advantageous than the use of nonnative plants. In Australia, there is a dearth of information on the benefits of native plants to natural enemies and their selectivity against pests. Accordingly, we examined the longevity of the parasitoids Diaeretiella rapae (McIntosh) and Cotesia glomerata (L.) (both Hymenoptera: Braconidae), and Diadegma semiclausum (Hellen) (Hymenoptera: Ichneumonidae) exposed to flowering shoots from Australian native plants which was compared with the nonnative buckwheat (Fagopyrum esculentum), often used in conservation biological control. Longevity of parasitoids was significantly enhanced by the Australian natives Westringia fruticosa, Mentha satureioides, Callistemon citrinus, Leptospermum cv. ‘Rudolph’, Grevillea cv. ‘Bronze Rambler’, Myoporum parvifolium, Lotus australis, and nonnative F. esculentum. The highest mean survival by native plant species was 3.4× higher for D. rapae with Leptospermum sp. and 4.3× higher for D. semiclausum with M. parvifolium. For C. glomerata, Grevillea sp. increased longevity by 6.9× compared with water only. Longevity of Plutella xylostella (L.) (Lepidoptera: Plutellidae), a major crop pest, was enhanced by all plants against which it was screened except Acacia baileyana, a species that had no effect on parasitoid longevity. Several Australian native plant species that benefit parasitoids were identified. None of the plant species provided a selective benefit to the parasitoid D. semiclausum compared with its host P. xylostella; however, the benefit of M. parvifolium and Grevillea sp. on the longevity of D. semiclausum was relatively higher compared with the pest. These results suggest the need for field studies to determine whether native Australian plants increase P. xylostella impact in nearby brassica crops.

Life cycle and host range ofPhycitasp. rejected for biological control of prickly acacia in Australia

Prickly acacia (Vachellia nilotica subsp. indica), a native of the Indian subcontinent, is a serious weed of the grazing areas of northern Australia and is a target for classical biological control. Native range surveys in India identified a leaf webber, Phycita sp. (Lepidoptera: Pyralidae) as a prospective biological control agent for prickly acacia. In this study, we report the life cycle and host-specificity test results Phycita sp. and highlight the contradictory results between the no-choice tests in India and Australia and the field host range in India. In no-choice tests in India and Australia, Phycita sp. completed development on two of 11 and 16 of 27 non-target test plant species, respectively. Although Phycita sp. fed and completed development on two non-target test plant species (Vachellia planifrons and V. leucophloea) in no-choice tests in India, there was no evidence of the insect on the two non-target test plant species in the field. Our contention is that oviposition behaviour could be the key mechanism in host selection of Phycita sp., resulting in its incidence only on prickly acacia in India. This is supported by paired oviposition choice tests involving three test plant species (Acacia baileyana, A. mearnsii and A. deanei) in quarantine in Australia, where eggs were laid only on prickly acacia. However, in paired oviposition choice trials, only few eggs were laid, making the results unreliable. Although oviposition choice tests suggest that prickly acacia is the most preferred and natural host, difficulties in conducting choice oviposition tests with fully grown trees under quarantine conditions in Australia and the logistic difficulties of conducting open-field tests with fully grown native Australian plants in India have led to rejection of Phycita sp. as a potential biological control agent for prickly acacia in Australia.

Pollinators and predators at home and away: do they determine invasion success for Australian Acacia in New Zealand?

AbstractAimInteractions with pollinators and pre‐dispersal seed predators are important determinants of reproductive output and could influence the success of plant species introduced to areas outside their native range. We identified the role of these interactions in determining reproductive output and invasion outcomes for species of Australian Acacia introduced to New Zealand.LocationAustralia and New Zealand.MethodsWe studied three species of Australian Acacia with different invasion success in New Zealand. In both Australia and New Zealand, we measured pollination success as the number of pods per inflorescence and the proportion of aborted seeds per pod, determined losses to pre‐dispersal seed predators, and measured overall seed output. For each species, we compared performance in New Zealand with that in Australia, then examined whether there was any variation among species in their relative performance in each country.ResultsThe number of pods per inflorescence and proportion of seeds aborted were similar in each country and among species. There was little difference in pre‐dispersal seed predation rate between Australia and New Zealand for Acacia dealbata, an invasive species, and Acacia baileyana, a species widely naturalized in New Zealand. However, pre‐dispersal seed predation rate was lower in New Zealand for Acacia pravissima, currently considered to be a casual species there. Both the invasive A. dealbata and the casual A. pravissima produced more seeds per tree in New Zealand than Australia.Main conclusionsDifferences in reproductive success between the native and introduced range could not explain the differences in invasion success among the three Acacia species. Although per capita reproductive output was higher in New Zealand for two species, neither mutualistic interactions with pollinators nor antagonistic interactions with pre‐dispersal seed predators explained those differences. The high seed output of A. pravissima suggests it has the potential to become invasive. These findings highlight the value of broad comparative studies in elucidating the drivers of invasion.

