Contributions to the cytotaxonomy of the Commelinaceae. Chromosome evolution in Tradescantia section Cymbispatha

The five species of Tradescantia section Cymbispatha studied, including one species T. poelliae D. R. Hunt, have chromosome numbers of In = 12, 14, 16, 22, 28, 30 and 36 and karyotypes of acrocentric, metacentric or telocentric chromosomes, or mixtures of both acrocentric and metacentric chromosomes. The numbers of major chromosome arms of these cytotypes give a nombre fondamentaP series of 14, 28, 42 and 56 which, in combination with meiotic analyses, indicates plants which, in genetical terms at least, are diploid, tetraploid, hexaploid and octoploid. This series has evolved from a 2 n = 14 acrocentric or telocentric karyotype by a combination of Robertsonian fusion and polyploidy. Pseudo-iso-chromosomes are sometimes formed in this evolutionary development and can persist as stable members of normal complements.     

Contributions to the cytotaxonomy of the Commelinaceae. Chromosome evolution in Tradescantia section Cymbispatha

The five species of Tradescantia section Cymbispatha studied, including one species T. poelliae D. R. Hunt, have chromosome numbers of In = 12, 14, 16, 22, 28, 30 and 36 and karyotypes of acrocentric, metacentric or telocentric chromosomes, or mixtures of both acrocentric and metacentric chromosomes. The numbers of major chromosome arms of these cytotypes give a nombre fondamentaP series of 14, 28, 42 and 56 which, in combination with meiotic analyses, indicates plants which, in genetical terms at least, are diploid, tetraploid, hexaploid and octoploid. This series has evolved from a 2 n = 14 acrocentric or telocentric karyotype by a combination of Robertsonian fusion and polyploidy. Pseudo-iso-chromosomes are sometimes formed in this evolutionary development and can persist as stable members of normal complements.     

Effects of some fungicides used against cereal pathogens on the growth of Rhizobium trifolii and its capacity to fix nitrogen in white clover

Fungicide residues in soils may affect nitrogen fixation by legumes. Effects of nine systemic fungicides, used against cereal pathogens, on Rhizobium trifolii and white clover were measured. Fenarimol and oxycarboxin inhibited growth of R. trifolii in vitro. The weight of clover plants after 10 weeks' growth in soil containing carboxin, oxycarboxin, benodanil, tridemorph and pyracarbolid was reduced. Symbiotic nitrogen fixation was decreased by carboxin, oxycarboxin and tridemorph present in soil at concentrations somewhat greater than that likely to result from several applications of the fungicide. Only tridemorph reduced nodulation. None of the compounds seems likely to affect nitrogen fixation in the field if applied at the recommended rate.     

DNA Polymerase Activity associated with Purified Kilham Rat Virus

RNA tumour viruses contain an enzyme which can transcribe DNA from an RNA template^1,2, an endonuclease and a DNA-dependent DNA polymerase activity^3,4. RNA polymerase has been reported in vaccinia virus^5,6, reovirus^7,8 and cytoplasmic polyhidrosis virus⁹. I wish to describe a DNA polymerase activity associated with a highly purified preparation of the parvovirus, Kilham rat virus (KRV), which is thus the first report of a DNA polymerase associated with a DNA virus. KRV, a small virus first isolated from a rat sarcoma¹⁰, is antigenically related to the H viruses isolated from human transplantable tumours¹¹. Those parvoviruses which have been characterized all contain single stranded DNA with molecular weights of 1.5 to 2.5 × 10⁶ (refs. 12,13 and 14).     

The Nutrition of Tetrahymena setifera HZ-1; Sterol and Alcohol Requirements

SYNOPSIS. In a chemically-defined medium Tetrahymena setifera HZ-1 required a sterol, an alcohol, eleven amino acids, a purine, a pyrimidine, and six B-complex vitamins. The sterol requirement was met by a variety of 3β-OH, C₂₇-C₂₉ sterols including cholesterol and stigmasterol, but not by precursors of cholesterol which precede desmosterol or Δ⁷-cholestenol. Some combinations of long-chain fatty acids with a synthetic dipalmitoyl phosphorylethanolamine partly substituted for sterol. Ethyl and methyl alcohols (but not a variety of other alcohols and organic acids) satisfied the alcohol requirement.     

Genetic Analysis of Developmental Mechanisms in Hydra. XV. Nematocyte Differentiation in Strains with Altered Developmental Gradients*

Nematocyte differentiation from the interstitial stem cells in hydra occurs non-uniformly along the body column. The relative ratios of the 4 nematocyte types produced vary gradually from head to foot along the body axis (Bode and Smith, 1977). To find out whether this regional variation in nematocyte differentiation along the body column is related to the gradients of the head-activation and head-inhibition potentials, nematocyte differentiation patterns were examined in strains which have significantly different developmental gradients along their body columns. Five strains of hydra, including a wild-type, two mutant strains and two chimeric (mutnt/wild-type) strains, were investigated. It was found that the regional variations in the nematocyte differentiation were similar in all the strains examined, and that no significant differences of the variation existed that could be attributed to the differences of the developmental gradients in these strains. This suggests that nematocyte differentiation is strongly affected by the axial position along the body column, but that the gradients of the morphogenetic potentials involved in head formation are not involved in this effect. Instead, some other parameter(s) of axial position not directly associated with these gradients must be responsible for the positional effect on nematocyte differentiation.     

Prey species and prey diet affect growth of invertebrate predators

1. The effects of prey species and leaf age used by prey on performance of two generalist invertebrate predators were studied. The focal plant was Plantago lanceolata , which contains iridoid glycosides.
2. Diet of the herbivorous prey influenced their growth rate.
3. The generalist herbivore ( Vanessa cardui ) and the novel-plant feeder ( Manduca sexta ) contained very low levels of iridoid glycosides in their haemolymph, whereas the specialist ( Junonia coenia ) levels were 50–150-fold higher.
4. Predatory stinkbugs ( Podisus maculiventris ) fed either the novel-plant feeder or the specialist exhibited similar developmental rates. However, stinkbugs ate less of the generalist but grew faster. The growth rate of the stinkbugs was higher when the caterpillar species were raised on the new-leaf powder diet, which contained twice as much protein and iridoid glycosides as the mature-leaf powder diet.
5. Jumping spiders ( Phidippus audax ) ate more mealworms ( Tenebrio molitor ) than specialist J. coenia caterpillars, fed either new- or mature-leaf powder diets, and could not gain weight when fed J. coenia.
6. These results indicate that prey quality was not determined solely by the iridoid glycoside concentration in the diet.