Stem End blockaged in Cut grevillea 'Crimson Yul-lo' inflorescences

Grevillea 'Crimson Yul-lo' inflorescences have cut flower potential, but their vase life is short. End of vase life is characterized by early wilting. The possibility of physiologically mediated stem end blockage was investigated. Hydraulic conductance of 2 cm long stem end segments declined rapidly and remained lower throughout vase life than that of 2 cm long stem segments from immediately above. Recutting daily to remove basal 2 cm stem ends increased solution uptake, delayed declines in inflorescence water potential and water content, and improved inflorescence vase life. S-carvone is a potential inhibitor of wound related suberin formation, via inhibition of phenylalanine ammonia-lyase. Vase solution treatments with S-carvone (0.318 and 0.636 mM) delayed the decline in hydraulic conductance of basal 2 cm long stem end segments and decreases in vase solution uptake and relative fresh weight of cut stems, and extended vase life. Treatments with the catechol oxidase inhibitor 4-hexylresorcinol (2.5-10 mM) also delayed stem end blockage. These findings suggest that stem end blockage in cut G. 'Crimson Yul-lo' stems is physiologically mediated. (C) 2006 Elsevier B.V. All rights reserved.

Reciprocal N ((NH4+)-N-15 or (NO3-)-N-15) transfer between nonN(2)-fixing Eucalyptus maculata and N-2-fixing Casuarina cunninghamiana linked by the ectomycorrhizal fungus Pisolithus sp.

Two-way N transfers mediated by Pisolithus sp. were examined by excluding root contact and supplying (NH4+)-N-15 or (NO3-)-N-15 to 6-month-old Eucalyptus maculata or Casuarina cunninghamiana grown in two-chambered-pots separated by 37 m screens. Mycorrhizal colonization was 35% in Eucalyptus and 66% in Casuarina (c. 29% N-2-fixation). Using an environmental scanning electron microscope, living hyphae were observed to interconnect Eucalyptus and Casuarina. Biomass and N accumulation was greatest in nodulated mycorrhizal Casuarina/mycorrhizal Eucalyptus pairs, less in nonnodulated mycorrhizal Casuarina/mycorrhizal Eucalyptus pairs, and least in nonnodulated nonmycorrhizal Casuarina/nonmycorrhizal Eucalyptus pairs. In nonnodulated mycorrhizal pairs, N transfers to Eucalyptus or to Casuarina were similar (2.4-4.1 mg per plant in either direction) and were 2.6-4.0 times greater than in nonnodulated nonmycorrhizal pairs. In nodulated mycorrhizal pairs, N transfers were greater to Eucalyptus (5-7 times) and to Casuarina (12-18 times) than in nonnodulated mycorrhizal pairs. Net transfer to Eucalyptus or to Casuarina was low in both nonnodulated nonmycorrhizal (< 0.7 mg per plant) and nonnodulated mycorrhizal pairs (< 1.1 mg per plant). In nodulated mycorrhizal pairs, net transfer to Casuarina was 26.0 mg per plant. The amount and direction of two-way mycorrhiza-mediated N transfer was increased by the presence of Pisolithus sp. and Frankia, resulting in a net N transfer from low-N-demanding Eucalyptus to high-N-demanding Casuarina.

Rhizoctonia crown and root rot of the pasture legume, sulla (Hedysarum coronarium)

Rhizoctonia solani AG-2-2 was isolated from wilting and dying plants of sulla ( Hedysarum coronarium), which is currently being assessed in eastern and southern Australia for its potential as a pasture and forage legume. Infected plants in the field had extensive rotting of the taproot, lateral roots and crown. Koch's postulates were fulfilled using three inoculation methods. The disease may pose a considerable threat to the potential use of H. coronarium in the dryland, grazing farming systems of Australia, with resistance offering the most viable option for minimising its impact.

Laboratory evaluation of the effect of alternative prey and vegetation on predation of Culex annulirostris immatures by Australian native fish species

The impact of alternative prey and simulated vegetation on Culex annulirostris Skuse predation efficacy by Australian smelt, Retropinna semoni (Retropinnidae); crimson-spotted rainbowfish, Melanotaenia duboulayi (Melanotaeniidae); empire gudgeon, Hypseleotris compressa (Eleotridae); estuary perchlet, Ambassis marianus (Ambassidae); firetail gudgeon, Hypseleotris galii (Eleotridae); fly-specked hardyhead, Craterocephalus stercusmuscarum (Atherinidae); and Pacific blue-eye, Pseudomugil signifer (Atherinidae), was evaluated in Queensland, Australia. The presence of chironomid midge larvae and tusked frog, Adelotus brevis (Leptodactylidae), tadpoles did not have a significant negative impact on the predation rates of Cx. annulirostris by these 7 fish species. Hypseleotris galii, M. duboulayi, and R. semoni demonstrated strong preference for larvae of Cx. annulirostris over both alternative prey species. In the presence of alternative prey species, the mean predation rate of M. duboulayi on larvae of Cx. annulirostris remained greater than that of other fish species tested. When evaluated at varying densities of simulated vegetation, predation rates of all fish species were similar to those reported in open conditions.

Theft of bower decorations among male Satin Bowerbirds (Ptilonorhynchus violaceus): why are some decorations more popular than others?

Male Satin Bowerbirds (Ptilonorhynchus violaceus) build stick structures known as bowers that serve as the focus for courtships and matings. Males decorate their bowers with numerous coloured decorations and are known to steal these decorations from one another. We investigated the stealing of bower decorations among males at the Bunya Mountains in Queensland, Australia. We aimed to (1) determine which classes of decorations were targets for theft in the studied population, and (2) examine whether the frequency at which individual decorations were stolen related to their intrinsic properties. To address our first aim, all decorations on the bowers of 21 adult males were labelled and their movements tracked throughout one mating season. To address our second aim, decorations stolen at least three times during the season were collected and their morphological and reflectance properties compared to those of decorations that were not stolen. In terms of the classes of decorations, tail feathers of Crimson Rosella (Platycercus elegans) were stolen more than any other class of decoration, but blue plastic bottletops were the most popular decorations relative to their availability on bowers. Frequently stolen individual decorations were similar to non-stolen items in their weights and surface areas, but were darker blue in colour than the decorations never stolen. Both bottletops and feathers reflected higher levels of ultraviolet (UV) light than did all other classes of bower decorations tested, thus suggesting that males may be using UV reflectance in sexual signalling. The darker blue, stolen decorations may increase contrast between the decoration collection and the platform, while the UV-reflecting subset of most frequently stolen decorations (bottletops and feathers) may increase contrast within the decoration collection. This in turn may increase the attractiveness of the display to females.