Chlorsulfuron Reduces Extension of Wheat Root Tips in Low-zinc Solution Culture

Root tip extension was used as a measure of wheat root responseto exposure to the sulfonylurea herbicide chlorsulfuron. Plantspre-grown in low-zinc (0.2 µMZnHEDTA) solutions were placedin a perspex chamber with nutrient solution on both sides ofa partition separating the root tip from the rest of the plant.The root tip was exposed to different concentrations of chlorsulfuronand observations were made during 22 h. Increasing the concentrationof zinc in the solution around the root tip to 4 µMZnHEDTAdid not alter root tip extension in the absence of chlorsulfuron.Significant decreases in root growth after 22 h were obtainedwith concentrations of 120 µg chlorsulfuron l^-1and greater.Increasing the Zn concentration from 0.2 to 20 µMZnHEDTAin the nutrient solution around the root tip decreased controlroot growth but stimulated chlorsulfuron-treated roots to extendat the same rate as chlorsulfuron-free control plants. AddingZn and chlorsulfuron to the more mature root parts above theroot tip partition did not significantly influence root tipextension. It is concluded that chlorsulfuron inhibits wheatroot growth and that increased Zn concentrations can alleviateor prevent the deleterious effects of chlorsulfuron.Copyright1998 Annals of Botany Company Wheat,Triticum aestivumL., chlorsulfuron, root growth, zinc.     

Stability in temperate reef communities over a decadal time scale despite concurrent ocean warming

Despite increasing scientific and public concerns on the potential impacts of global ocean warming on marine biodiversity, very few empirical data on community-level responses to rising water temperatures are available other than for coral reefs. This study describes changes in temperate subtidal reef communities over decadal and regional scales in a location that has undergone considerable warming in recent decades and is forecast to be a 'hotspot' for future warming.
Plant and animal communities at 136 rocky reef sites around Tasmania (south-east Australia) were censused between 1992 and 1995, and again in 2006 and 2007. Despite evidence of major ecological changes before the period of study, reef communities appeared to remain relatively stable over the past decade. Multivariate analyses and univariate metrics of biotic communities revealed few changes with time, although some species-level responses could be interpreted as symptomatic of ocean warming. These included fishes detected in Tasmania only in recent surveys and several species with warmer water affinities that appeared to extend their distributions further south. The most statistically significant changes observed in species abundances, however, were not related to their biogeographical affinities. The majority of species with changing abundance possessed lower to mid-range abundances rather than being common, raising questions for biodiversity monitoring and management. We suggest that our study encompassed a relatively stable period following more abrupt change, and that community responses to ocean warming may follow nonlinear, step-like trajectories.     

Visual fields in Blue Ducks Hymenolaimus malacorhynchos and Pink-eared Ducks Malacorhynchus membranaceus: visual and tactile foraging

Blue Ducks Hymenolaimus malacorhynchos (Anatidae), an IUCN Red Listed Endangered species, reside in headwaters of New Zealand rivers and feed primarily on aquatic invertebrates. However, whether such food items are detected by tactile or visual cues is unknown. That Blue Ducks may use tactile cues when foraging is suggested by the presence of specialized flaps of thickened, keratinized epidermis containing Herbst's corpuscles along the ventral margins of the upper mandibles near the bill tip. Similar bill flaps are found only in one other duck species, Pink-eared Ducks Malacorhynchus membranaceus , that surface filter-feed on a range of planktonic organisms. Using an ophthalmoscopic reflex technique we determined the visual fields of both species. In Blue Ducks the eyes are frontally placed resulting in a relatively wide binocular field into which the narrow tapering bill intrudes. There is a large blind area to the rear of the head. This visual field topography is similar to that of other visually guided foragers including those that take mobile prey from the water column, e.g. penguins (Spheniscidae). By contrast, Pink-eared Duck visual fields show features found in other tactile feeding ducks: a narrow frontal binocular field with the bill falling at the periphery, and comprehensive visual coverage of the celestial hemisphere. We conclude that although Blue Ducks may take prey from rock surfaces they are primarily visual feeders of the water column and we suggest therefore that their foraging may be significantly disrupted by changes in water clarity. This introduces a previously unconsidered factor into the selection of sites for population enhancement or re-introductions, a current conservation focus.     

