Paul Reddell

Earthworms as vectors of viable propagules of mycorrhizal fungi

Abstract Casts of 13 earthworm species with differing ecological strategies were collected from more than 60 sites and examined for the presence of propagules of vesicular arbuscular mycorrhizal (VAM) fungi. Intact spores of VAM fungi were found in all but one collection. VAM root fragments were also present in some cast samples. The diversity of VAM spore types found in casts was similar to that in adjacent, uningested soils. However, the relative concentration of spores (No. g−1 dry wt) in casts was higher than in the general soil for the two earthworm species (Pontoscolex corethrurus and Diplotrema heteropora) for which this was assessed. There was a strong seasonality in the number of spores recovered from casts of D heteropora and this reflected seasonal patterns of spore production in soil. Glasshouse experiments demonstrated that spores recovered from casts of P. corethrurus and D. heternpora maintained viability and initiated mycorrhizal infection on Sorghum bicolor. Similarly, some VAM root fragments found in casts were also able to infect S. bicolor. Spores of ectomycorrhizal fungi and fragments of ectomycorrhizal roots were observed at low frequencies in some cast samples from sites dominated by sclerophyllous vegetation. The infectivity of these propagules was not determined. The ubiquity and ecological significance of short distance transport of VAM propagules by earthworms is discussed in relation to the ecological strategics of earthworms.

Growth responses in Casuarina cunninghamiana plantings to inoculation with Frankia.

Growth responses ofCasuarina cunninghamiana to inoculation withFrankia are described in unsterilized field soils at three sites.At Mt Crawford, South Australia, seedlings of three provenances ofC. cunninghamiana were inoculated with a singleFrankia source just prior to planting out. Forty-four months after planting, inoculation had more than doubled wood production by twoC. cunninghamiana provenances, whilst a third provenance grew poorly and did not respond to inoculation.In Zimbabwe, seedlings of one provenance ofC. cunninghamiana were inoculated in the nursery with one of four differentFrankia strains. In an N deficient soil at Kadoma, three of theseFrankia increased tree height 14 months after planting by between 50% and 70% in comparison to the uninoculated seedlings. The fourthFrankia strain resulted in increased tree height to three times that of the uninoculated controls and up to double that of the other threeFrankia strains.At Gympie, Queensland, Australia, seedlings ofC. cunninghamiana raised open-rooted in a nursery bed were inoculated withFrankia seventeen weeks before planting out. During the 22 months following planting in the field, tree growth was limited by soil P status and there was no response in tree height or stem diameter to inoculation withFrankia or to N fertilizer unless P was applied. In the presence of added P there was a significant response both toFrankia inoculation and to N fertilizer. This positive interaction between P application and N treatment was reflected in wood volumes-inoculated trees and those trees supplied N fertilizer produced 34% and 95% more wood volume than did the uninoculated trees.These results demonstrate the potential to increase the productivity of Casuarina plantings by inoculation withFrankia and by alleviation of P deficiency.

Arbuscular mycorrhizas and ectomycorrhizas on Eucalyptus grandis (Myrtaceae) trees and seedlings in native forests of tropical north-eastern Australia

Eucalypts have been shown to form both arbuscular mycorrhizas (AM) and ectomycorrhizas (ECM) in glasshouse experiments. Little is known, however, about the relative dominance of these two mycorrhiza types on individual eucalypt species across their natural range. This study examined mycorrhizal colonisation levels of Eucalyptus grandis Hill ex Maiden roots at 29 sites representing a broad range of wet sclerophyll forest types in the wet tropics of north-eastern Australia. Adult E. grandis trees sampled in situ were invariably heavily ectomycorrhizal, with 76–100% fine root length colonised (% RLC). There were comparatively low levels of AM, with typically less than 10% RLC. Seedling E. grandis grown in intact soil cores from the field sites under glasshouse conditions had lower total levels of mycorrhiza formation compared with adult trees, with more variable ECM formation (10–95% RLC) and more extensive AM formation (10–40% RLC). There were no apparent trends in mycorrhiza formation across different soil parent material, rainfall or vegetation categories used. The current research suggests that arbuscular mycorrhizas are more prominent on seedlings, whereas ectomycorrhizas predominate in adult trees of E. grandis. Possible reasons for these differences and a comparison with other studies of eucalypt mycorrhizas under natural conditions are presented.

