The role of cytokinins in chloroplast lamellar development

The accumulation of chlorophyll, production of two specific lamellar chlorophyll-protein complexes, onset of O(2) evolution, and detection of P700 were examined in intact Jack bean (Canavalia ensiformis [L.] D.C.) leaves treated with 10(-5)m kinetin or benzyladenine and allowed to green under low (30-35%) and high (80-85%) relative humidity. In contrast to reports of the promotion of chlorophyll accumulation by cytokinin treatment in excised tissue or cotyledons, intact greening leaves showed neither promotion of chlorophyll accumulation nor alteration in formation of the lamellar chlorophyll-protein complexes or development of photosynthetic function. Furthermore, cytokinin was ineffective in relieving the consequences of low relative humidity water stress on chlorophyll accumulation and on the formation of at least one lamellar chlorophyll-protein.     

P(700) Chlorophyll a-Protein : Purification, Characterization, and Antibody Preparation

The P₇₀₀ chlorophyll α-protein was purified by preparative sodium dodecyl sulfate (SDS) gel electrophoresis from SDS-solubilized barley (Hordeum vulgare L., cv Himalaya) chloroplast membranes. After elution from the gel in the presence of 0.05 to 0.1% Triton X-100, the recovered protein had a chlorophyll/P₇₀₀ ratio of 50 to 60/1 and contained no chlorophyll b or cytochromes. Analysis of the polypeptide composition of the chlorophyll-protein revealed a 58 to 62 kilodalton (kD) polypeptide component but no lower molecular weight polypeptides. The 58 to 62 kD component was further resolved into two distinct polypeptide bands which were subsequently mapped by partial cyanogen bromide digestion and Staphylococcus aureus proteolysis. Based on results from the mapping experiments and other data, we suggest that the two components are conformational variants of a single polypeptide. Measurement of the chlorophyll to protein ratio by quantitative amino acid analysis and consideration of the yield of P₇₀₀ in the protein isolate suggest that, contrary to previous models (Bengis and Nelson, 1975, 1977), P₇₀₀in vivo is associated with a minimum of four subunits of approximately 60 kD.

Antibodies raised against the photochemically active chlorophyll-protein complex from barley reacted specifically with the 58 to 62 kD apoprotein. The same preparative electrophoresis procedure was used to isolate photochemically active P₇₀₀ chlorophyll a-protein from soybean (Glycine max L.), tobacco (Nicotiana tobacum L.), petunia (Petunia × hybrida), tomato (Lycopersicum esculentum), and Chlamydomonas reinhardti. The isolated complex from all species exhibited identical polypeptide compositions and chlorophyll/P₇₀₀ ratios. Antibodies to the barley protein cross reacted with all species tested demonstrating the highly conserved structure of the apoprotein.

     

Light-Harvesting System of the Red Alga Gracilaria tikvahiae: II. Phycobilisome Characteristics of Pigment Mutants

Phycobilisomes were isolated from wild type Gracilaria tikvahiae and a number of its genetically characterized Mendelian and non-Mendelian pigment mutants in which the principal lesions result in an increase or decrease in the accumulation of phycoerythrin. Both the size and phycoerythrin content of the phycobilisomes are proportional to the phycoerythrin content of the crude algal extracts. In most of the strains examined, the structure and function of the phycocyanin-allophycocyanin phycobilisome cores are the same as in wild type. The phycobilisome architecture is derived from wild type by the addition or removal of phycoerythrin. The same pattern is observed for the phycobilisome of mos² which contains a large excess of phycocyanin that is not bound to the phycobilisome. The single exception is a yellow, non-Mendelian mutant, NMY-1, which makes functional phycobilisomes composed of phycoerythrin and allophycocyanin with almost no phycocyanin. Characterization of the `linker' polypeptides of the phycobilisome indicates that a 29 kilodalton protein is required for the stable incorporation of phycocyanin into the phycobilisome. Evidence is provided for the requirement of nuclear and cytoplasmic genes in phycobilisome synthesis and assembly. The symmetry properties of the phycobilisome are considered and a structural model for the reaction center II-phycobilisome organization is presented.     