A new genus of gall midge (Diptera: Cecidomyiidae) from Australian Acacia

A new species of gall midge, Austroacacidiplosis botrycephalae Kolesik gen. et sp. n. induces conspicuous spherical, often red coloured, galls on leaves of Acacia deanei (R. T. Baker), Acacia decurrens Willd., Acacia baileyana F. Muell. and Acacia dealbata Link in south-eastern Australia. A new genus is erected to contain the new species. Austroacacidiplosis belongs to the tribe Cecidomyiini and its closest relative is Acacidiplosis Gagne, an African genus containing species that induce galls on leaves and flower buds of acacias in Kenya.

Effect of Heat Treatment and Short-Duration Composting on Germination of Weeds in Green Waste

The use of minimally processed green (or yard) waste as a mulch for tree crops and vines has the potential to spread weeds. In a laboratory study, the germination of cootamundra wattle (Acacia baileyana) and tomato seeds in green waste was determined at four temperatures (35C, 45C, 55C, and 65C) and three moisture contents (40%, 50%, and 60% w w-1 w.b.). Moisture content had no significant effect on tomato seed germination at 35C or 45C. At 55C, seed germination was generally greater at 40% or 50% than at 60% moisture content, but the differences were not significant after the first hour of exposure. Cootamundra wattle seeds survived more than 5 h exposure to 55C and 65C with no decrease in germination and were not affected by increasing moisture content. In field composting conditions conducted in windrows, 8% of cootamundra wattle seeds germinated after 136 h exposure to temperatures above 55C. Bermudagrass did not survive much longer than eight days on the outside edge of a windrow (3.3% of stem fragments germinated after eight days), but the bulbils of watsonia (Watsonia meriana) were able to germinate after more than 5 days buried 1 m deep in a windrow (3.3% germination) where temperatures reached over 60C. This study indicates that in order to control heat-resistant weeds like cootamundra wattle, green waste feedstock should be adequately prepared for composting and managed with careful process control, especially when the duration of composting is short.

Breeding system, reproductive efficiency and weed potential of A. baileyana

Acacia baileyana F.Muell. is a native environmental weed which has invaded bush areas of south-eastern Australia from ornamental plantings. There are two main colour forms, the typical green-leaf form and the variety `purpurea', which has purple new growth. Only the green form appears to have invaded natural bush. The weed potential of A. baileyana was investigated in terms of its breeding system and seed production. It was found that the purple form is as reproductively efficient as the green form. Both forms were outcrossing, highly self-incompatible, grew very rapidly and flowered by two years of age. For open, natural pollination, final pod set was low-less than 0.41%. However, seed production was high due to the high number of flowers present. Maximum flower production for a 2-year-old plant was over 300 000, resulting in more than 8000 seeds. Precocity and high flower numbers appear to be the reasons for the weed status of A. baileyana. Given the similarity in reproductive efficiency between both forms, it is postulated that the absence of the purple form as a weed could be due to it being a relatively new horticultural variety, or to the purple colour being a recessive trait.

Environmental control of bud formation and flowering of clonal Acacia baileyana F. Muell. for ornamental horticulture

To study the temperature requirements for flowering, cuttings of A. baileyana were either transferred between different temperatures in controlled-environment growth cabinets, kept outside or in a shadehouse. Plants in the growth cabinets were transferred from a low (13/9˚C) to high (23/19˚C) temperature, from a high to low temperature, or kept at a constant intermediate (18/13˚C) temperature, and then transferred outside. Acacia baileyana required temperatures at or above a mean maximum of 18˚C and a minimum of 13˚C for bud formation, and at or below a mean maximum of 16˚C and a minimum of 9˚C for flowering. Nearly twice the number of plants transferred from high to low temperature flowered compared with outside plants. Bud formation was inhibited at a temperature of 13˚C maximum and 9˚C minimum. Large buds dropped when the temperature was above 18˚C maximum and 13˚C minimum, indicating that the timing of plant transfer between the warm and cool conditions should be when the buds are at a medium size. Light intensity also affected flowering, with less than half the number of plants flowering in the shadehouse compared with outside. Plants transferred from high to low temperature were induced to flower 4 months earlier than outside plants by manipulating the temperature. Flowering cut stems or pot plants of A. baileyana could be produced for Mother’s Day in May and for other key markets.

