Australian Rainforest Tree Research Articles

Growth and physiological response of six Australian rainforest tree species to a light gradient

An understanding of growth and photosynthetic potential of subtropical rainforest species to variations in light environment can be useful for determining the sequence of species introductions in rainforest restoration projects and mixed species plantations. We examined the growth and physiology of six Australian subtropical rainforest tree species in a greenhouse consisting of three artificial light environments (10%, 30%, and 60% full sunlight). Morphological responses followed the typical sun-shade dichotomy, with early and late secondary species ( Elaeocarpus grandis, Flindersia brayleyana, Flindersia schottiana, and Gmelina leichhardtii) displaying higher relative growth rate (RGR) compared to mature stage species ( Cryptocarya erythroxylon and Heritiera trifoliolatum). Growth and photosynthetic performance of most species reached a maximum in 30–60% full sunlight. Physiological responses provided limited evidence of a distinct dichotomy between early and late successional species. E. grandis and F. brayleyana, provided a clear representation of early successional species, with marked increase in A max in high light and an ability to down regulate photosynthetic machinery in low light conditions. The remaining species ( F. schottiana, G. leichhardtii, and H. trifoliolatum) were better represented as falling along a shade-tolerant continuum, with limited ability to adjust physiologically to an increase or decrease in light, maintaining similar A max across all light environments. Results show that most species belong to a shade-tolerant constituency, with an ability to grow and persist across a wide range of light environments. The species offer a wide range of potential planting scenarios and silvicultural options, with ample potential to achieve rapid canopy closure and rainforest restoration goals.

Gynocardin from Baileyoxylon lanceolatum and a revision of cyanogenic glycosides in Achariaceae

The cyclopentenone cyanhydrin glycoside gynocardin was the only cyanogen isolated from foliage of monotypic Australian rainforest tree, Baileyoxylon lanceolatum (Achariaceae). The presence of cyanogenic compounds in plants can have considerable taxonomic utility. A review of previous reports of cyanogenesis in the recently revised Achariaceae revealed distinct taxonomic patterns as well as inconsistencies in the reporting of cyanogenic compounds. This variation appears to be due to tissue level localisation of cyanogenic compounds as well as discrepancies in results obtained from different detection methods. Recommendations are made for future investigations.

Alkaloids with Human δ-Opioid Receptor Binding Affinity from the Australian Rainforest Tree Peripentadenia mearsii

Three new pyrrolidine alkaloids, peripentonine A-C ( 2- 4), one known pyrrolidine alkaloid, peripentadenine ( 1), and one novel indolizidine alkaloid, mearsamine ( 5), were isolated from the leaves of Peripentadenia mearsii and their structures determined by 1D and 2D NMR spectroscopy. Peripentonines A ( 2) and B ( 3) were isolated as a 1:1 mixture of inseparable diastereomers. Mearsamine ( 5) contains a novel tricyclic ring system. Peripentadenine and peripentonines A/B and C showed receptor binding affinity for the human delta-opioid receptor with IC 50 values of 11.4, 69.2, and 30.9 microM, respectively. Mearsamine did not bind to the delta-opioid receptor.

Constitutive polymorphic cyanogenesis in the Australian rainforest tree, Ryparosa kurrangii (Achariaceae)

Cyanogenesis, the liberation of volatile hydrogen cyanide from endogenous cyanide-containing compounds, is a proven plant defence mechanism and the particular cyanogens involved have taxonomic utility. The cyclopentenoncyanhydrin glycoside gynocardin was the only cyanogen isolated from foliar tissue of the rare Australian rainforest tree, Ryparosa kurrangii (Achariaceae). Mechanical damage simulating foliar herbivory did not induce a significant increase in the expression of cyanogenesis over a 24 h period, indicating cyanogenic herbivore defence in R. kurrangii is constitutive. The cyanogenic potential of mature leaves was quantitatively polymorphic between trees in a natural population, ranging from 0.54 to 4.77 mg CN g −1 dry wt leaf tissue.