Phenotypic variation in colour pattern and seasonal plasticity in Eristalis hoverflies (Diptera: Syrphidae)

Abstract.

• 1 An examination of phenotypic variation in colour pattern was carried out on four Eristalis hoverfly species using museum material.
• 2 The amount of phenotypic variation varied substantially among the species with E.arbustorum being the most variable. The other species showed a wide colour pattern range but less variation within that range (E.abusivus and E.nemorum), or a narrow range of colour variation (E.horticola).
• 3 Sexual colour dimorphism was apparent in all four species, but most pronounced in E.abusivus and E.nemorum.
• 4 There were good phenotype-season relationships shown by both sexes in all species, except for female E.abusivus and E.nemorum, with paler insects being more abundant during the warmer summer months.
• 5 Female, but not male, E.arbustorum collected at inland sites were on average paler than those collected at coastal sites. This observation is considered with respect to temperature during the developmental stages.
• 6 The function of colour plasticity in hoverflies is discussed with reference to the need to maintain optimal thermal conditions for activity.

     

Cladistic analysis of the Lythraceae sensu lato based on morphological characters

GRAHAM, S. A., CRISCI, J. V. & HOCH, P. C, 1993. Cladistic analysis of the Lythraceae sensu lato based on morphological characters. The Lythraceae s. I. comprise 31 mostly highly distinctive genera distributed worldwide. Cladistic analyses of the family were undertaken using 26 characters from anatomy, floral morphology, pollen, and seed morphology. Of four outgroup hypotheses, the Onagraceae offered the best heuristic assessment, generating 3746 trees with a tree length of 83 and consistency index and (C.I.) of 0.41. A strict consensus tree from the 3746 trees produced a basal monophyletic group of five genera (Sonneratia, Duabanga, Punka, Lagerstroemia, Lawsonia) characterized by anthotelic (determinate) inflorescences and wet stigmas, and a second clade with blastotelic (indeterminate) inflorescences, dry stigmas, and reduced carpel number. Successive weighting with Onagraceae as outgroup generated five most parsimonious trees with a tree length of 164 and C.I. of 0.75. Internal branches are weakly supported by only seven non-homoplasious characters. Significant results of the analysis include: (1) recognition of the two major clades and a total of seven monophyletic groups within the family; (2) the paraphyly of subfamily Lythroideae (Lythraceae s. s .); and (3) indication that genera endemic to the New World have been derived from more than one ancient Old World evolutionary line. The current taxonomic classification of the family is not closely correlated with results of the cladistic analysis.     

Foraging movements of the Shy Albatross Diomedea cauta breeding in Australia; implications for interactions with longline fisheries

Satellite telemetry was used to identify the foraging zones of Shy Albatrosses Diomedea cauta breeding at two sites off Tasmania, Australia (Albatross Island in western Bass Strait and Pedra Branca to the south) to assess their level of interaction with longline fisheries. Adult birds from both colonies fed locally both in and outside the breeding season. Breeding birds from Albatross Island foraged over the Australian continental shelf or slope waters off northwest Tasmania, while those from Pedra Branca foraged between the colony and the southeastern edge of the continental shelf. The distances travelled by the birds and the duration of their foraging trips varied during the breeding cycle and tended to decrease as eggs approached hatching. Adults which were tracked near the end of the breeding season (March-April, n = 7 birds) deserted their chicks prematurely, and while dispersing further than incubating or brooding birds, they remained over the continental shelf and slope waters off southeast Australia. Home range analyses indicated 41% overlap between foraging zones of birds during successive breeding stages. Dispersal during the postbreeding period extended the foraging zones with less overlap between individuals (10% for Albatross Island and 19% for Pedra Branca). The recent contraction of the Japanese Southern Bluefin Tuna longline fishery to the south and east coasts of Tasmania has resulted in extensive overlap with adult Shy Albatrosses from Pedra Branca, but appears to pose a minimal threat to adult birds from Albatross Island. Coupled with the concomitant increase in the Australian domestic tuna longlining industry, adult Shy Albatrosses from southern Tasmania (Pedra Branca and the Mewstone) are vulnerable to incidental capture through out their annual cycle.     

