Kingsley S. Rowan

Extraction of soluble leaf enzymes with thiols and other reducing agents

Abstract The activity of peptidase extracted from tobacco leaf was higher if thiols or other reducing agents were included in the extracting medium. The minimum concentration of the reducing agent (critical concentration) required in the extracting medium for maximum activity of peptidase was inversely correlated with the strength of the reducing agent. Chlorogenic acid inhibited peptidase activity in extracts prepared using the critical concentration of thioglycollate but not in extracts prepared with the critical concentration of metabisulphite. The critical concentration of metabisulphite was independent of concentration of enzyme but the critical concentration of thioglycollate increased with increasing concentration of enzyme. The mechanism whereby thiols and other reducing agents yield extracts with high peptidase activity is discussed in relation to inhibiting the synthesis of o-quinones and tannins from endogenous o-diphenols.

The isolation of mitochondria from potato-tuber tissue using sodium metabisulphite for preventing damage by phenolic compounds during extraction

Abstract Products of the oxidation of endogenous phenolics formed during extraction uncouple mitochondria isolated from potato-tuber (RCR=1, P/O=0 for all substrates tested). Potato mitochondria prepared in media containing low concentrations of metabisulphite are as active as those prepared by Verleur using cysteine. Since metabisulphite acts only by inhibiting phenoloxidases, then the method described should apply to the extraction of mitochondria from all tissues free from endogenous tannins, for the method is independent of concentration of endogenous phenolics and activity of phenoloxidase in the tissue.

CHARACTERIZATION AND PHYLOGENETIC POSITION OF THE ENIGMATIC GOLDEN ALGA PHAEOTHAMNION CONFERVICOLA: ULTRASTRUCTURE, PIGMENT COMPOSITION AND PARTIAL SSU rDNA SEQUENCE

The morphology, ultrastructure, photosynthetic pigments, and nuclear‐encoded small subunit ribosomal DNA (SSU rDNA) were examined for Phaeothamnion confervicola Lagerheim strain SAG119.79. The morphology of the vegetative filaments, as viewed under light microscopy, was indistinguishable from the isotype. Light microscopy, including epifluorescence microscopy, also revealed the presence of one to three chloroplasts in both vegetative cells and zoospores. Vegetative filaments occasionally transformed to a palmelloid stage in old cultures. An eyespot was not visible in zoospores when examined with light microscopy, but small droplets, similar to eyespot droplets, were apparent beneath the shorter flagellum when cells were viewed with electron microscopy. Zoospores had two flagella that were laterally inserted in the cell approximately one‐third of the cell length from the apex. The longer flagellum was directed anteriorly and the shorter flagellum was directed posteriorly. Electron microscopy revealed the presence of tubular tripartite flagellar hairs on the longer flagellum, but no lateral filaments were found on the tripartite hairs. The general organization of the flagellar root system was similar to that of zoospores belonging to the Xanthophyceae and Phaeophyceae. However, the transitional region of the flagella contained a transitional helix with four to six gyres. Microtubular root R1 consisted of six microtubules at its proximal end and one microtubule at its distal end. Roots R2 and R4 consisted of one microtubule each and root R3 consisted of two microtubules. No rhizoplast was found. Thin‐layer chromatography revealed the presence of fucoxanthin, diadinoxanthin, neoxanthin, and heteroxanthin as well as chlorophylls a, c1 and c2. High‐performance liquid chromatography revealed the presence of fucoxanthin, diadinoxanthin, diatoxanthin, heteroxanthin, and β,β‐carotene as well as chlorophylls a and c. The complete sequence of the SSU rDNA could not be obtained, but a partial sequence (1201 bases) was determined. Parsimony and neighbor‐joining distance analyses of SSU rDNA from Phaeothamnion and 36 other chromophyte algae (with two Öomycete fungi as the outgroup) indicated that Phaeothamnion was a weakly supported (bootstrap = <50%, 52%) sister taxon to the Xanthophyceae representatives and that this combined clade was in turn a weakly supported (bootstrap = <50%, 67%) sister to the Phaeophyceae. Based upon ultrastructural observations, pigment analysis, and SSU rDNA phylogenetic analysis, Phaeothamnion is not a member of the Chrysophyceae and should be classified as incertae sedis with affinities to the Xanthophyceae and Phaeophyceae.

