Anthony M. Haigh

Stem tissue phosphorus as an index of the phosphorus status of Banksia ericifolia L. f.

The effects of P fertilizer rate on shoot growth and the total P concentration of the whole shoot, new and mature leaves, symptom leaves and stems of Banksia ericifolia L. f., a P-sensitive species, were investigated in a six month greenhouse pot experiment. Shoot dry weight of plants growing in an Australian sedge peat, coarse sand and perlite potting mix (1:1:1) increased with up to 100 mg P L−1 supplied as a six month controlled release P (0:18:0) fertilizer, but was reduced by toxicity at the highest application rate (200 mg P L−1). Plants receiving this treatment developed chlorotic new and mature leaves. Leaf symptoms observed at rates of 60–100 mg P L−1 were confined to old leaves and were related to the P concentration of the shoot. Growth was not affected at these rates. The P concentration of stems was strongly influenced by P supply. This tissue acted as a sink for excess P, helping to regulate the P concentration of leaves. The approximate range of P concentrations in stem tissue, associated with greater than 90% of maximum shoot dry weight, was 0.5–1.5 g P kg−1 tissue dry weight. This was greater than that calculated for mature leaves (0.5–0.8 g kg−1) or for whole shoots (0.5–1.2 g kg−1). This wider range, and the capacity to store P in excess to requirement, makes the stem a better index tissue for plant P status than either leaves or whole shoots.

Relationship between accumulated hydrothermal time during seed priming and subsequent seed germination rates

Seed germination rates are sensitive to both temperature ( T ) and water potential (ψ). The times to germination of seeds imbibed at suboptimal T and/or reduced ψ are inversely proportional to the amounts by which T exceeds a base temperature ( T b ) and ψ exceeds a base water potential (ψ b ). Germination rates across a range of suboptimal T and ψ can be normalized on the basis of the hydrothermal time accumulated in excess of these thresholds. However, seeds can also progress metabolically toward germination even at T or ψ too low to allow radicle emergence to occur. Seeds preimbibed at low ψ and dried back, or primed, germinate more rapidly upon subsequent reimbibition. We show here that the increase in germination rates of tomato ( Lycopersicon esculentum Mill.) seeds resulting from seed priming is linearly related to the hydrothermal time accumulated during the priming treatment. The threshold temperature ( T min = 7.05°C) and water potential (ψ min = −2.50 MPa) for metabolic advancement were considerably lower than the corresponding thresholds for radicle emergence of the same seed lot ( T b = 11°C; ψ b = −0.71 MPa), allowing the accumulation of hydrothermal priming time that is subsequently expressed as more rapid germination when T or ψ increase. The hydrothermal time model can now be applied to quantify and analyse germination rates of seeds across the entire range of suboptimal T and ψ at which metabolic progress toward radicle emergence is possible.

Pollination of Greenhouse Tomatoes by the Australian Bluebanded Bee Amegilla (Zonamegilla) holmesi (Hymenoptera: Apidae)

The pollination effectiveness of bluebanded bees of the species Amegilla (Zonamegilla) holmesi Rayment (Hymenoptera: Apidae) was evaluated in tomato plants, Lycopersicon esculentum Miller (Solanaceae), cultivated in two greenhouse chambers. Bluebanded bee pollination was compared with mechanical pollination and no supplementary pollination. Pollination effectiveness was compared between treatments by using the percentage of fruit set, fruit weight, fruit diameter, fruit roundness, and the number of seeds per fruit. Both the bluebanded bee pollination and the mechanical pollination treatments significantly increased fruit set, individual fruit weight, and diameter compared with the control treatment. Fruit were also significantly rounder and contained significantly more seeds. Positive correlations were found for fruit weight versus seed number, maximum diameter versus seed number and minimum diameter versus seed number. We conclude that the use of A. holmesi for pollinating greenhouse tomatoes in Australia may be an effective alternative to the use of mechanical pollination.

