Flag Leaf Anatomy of Triticum and Aegilops Species in Relation to Photosynthetic Rate

Quantitative anatomical and other measurements were made onfully expanded flag leaves of a series of diploid, tetraploidand hexaploid Triticum and Aegilops species, and photosyntheticrates per unit leaf area were measured at light saturation (P_max). Diploids had the highest P_max, hexaploids the lowest with tetraploidsbeing intermediate. The anatomical features of tetraploids andhexaploids were generally similar, but different from the diploids.The diploids had thinner leaves with less dry matter and chlorophyllper unit area. The surface area of the mesophyll cells per unitvolume of mesophyll tissue was similar for all ploidy levels,as was the ratio mesophyil cell surface area per unit leaf area.It is argued that while these anatomical features are unlikelyto account for the observed variation in Pmax, it is possiblethat other structural factors with which they are correlatedmay causally influence P_max. One such feature is the averagediffusion path length from the plasmalemma at the cell surfaceto the sites of carboxylation. Anatomy, photosynthesis, mesophyll, cell size, Triticum, Aegilops, polyploidy     

Permeability of Whole Dunaliella Cells to Glucose

Ginzburg, M. and Richman, L. 1985. Permeability of whole Dunaliellacells to glucose.—J. exp. Bot. 36: 1959–1968.Whenglucose was dissolved in medium in which Dunaliella cells weresuspended, the amount recovered from pellets of centrifugedcells was greater than that expected if the glucose had beenrestricted to intercellular space, as measured with Blue Dextran.Glucose is not metabolized by whole Dunaliella cells. The glucoseadditional to that in the intercellular space must be eitheradsorbed in the coating outside the cells or must penetratethe cell through the cell membrane. Grounds are given for suggestingthat the latter hypothesis is correct and that the glucose comesto equilibrium with a space within the cell (the glucose–space)equivalent to 20–40% of the cell–water. It is suggestedthat most of the cell Na⁺ is restricted to the glucose-space. Key words: Dunaliella, glucose, permeability     

Aminopeptidases from Plasmodium falciparum, Plasmodium chabaudi chabaudi and Plasmodium berghei

ABSTRACT. Using fluorogenic substrates and polyacrylamide gels we detected in cell-free extracts of Plasmodium falciparum, Plasmodium chabaudi chabaudi and Plasmodium berghei only a single aminopeptidase. A comparative study of the aminopeptidase activity in each extract revealed that the enzymes have similar specificities and kinetics, a near-neutral pH optima of 7.2 and are moderately thermophilic. Each has an apparent molecular weight of 80,000 ± 10,000, determined by high performance liquid chromatography on a calibrated SW500 column. Whilst the P. c. chabaudi and P. berghei activity co-migrate in native polyacrylamide gels, that of P. falciparum migrates more slowly. The three enzymes can be selectively inhibited by ortho -phenanthroline and are thus metallo-aminopeptidases; however, in contrast to other aminopeptidases the metal co-factor does not appear to be Zn²⁺.     

Subdivision of equine Tf into H1 and H2

Subdivision of equine TfH into two variants, designated H1 (faster) and H2 (slower), has been accomplished by high voltage, thin layer polyacrylamide gel electrophoresis at pH 7.9. Transferrin H1 and H2 have been shown to be controlled by codominant alleles and gene frequencies of the Tf alleles have been determined in the Australian Thoroughbred, Standardbred. Quarter Horse and Arabian Horse breeds.     

Studies on the Ship-fouling Alga Enteromorpha II. The Effect of Certain Enzymes on the Adhesion of Zoospores

A method for assessing the adhesion of settled zoospores ofEnteromorpha intestinalis is described. Using this method, the effect of certain enzymes on the attachmentprocess has been studied and the biochemical nature of the secretedadhesive inferred from the results. Although considerable variation in adhesive ability has beenshown to exist between spores from different parent sourcescertain enzymes produce a consistent weakening action on adhesion.Trypsin, pronase, and a-amylase are especially active in thisrespect. The experimental results demonstrate that the -amylaseeffect, although not quite so great as that of the two proteolyticenzymes is, however, genuine. In conjunction with the previous paper it has been shown thatadhesive production is a rapid process, completed within minutesof initial contact and that at this early stage the adhesivematerial is particularly susceptible to proteolytic attack. The results offer the possibility of a biological method forthe control of algal fouling.     

