The chlorophyll fluorescence induction curves from mesophyll and guard cell chloroplasts of Saxifiaga cernmua, including both the fast (O to P, the transients involved in the rise in variable fluorescence) and slow (P to steady state fluorescence due to quenching) components, were characterized over a range of excitation intensities using microspectrophotometry (with epi-lumination) equipped with apertures designed to eliminate cross contamination of the fluorescence signal between the two chloroplast types. At low excitation intensities, the fast fluorescence kinetics from guard cell plastids showed an extended I to D phase and a more rapid appearance of P while minimal quenching from P to steady state fluorescence was observed compared to the transients from mesophyll chloroplasts suggesting a lower activity of photochemical (electron movement via carriers between donor and acceptor sites) and nonphotochemical (such as membrane conformational changes) events which regulate the fluorescence induction curve kinetics. As the excitation intensity was increased, the quenching rates of guard cells were faster at initiating conditions for photophosphorylation and the fast and slow fluorescence kinetics from guard cells resembled those of the mesophyll cells.Guard cell chloroplasts of S. ceraua from intact epidermal peels showed a low temperature (77 K) fluorescence emission spectrum having three major peaks (at 685, 695, and 730 nanometers when excited at 440 nanometers) which were qualitatively similar to those in the spectrum obtained from mesophyll tissue.These data suggest that S. cernua guard cell chloroplast photosystems I and II contribute to light-dependent stomatal activity only at high light intensities.

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Armillaria mellea, a phytopathogenic fungus, is the only member of the Agaricales (Basidiomycetes) whose fertile vegetative phase in nature is thought to be diploid, rather than dikaryotic. To examine the vegetative ploidy of A. mellea, we used the DNA-binding antibiotic, mithramycin, for fluorometry of in situ nuclear DNA. The measurements of nuclear DNA content indicated that strains derived from single basidiospores of A. mellea were haploid and that strains derived from matings of isolates of single spores were diploid. These data confirm the results of earlier genetic experiments, which show haploidy and diploidy in unmated and mated strains, respectively. Nuclear DNA measurements in known haploid and diploid strains of Aspergillus nidulans confirmed the validity of our protocol.

Spinach (Spinacia oleracea L. cultivar Longstanding Bloomsdale) grown at 20 °C was subjected to a range of rapid thermal shifts as high as 42 °C. There was a decrease in the level of protein synthesis following heat-shock treatments above 34 °C as indicated by the level of incorporation of L-[35S]methionine. In vivo labelled polypeptides and in vitro translation products of RNA isolated from leaf tissue and analyzed using one-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis and fluorography, indicated that the temperature of induction of all 15 heat-shock proteins in the 20 °C grown plants was 36 °C. In addition, heat-shock RNA was coordinately expressed and the translation of heat-shock proteins was noncoordinate with respect to temperature. Treatment with cycloheximide and with chloramphenicol demonstrated that heat-shock protein synthesis in spinach was restricted to cytosolic ribosomes. Synthesis of some low molecular weight heat-shock proteins were insensitive to actinomycin D, suggesting greater stability of these heat-shock RNAs. The heat-shock polypeptide profile of plants grown at 10 °C was similar to that of plants grown at 20 °C, with 14 heat-shock proteins being induced at 36 °C. The growth temperature did not influence the final array of heat-shock proteins synthesized nor alter the temperature of induction of the heat-shock response.Key words: heat-shock response, heat-shock proteins, Spinacia oleracea.

Cytological and histological studies were carried out on a male‐sterile clone, OD‐1, of Dactylis glomerata L. The chromosome number and meiotic chromosome behavior of this clone were normal for the species. During microsporogenesis, degeneration of some sporogeneous tissue was observed at the initial stages of meiosis. Later, there was a very rapid degeneration of the tapetum and microspores. At anthesis, there was no evidence of pollen. The cell layers of the anther wall did not develop characterisfically, resulting in a small nondehiscent anther.