MAJOR CLADES OF THE ANGIOSPERMS

Abstract— Our knowledge of fundamental angiosperm interrelationships is still very incomplete. The absence of a narrowly circumscribed gymnosperm outgroup, ideally the sister group, makes character evaluation, necessary for a cladistic analysis, difficult. According to current views the superorder Magnoliiflorae with a number of other groups, for example the monocotyledons, may represent a complex of families near the base of the angiosperms. Interrelationships of groups within the monocotyledons are much better understood than those between groups within the dicotyledons. A cladogram of monocotyledon orders based on earlier work by R. Dahlgren, H. T. Clifford, and F. N. Rasmussen is presented. A data matrix for a sample of the angiosperms with 61 characters for 49 taxa, mostly magnoliifloran and related families, is presented. The characters are polarized mainly according to the current view that the primitive angiosperm morphotype is a woody dicotyledon with strobiloid flowers. As an alternative the matrix is adjusted following W. C. Burger's conjecture that the primitive angiosperm was a herbaceous monocotyledon with trimerous flowers. Both matrices were run in a computerized parsimony analysis, resulting in numerous equally parsimonious solutions. This result is illustrative of the great homoplasy in the available character information, and also of how little actually is known about fundamental angiosperm interrelationships or phylogeny.     

Assignment of orthologous relationships among mammalian alpha-globin genes by examining flanking regions reveals a rapid rate of evolution

In order to study the relationships among mammalian alpha-globin genes, we have determined the sequence of the 3' flanking region of the human alpha 1 globin gene and have made pairwise comparisons between sequenced alpha-globin genes. The flanking regions were examined in detail because sequence matches in these regions could be interpreted with the least complication from the gene duplications and conversions that have occurred frequently in mammalian alpha-like globin gene clusters. We found good matches between the flanking regions of human alpha 1 and rabbit alpha 1, human psi alpha 1 and goat I alpha, human alpha 2 and goat II alpha, and horse alpha 1 and goat II alpha. These matches were used to align the alpha-globin genes in gene clusters from different mammals. This alignment shows that genes at equivalent positions in the gene clusters of different mammals can be functional or nonfunctional, depending on whether they corrected against a functional alpha-globin gene in recent evolutionary history. The number of alpha-globin genes (including pseudogenes) appears to differ among species, although highly divergent pseudogenes may not have been detected in all species examined. Although matching sequences could be found in interspecies comparisons of the flanking regions of alpha- globin genes, these matches are not as extensive as those found in the flanking regions of mammalian beta-like globin genes. This observation suggests that the noncoding sequences in the mammalian alpha-globin gene clusters are evolving at a faster rate than those in the beta-like globin gene clusters. The proposed faster rate of evolution fits with the poor conservation of the genetic linkage map around alpha-globin gene clusters when compared to that of the beta-like globin gene clusters. Analysis of the 3' flanking regions of alpha-globin genes has revealed a conserved sequence approximately 100-150 bp 3' to the polyadenylation site; this sequence may be involved in the expression or regulation of alpha-globin genes.      

THE BIOCHEMISTRY OF NITRIFYING MICROORGANISMS

• 1 Biological nitrification is mediated primarily by two genera of bacteria, Nitrosomonas and its marine form Nitrosocystis, oxidizing ammonia to nitrite, and Nitrobacter, converting nitrite into nitrate. These are chemoautotrophic organisms since they usually derive their energy for growth by oxidizing these inorganic nitrogen compounds and their carbon from carbon dioxide, carbonates or bicarbonates.
• 2 The morphology and structure of these Gram-negative bacteria studied by electron microscopy show numerous intracellular membranes reminiscent of those in photosynthetic bacteria and blue-green algae. These structures may therefore be associated with the production of ATP.
• 3 The bacteria are difficult to grow in pure cultures in sufficient amounts for biochemical work since their generation time is around 10 hr. and the yields are only about one hundredth of those obtained with heterotrophic bacteria. Thus in continuous cultures great care must be taken to avoid ‘wash-out’ of the cells. Since Nitrosomonas and Nitrosocystis produce copious amounts of nitrous acid, which would eventually retard growth, pH stat units are used to titrate the cultures continuously with a solution of sodium carbonate, to hold the pH around 7–8.
• 4 The respiratory chain which is associated with cell membranes, contains flavin, quinones and many cytochromes linking to oxygen as a terminal acceptor. In Nitro-somonas-Nitrosocytis hydroxylamine is oxidized by the electron transfer chain and in Nitrobacter nitrous acid is utilized. The ammonia-oxidizing system, which in Nitrosomonas probably resides near the cell surface, does not appear to survive cell breakage. During the oxidation of hydroxylamine and nitrous acid by the respiratory chains, a phosphorylation occurs but the P/O ratios around 0–30 are low. There is little energy reserve material in the cells, possibly β-hydroxybutyrate and some metaphosphates and as soon as the oxidative processes are impaired the cells cease dividing.
• 5 Chemoautotrophic bacteria have a novel way of producing reduced nicotinamide adenine dinucleotide (NADH). This involves a reversal of electron flow from reduced cytochrome c to nicotinamide adenine dinucleotide (NAD) that is energy-dependent, thus requiring adenosine triphosphate.
• 6 Reductase enzymes, nitrate, nitrite and hydroxylamine reductases in Nitrobacter and nitrite and hydroxylamine reductases in Nitrosomonas, have been described. They appear to be readily extracted in soluble form and are probably assimilatory enzymes since ¹⁶N labelled nitrate, nitrite and hydroxylamine respectively in Nitrobacter and the last two in Nitrosomonas are readily incorporated into cell nitrogen. It has been suggested that a particulate nitrate reductase in Nitrobacter is coupled to the synthesis of adenosine triphosphate but adequate experimental evidence for this concept has not been produced.
• 7 Some recent observations with Nitrobacter suggest that it grows on acetate, deriving all its energy and carbon skeletons from this source but the mean generation time for the bacterium is unchanged. Under these conditions the carbon dioxide fixing enzymes of the pentose pathway are suppressed. This then is a case of facultative chemoautotrophy but there is no increase in the biosynthesis of the TCA enzymes. Whether this is a widespread phenomenon in other chemoautotrophic bacteria remains to be established. If this does prove to be the case it would aid their survival in a variety of habitats and extend their distribution in soils and seas.
• 8 The carbon dioxide fixing enzymes of the pentose pathway are found in the soluble parts of the cells. The major route is via the carboxydismutase system with only a small incorporation via the phosphoenolpyruvate carboxylase enzyme. Enzymes of the tricarboxylic acid cycle have low activities compared with those in heterotrophs and this overall slow metabolism, rather than the lack of a specific enzyme such as NADH oxidase, may well account for the slow growth of these bacteria. Although there is very active glutamic dehydrogenase in Nitrosomonas that utilizes ammonia, the enzyme has a very small activity in Nitrobacter. This poses a problem of the route of incorporation of nitrite nitrogen into cell nitrogen in the latter bacterium.
• 9 A few heterotrophic fungi have been described which oxidize ammonia to nitrate but their activity is small compared with that of the nitrifying bacteria.
• 10 It is concluded that the nitrifying bacteria which have many novel biochemical features not met with in other organisms merit further study.