Effect of Chilling Temperatures on the Protoplasmic Streaming of Plants from Different Climates

A microscope mount was designed so that specimen temperaturescould be monitored and controlled without impairing phase contrastoptics and used to measure rates of protoplasmic streaming between0 and 25 ?C in trichome cells of Lycopersicon esculentum, Lycopersiconhirsutum, Citrullus vulgaris, Tradescantia albiflora, Digitalispurpurea, and Veronica persica. Between 10 and 20 ?C the rates of streaming varied from 2–6µm s^–1 depending on the temperature, and differencesbetween the species were small. The temperature coefficientof streaming rates was found to increase as the temperaturewas lowered so that the plot of log rate against temperaturehad a steeper slope at the lower temperatures. The largest temperature cofficients were for the warmth-requiringL. esculentum (tomato) and C. vulgaris (water melon), and thesmallest for the temperate-zone plants V. persica (speedwell)and D. purpurea (foxglove). The changes in rate always occurredover a range of temperature; no ‘critical temperature’wasobserved below which streaming abruptly stopped and above whichit was active, although the amount of streaming as well as therate decreased as the lowest temperatures were approached. The temperatures experienced by the specimens during the experimentdid not affect the recovery of normal streaming rates betweenabout 10 and 20 ?C. In a population of a wild tomato, Lycopersicon hirsutum Humb.and Bonpl., collected from different altitudes in Peru and Ecuador,i.e. from locations of different environmental temperature,the rate of protoplasmic streaming at 5 ?C was greatest in thevarieties collected from the highest altitudes. The resultssuggest that streaming rates correlate with genetic adaptationto low temperature in the species examined.     

Trypanosoma Manulis N. Sp. From the Russian Pallas Cat Felis Manul

ABSTRACT. The morphology of Trypanosoma manulis n. sp. is described from living and stained specimens obtained from the blood of a Pallas cat, Felis manul , from Kazakhstan. the cat was also infected with a Hepatozoon sp. and feline immunodeficiency virus. the morphology of the trypanosome most closely resembles that of Trypanosoma mpapuense Reichenow and Trypanosoma heybergi Rodhain found in bats. Trypanosoma manulis does not grow well in conventional media, but co-culture with African green monkey kidney cells in Eagle's Minimum Essential Medium supplemented with 10% fetal calf serum at approximately 27° C resulted in luxuriant growth of trypanosomes. Under these growth conditions, epimastigotes adhered to the surface of the culture flask and to African green monkey kidney cells, as well as forming large rosettes. At 37° C, although growth was poor, transformation of the epimastigotes into the bloodstream forms occurred. This represents the first report of a trypanosome of the subgenus Megatrypanum in a felid.     

Effects of Selected Herbicides on Plant Protoplasts

Plant protoplasts were released from immature tomato fruits by incubation with a 20% solution of polygalacturonase (Pectinol R-10, Rhom & Haas) dissolved in 0.1 M KCl + 0.1 M MgCl₂. In this salt solution the protoplasts remained stabilized for up to 8 h and were used as a source of exposed plasma membrane. Gross responses of protoplasts to selected chemicals and herbicides were recorded photomicroscopically. Paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) treatments resulted in a characteristic response which was different from that of general denaturants (trichloroacetic acid, ethanol, and detergents) and of osmotic shock. Initial phases of the paraquat response were characterized by a segregation of the cytoplasm into isolated areas on the inner membrane surface. The final phase was a rupture of the plasma membrane and collapse of the cell. The herbicides, 2,4′-dinitro-4-trifluoromethyl-diphenylether (preforan); 1,1-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea (fluometuron); 3-(3-chloro-4-bromophenyl)-1-methoxy-1-methylurea (chlorbromuron); and α,α,α-trifluoro-2,6-dinitro-N-N-dipropyl-p-toluidine (trifluralin) produced no apparent structural effect on the protoplasts.