The Australian stingless bee industry: a follow-up survey, one decade on

Summary In 2010, an online survey was conducted to assess the current status of the Australian stingless bee industry and its recent development. This was a follow-up survey conducted approximately one decade after the first study, by Heard and Dollin in 1998/99. It showed that the Australian industry had grown over the past ten or so years but is still underdeveloped. There was a 2.5-fold increase in the number of bee keepers and a 3.5 fold increase in the number of domesticated colonies. Seventy-eight percent of bee keepers were hobbyists, 54% of whom owned only one colony. Most colonies were kept in suburban areas. Two species, Tetragonula carbonaria and Austroplebeia australis, dominated the relatively short list of species kept. There was a high demand for Australian stingless bee colonies and their honey, but with less than 250 bee keepers currently propagating colonies, and many of them on a small scale, it is difficult to meet this demand. Pollination services were provided by less than 4% of the major stakeholders within the industry. Further research and development in the area of colony propagation may see this industry grow more quickly.

Stomatal sensitivity to vapour pressure deficit relates to climate of origin in Eucalyptus species.

Selecting plantation species to balance water use and production requires accurate models for predicting how species will tolerate and respond to environmental conditions. Although interspecific variation in water use occurs, species-specific parameters are rarely incorporated into physiologically based models because often the appropriate species parameters are lacking. To determine the physiological control over water use in Eucalyptus, five stands of Eucalyptus species growing in a common garden were measured for sap flux rates and their stomatal response to vapour pressure deficit (D) was assessed. Maximal canopy conductance and whole-canopy stomatal sensitivity to D and reduced water availability were lower in species originating from more arid climates of origin than those from humid climates. Species from humid climates showed a larger decline in maximal sap flux density (JSmax) with reduced water availability, and a lower D at which stomatal closure occurred than species from more arid climates, implying larger sensitivity to water availability and D in these species. We observed significant (P < 0.05) correlations of species climate of origin with mean vessel diameter (R(2) = 0.90), stomatal sensitivity to D (R(2) = 0.83) and the size of the decline in JSmax to restricted water availability (R(2) = 0.94). Thus aridity of climate of origin appears to have a selective role in constraining water-use response among the five Eucalyptus plantation species. These relationships emphasize that within this congeneric group of species, climate aridity constrains water use. These relationships have implications for species choices for tree plantation success against drought-induced losses and the ability to manage Eucalyptus plantations against projected changes in water availability and evaporation in the future.

Climate change, nutrition and immunity: Effects of elevated CO2 and temperature on the immune function of an insect herbivore.

Balanced nutrition is fundamental to health and immunity. For herbivorous insects, nutrient-compositional shifts in host plants due to elevated atmospheric CO2 concentrations and temperature may compromise this balance. Therefore, understanding their immune responses to such shifts is vital if we are to predict the outcomes of climate change for plant-herbivore-parasitoid and pathogen interactions. We tested the immune response of Paropsis atomaria Olivier (Coleoptera: Chrysomelidae) feeding on Eucalyptus tereticornis Sm. seedlings exposed to elevated CO2 (640 μmol mol(-1); CE) and temperature (ambient plus 4 °C; TE). Larvae were immune-challenged with a nylon monofilament in order to simulate parasitoid or pathogen attack without other effects of actual parasitism or pathology. The cellular (in vivo melanisation) and humoral (in vitro phenoloxidase PO activity) immune responses were assessed, and linked to changes in leaf chemistry. CE reduced foliar nitrogen (N) concentrations and increased C:N ratios and concentrations of total phenolics. The humoral response was reduced at CE. PO activity and haemolymph protein concentrations decreased at CE, while haemolymph protein concentrations were positively correlated with foliar N concentrations. However, the cellular response increased at CE and this was not correlated with any foliar traits. Immune parameters were not impacted by TE. Our study revealed that opposite cellular and humoral immune responses occurred as a result of plant-mediated effects at CE. In contrast, elevated temperatures within the tested range had minimal impact on immune responses. These complex interactions may alter the outcomes of parasitoid and pathogen attack in future climates.