ORGAN INITIATION AND DEVELOPMENT OF INFLORESCENCES AND FLOWERS OF ACACIA BAILEYANA

Inflorescence and floral ontogeny are described in the mimosoid Acacia baileyana F. Muell., using scanning electron microscopy and light microscopy. The panicle includes first‐order and second‐order inflorescences. The first‐order inflorescence meristem produces first‐order bracts in acropetal order; these bracts each subtend a second‐order inflorescence meristem, commonly called a head. Each second‐order inflorescence meristem initiates an acropetally sequential series of second‐order bracts. After all bracts are formed, their subtended floral meristems are initiated synchronously. The sepals and petals of the radially symmetrical flowers are arranged in alternating pentamerous whorls. There are 30–40 stamens and a unicarpellate gynoecium. In most flowers, the sepals are initiated helically, with the first‐formed sepal varying in position. Petal primordia are initiated simultaneously, alternate to the sepals. Three to five individual stamen primordia are initiated in each of five altemipetalous sectorial clusters. Additional stamen primordia are initiated between adjacent clusters, followed by other stamens initiated basipetally as well as centripetally. The apical configuration shifts from a tunica‐corpus cellular arrangement before organogenesis to a mantle‐core arrangement at sepal initiation. All floral organs are initiated by periclinal divisions of the subsurface mantle cells. The receptacle expands radially by numerous anticlinal divisions in the mantle at the summit, concurrently with proliferation of stamen primordia. The carpel primordium develops in terminal position by conversion of the floral apex.

Weed control among planted and direct-seededEucalyptus, AcaciaandCasuarinawith the herbicides diphenamid, oryzalin, clopyralid and fluazifop-butyl

Summary In a glasshouse pot trial, applications of the pre-emergence herbicide oryzalin at rates equivalent to 4 and 8 kg a.i. ha−1 were toxic to germinating seeds of Eucalyptus maculata, Casuarina glauca and Acacia saligna. The pre-emergence herbicide diphenamid was toxic at rates of 7 and 14 kg a.i. ha−1 to germinating C. glauca and A. saligna, but not to E. maculata. Both oryzalin and diphenamid were selective at these rates when applied over newly-planted seedlings of Eucalyptus melliodora, Casuarina cunninghamiana and Acacia baileyana on a former pasture site. Diphenamid gave greater pre-emergence control of grass weeds, while oryzalin was more effective against the broad-leaved weeds. Overall, the most satisfactory long-term weed control and tree response was achieved with oryzalin. The post-emergence herbicides fluazifop-butyl at 0.6 and 1.2 kg a.e. ha−1 and clopyralid at 0.25 and 0.5 kg a.e. ha−1, were mostly selective to the planted seedlings on the former pasture site, but they gave unsatisfactory weed control, probably because of a combination of poor timing of application and a herbicide-tolerant weed flora.

Phenology and Relative Abundance of Coleoptera on Some Australian Acacias.

Adult Coleoptera were sampled weekly by beating from four Acacia species (Acacia baileyana, Acacia dealbata, Acacia decurrens and Acacia pravissima) near Melbourne for up to 2 l/2 years. Some 34,000 individuals, representing nearly 200 'species', are used to analyse seasonal trends in occurrence and abundance on different tree species. Few species were abundant, and these (predominantly univoltine 'summer' species) occurred on all host species. Aspects of seasonal incidence and changes in similarity between beetle assemblages on different tree species are briefly discussed.

Molecular structure of the polysaccharide exudate from Acacia baileyana F. Muell

Study of the molecular-weight distribution of the raw gum exuded from Acacia baileyana F. Muell., of partially hydrolysed material, and of products of successive Smith-degradations of the gum suggests the occurrence of sub-units having a molecular weight of ∼4000. These sub-units consist of β-(1→3)-linked d-galacto-pyranose residues, to most of which are attached residues of l-arabinofuranose or d-galactopyranose; the bulk of the pendant groups are removed by a single Smith-degradation to give a monodisperse fragment of molecular weight 2500. Further, successive degradations by the oxidation-reduction-hydrolysis procedure yielded a galactan which contains about ten hexose residues and which is essentially linear.

