Inhibition of Cell Wall-Associated Peroxidase Isozymes with British Anti-Lewisite

Conditions were established for the use of British Anti-Lewisite(BAL) to inhibit preferentially the extracellular isoperoxidasesin pea stems. After a 2 h incubation period with 9.09 x 10⁴M BAL, approximately half of the activity of cell wall-associatedperoxidase was lost, while little inhibition of cytoplasmicenzyme was observed. Four isozymes from cell wall material wereidentified on starch gel e0lectrophoresis and stained with eugenol.Activity was tested with eugenol, ferulic and caffeic acids,and several redox dyes to probe the possible involvement ofthese isozymes in lignin biosynthesis. All isozymes had similarK_m values with eugenol and caffeic acid as compared to benzidine,a standard redox dye.     

A re-examination of the induction of phloem transfer cell development in pea leaves (Pisum sativum)

Abstract The development of phloem transfer cells in expanded dark grown leaflets of pea seedlings (Pisum sativum) has been re-examined. In agreement with previous observations transfer cells in leaflets maintained in the dark did not form wall ingrowths to the same extent as those placed in the light. A previous report that exposure to light in a carbon dioxide depleted atmosphere inhibited wall ingrowth formation could not be confirmed. It was found that dark grown leaflets could be induced to form wall ingrowths without illumination by immersing them in a glucose solution, demonstrating for the first time that light is not necessary for phloem transfer cell differentiation in leaves. Attempts were made to alter the carbohydrate level in the whole seedling by removing the cotyledons, but this had no recognizable effect on wall ingrowth formation in any of the treatments. Starch grain formation in the plastids was taken as an indication of available soluble carbohydrate level in the leaflets. It is concluded that both light and the presence of soluble carbohydrate can independently induce wall ingrowth formation in phloem transfer cells of pea leaflets.     

Homology of Holocene ostracode biramous appendages with those of other crustaceans: the protopod, epipod, exopod and endopod

Unambiguously biramous appendages with a proximal precoxa, well-defined coxa and basis, setose plate-like epipod originating on the precoxa, and both an endopod and exopod attached to the terminal end of the basis are described from several living Ostracoda of the order Halo-cyprida (Myodocopa). These limbs are proposed as the best choice for comparison of ostracode limbs with those of other crustaceans and fossil arthropods with preserved limbs, such as the Cambrian superficially ostracode-like Kunmingella and Hesslandona. The 2nd maxilla of Metapolycope (Cladocopina) and 1st trunk limb of Spelaeoecia, Deeveya and Thaumatoconcha (all Halocypridina) are illustrated, and clear homologies are shown between the parts of these limbs and those of some general crustacean models as well as some of the remarkable crustacean s.s. Orsten fossils. No living ostracodes exhibit only primitive morphology; all have at least some (usually many) derived characters. Few have the probably primitive attribute of trunk segmentation (two genera of halocyprid Myodocopa, one order plus one genus of Podocopa, and the problematic Manawa); unambiguously biramous limbs are limited to a few halo-cyprids. Homologies between podocopid limbs and those of the illustrated primitive myodocopid limbs are tentatively suggested. A setose plate-like extension, often attached basally to a podocopid protopod, is probably homologous to the myodocopid epipod, which was present at least as early as the Triassic. Somewhat more distal, less setose, and plate-like extensions, present on some podocopid limbs (e.g., mandible), may be homologous instead to the exopod (clearly present on myodocopid mandibles). The coxa (or precoxa) is by definition the most basal part of the limb. A molar-like tooth is present proximally on the mandibular protopod of many ostracodes; it is the coxal endite and projects medially from the coxa (or proximal protopod). The Ostracoda is probably a monophyletic crustacean group composed of Myodocopa and Podocopa. All have a unique juvenile (not a larva) initially with three or more limbs. Except that juveniles lack some setae and limbs, they are morphologially similar to the adult. Thus the following suite of characters in all instars may be considered a synapomorphy uniting all Ostracoda: (1) Each pair of limbs is uniquely different from the others. (2) The whole body is completely enclosed within a bivalved carapace that lacks growth lines. (3) No more than nine pairs of limbs are present in any instar. (4) The body shows little or no segmentation, with no more than ten dorsally defined trunk segments. No other crustaceans have this suite of characters. A probable synapomorphy uniting the Podocopa is a 2nd antenna with exopod reduced relative to the endopod.     

Phylogenetics and differentiation among the western taxa of the Erebia tyndarus group (Lepidoptera: Nymphalidae)

The phylogenetic relationships among six members of the 'tyndarus' group in the Erebia genus of Satyrid butterflies, i.e. E. tyndarus, E. cassioides, E. nivalis, E. calcaria, E. hispania and E. ottomana were analysed using data from 19 presumptive enzyme loci, as well as 440 and 429 bp, respectively, from the mitochondrial large ribosomal subunit (16S) and subunit 1 from the NADH dehydrogenase (ND1) genes. The two types of molecular data (allozymes and mtDNA) yielded largely congruent tree topologies. The two basal, independent lineages formed by E. ottomana and E. hispania are contrasted by a group of Genétically closely related taxa, suggestive of a recent radiation associated with allopatric speciation, and competitive exclusion. The time of divergence for the radiation event is similar for both allozymes and mtDNA with an estimation of 440000 years ago. The lineages involved in this radiation do not comply with all the criteria necessary to assign to each of them full species rank, but they can no more be included in one single species unit. Such situations involving more than two alio- or parapatric lineages may explain why polytomies are so often met in phylogenetic reconstructions, after the lineages have reached full species rank. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 75 , 319–332.     