Transmission of infective Frankia (actinomycetales) propagules in casts of the endogeic earthworm Pontoscolex corethrurus (Oligochaeta:Glossoscolecidae)

Abstract A glasshouse experiment was used to investigate the transfer of infective Frankia propagules in soil by the endogeic earthworm Pontoscolex corethrurus. Seedlings of Casuarina equisetifolia were inoculated, either with a crushed nodule suspension of Frankia, or with casts of P. corethrurus that had been raised in a sterilized soil through which crushed nodules of C. equisetifolia had been thoroughly mixed. Two concentrations of cast material were applied: casts from 3 earthworms and casts from 11 earthworms. Uninoculated plants grew poorly and did not nodulate. All seedlings inoculated directly with the crushed nodule suspension formed nodules; shoot dry weights of these seedlings 10 weeks after inoculation were 70% higher than those of the uninoculated plants. All plants inoculated with casts from 11 earthworms formed nodules. Shoot and nodule dry weights of these seedlings were similar to those of the plants that were directly inoculated with the crushed nodules. Decreasing the number of earthworm casts applied to 3 per plant substantially reduced plant growth compared to the higher cast concentration. Nodulution was erratic in this treatment with only 3 of the 7 plants forming nodules. Shoot dry weights of plants inoculated wih 3 casts were similar to those of the uninoculated treatment. The possible ecological significance of these findings is discussed in relation to the ecology of earthworms in soil.

δ13C values of selected termites (isoptera) and termite-modified materials

Abstract The δ 13 C values of the tissue carbon of 14 termite species showed clear differences, related to the ranges of their putative diets. Only small differences in tissue δ 13 C values were apparent between worker and soldier castes in the seven species examined. δ 13 C values were higher in the mounds and other constructs of grass-harvesting species consuming C4 materials than in the surrounding surface soils. In contrast, mound δ 13 C values were similar to, or lower than the surface soils in species consuming materials from mixed C3 and C4 or C3 sources. Over all mound and other termite-modified materials, δ 13 C values were positively and highly correlated with surface soil and tissue values.

Do single nodules of Casuarinaceae contain more than oneFrankia strain

SummaryStudies using inoculum suspensions prepared from single nodules of Casuarinaceae suggest that more than oneFrankia strain may be found in some nodules. Evidence is also presented to support the concept of intergeneric specificity in host-Frankia relations in the family Casuarinaceae.

Structure and Absolute Stereochemistry of the Anticancer Agent EBC-23 from the Australian Rainforest

EBC-23 (2), a prostate anticancer agent, was isolated from the fruit of Cinnamomum laubatii (family Lauraceae) in the Australian tropical rainforest. Extensive NOE experiments enabled the relative stereochemistry of the proposed EBC-23 (2) structure to be determined. Total synthesis of both enantiopodes over nine linear steps, involving challenging RCM and spiroacetal cyclizations, confirmed the gross structure and relative and absolute stereochemistry.

Anticancer agents from the Australian tropical rainforest: Spiroacetals EBC-23, 24, 25, 72, 73, 75 and 76

EBC-23, 24, 25, 72, 73, 75 and 76 were isolated from the fruit of Cinnamomum laubatii (family Lauraceae) in the Australian tropical rainforests. EBC-23 (1) was synthesized stereoselectively, in nine linear steps in 8 % overall yield, to confirm the reported relative stereochemistry and determine the absolute stereochemistry. Key to the total synthesis was a series of Tietze-Smith linchpin reactions. The novel spiroacetal structural motif, exemplified by EBC-23 (1), was found to inhibit the growth of the androgen-independent prostate tumor cell line DU145 in the mouse model, indicating potential for the treatment of refractory solid tumors in adults.

Isolation and confirmation of the proposed cleistanthol biogentic link from Croton insularis.

The proposed cleistanthol biosynthetic intermediate en route to spruceanol, and other related family members, was isolated for the first time from Croton insularis, confirming the Jacobs-Reynolds hypothesis. Anticancer evaluation of the new isolates and their aerial oxidation products is also reported.

A Comparison of 2 Methods and Different Media for Isolating Frankia From Casuarina Root-nodules

Four species of Casuarina were raised in the glasshouse and inoculated with nodules collected from nine different geographical areas within Australia. Isolations ofFrankia were attempted from 10 of the Casuarina-Frankia nodule combinations using two methods, a nodule dissection and a filtration method. With both techniquesFrankia isolates were obtained from four of the 10Frankia sources. Spores were not observed in sections of nodules from the four sources from whichFrankia was isolated, whereas spores were observed in the remaining six nodule sources. For selected nodule sources a range of isolation media were tried, but no improvement in the isolation success rate was achieved.The effect of host species on ease of isolation was studied. The results obtained suggested it was theFrankia strain and not the host plant species which determined the ease of isolation from Casuarina nodules.