Changes in the chlorophylls and carotenoids of leaves of Nicotiana tabacum during senescence

Abstract In addition to chlorophylls a and b , β-carotene, lutein, violaxanthin and neoxanthin, leaves of tobacco ( Nicotiana tabacum L. cv. Virginia Gold) contain antheraxanthin in some harvests. In lower leaves, chlorophylls decreased more rapidly than carotenoids during senescence, but both types of pigment decreased at equal rates in upper leaves. The chlorophyll a:b ratio decreased only in post-mature leaves. Total carotenoid decreased with age, with the relative proportion of β-carotene increasing in lower leaves. Seasonal influences rather than age of leaf determines whether antheraxanthin is present. No esterified xanthophylls were found in senescent leaves.

Bromo-compounds of the red alga Lenormandia prolifera

Abstract Six bromo-compounds and one bromo-chloro-compound have been detected in Lenormandia prolifera (C.Ag.) J. Agardh (Amansieae; Rhodomelaceae). Hydrolysis of the red pigment floridorubin from the same alga yielded five bromo-, one bromo-chloro and one chloro-phenol. The two main phenols of floridorubin were 2,3-dibromo-4,5-dihydroxy benzyl alcohol (lanosol) and 3,5-dibromo- p -hydroxybenzyl alcohol.

Morphological and physiological characteristics of a non-heterocystous strain of the cyanobacterium Mastigocladus laminosus Cohn from fumarolic soil on Mt Erebus, Antarctica

SummaryAn unusual strain of the thermophilic cyanobacterium Mastigocladus laminosus occurs on warm soils on the volcano Mt Erebus (77°32′S, 167°8′E). It differs morphologically from the two genetically distinct forms described from thermal habitats elsewhere. Heterocysts are lacking and true-branching is rare. Its photosynthetic rate, and the contrasting rates of two less thermotolerant algae from Mt Erebus soils, Phormidium fragile (Cyanobacteria) and Pseudococcomyxa simplex (Chlorophyta), were measured over the range -2° to 62°C. The optimum temperature range of M. laminosus was 35° to 50°C. Photosynthetic response to temperature of all three algae in the laboratory correlated well with distribution patterns in the field, confirming that zonation patterns were temperature controlled. M. laminosus retained viability following exposure to deep-freezing, freeze-thaw cycles and desiccation. Viability of the alga in culture was lost following exposure to 50°C in darkness for 42 days and following 42 days in the light at 0°C. Discussion suggests the alga would survive long distance airborne dispersal in the desiccated condition but would not survive the duration of overwinter darkness on moist soils at the warmer end of its range of occurrence in the field.

Distribution of podolactone-type plant growth inhibitors in the coniferae

Abstract Plant growth inhibitors of the podolactone-type have been detected by bioassay in ten further species of Podocarpus . The most active extracts in P. elatus were from root tips, root cortex and very young leaves. Fifty-seven other conifers were examined for this type of activity. It is present in Cephalotaxus harringtonia where it is probably due to the presence of harringtonolide, which, like momilactone B from rice husks, shows podolactone-type inhibition of the growth of etiolated dwarf pea hooks.

The lipid-soluble pigments of the marine red alga Lenormandia prolifera

KurzfassungIn der RotalgeLenormandia prolifera (C. AG.) J. AG. ist neben den Xanthophyllen Lutein und Zeaxanthin auch das Xanthophyll α-Kryptoxanthin gefunden worden. Chlorophylla ist vorhanden, nicht jedoch Chlorophylld. α-Carotin tritt in größeren Mengen alsβ-Carotin auf, während Lutein häufiger als Zeaxanthin vorkommt. Der Gehalt an α-Kryptoxanthin beträgt nur 2,4% der Gesamtmenge an Carotinoiden.Summary1.The marine red algaLenormandia prolifera containsα-cryptoxanthin, a monohydroxy derivative ofα-carotene, as well asα- and β-carotene, lutein and zeaxanthin.2.Chlorophylla and a trace of chlorophyllidea is present but no chlorophylld.3.The chlorophyll/carotenoid ratio is 2.5 ± 0.7 (w/w), falling within the range reported for other species of the Rhodophyta.4.α-Carotene is more abundant thanβ-carotene while lutein is the most abundant xanthophyll;α-cryptoxanthin accounts for only 2.4% of the total carotenoid content.5.The possibility that theAmansia group is distinguished by containingα-cryptoxanthin and moreα- thanβ-carotene is discussed.

The use of thioglycollate for extracting phenylboronic acid from roots of bean seedlings

Abstract Phenylboronic acid is rendered insoluble in diethyl ether during extraction from roots of the bean ( Vicia faba L.) by binding with tannins. Including thioglycollate in the extracting medium inhibits both enzymic and non-enzymic formation of tannins and results in recovery of phenylboronic acid in the ether phase.