     

MOVEMENT OF EELWORMS: V. OBSERVATIONS ON APHELENCHOIDES RITZEMA-BOSI (SCHWARTZ, 1912) STEINER, 1932 ON FLORISTS' CHRYSANTHEMUMS

Adults of Aphelenchoides ritzema-bosi tend to migrate up the stems of chrysanthemum plants in stationary water films possibly by a negatively geotropic response. A current of water down the stem opposes such an upward movement. Greatest mobility occurred in thick films of water in places with a high concentration of epidermal hairs as at the top of the stem and on the undersurface of leaves. Ciné films of movement in thick and thin films showed that there were fundamental differences in the type of locomotion in these two environments. Invasion of leaves via stomata was observed and the method of movement is described. The presence of A. ritzema-bosi in leaves appears to render the epidermis permeable to water. During dry weather there is little movement inside the leaf, but after rainfall activity increases as water enters the leaf. Spread of eelworm infestation in the leaf occurs in the mesophyll and across veins although initially these act as barriers. Emergence occurs via the stomata, chiefly on the undersurface. When the leaf is wet, about 50% of the eelworms emerge in the first hour. During wet weather many eelworms were recovered from the surfaces of leaves and it is suggested that eelworms spread mostly under these conditions.     

Secondary production of chironomid communities in insecticide-treated and untreated headwater streams

SUMMARY.

• 1 Production of chironomid communities of three first order, Appalachian Mountain streams was estimated and the effects of an insecticide-induced disturbance on chironomid production was examined.
• 2 Annual production of non-Tanypodinae chironomids in the streams during the first study year (no treatment) ranged from 1366 to 3636 mg m^?2, while production of Tanypodinae chironomids ranged from 48 to 116 mg m ^?2. Production/biomass ratios ranged between 19 and 23 for non-Tanypodinae and from 6 to 7 for Tanypodinae chironomids.
• 3 Insecticide applications resulted in significantly lower chironomid densities and biomass in the treated stream relative to the pretreatment year and reference stream. Annual production of non-Tanypodinae (703 mg m^?2) and Tanypodinae (32 mg m ^?2) chironomids in the treated stream decreased by 64% and 67%, respectively, compared with the pretreatment year. In contrast, production of non-Tanypodinae (2084 mg m^?2) increased by 34% and production of Tanypodinae (96 mg m^?2) by 57% in the reference stream.

     

P48-Triggered transmembrane signaling transduction of human monocytes:mobilization of calcium ion and activation of protein kinase C(PKC)

INTRODUCTI0NThedifferentiati0nofcelIsalongthemonocyte-macr0phagepathwayandthesig-nalsinvo1vedinthesecel1sacquiringtheabilitytokilltum0rcellsarenotfllllyundersto0d.Wehavebeenstudingamoleculewhichappearst0beanimportantmemberofthecytokinenetworkinvo1vedintheregulati0nmonocyteactivation.ThiscytokinetermedP48wasisolatedfr0mthehllmannullcellleukemiacell1ineReh.IthasbeenpurifiedtohomogeneityandfOundtobedistinctfrominterferongamma,col0nystimulatingfactors(CSFs)andTNFalphaalldbeta[1,2].Func-ti…     

Cavity size, clutch-size and the breeding ecology of Tree Swallows Tachycineta bicolor

Previous studies provide evidence that cavity size influences clutch-size and reproductive success in some hole-nesting birds, because overcrowding in cavities may cause brood mortality due to trampling or hyperthermia. We tested this hypothesis with two experiments at nestbox populations of Tree Swallows Tachycineta bicolor in southeastern Ontario. Female Tree Swallows showed a preference for nesting in large boxes over small ones in the first experiment, and they laid significantly smaller clutches in small nestboxes during both experiments. Differences in clutch–size between large and small nestboxes could not be attributed to other factors known to influence clutch-size in birds (e.g. parental quality, habitat quality, laying date). Reproductive success, however, did not differ between pairs using the two box types during either experiment, nor did it differ during within-clutch-size comparisons between box types. Some measures of nestling quality were significantly lower for broods in large boxes, but during most comparisons there were no differences. These results do not support the adaptive reason for why cavity size affects clutch-size. We suggest that broods in our experiments did not experience the microhabitat conditions necessary to induce the expected differences in brood mortality.