Botany in the University of Sydney

VOL. 2 of Botanical Reprints from the University of Sydney shows very valuable work in progress on characteristic groups of the Australian flora. A. Burges has a first paper upon the rust fungi of the Dominion, which deals most appropriately with the genus Uromycladium, in which six of the seven species are endemic to Australia and restricted to the genus Acacia for their host plants. Gladys Carey continues her study of the embryology of viviparous seeds, examining two of the mangrove species from tropical Queensland. Lilian Fraser has two papers upon the sooty moulds of New South Wales those curious fungi that are found superficial upon branches and leaves, living upon the honey-dew secreted by scale insects and aphides; she also describes some of the Mycetozoa of the same State. I. V. Newman, in continuation of earlier studies of the Australian acacias, has two papers dealing with the floral organs and their development, fertilisation and embryology in Acacia Baileyana, whilst Joyce W. Vickery deals with the vegetative reproduction by underground tubers of two species of Drosera common as winter herbs in the Sydney district. The Botanical Department thus bears witness to its active interest in the flora of the Australian dominion.

Polyspermy and the Endosperm

IN preparing an account of the life-history of Acacia Baileyana, I have found strong evidence of polyspermy in connexion with endosperm formation. The polar nuclei, unfused before fertilisation, have one large nucleolus each. The sperm, which on first contact with the polar nuclei has 13 chromosomes present1 (presumably telophase) (Fig. 1a), proceeds to the resting condition, with a small nucleolus (Fig. 1b). In normal cases this group of two large and one small nucleoli is the most prominent feature of the centre of the sac at this stage. Fusion is first between the sperm and one polar nucleus (Fig. 1c), the product then fusing with the other polar nucleus to form a nucleus with three nucleoli—one small and two large (Fig. 1d). Some instances were found of divergence from the above normal conditions ; for example, there would be in the centre of the sac one nucleus with one large and one small nucleolus, and another nucleus with one large and two small nucleoli (Fig. 2a) ; or there might be altogether four or five small nucleoli (Fig. 2b, c) ; but always at this stage the large nucleoli numbered two. The inference from the above is that sometimes there are more than two sperms to be found in the sac. There was never any indication that more than one sperm became associated with the egg.

ATTEMPTS TO DEMONSTRATESYMBIOTIC NITROGEN‐FIXING BACTERIA WITHIN THE TISSUES OF CASSIA TORA

From the standpoint of soil fertility the leguminous plants have for a long time maintained an exceptional position because of their symbiotic relationship with nitrogen-fixing bacteria. This symbiosis between plant and microorganism is commonly recognized by the visible manifestation of nodules on the root systems of these plants. Members of the sub-family Papilionatae are among the most common examples. Fewer data on the presence of nodules in the sub-families Mimosoideae and Caesalpinioideae are available, probably because their members are trees, shrubs or plants distinctly unsuitable as field crops. Of twenty-four members of the Mimosoideae cited by Leonard (9) only one, Acacia Baileyana F. Muel., lacked nodules, whereas twenty members of the Caesalpinioideae, also cited by Leonard, were found by various investigators to lack nodules. Chamaechrista nictitans (L.) Moench., Chamaechrista fasciculata (Michx.) Greene and Chamaechrista Simpsoni Pollard were exceptions. It has often been suggested that the absence of nodules on various leguminous plants does not necessarily preclude the presence of nitrogen-fixing bacteria within the root tissue. For several reasons this question has never been thoroughly investigated. Joshi (7) was probably the first to suggest that root nodule bacteria existed in the root tissues of certain papilionaceous plants although root nodules were not formed. He proposed this explanation for the substantial increases in yield and high nitrogen contents which were obtained in the culture of these plants. Joshi further conjectured that such a condition might occur due either to a lower virulence of the specific organism or to a slower reaction of the plant to the stimulus of the organismal attack. His histological studies failed to show the presence of any organisms in the root tissues. It is now obvious that some of his results can be explained on a cross-inoculation basis. Feher and Bokor (5) and Friesner (6) have also proposed the idea that root nodule bacteria might benefit plant growth without forming nodules. Critical examination of the above papers is difficult since the techniques were not satisfactorily described. On the basis of Joshi's paper one might

Studies in the Australian Acacias—II. The life-history of Acacia Baileyana (F. v. M.). Part I. Some ecological and vegetative features, spore production, and chromosome number*

Studies in the Australian Acacias—II. The life-history of Acacia Baileyana (F. v. M.). Part I. Some ecological and vegetative features, spore production, and chromosome number*