Salinity and in vitro Ageing Effects on Primary Photosynthetic Processes of Thylakoids Isolated from Pisum sativum and Spinacia oleracea

The effects of in vitro ageing and salinity of the reactionmedium on the primary photochemistry of photosystem II and thepattern of energy distribution within the photochemical apparatusof thylakoids isolated from Pisum sativum and Spinacia oleraceaare described. Analyses of the low temperature induction curvesof fluorescence emission at 695 and 735 nm and of low temperatureabsorption and fluorescence emission spectra were used to examinethese processes. In vitro ageing over short periods reducedthe photochemical activity and changed the energy distributionwithin thylakoids of P. sativum, but had little effect on thylakoidsof S. oleracea. A synergistic effect of in vitro ageing andsalinity of the reaction medium was observed for P. sativumthylakoids. Ageing effects could be minimized by addition of100 mM NaCl to the resuspension medium. Changes in NaCl concentrationin the reaction medium produced large and similar changes inthe primary photochemical functioning of thylakoids from P.sativum and S. oleracea, which could be attributed mainly tothe cation species, Na^$; however, experiments using mannitolto produce osmotic stress indicated some small osmotically inducedchanges in photofunction of the thylakoids. Optimal primaryphotochemical activity of photosystem II, for both species,was observed with 200 mM NaCl. Cation-induced regulation ofexciton distribution appears to be facilitated by controllingthe degree of energy coupling between the light-harvesting chlorophylla/b complex and the two photosystems, I and II, and not by regulationof coupling between photosystems I and II.     

Use of the Pressure Chamber in Membrane Damage Studies

The ability to detect membrane damage in plant leaves by thepressure chamber technique was evaluated. Membrane damage wasinduced by freezing and thawing, absorption of the host-specifictoxin victorin, ozonation, inoculation with Helminthosporiummaydis, and spraying with the phytotoxin, fusicoccin. The pressure-volumerelationships, i.e. the volume of sap expressed from a leafwith incremental increases in pressure, were compared in leaveswith intact or damaged membranes. Where membrane damage waswidespread throughout the leaf, sap was expressed at pressuresas low as one tenth of those needed in leaves with intact membranesand at low pressures the amount of water expressed from leaveswith damaged membranes was up to 10 times that from leaves withintact membranes. Further, the pressure-volume curves of healthyleaves became linear when the leaf turgor potential was reducedto zero, but were non-linear in leaves with damaged membranes.Ozone treatment, inoculation with H. maydis, or spraying withfusicoccin damaged only a proportion of the leaf cells, andpressure-volume relationships more nearly resembled those obtainedwith healthy leaves rather than those obtained with freezingand thawing and absorption of victorin. It is concluded that the pressure chamber can be used to observemembrane integrity, but its ability to detect damage may belimited to conditions in which the majority of cells in theleaf are damaged.     

The subspecies concept in butterflies: has its application in taxonomy and conservation biology outlived its usefulness?

Subspecies lie at the interface between systematics and population genetics, and represent a unit of biological organization in zoology that is widely used in the disciplines of taxonomy and conservation biology. In this review, we explore the utility of subspecies in relation to their application in systematics and biodiversity conservation, and briefly summarize species concepts and criteria for their diagnosis, particularly from an invertebrate perspective. The subspecies concept was originally conceived as a formal means of documenting geographical variation within species based on morphological characters; however, the utility of subspecies is hampered by inconsistencies by which they are defined conceptually, a lack of objective criteria or properties that serve to delimit their boundaries, and their frequent failure to reflect distinct evolutionary units according to population genetic structure. Moreover, the concept has been applied to populations largely comprising different components of genetic diversity reflecting contrasting evolutionary processes. We recommend that, under the general lineage (unified) species concept, the definition of subspecies be restricted to extant animal groups that comprise evolving populations representing partially isolated lineages of a species that are allopatric, phenotypically distinct, and have at least one fixed diagnosable character state, and that these character differences are (or are assumed to be) correlated with evolutionary independence according to population genetic structure. Phenotypic character types include colour pattern, morphology, and behaviour or ecology. Under these criteria, allopatric subspecies are a type of evolutionarily significant unit within species in that they show both neutral divergence through the effects of genetic drift and adaptive divergence under natural selection, and provide an historical context for identifying biodiversity units for conservation. Conservation of the adaptedness and adaptability of gene pools, however, may require additional approaches. Recent studies of Australian butterflies exemplify these points. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.     

Effects of neonatal nutrition on adult reproduction in a passerine bird

Effects of neonatal nutrition on adult reproductive performance have been little studied. In Zebra Finches Taeniopygia guttata , poor neonatal nutrition is known to be associated with reduced blood antioxidant levels in adulthood, which could impair reproductive performance. Here, we compare the effects of standard-quality (SQ) or lower-quality (LQ) neonatal nutrition on components of fecundity. Compared with controls, LQ birds took longer to initiate egg-laying, and then laid eggs at a slower rate. LQ birds did not, however, show reduced clutch mass or size, or yolk antioxidant levels (retinol; α- or γ-tocopherol; carotenoids). Zebra Finches breed opportunistically, often only once in their short lifetime. Therefore, the timing but also the number and quality of eggs are critical fitness-related traits. Our results indicate that LQ birds had impaired reproductive capacity, suggesting resource accumulation constraints. Maximizing egg number and quality appears to have been more important than rapid egg production.     