Responses of six species of proteaceae, in containers, to controlled-release fertilizer

Abstract Seedlings of Adenanthos sericeus, Banksia ericifolia, Banksia hookeriana, Conospermum caeruleum, Protea cv. Masquerade, and Leucadendron cv. Sundance were grown in a soilless potting medium containing controlled‐release Osmocote® fertilizer (17:1.6:8.7) at eight treatment levels: 0, 1.25, 2.5, 3.75, 5.0, 6.25, 12.5, and 18.75 kg m−3. After 6 months, shoot dry mass and the concentrations of nitrogen (N), phosphorus (P), and potassium (K) in recently matured leaves were determined. At the lowest rate of applied fertilizer, growth was stunted for all species. Maximum shoot dry mass was associated with a fertilizer rate of 2.0 kg m−3 for L. cv. Sundance, 2.5 kg m−3 for C. caeruleum and B. ericifolia, and 3.75 kg m−3 for P. cv. Masquerade, B. hookeriana, and A. sericeus. At the highest fertilizer rate, for all species except A. sericeus, plants displayed foliar symptoms typical of fertilizer excess, and growth was reduced. A range of concentrations of N, P, and K in leaves at optimum growth was determined for each species.

Population structure, seed loads and flowering phenology in three common (Melaleuca styphelioides, M. thymifolia, M. nodosa) and one rare (M. deanei) Melaleuca (Myrtaceae) species of the Sydney region

Melaleuca deanei F.Muell. is listed under state and national protection legislation occurring as small, disjunct populations restricted to the Central Coast botanical district of New South Wales. This paper reports on the population structure, reproductive output and phenology of large and small field populations of M. deanei, compared with three common congeneric species in the area, namely, Melaleuca nodosa (Sol. ex Gaertn.) Sm., Melaleuca thymifolia Sm. and Melaleuca styphelioides Sm. Both M. deanei and M. styphelioides had few seedlings per population at the sites studied. Results indicated that seedling recruitment is rare and would appear to require specific conditions. In addition, M. deanei had a low incidence of flowering within the small populations, significantly fewer fruiting plants per population and significantly lower numbers of viable seeds per square metre, most likely compounding its limited recruitment. Flowering, when it occurred in M. deanei, was from mid to late October through to late November–early December with increased flowering in response to fire and along road edges. Further study is needed to determine reproductive success at the individual-plant level, the breeding system and recruitment requirements of these species.

Can synchrotron micro-x-ray fluorescence spectroscopy be used to map the distribution of cadmium in soil particles?

Plants take up cadmium (Cd) from the soil, and the concentration of Cd in some plant products is a health concern. Plant uptake of Cd is poorly predicted by its concentration in soils; consequently, there is interest in the binding and distribution of Cd in soil. Synchrotron micro-X-ray fluorescence spectroscopy (micro-XRFS) is the most sensitive method of observing this distribution. We used beam-line 2-ID-D of the Advanced Photon Source (APS), Argonne, to test whether this technique could map the Cd distribution in 5 soils from Greater Sydney that contained 0.3-6.4 mg Cd/kg. A subsample of one soil was spiked to contain ∼100 mg Cd/kg. Cadmium was readily mapped in the Cd-enriched subsample, whereas in the unamended soils, only one Cd-rich particle was found; that is, sensitivity generally limited Cd mapping. We also examined a sample of Nauru phosphorite, which was a primary source of much of the Cd in farm soils on the peri-urban fringe of Greater Sydney. The phosphorite contained ∼100 mg Cd/kg and the Cd was relatively uniformly distributed, supporting the findings of an earlier study on an apatite from Africa. The micro-XRFS at beam-line 2-ID-D of the APS can be reconfigured to increase the sensitivity at least 10-fold, which may allow the distribution of Cd and its elemental associations to be mapped in particles of most agricultural soils and facilitate other spectroscopic investigations.

Delimiting the species within the genus Austroplebeia, an Australian stingless bee, using multiple methodologies

Austroplebeia Moure is an Australian stingless bee genus. The current descriptions for the species within this genus are inadequate for the identification of specimens in either the field or the laboratory. Here, using multiple diagnostic methodologies, we attempted to better delimit morphologically identified groups within Austroplebeia. First, morphological data, based on worker bee colour, size and pilosity, were analysed. Then, males collected from nests representing morphologically similar groups were dissected, and their genitalia were imaged using light microscopy and scanning electron microscopy. Next, data for the geometric morphometric analysis of worker wing venations were obtained. Finally, molecular analysis, using mitochondrial 16S ribosomal RNA (16S rDNA), was conducted on workers from representative nests for each group which displayed morphological similarities. Data deriving from the four different diagnostic approaches were compared, resulting in the separation of two groups, plus an unresolved species complex.