Abscisic Acid Simultaneously Decreases Carboxylation Efficiency and Quantum Yield in Attached Soybean Leaves

Injecting abscisic acid (ABA) into the petiole of attached soybeanleaves simultaneously decreased quantum yield and carboxylationefficiency. These decreases were proportional to the accompanyingdecrease of light-saturated photosynthetic rate under normalatmosphere. ABA did not affect the CO² compensation point atsaturating irradiance, or the stimulation of net photosynthesisproduced when the partial pressure of oxygen was reduced from210 to 20 mPa Pa^–1 at a rate-limiting irradiance. Thedecreased carboxylation efficiency could not be attributed toa deactivation of RuBP carboxylase since the activation statusof the enzyme in leaves was insensitive to ABA. Although photosyntheticcapacity was decreased, the content of RuBP present was increasedin leaves treated with ABA at saturating irradiance and normalatmosphere. The increase in RuBP content was proportional tothe corresponding inhibition of photosynthetic capacity. Followingexposure to incident irradiances close to the light compensationpoint, the photosynthetic rate of ABA-treated leaves did notincrease when exposed to a subsequent increase of irradiancein the light-limited range. This response was not due to stomatalclosure. Key words: Abscisic acid, quantum yield, RuBP, RuBP carboxylase, carboxylation efficiency     

Purification and Partial Characterization of Polysaccharides From Coconut Milk

Ethanol-precipitated polysaccharides of the liquid endospermof coconut, Cocos nucifera L., were composed predominantly ofgalactose and arabinose with minor amounts of mannose and glucose.Gel filtration chromatography on Bio-Gel A-0.5 m revealed asingle major peak (Peak A) at the void volume and a minor peak(Peak B) partially included in the column volume. Peak A containedsome uronosyl residues, but was not susceptible to cleavageby endopolygalacturonase, indicating that it does not containsignificant amounts of polygalacturonic acid. Neutral glycosylresidue composition analysis of Peak A showed that it consistedof 72% galactose and 24% arabinose with minor amounts of glucoseand rhamnose. Coconut milk, Cocos nuciferaL, polysaccharides, glycosyl composition     

Treatment of Experimental Pneumocystis carinii Pneumonia with Analogs of Pentamidine

Seven analogs of pentamidine were tested for their activity against an immunosuppressed rat model of Pneumocystis carinii pneumonia. Structural alterations of the pentamidine molecule included variations of the alkyl chain linking the two p-amidino phenoxy moieties and relocation of the amidine groups from the para to the meu position on the phenoxy rings. All analogs of pentamidine were active against P. carinii pneumonia when compared to a saline-treated control group. One derivative, 1, 4-di(4'-amidinophenoxy)butanc, proved to be statistically more active than the parent drug.     

Development of Edhazardia aedis (Kudo, 1930) N. G., N. Comb. (Microsporida: Amblyosporidae) in the Mosquito Aedes aegypti (L.) (Diptera: Culicidae)

A microspondium of the mosquito Aedes aegypti (L.), identified as Nosema aedis Kudo, 1930, was found to be a heterosporous species with 3 sporulation sequences. Usually, I sequence developed in a parental generation host individual that was infected per os as a larva and the other 2 developed concurrently in a filial host larva that was infected transovarially. Under some conditions there were deviations from the parental host-filial host alternation. The 1st sporulation sequence was diplokaryotic (diploid in a particular sense) throughout; the other 2 arose from diplokaryotic meronts, developed concurrently and ended with haploid spores. Haplosis in 1 case was by means of dissociation of the diplokaryon. In the other case it was by meiosis. Conflicting reports about whether the members of the diplokaryon in the latter sequence separate and undergo meiosis individually or coalesce and undergo meiosis as I nucleus were resolved in favor of the latter idea. A new genus in family Amblyosporidae was created to contain this species. which then became Edhazardia aedis (Kudo. 1930) n. g., n. comb.     

Late Ordovician extinction of North American and British crinoids

After reaching a diversity peak in the Caradocian, North American Ordovician crinoids underwent a gradual decline to a nadir in the early Ashgillian (Maysvillian). This interval, recording extinction of the Cleiocrinidae, Merocrinidae, Ottawacrinidae, Hybocystitidae, and several lineages of camerate crinoids, was apparently caused by major environmental shifts in seas of eastern North America resulting from a westward-prograding wedge of terrigenous clastics derived from the Taconic Highlands, possibly coupled with a marine transgression in the Maysvillian that allowed colder water slope biofacies to invade the craton. Crinoids suffered a major episode of extinction in the late Ashgillian (late Richmondian/Rawtheyan). This event, preceding the end of the Ordovician by at least one stage or 2 to 4 million years, resulted in extinction of 12 families of crinoids including the Xenocrinidae, Tanaocrinidae, Reteocrinidae, Archaeocrinidae, Anthracocrinidae, Cincinnaticrinidae, Iocrinidae, Anomalocrinidae, Carabocrinidae, Cupulocrinidae, Porocrinidae, and Hybocrinidae. Glacio-eustatic lowering of sea level may have triggered this crisis by partially draining the North American craton, resulting in changes in oceanic circulation, salinity, and temperature. Latest Ordovician (Hirnantian) carbonates of the North American mid-continent region contain pelmatozoan assemblages from which Silurian crinoids radiated. These taxa were largely unaffected by a minor extinction event at the Ordovician/Silurian boundary.     