Controls on trace fossil diversity in an Early Cambrian epeiric sea: new perspectives from northwest Scotland

The Lower Cambrian Eriboll Formation of northwest Scotland is renowned for the high density, low diversity trace fossils (Skolithos ichnofacies) found in its upper Pipe Rock Member. Ichnofabric analysis of the member indicates that relatively small examples of Skolithos terminating at the same foreset boundary were formed during a brief colonization window after a single depositional event, that particularly long Skolithos specimens are equilibrichnia, and that palimpsests of Skolithos represent the marginal, slightly deeper water fringes of the Pipe Rock Member depositional environment. Nearest neighbour analysis, however, suggests that such palimpsests were uncommon. A much more diverse trace fossil assemblage is present in the overlying Fucoid Member (An t‐Sròn Formation), comprising Cruziana barbata, Dactylophycus, Didymaulichnus, Halopoa imbricata, ?Margaritichnus, Monocraterion, Monomorphichnus, Palaeophycus striatus, P. tubularis, ?Phycodes, Planolites montanus, ?Polarichnus, Rusophycus ramellensis, ?Psammichnites, Skolithos and various unidentified traces, and represents the Cruziana ichnofacies. Above the Fucoid Member, the Salterella Grit Member ichnofauna is more impoverished, yielding only Cruziana, Monocraterion, Rusophycus, Skolithos and ?Spirophyton. The ichnological variations between the Pipe Rock, Fucoid and Salterella Grit members are interpreted as being driven by changes in sea level. The low trace fossil diversity in the Pipe Rock Member indicates opportunistic colonization of laterally extensive, shoreface sediments deposited by regular influxes of terrigenous material, which were overlain by more distal, ichnologically diverse sediments (Fucoid Member) as sea level rose. A minor regression then caused an increase in terrigenous sediment input, producing an impoverished, proximal Cruziana ichnofacies (Salterella Grit Member).     

Water Relations of the Mistletoe Amyema fitzgeraldii and its Host Acacia acuminata

Water relations of the mistletoe Amyema fitzgeraldii and itshost Acacia acuminata were studied near Geraldton, Western Australia.Transpiration rates of host and parasite under unstressed winterconditions varied more than 300–fold between day and nightwhile leaf water potential gradients between the partners remainedwithin the range 0·4–0·6 MPa. Plots of transpirationagainst leaf water potential indicated closely similar fluidphase resistances in host and parasite during daytime but divergentbehaviour at night due to an apparently large increase in resistanceof the haustorial junction between the partners. Data for summerand winter studies across a full range of light intensitiesshowed the parasite to transpire, on average, 1·4 timesfaster and to exhibit noticeably lower water use efficienciesthan its host. Experiments following restorative changes atnight in leaf water potentials of host and parasite on detachedhost branches supplied through their cut ends with water indicatedthat the haustorium offered a major resistance to water uptakeby the parasite. Restoration of leaf water potentials by theparasite lagged markedly behind that of the host, especiallyduring winter, leading to a rapid build up in potential gradientbetween partners. A phase of rapid flow into the parasite thenfollowed, presumably motivated by lowering of the haustorialresistance. Reversal of the potential gradient between hostand parasite was recorded in a night-time study involving abagged (non-transpiring) mistletoe attached to a host branchfrozen at the base to prevent further water uptake. Mechanismsare proposed to account for the apparently highly variable natureof the resistance of the haustorium. Key words: Mistletoe, transpiration, haustorial resistance, Amyema fitzgeraldii, Acacia acuminata     

Relationships between height and girth of mangroves and soil-water conditions in the Mary and Hawkesbury River estuaries,eastern Australia

Abstract The height and diameter at breast height (DBH) of mangroves on the Hawkesbury River, New South Wales and the Mary River, Queensland were related to soil-water salinity, soil-water content and distance from the mouth of the estuary. On the Hawkesbury River, both Avicennia marina and Aegiceras corniculatum declined in height and DBH with increasing soil-water salinity and soil-water content, and increased in height with distance from the mouth of the estuary. Both species showed an extensive range of all variables. On the Mary River, where species diversity was higher, no relationship was found between the height and DBH of A. marina and A. corniculatum and soil-water salinity and soil-water content. Both species increased in height with increasing distance from the mouth of the estuary, a characteristic shared with all other species studied (Excoecaria agallocha, Ceriops tagal var. australis, Rhizophora stylosa). The results suggest that growth characteristics of mangroves are not a simple response to salinity gradients in diverse systems and that other variables such as nutrient availability may be important controls on mangrove growth.