USE OF MINERALISED WATER BY KALAHARI WILDLIFE AND ITS EFFECTS ON HABITATS

This study surveyed the use made by springbok, hartebeest, wildebeest and gemsbok, in particular, of mineralised artificial waterholes along the Nossob river in the southern Kalahari and the effects of this use on the delicate surrounding habitats, as a basis for evaluating the uses and limitations of such water in the management of these species. Taking into account the chemical composition of the dissolved salts in the water; the status of the vegetation and conservation trends near water holes; the relative use made of the waterholes by the antelopes; and land use history, it was concluded that: (a) the animals made regular use of the water, some of which was more mineralised than that recommended for domestic stock, including sheep; (b) there was no relationship between the total dissolved salts and animal use, although there may have been some association between gemsbok use and certain ions; (c) wildlife attracted to boreholes had very little effect on the stability of some surrounding habitats, but may have retarded recovery in areas downgraded by past land use, and (d) under these circumstances the effects of this land use were still amply evident after 2¹/₂ decades. From this and other evidence, it is suggested that, at the present level of knowledge, mobile wildebeest populations can be stabilised by the provision of relatively potable water, and mineralised water may be used to raise the levels of springbok, hartebeest and gemsbok populations. However, as the water is less of a limiting factor than for species requiring regular drinking water, the increase in density may be relatively limited and so less of a danger to the maintenance of surrounding habitats.     

The emergence of midges (Diptera: Chironomidae) from a wet gravel-pit

SUMMARY. Emerging adult chironomids were captured from a wet gravel-pit in the Midlands in 1975 and 1976. The emergence period in 1976 was earlier than in 1975 and this change was attributed to the higher temperatures during the early part of 1976. Forty-seven species were identified of which twenty-one were found in both years. However, only eighteen species represented more than 5% of the monthly emergence from any one trap. The timing and location of emergence of the common species is discussed in relation to the physical parameters of substratum, depth of water and vegetation at each trap site. Similarity indices were used to compare samples from each trap site and revealed a progressive change in the chironomid assemblage with depth, caused by a succession of species and a change in the structure of the assemblage with 'equitability' decreasing with increasing depth. The predominant species in 1975 were Cricotopus sylvestris, C. intersectus and Procladius choreus with a number of Chironominae present in both May and June. A trap in the littoral zone caught maximum numbers earlier than traps in open water. In 1976 the above species were still predominant and Tanypus punctipennis and T. vilipennis were also numerous. The Chironominae became proportionally more abundant as the season progressed. The abundance of emerging midges was low compared with other surveys due to the restricted emergence period, imagines being abundant only in June, and also due to the low numbers emerging.     

Transport of copper and manganese to the xylem exudate of sunflower

Abstract Absorption of copper and manganese by sunflower roots from solution cultures of varying composition was followed by measuring the concentrations of the metals appearing in whole roots, root cell sap and xylem exudate. Total copper in the fibrous roots was linearly related to the concentration of copper in the external solution but the concentration of copper released to the xylem exudate was buffered somewhat against the changes made externally. No such buffering was observed for managenese. A copper-sensitive electrode, responsive only to free cupric ions was used in conjunction with total copper analysis by atomic absorption spectrophotometry to show that little of the copper (usually < 1%) existed as a free ion in any phase of the system. Copper in the xylem exudate may be strongly complexed. An electron paramagnetic resonance spectrum of the xylem exudate indicated that manganese probably was a free divalent ion. Calculation of the electrochemical potential gradient for free cupric ions showed that no special metabolically-linked mechanism need be postulated to account for absorption of copper (or manganese) other than that necessary to maintain the transmembrane potential.