Variability of Mn hyperaccumulation in the Australian rainforest tree Gossia bidwillii (Myrtaceae)

This study examines the heterogeneity of the Mn-hyperaccumulative trait in natural stands of the Australian rainforest tree species Gossia bidwillii (Myrtaceae). It is the only known Mn hyperaccumulator from Australia, and has an unusual spatial distribution of Mn in its leaves. G. bidwillii occurs naturally on a range of Mn-containing substrates including ultramafic soils. Leaf samples were collected from individual trees and four small stands, over a longitudinal range of ∼600 km. While no variation in the spatial distribution of foliar Mn was detected, considerable variation in Mn concentration was found. G. bidwillii was shown to accumulate Mn when growing on a variety of substrates, and dry weight (DW) foliar Mn concentrations of all trees sampled ranged between 2,740 and 27,470 μg g−1. The majority of samples exceeded 10,000 μg g−1, the threshold value for Mn hyperaccumulation. The overall frequency distribution of foliar Mn concentration was found to be bimodal, with a small outlier of extreme hyperaccumulators. Highest values were obtained from trees growing on a basaltic krasnozem clay, not ultramafic soil. Soil Mn concentrations were measured, and no relationship was found between foliar Mn concentrations and extractable Mn concentrations in host substrates. Some of the variation in the Mn-hyperaccumulative trait in G. bidwillii throughout its large natural distribution may reflect the unresolved taxonomy of this most widespread species in the genus Gossia. Ability to hyperaccumulate Mn may serve as an additional diagnostic tool for resolving this taxonomy.

Isolation and characterization of microsatellite loci from Macadamia

AbstractThirty‐three microsatellite loci were isolated for the Australian rainforest tree Macadamia integrifolia. Genotyping across a test panel of 43 commercial cultivars generated an average polymorphic information content of 0.480. Five loci showed no polymorphism across cultivars. Significant linkage disequilibrium was detected in 10 pairwise comparisons, including two pairs of loci identified from the same clone sequence. The 33 microsatellite loci represent a significant tool for genome mapping and population genetic studies.

Effects of vapour pressure deficit on growth of temperate and tropical evergreen rainforest trees of Australia

Little is known about the effect of vapour pressure deficit (VPD) on the growth of trees. Rainforest trees of eastern Australia provide an opportunity to investigate responses to VPD in species that occur in high precipitation areas but have contrasting dry seasons—summer in the temperate south and winter in the tropical north. Growth responses to VPD were measured in eight species of Australian rainforest trees from different latitudes to investigate possible differences in their response to atmospheric drought. Previous work on these species found that the tropical species have large reductions in gas exchange with increasing VPD whereas the temperate species were mainly unresponsive to increasing VPD. Plants were grown in glasshouses for a year under either low VPD or ambient conditions of a temperate climate. All species had non-significant increases in growth rates (1–9%) of plants grown under low VPD compared with plants grown under ambient VPD. In addition, growing the species under low VPD had no effect on allocation of biomass (leaf area ratio, leaf weight ratio and root/shoot ratio). Therefore, the high sensitivity of gas exchange to increasing VPD found in the tropical rainforest trees did not have a significant, long-term effect on growth under high VPD.

Cyanogenic glycosides from the rare Australian endemic rainforest tree Clerodendrum grayi (Lamiaceae)

The cyanogenic diglycoside lucumin (( R)-mandelonitrile-β- d-primeveroside) and monoglucoside prunasin (( R)-mandelonitrile-β- d-glucoside) were isolated from the foliage of the rare Australian rainforest tree species Clerodendrum grayi (Lamiaceae). This is the first reported isolation of the diglycoside lucumin from vegetative tissue (foliage), and the first reported co-occurrence of lucumin and prunasin. Furthermore, unusually, the diglycoside lucumin was the most abundant cyanogen accounting for approximately 60% of total cyanide in a leaf tissue.

Grandisine A (I) and B (II), Novel Indolizidine Alkaloids with Human δ‐Opioid Receptor Binding Affinity from the Leaves of the Australian Rainforest Tree Elaeocarpus grandis.

Grandisine A (I) and B (II), Novel Indolizidine Alkaloids with Human δ‐Opioid Receptor Binding Affinity from the Leaves of the Australian Rainforest Tree Elaeocarpus grandis.

