Genetic variation at enzyme loci in North Atlantic minke whales,Balaenoptera acutorostrata

Electrophoretic variation within and between North Atlantic minke whale samples(Balaenoptera acutorostrata) from West Greenland, Iceland, and Norway was investigated. In the West Greenland samples, 28 enzyme systems were examined, representing 36 loci, of which 6 were found to be polymorphic. In Icelandic and Norwegian samples, 22 enzyme systems were examined, representing 29 loci, of which 6 and 5 were found to be polymorphic, respectively. The average heterozygosity was 0.058 (SE=0.024) in samples from West Greenland, 0.074 (SE=0.028) in samples from Iceland, and 0.054 (SE=0.023) in samples from Norway. No significant deviations from the expected Hardy—Weinberg genotypic frequencies, within samples taken from the same area, were found. Significant differences in allele frequencies were observed, however, between samples from the three different areas. The average Nei's genetic distance was 0.014 and the averageF _st value was 0.126. The genetic differences between the samples from the different areas indicate that those from West Greenland, Iceland, and Norway represented different breeding populations.     

Weed and Crop Allelopathy

Allelopathy can be defined as an important mechanism of plant interference mediated by the addition of plant-produced secondary products to the soil rhizosphere. Allelochemicals are present in all types of plants and tissues and are released into the soil rhizosphere by a variety of mechanisms, including decomposition of residues, volatilization, and root exudation. Allelochemical structures and modes of action are diverse and may offer potential for the development of future herbicides. We have focused our review on a variety of weed and crop species that establish some form of potent allelopathic interference, either with other crops or weeds, in agricultural settings, in the managed landscape, or in naturalized settings. Recent research suggests that allelopathic properties can render one species more invasive to native species and thus potentially detrimental to both agricultural and naturalized settings. In contrast, allelopathic crops offer strong potential for the development of cultivars that are more highly weed suppressive in managed settings. Both environmental and genotypic effects impact allelochemical production and release over time. A new challenge that exists for future plant scientists is to generate additional information on allelochemical mechanisms of release, selectivity and persistence, mode of action, and genetic regulation. In this manner, we can further protect plant biodiversity and enhance weed management strategies in a variety of ecosystems. Referee: Dr. Steve Weller, Purdue University, Dept. of Horticulture, West Lafayette, IN 47907     

Tentoxin effects on variable fluorescence and P515 electrochromic absorbance changes in tentoxin-sensitive and -resistant plant species

The effects of the cyclic tetrapeptide phytotoxin, tentoxin, on variable chlorophyll fluorescence quenching and the P515 electrochromic absorbance change were examined in tentoxin-sensitive and -resistant species and an interspecies hybrid. Immediately after infiltration of leaf discs, up to 100 μM tentoxin had no effect on the O, I, D, or P portions of the fluoresence transients of either tentoxin-sensitive or -resistant plants. However, the quenching of fluorescence following maximal fluorescence was reduced by approximately fourfold in tentoxin-treated tissues of tentoxin-sensitive plants, but was unaffected in resistant plants. Tentoxin significantly increased the magnitude of the P515 electrochromic absorbance change in all tentoxin sensitive plants by an average of approximately twofold. However, it was unaffected by tentoxin in resistant species. These data suggest that there is a close correlation between interaction of tentoxin with CF₁ ATPase in vivo and the ability to cause chlorosis in developing chloroplasts.     

Characterization of soil phosphorus by anion exchange resin adsorption and P32-equilibration

Summary Adsorption of phosphate by the anion-exchange resin Dowex-2 was investigated. The resin adsorbed small quantities of P from solution quantitatively. The rate of P-adsorption by resin agitated in solution was proportional to the P-concentration in solution, and was independent of the rate of diffusion of adsorbed P in the resin. When 1 g of soil was shaken continuously with 1 g of resin in 100 ml of water, the rate of P-adsorption by the resin was controlled by the rate of P-release from the soil. Quantities of P adsorbed from soil by resin after different lengths of time were less than those equilibrated with P³² during the same time intervals. The curves showing quantity of P adsorbed vs. time could be satisfactorily described by the hypothesis that there were three simultaneous reactions differing in rate, each reaction being first-order with respect to P. The same was true of the P³²-equilibration data, except that the rate of the slowest reaction was apparently independent of time. In a group of 16 soils, the correlation between P adsorbed by the resin in 2 hours and P-availability to plants in the greenhouse, measured by the isotope-dilution method of Fried and Dean, was 0.95. The corresponding correlation between P extracted by the 0.25N HCl — 0.03N NH₄F extractant of Bray and Kurtz was 0.91.Joint contribution from the Iowa Agricultural Experiment Station and the Eastern Soil and Water Management Section, U.S. Department of Agriculture. Journal Paper No. J-2639 of the Iowa Agricultural Experiment Station, Ames, Iowa. Project No. 1183.Graduate Assistants, Professor of Soils, and Associate Professor of Chemistry, respectively.     