Differences between tree species in hydraulic press calibration of leaf water potential are correlated with specific leaf area

Abstract To determine the usefulness of the J-14 Hydraulic Press (Campbell Scientific, Inc., Logan, Utah, U.S.A.) in estimating leaf water potential, we calibrated the J-14 Press against a Scholander-type pressure chamber for leaves of various tree species. The species tested were: Acer saccharum, Acer negundo, Acer rubrum. Populus tremuloides, Populus grandidentata, Quercus rubra, and Brassaia actinophylla (Schefflera). The regression calibrations were linear with standard errors about the regression less than 0.1 MPa. The regression equations for the four genera were significantly different, with the y- intercept increasing and the slope decreasing in order of decreasing specific leaf area (SLA). There were no significant differences between species of the calibration lines within the genera Acer and Populus. These data may indicate that leaves with lower SLA resist mechanical compression by the hydraulic press, causing the J-14 Press to be less sensitive to differences of leaf water potential. Therefore the J-14 Press is only a relative measure of leaf water status and does not measure leaf water potential.     

Genes Encoding Antigenic Surface Glycoproteins in Pneumocystis from Humans

Pneumocystis is a eukaryotic microbe that causes pneumocystosis, an AIDS-associated pneumonia. Pneumocystosis also occurs in many other mammalian species, and animal-derived organisms have been extensively utilized in Pneumocystis research. Pneumocystis from diverse hosts contain a large glycoprotein (gpA/MSG) on the surface. Antibodies elicited against gpA/MSG of Pneumocystis from humans sometimes cross-react with epitopes on proteins of similar size from Pneumocystis from other host species. Here we report the isolation and partial sequence of two presumptive gpA/MSG genes from human-derived Pneumocystis. The cloned human-derived Pneumocystis gpA/MSG genes and predicted peptides were different from those previously isolated from Pneumocystis from rats and ferrets. The genome of human-derived Pneumocystis contained multiple copies of sequences related to the two cloned gpA/MSG genes.     

The Essential Role of "Minor" Phyla in Molecular Studies of Animal Evolution

SYNOPSIS. Molecular studies have revealed many new hypothesesof metazoan evolution in recent years. Previously, using morphologicalmethods, it was difficult to relate "minor" animal groups representingmicroscopic metazoans to larger, more well known groups suchas arthropods, molluscs, and annelids. Molecular studies suggestthat acanthocephalans evolved from rotifers, that priapulidsshare common ancestry with all other molting animals (Ecdysozoa),and that flatworms, gnathostomulids and rotifers form a sistergroup to the remaining non-molting protostomes (Lophotrochozoa),together forming Spiralia. The lophophorate phyla (phoronids,brachiopods and bryozoans) appear as protostomes, allied withannelids and molluscs rather than with deuterostomes. Thesefindings present a very different view of metazoan evolution,and clearly show that small and simple animals do not necessarilyrepresent ancestral or primitive taxa.     

Alterations in growth of tissue-cultured tansy (Tanacetum vulgare L.) treated with antibiotics

Effects of three antibiotics (cefotaxime, rifampicin and gentamicin) were tested on in vitro shoots cultures of tansy (Tanacetum vulgare L.)- These antibiotics were selected because endophytic bacteria isolated from the in vitro shoot cultures of tansy showed that all bacteria were Gram-negative and their growth was reduced by these three antibiotics. Five isolates were Enterobacteriaceae, three were fluorescent Pseudomonas, and two were aerobic bacteria. Increased concentrations of antibiotics caused usually linear or quadratic changes on the initiation of shoot growth, shoot number, growth rate, and shoot height. These changes and changes in pH of the culture media were tansy genotype-dependent following treatments with gentamicin. Also, the treatment with rifampicin or cefotaxime showed a genotype-dependent effect, because they resulted in significantly higher percentage of rooted plants in one of the three tansy genotypes tested. The growth rate and length of shoots were reduced in the media containing both gentamicin and rifampicin, but less so than in media containing both gentamicin and cefotaxime.     

Photosynthate costs associated with the utilization of different nitrogen–forms: influence on the carbon balance of plants and shoot–root biomass partitioning

The photosynthate costs of processes (amino acid and protein synthesis and turnover, and pH regulation) associated with the utilization of nitrate (NO₃⁻), ammonium (NH₄⁺) or glutamine (Gln) for plant growth were estimated. Based on these estimates, the effects of these forms of nitrogen (N) on the carbon balance of plants and on shoot–root biomass allocation were evaluated. The results indicated that NO₃⁻ as an N source for plant growth is not substantially more expensive to utilize than either NH₄⁺ or Gln, particularly in the long term when costs due to protein turnover dominate the total costs of N utilization. It is also suggested that the photosynthate use in processes associated with N assimilation has little impact on the carbon balance of plants, and hence on shoot–root biomass allocation.