Xanthones from a Microfungus of the Genus Xylaria.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Tyrosine kinase inhibitors from the rainforest tree Polyscias murrayi

A series of 3-(4-hydroxyphenyl) propanoic acid derivatives, which inhibit Itk (interleukin-2 inducible T-cell kinase), a Th2-cell target, were isolated from the Australian rainforest tree Polyscias murrayi. The new compound 3-(4-hydroxyphenyl) propionyl choline and a 2:1 mixture of the new compounds 3,4–di- O-3-(4-hydroxyphenyl) propionyl-1,5-dihydroxycyclohexanecarboxylic acid and 3,5–di- O-3-(4-hydroxyphenyl) propionyl-1,4-dihydroxycyclohexanecarboxylic acid were isolated along with two known compounds 3-(4-hydroxyphenyl) propanoic acid and 3-(3,4-hydroxyphenyl) propanoic acid. Their structures were determined by 1D and 2D NMR spectroscopy. The assay results suggest that both the 3-(4-hydroxyphenyl) propanoate and carboxyl moieties contribute to Itk activity of the compounds.

Photosynthetic responses to vapour pressure deficit in temperate and tropical evergreen rainforest trees of Australia

Rainforests occur in high precipitation areas of eastern Australia, along a gradient in seasonality of precipitation, ranging from a summer dry season in the temperate south to a winter dry season in the tropical north. The response of net photosynthesis to increasing vapour pressure deficit (VPD) was measured in a range of Australian rainforest trees from different latitudes to investigate possible differences in their response to atmospheric drought. Plants were grown in glasshouses under ambient or low VPD to determine the effect of growth VPD on the photosynthetic response. Temperate species, which experience low summer precipitation, were found to maintain maximum net photosynthesis over the measurement range of VPD (0.5-1.9 kPa). In contrast, the tropical species from climates with high summer precipitation showed large reductions in net photosynthesis with increasing VPD. Temperate species showed higher intrinsic water-use efficiencies under low VPD than the tropical species, whereas their efficiencies were similar under high VPD. Growing plants under a low VPD had little effect on either the photosynthetic response to VPD or the intrinsic water-use efficiency of the species. These different responses of gas exchange to VPD shown by the tropical and temperate rainforest species may reflect different strategies to maximise productivity in their respective climates.

Xanthones from a microfungus of the genus Xylaria

Chemical investigations of a microfungus Xylaria sp. isolated from the Australian rainforest tree Glochidion ferdinandi have afforded two new natural products, 2-hydroxy-6-methyl-8-methoxy-9-oxo-9 H-xanthene-1-carboxylic acid ( 1) and 2-hydroxy-6-hydroxymethyl-8-methoxy-9-oxo-9 H-xanthene-1-carboxylic acid ( 2). Compound 1 has previously been synthesised but only partially characterised. Methylation of 1 using diazomethane afforded the crystalline compound 2,8-dimethoxy-6-methyl-9-oxo-9 H-xanthene-1-carboxylic acid methyl ester ( 3), whose structure was determined by single crystal X-ray analysis. This paper reports the full spectroscopic characterisation of compounds 1– 3 by NMR, UV, IR and MS data. All compounds were inactive in a brine shrimp lethality assay and several antimicrobial screens.

Seed reserves and light intensity affect the growth and mycorrhiza development of the seedlings of an Australian rain-forest tree

Interspecific variation in seed size can affect seedling establishment in the light-limited understorey of rain forests. Large seeds with extensive seed reserves may allow seedlings to (1) persist in the deep shade, thereby increasing the likelihood of exposure to a canopy gap (Leishman & Westoby 1994, Saverimuttu & Westoby 1996); (2) promote growth, thereby allowing seedlings to reach higher light strata or to develop sufficient photosynthetic tissue to meet their energy needs in low light (Foster 1986); and (3) allow compensation for tissue losses to herbivores and pathogens (Armstrong & Westoby 1993, Foster 1986, Harms & Dalling 1997). However, comparisons of shade tolerance among species that vary in seed size have produced conflicting results; short-term seedling survival was strongly positively associated with seed size in several studies (Grime & Jeffrey 1965, Leishman & Westoby 1994), but only weakly in others (Augspurger 1984, Grubb & Metcalfe 1996).

Cassowary frugivory, seed defleshing and fruit fly infestation influence the transition from seed to seedling in the rare Australian rainforest tree, Ryparosa sp. nov. 1 (Achariaceae).