Diverse Responses of Maple Saplings to Forest Light Regimes

Seedlings of 11 species of forest maples (AcerL.) were grownoutdoors from budburst to senescence under three light regimes:‘gap centre under clear skies’ (approx. 20% opensky irradiance; red:far-red ratio=1.12); ‘gap centre undercloudy skies’ (1.5%, ratio=1.03); and ‘gap edge’(2.5%, ratio=0.6). Seedlings grown under the gap centre (clearsky) regime had significantly greater height growth, greaterspecific leaf mass, higher root:shoot ratio, greater investmentin roots, higher leaf nitrogen concentrations, greater chlorophylla:bratio,lower photosynthetic rates under dim light, higher maximum photosyntheticrate, higher stomatal conductance, and lower leaf internal CO₂concentrationscompared with those grown in either gap edge or gap centre (cloudy)regimes. Responses to the gap edgevs.gap centre (cloudy) treatmentsdiffer little, suggesting that shade acclimation in forest mapleseedlings is mainly a response to light intensity rather thanspectral quality. The ubiquitous and, except for leaf internalCO₂concentration, highly significant interspecific variationin traits was broad-ranging and continuous. These results suggestthat (1) the responses to light quality found in shade intolerantherbaceous and woody species growing in more open habitats maynot have a selective advantage in seedlings of shade tolerantforest trees, and (2) the adaptive plastic response to understoreyvs.gapenvironments in forest maples, which is qualitatively consistentacross species, is founded on co-ordinated, small shifts insets of functionally inter-related traits.Copyright 1998 Annalsof Botany Company Acer,forest gap heterogeneity, plasticity, specific leaf mass, photosynthesis, leaf chlorophyll, nitrogen, stomatal density, root growth, root:shoot ratio, growth form.     

Sex roles, parental effort and offspring desertion in the monogamous Eurasian Curlew Numenius arquata

The reasons for female desertion of offspring and the evolution of predominantly male care among monogamous bird species are not clearly understood. We studied parental effort during the incubation and chick rearing periods in the Eurasian Curlew Numenius arquata in western Finland, and compared timing of brood desertion with other populations in Europe. Males and females contributed equally to incubation and showed no differences in the intensity of mobbing behaviour towards a potential nest predator (stuffed crow) shortly after hatching. However, females deserted their offspring approximately halfway through the brooding period ( c. 16 d after hatching), while males remained with chicks until independence ( c. 35 d). Females with late-laid clutches deserted their offspring sooner after hatching than those with clutches produced earlier in the season. Curlew females deserted younger chicks in northeast Europe, where laying dates were later, breeding seasons shorter and migration distances were longer, than in western and central Europe. We suggest that the most likely reasons for offspring desertion by females may be associated with increased female survivorship and maintenance of pairbond between years.     

Carbon and nitrogen dynamics in a maritime Antarctic stream

• 1 The carbon and nitrogen dynamics in a maritime Antarctic lake outflow stream were investigated. The stream and the algal communities could be split into two zones: a semi-aquatic margin consisting of a perennial cyanobacteria/diatom mat and a flowing channel with a similar perennial mat that was overgrown by annual filamentous chlorophytes during the course of the summer.
• 2 Neither algal community was limited by nutrient availability. Major nutrients were always available in the stream water. There were slight differences in the atomic ratios of the mats, the N:P ratios in the channel mat being lower than those in the marginal mat. However, both these and the total dissolved N:P ratio in the stream water were all close to those that indicate a balanced supply.
• 3 There was no net carbon or nitrogen accumulation by the marginal mat suggesting that uptake processes were balanced by loss processes.
• 4 Maximum rates of carbon fixation (0.1–0.5mgCg^?1 dry weight h^?1) were similar to those of other perennial Antarctic algal mats. Productivity appeared to be limited by physical factors, but the effects of irradiance and temperature could not be separated.
• 5 There were no heterocystous cyanobacteria in the mat communities and rates of atmospheric nitrogen fixation were very low (0–10ngNmg^?1 mat Nh^?1). Fixation accounted for only 0.3% of the nitrogen accumulation of the channel mats, but was higher in the marginal mat where uptake of other sources of nitrogen was also low.
• 6 Nitrogen accumulation by the channel mat averaged 0.34gNm^?2 day^?1. Only 0.05gNm^?2 day^?1 was accounted for by the uptake of dissolved inorganic nitrogen (nitrate plus ammonium). The major (80%) source of nitrogen appeared to be dissolved organic nitrogen. Recycling of nitrogen within the stream ecosystem may also be important.