Prediction of benthic macroinvertebrate composition using microhabitat characteristics derived from stereo photography

1. Benthic macroinvertebrate community and habitat features varying at the microscale ( 0.09 m ² ) were measured on one sampling occasion in the Thredbo River, Kosciusko National Park, NSW, Australia.
2. Most of the substratum habitat variables were measured in three dimensions using stereo photography. This is the first time that this method has been used so extensively for this purpose in freshwater ecology.
3. Microhabitat variables most related to benthic macroinvertebrate distribution and abundance were selected with multivariate analyses included rock length, height, area and water velocity. Individual variables alone could not account for macroinvertebrate variation, indicating the importance of interactions among variables.
4. Nine selected habitat variables were used to predict macroinvertebrate taxonomic content of additional sites. Predictions were 87% accurate for taxa with a > 50% chance of occurrence and 93% accuracy for taxa with a > 70% chance of occurrence. Variability observed in macroinvertebrate assemblages at the time of sampling was largely physically controlled and highly deterministic.     

Requirements for Floral Induction in Contrasting White Clover (Trifolium repens) Populations

Norm, I. B. 1987. Requirements for floral induction in contrastingwhite clover (Trifolium repens) populations.—J. exp. Bot.38: 900–907. Floral initiation and development of four contrasting whiteclover (Trifolium repens) populations was examined after differentinduction treatments (16 h, 5 ?C and 8 h, 5 ?C. The number of reproductive stolons and of reproductive budsper stolon was increased after cold induction. Varietal differencesin response to daylength were large; some varieties respondingbetter to a long day cold period, others to a short day coldperiod while one variety required no induction at all. Whetherthe daylength effect was due to photoperiod, irradiance or totheir interaction was not known. The induction periods had a subsequent effect upon pedunclelength, floret and ovule number. Short days and chilling reducedpeduncle length but increased ovule number, whereas long daysand chilling tended to increase floret number. Nectar concentrationwas highest after short day induction. Key words: White clover, floral initiation, floral induction     

Phytotoxic Compounds produced by Fusarium equiseti

Culture filtrates of several strains of Fusarium equiseti (Corda)Sacc. were found to be highly phytotoxic. Several phytotoxicsubstances were isolated; the most important of these was acolourless crystalline compound, diacetoxyscirpenol, m.p. 161-2°,C₁₉H₂₆O₇. Though highly phytotoxic in many respects, it markedlystimulates elongation of cress roots at 0.01–0.5 µg./ml.This is not an anti-auxin effect. Diacetoxyscirpenol is at mostonly slightly inhibitory to fungi and bacteria, but is highlytoxic to rats. Two minor metabolic products, m.p. 135-6°and 185-8° respectively, are also described. They, too,were highly phytotoxic, though their spectra of activity weresomewhat different from that of diacetoxyscirpenol. They alsowere highly toxic to rats. Production of these substances isprobably not important in the aetiology of disease symptomsin plants parasitized by F. equiseti, but may be significantin cases of toxicosis of animals fed with grain infected byFusaria. Scirpentriol, a hydrolysis product of diacetoxyscirpenol,is much less phytotoxic but of equal toxicity to rats.