The rare Australian rainforest tree Ryparosa sp. nov. 1 aff. javanica (sensu Webber & Curtis, BW-017; Achariaceae) has large fleshy fruits that undergo a distinctive colour change during ripening. Fruit seem highly suited to frugivore interactions with large ground-dwelling avian or marsupial frugivores, a role primarily filled by the endangered cassowary. We found that fruits had chemical defence traits that closely paralleled morphological ripening signals. Young fruit seeds had amongst the highest concentrations of plant tissue cyanogens ever recorded (some in excess of 12 mg g-1 dw), yet the flesh of ripe fruits had negligible cyanogen defence. A seed treatment trial found that cassowary gut passage significantly improved germination from 4% to 92%, and we were not able to replicate this result with simulated treatments. While high levels of fruit fly larval infestation accounted for reduced seed viability, this predation was apparently reduced by cassowary gut passage. Post-germination seedling traits such as haustorial cryptocotylar cotyledons and epigeal germination may increase the chance of survival for establishing seedlings. We conclude that the range of traits seen in Ryparosa recruitment is particularly suited to interactions with frugivores and survival in a rainforest ecosystem.

Estimation of microfungal diversity in tropical rainforest leaf litter using particle filtration: the effects of leaf storage and surface treatment

Fungal species richness and abundance were assessed in leaf litter of the Australian rainforest tree Neolitsea dealbata (Lauraceae) using particle filtration. Results were comparable to the species richness and abundance reported in previous studies of tropical leaf litter microfungi. Eight leaf samples yielded 1365 strains. In an assessment of the effect of surface treatments, 736 strains in 112 morphotaxa were isolated, while 639 strains in 141 morphotaxa were recovered to assess the effect of surface treatment. Isolation rates in airdried leaves stored at room temperature for four weeks declined linearly, while the number of morphotaxa remained essentially constant for the first three weeks. Isolates of common morphotaxa were lost preferentially over those of rarer taxa. Such losses of isolates may be acceptable if only presence/absence data are collected. If frequency data are vital for community analysis, only fresh material should be utilised. Two surface sterilisation treatments were applied to N. dealbata leaves. An ethanol/sodium hypochlorite treatment was considered unsuitable because it significantly reduced the number of morphotaxa derived from the leaf lamina. A sodium hypochlorite treatment reduced the number of detectable propagules in the wash water without changing the number of morphotaxa derived from leaf particles in comparison with those of the control group.

The potential contribution of biomechanical properties to anti-herbivore defence in seedlings of six Australian rainforest trees

Biomechanical properties of leaves, such as strength and toughness, may contribute to anti-herbivore defence by making it physically difficult or energetically costly for animals to eat them. We investigated leaf strength and toughness in seedlings of six rainforest trees from eastern Australia and their potential contribution to defence. Strength and toughness (work to fracture) were measured at the scale of the whole leaf and of different leaf parts. Resources for herbivores (water and nitrogen) and potential chemical defences (phenolics, alkaloids and cyanogenic glycosides) were also investigated.Leaves of Nothofagus moorei (F.Muell.) Krasser, Ceratopetalum apetalum D.Don and Doryphora sassafras Endl. were generally the toughest and strongest of those studied. Toona ciliata M.Roemer showed high concentrations of nutritive resources and little investment in the defences investigated, consistent with its shorter leaf lifespan and higher growth rate. There were no significant correlations of mechanical properties with palatability, but the softest leaf (T. ciliata) was associated with high levels of leaf damage in bioassay trials. There was also evidence that some leaves that are well-defended mechanically (involving carbon-rich cell wall) may invest less in competing carbon-based chemical defences, such as phenolics.

