Microbiological Synthesis of Fat: THE EFFECTS OF NITROGEN LEVEL ON THE METABOLISM OF PENICILLIUM LILACINUM THOM IN A SUCROSE MEDIUM

1. A study has been made of the relationships between the synthesesof carbohydrate, protein, and fat by Penicillium lilacinum Thomin presence of different amounts of sodium nitrate us a definedsucrose salts medium.
2. Under the defined experimental conditionsincreases in the concentrationof NO^–₂ in the medium werefollowed by increases in therates at which nitrogen and sugarwere taken up by the fungus,in the quantities assimilated,and in total and protein nitrogenin the felt. These conditionsprevailed so long as unassimilatedsugar was available.
3. Mediaof lower NO^–₃ concentration (for example, 0·32or 0·64 per cent. (w/v) NaNO^–₂;) yielded feltsricher in carbohydrate than were those grown in media of higherNO^–₂; content (0·96 or 1·28 per cent. (w/v)NaNO₃ The carbohydrate content of the felts increased graduallyuntil the sugar in the medium was exhausted; carbohydrate contentthen decreased.
4. Media of lower NO^–₃; concentration weremore conduciveto fat synthesis than those of higher NO^–₃;content.

     

Photosynthetic induction in wheat protoplasts and chloroplasts. Autocatalysis and light activation of enzymes

Abstract Unlike wheat chloroplasts, wheat protoplasts showed a pronounced restoration of the induction phase after a short period of darkness. This difference was used to investigate the relative roles of light-induced reductive activation of enzymes and the auto-catalytic increase in the level of substrates in the control of the rate of photosynthesis during induction. Light activation and dark inactivation of ribulose 5-phosphate kinase, fructose 1,6-biphosphatase and NADP⁺-specific glyceraldehydephosphate dehydrogenase were measured. In this respect there was no appreciable difference between protoplasts and chloroplasts. In contrast, the level of photosynthetic intermediates remained constant in darkened isolated chloroplasts, but declined rapidly in chloroplasts isolated from darkened protoplasts. When fructose 1,6-bisphosphatase was pre-activated by treating protoplasts with dithiothreitol the lag was only slightly shortened. These results are discussed in terms of control of the rate of the photosynthesis during the lag by substrates rather than limitation imposed by activity of any of the enzymes measured.     

The Tomato Fruit: Import, Growth, Respiration and Carbon Metabolism at Different Fruit Sizes and Temperatures

Measurements of a complete carbon balance sheet over a 48 hperiod for growing tomato fruits at different fruit sizes andtemperature have been carried out. The rates of carbon import,respiration, and growth have been calculated and related toeach other and to the levels of certain carbon metabolites inthe fruit. It was found that there is an excellent linear relationshipbetween the import rate and the sucrose level in the fruit,consistent with the hypothesis that, for the tomato fruit, carbonflows down the sucrose concentration gradient at a rate proportionalto the gradient. This agrees with the findings of Mason andMaskell in cotton. Moreover, the resistance to transport wasrelatively independent of fruit size and temperature. The usualanalysis of respiration in terms of growth and maintenance componentsallowed the determination of conversion efficiencies and maintenancecoefficients for different fruit sizes and temperatures. Asobserved by other authors with other plants, the growth conversionefficiencies were temperature-independent, whereas the maintenancecoefficients were strongly temperature-dependent. The overallconversion efficiency was optimum at 25°C. The specificgrowth rate and the starch level in the tomato fruit were foundto be related.     

Control of Passive Permeability in the Chara Plasmalemma

Conductance to K⁺ alters as a function of membrane potential(_m). Conductance to H⁺ (or OH^–) changes with externalpH (pH^o) This conductance change can be modulated by alteringcytoplasmic pH or external K⁺ concentration, both of which alsoalter _m. We suggest a role for H⁺ conductance in regulatingcytoplasmic pH above pH^o 7.0.     

Intercellular Transport in Plants: II. CYCLOSIS AND THE RATE OF INTERCELLULAR TRANSPORT OF CHLORIDE IN CHARA

The effect of streaming speed on intercellular transport ofchloride has been studied using pairs of internodal cells ofChara. The rate of transport was measured by that fraction ofthe chloride that entered one internode which was transportedout of it into the cells of the node and the next internode.The speed of cytoplasmic streaming was altered by treating thefirst cell with cytochalasin B. The relative rate of intercellular transport depended markedlyon the streaming speed at all speeds up to those found in untreatedcells. The chloride influx into the treated cell did not dependon the streaming speed. It is concluded that the rate of intercellular transport oflow molecular weight solutes in Chara will be normally limitedby the rate at which cytoplasmic streaming brings solute tothe plasmodesmata, rather than by the diffusion permeabilityof the plasmodesmata. This conclusion may well apply to othercharophyte plants, and could in principle apply to higher plants.     

A MUCILAGE-FORMING LACTOBACILLUS SPECIES ISOLATED FROM CIDER. PART II. POLYSACCHARIDE FORMATION

SUMMARY: Cultures grown at 25° under an atmosphere of CO₂ in a medium containing maltose, inorganic salts and ethanolic extracts of peptone and yeast autolysate produced a polysaccharide, which was isolated and purified. Examination by a variety of chemical and biological methods indicated that it was a dextran of low molecular weight.     

Dispersal Characteristics of Juvenile Bobcats in South-Central Indiana

ABSTRACT Bobcat (Lynx rufus) populations in the Midwestern United States experienced historic declines due to habitat loss and exploitation but have rebounded in recent decades. We investigated natal dispersal of juvenile bobcats from a population in south-central Indiana, USA, from 1999 to 2006. We radiocollared 16 juvenile bobcats (11 M, 5 F) and monitored them for 237–1,014 days (x̄ = 506). One female (20%) and 11 males (100%) dispersed from natal home ranges that averaged 14.6 km² in size. Most juveniles (70%) initiated dispersal from mid-February through March, late in their first year. Only 5 bobcats (42%) ultimately established a final home range 63 ± 35 km² in size 13–92 km (x̄ = 44) from their natal range 140 ± 45 days after initiating dispersal. Survival did not differ (P = 0.93) between dispersing (S = 0.73) and philopatric (S = 0.75) individuals, although 4 bobcats (3 M, 1 F) were killed in collisions with vehicles. We found dispersal of bobcats in fragmented landscapes is prolonged and often unsuccessful; the ability of dispersers to locate suitable vacant habitat patches may be vital to the continued growth of bobcat populations recolonizing the agricultural Midwest.