Macronuclear Variation During the Life Cycle of Blepharisma dawsoni n.sp. and B. wardsi

SYNOPSIS. From characteristics of binary fission, conjugation, size and number of micronuclei, body size and incidence of giantism, a Blepharisma isolate hitherto called B. undulans is classified as B. dawsoni sp. nov. Binary fission in B. wardsi differs from fission in B. dawsoni in that the strand connecting the macronuclear nodes is severed; in B. dawsoni the strand persists.     

Elevated CO2 and temperature alter nitrogen allocation in Douglas-fir

The effects of elevated CO₂ and temperature on principal carbon constituents (PCC) and C and N allocation between needle, woody (stem and branches) and root tissue of Pseudotsuga menziesii Mirb. Franco seedlings were determined. The seedlings were grown in sun‐lit controlled‐environment chambers that contained a native soil. Chambers were controlled to reproduce ambient or ambient +180 ppm CO₂ and either ambient temperature or ambient +3.5 °C for 4 years. There were no significant CO₂ × temperature interactions; consequently the data are presented for the CO₂ and temperature effects. At the final harvest, elevated CO₂ decreased the nonpolar fraction of the PCC and increased the polar fraction and amount of sugars in the needles. In contrast, elevated temperature increased the nonpolar fraction of the PCC and decreased sugars in needles. There were no CO₂ or temperature effects on the PCC fractions in the woody tissue or root tissue. Elevated CO₂ and temperature had no significant effects on the C content of any of the plant tissues or fractions. In contrast, the foliar N content declined under elevated CO₂ and increased under elevated temperature; there were no significant effects in other tissues. The changes in the foliar N concentrations were in the cellulose and lignin fractions, the fractions, which contain protein, and are the consequences of changes in N allocation under the treatments. These results indicate reallocation of N among plant organs to optimize C assimilation, which is mediated via changes in the selectivity of Rubisco and carbohydrate modulation of gene expression.     

Methods for the Large-Scale Cultivation of an Oxytricha (Ciliophora: Hypotrichida)1

ABSTRACT. Oxytricha strains used in biochemical studies have traditionally been grown in unaerated, unagitated culture tubes or Fernbach flasks. These cultures are limited in volume to about one liter and have a very nonuniform distribution of cells, with the majority of the cells at the very top or bottom of the medium. We have found conditions in which Oxytricha can be grown in 50-liter fermentation vats. The cultures grow to a uniform density of about 6000 cells/ml.     

Suppression of the Tumorous State in Crown Gall Teratomas of Tobacco A Clonal Analysis

Two types of experimental approaches designed to test the possible involvement of chimeras in the persistent but readily reversible suppression of the tumorous state and in a recovery from that state in crown gall teratomas of tobacco were investigated. These studies showed that the tumorous state was suppressed in specialized cells present in the different tissues derived from each of the three layers of the apical meristem of teratoma-derived shoots of clonal origin. Although differences existed in the exogenous requirements needed for the reestablishment of the tumorous state in the different specialized cell types present in the different tissues, all again acquired a capacity for autonomous growth when appropriately stimulated. No evidence was found for the existence of periclinal or sectoral chimeras in teratoma-derived shoots of a single cell origin. Chimerism was, however, found to exist in one noncloned teratoma-derived shoot. Analysis of more than 500 clones derived from leaf mesophyll cells of cloned teratoma shoots showed that the vast majority of them (> 99%) were tumorous, while all of the 144 seed-grown plants from these shoots had completely recovered from the tumorous state. The results of these studies suggest that (a) a teratoma shoot does not depend for its development on the presence of significant numbers, if any, of cells that had recovered from the tumorous state; (b) the tumorous state may be suppressed in even the most highly specialized cells; (c) some special mechanism exists in the meiotic process for the elimination of all or most of the foreign DNA from transformed cells.