Growth responses to arbuscular mycorrhizae by rain forest seedlings vary with light intensity and tree species

Light intensity and root colonization by arbuscular mycorrhizal (AM) fungi are considered important factors affecting the performance of rain forest plants, yet few studies have examined how these two factors interact. Whether AM colonization promoted growth or caused shifts in biomass allocation in seedlings of four species of Australian rain forest tree (Flindersia brayleana, Acmena resa, Cryptocarya mackinnoniana and Cryptocarya angulata), grown in a glasshouse under light conditions that mimicked the shaded understory (3% PAR) and small light gaps (10% PAR), was examined. Seedlings were grown in sterilized field soil and either inoculated with AM fungi or provided sterile inoculum. Four major findings emerged. First, in all species, seedlings grown in small gap light intensities were larger than seedlings grown in understory light intensities. Second, when seedling biomass was included as a covariate, variation in light intensity was associated with significant shifts in biomass allocation. In all species, leaf area ratio was lower at 10% PAR than at 3% PAR, while root-to-shoot ratio showed the opposite pattern in one of the four species (C. mackinonniana). Third, although percentage root length colonized by AM fungi was greater at 10% PAR than 3% PAR in all species, this difference could be accounted for by variation in seedling size in all species except C. angulata. Fourth, growth and biomass allocation responses to AM colonization varied with light intensity and plant species. AM colonization promoted growth in both light regimes only in F. brayleana, while it had no effect on growth in C. mackinnoniana and C. angulata in either light regime and promoted growth only under high light in A. resa. AM colonization had no effect on leaf area ratio or root-to-shoot ratio in any of the species, and significantly altered specific root length in only one of the four species (C. mackinnoniana). These findings suggest that rain forest seedlings are highly variable in their growth responses to AM colonization and that some of this variability is related to the light intensity of the environment. Given that seedlings may spend many years in the shaded understory, these differences among species could have important effects on long-term seedling performance and seedling community dynamics.

Comparison of temperate and tropical rainforest tree species: growth responses to temperature

Abstract Aim To investigate whether the latitudinal distribution of rainforest trees in Australia can be explained by their growth responses to temperature.Methods The rainforest canopy trees Acmena smithii (Poir.) Merrill & Perry, Alstonia scholaris (L.) R. Br., Castanospermum australe Cunn. & C. Fraser ex Hook., Eucryphia lucida (Labill.) Baill., Heritiera trifoliolata (F. Muell.) Kosterm., Nothofagus cunninghamii (Hook.) Oerst., Sloanea woollsii F. Muell. and Tristaniopsis laurina (Sm.) Wilson & Waterhouse were selected to cover the latitudinal range of rainforests in eastern Australia. Seedlings of these species were grown under a range of day/night temperature regimes (14/6, 19/11, 22/14, 25/17, and 30/22 °C) in controlled‐environment cabinets. These seedlings were harvested after 16 weeks to determine differences in growth rate and biomass allocation among species and temperature regimes.Results The temperate species showed maximum growth at lower temperatures than the tropical species. However, there was considerable overlap in the growth rates of the temperate and tropical rainforest types across the temperature range used. Maximum growth of the tropical rainforest types was associated with changes in biomass allocation whereas the temperate rainforest types showed no significant changes in biomass allocation across the temperature range.Main conclusions All species showed temperatures for maximum growth that were considerably higher than those previously shown for maximum net photosynthesis. The growth responses to temperature of the rainforest species under these experimental conditions provided limited evidence for their restriction to certain latitudes. These growth responses to temperature showed that the physiological assumptions used in various types of vegetation‐climate models may not be true of Australian rainforest trees.

Do temperate rainforest trees have a greater ability to acclimate to changing temperatures than tropical rainforest trees?

• Photosynthetic responses to acclimation temperature were investigated in seedlings of eight Australian rainforest tree species. Australian rainforests extend over 33° of latitude, providing an opportunity to compare temperature responses of temperate and tropical species. • Net photosynthesis was measured in leaves developed under a constant (22°C:14°C) or fluctuating (17°C:9°C-27°C:19°C) day/night temperature regime. These leaves were then subjected to a series of constant temperature regimes and net photosynthesis was measured 14d after acclimation to each new regime. • Acclimation potential was not affected by the contrasting temperature regimes. The temperate species showed at least 80% of maximum net photosynthesis over a larger span of acclimation temperature than the tropical species. • The lack of an effect of the contrasting temperature regimes on acclimation potential may reflect either that adjustments were unnecessary for temperate species, which already have broad photosynthetic responses to temperature, and tropical species were incapable of adjustments, or that in general species respond to the mean temperature regime and not to the amount of fluctuation in the regime. The higher acclimation potential shown by the temperate species is consistent with the larger seasonal and day-to-day variation in temperature of the temperate climate compared with the tropical climate.