Rhythmic Oscillations in Starch Concentration and Activities of Amylolytic Enzymes and Invertase in Medicago sativa Nodules

Alfalfa (Medicago sativa L.) nodule amylase, starch phosphorylaseand invertase activities and concentrations of starch and proteinwere determined every 4 h for 44 h to determine if daily fluctuationsoccur. Plants experienced 12 h light: 12 h dark (LD) duringentrainment and the first 24 h of the experiment. The last 20h were under continuous darkness (DD). Temperature (21°C)and relative humidity (72%) were always constant. Data wereanalyzed by the cosinor method to determine probabilities ofsinusoidal rhythms with periods between 12.0 and 30.0 h. UnderLD conditions, significant 12.1 h rhythms were found for activitiesof amylase and starch phosphorylase and for starch content.Rhythms in amylase activities and starch content were inverselycorrelated whereas rhythms of starch content and starch phosphorylaseactivity were positively correlated. These data indicate thatnodule starch can be rapidly turned over and that amylases maybe responsible for the degradation. None of these rhythms persistedunder DD conditions. In contrast, invertase activity was rhythmicunder LD (24 h period) and DD conditions (30 h period). No significantrhythmic variations were detected in protein levels throughoutthe entire experiment. (Received August 12, 1985; Accepted November 22, 1985)     

Cytotoxic lymphocyte-derived lytic granules do not induce DNA fragmentation in target cells

When target cells are exposed to CTL, they very quickly sustain nuclear damage, including DNA cleavage, and then they lyse. Nuclear damage of this type is not seen when cells are killed by antibody and C. The role of nuclear damage in the T cell-mediated killing process as well as the mechanism by which the killer cell induces this damage are unknown; however, accumulating evidence suggests that cytolysis may depend on induction of nuclear damage. The exocytosed contents of CTL granules are thought by many workers to mediate target cell lysis. We have now determined whether lytic granules also induce nuclear damage (DNA fragmentation) in cells which they lyse. They do not. In addition, no DNA fragmentation was detected in nuclei incubated with lytic granules or activated CTL. In summary, our results suggest that target cell DNA fragmentation induced by CTL is mediated neither by lytic granules nor by a CTL-derived endonuclease and support the view that the target cell is itself responsible for the internal damage it sustains.     

Genetic and biochemical aspects of lactate dehydrogenase isozymes in the salmonid eye

Polyacrylamide gel electrophoresis reveals similar differences between the retinal-specific lactate dehydrogenase (LDH) isozymes of the salmon (Salmo salar L.) and the sea-trout (Salmo trutta forma trutta L.) as those previously described for the salmon and the brown trout (Salmo trutta L.). F₁ salmon × sea-trout hybrids give a classic hybrid isozyme pattern, but the F₂ hybrids all possess the parental sea-trout type pattern. Loss of part of the salmon genome in these latter hybrids is the most likely explanation. It was observed that when the individual eye isozymes of the salmon, the sea-trout, and the rainbow trout (Salmo gairdneri Richardson) were eluted from preparative polyacrylamide gels and re-electrophoresed, an apparent interconversion of certain isozyme bands occurred. This phenomenon was also evident using starch gel. However, the major cathodally migrating isozyme in each case (presumably the E4 isozyme) re-electrophoresed pure. The reasons for these interconversions are, as yet, unclear. Attempts to produce in vitro hybridization between the various isolated individual isozymes were unsuccessful. K_m pyruvate values for the different salmon isozymes were of the order expected from results already published for other teleosts.