Phyllotaxy and water relations in tobacco

Summary The relative effectiveness of vascular connections between adjacent leaves of tobacco is demonstrated. It is shown that water movement between adjacent leaves is more difficult than between phyllotactically related leaves. Total and specific resistance ratios between adjacent and phyllotactically related leaves are calculated. These figures indicate that vertical water potential profiles need to be interpreted with a full knowledge of the vascular structure and phyllotaxy as well as gross structural and environmental parameters.     

GENETIC VARIABILITY WITHIN A POPULATION AND BETWEEN DIPLOID/HAPLOID TISSUE OF MACROCYSTIS PYRIFERA (PHAEOPHYCEAE)1

Multi-locus DNA fingerprints using an M13 probe were obtained for eight individuals of giant kelp Macrocystis pyrifera (L.) C. Ag. collected from Monterey Bay, California. For each individual, DNA was extracted from a diploid blade and from ca. 10⁹ haploid spores that were released from four to Jive sporophylls. Viable or swimming spores from one individual were pooled and referred to as a spore group. A total of 34 bands (4–19 kb) was detected in DNA fingerprints from the eight blades and eight spore groups, with individual blade or spore groups exhibiting 7–18 bands (mean = 12.6). One band (4.5 kb) was present in all 16 samples. Eight bands were detected in 11–14 of the 16 samples. Similarity indices were calculated for all pairwise comparisons of fingerprint bands among all possible combinations of blades and spore groups. Mean similarity indices for the eight blades (0.51, SE = 0.032) and spore groups (0.56, SE = 0.031) were significantly lower than for the eight comparisons of the blade and spore groups from a single individual (0.86, SE = 0.052). The data indicate that DNA fingerprints can be used to measure genetic variation within populations of M. pyrifera because variation of DNA fingerprints associated with meiotic products (spores) of a given individual is small relative to variation observed among individuals within the population. Additionally, fingerprint variation between diploid vegetative tissue and haploid meiotic products may be a measure of genetic change due to recombination or DNA turnover mechanisms.     

Photosynthetic adaptation of Solanum dulcamara L. to sun and shade environments

Summary The photosynthetic response properties of individuals of Solanum dulcamara L. collected from sun and shade habitats were compared in controlled environments. Light-saturated photosynthetic rates and seven additional parameters associated with photosynthetic and growth performance were measured over a range of 12 environmental conditions that simulated natural habitat differences in light intensity, moisture availability and daily temperature amplitude. In contrast to previous studies, the results suggest there is no ecotypic differentiation with respect to the sun and shade environments from which the individuals were collected. It appears that all but one of the field-collected individuals are capable of successfully inhabiting the full range of light environments from which the species was collected.     

Functional symmetries in the schmelzmuster and morphology of rootless rodent molars

Morphology and schmelzmuster of rootless cheek teeth of 25 extant rodent genera were studied in relation to jaw movement. A differentiation between leading and trailing edges is observed regularly in enamel thickness and schmelzmuster. Similarities between antagonists are interpreted as 'functional symmetries'. Differences in the enamel thickness, the schmelzmuster and orientation of cutting edges are controlled by functional and phylogenetic constraints. The heterogenous sample allows discrimination between these two constraints. The most obvious functional constraint leads to the almost regular occurrence of radial enamel on the push sides of cutting edges. The degree of functional symmetry seems to be determined by phylogenetic limitations.     

Block of outward current in cardiac purkinje fibers by injection of quaternary ammonium ions

We have studied the effects of iontophoretic injection of the quaternary ammonium compounds tetraethylammonium (TEA) and tetrabutylammonium (TBA) in cardiac purkinje fibers. We find that TBA(+) is a more effective blocker than TEA(+), but injection of either compound reduces the time-dependent outward plateau currents, transient outward current (I(to)), and the delayed rectifier (I(x)). Our findings provide evidence that these outward cardiac currents are carried by channels that in some respects are pharmacologically similar to squid axon potassium channels. We demonstrate that this procedure is a new tool that can be useful in the analysis of membrane currents in the heart.     

Quantification of the magnification and distortion effects of a pediatric flexible video-bronchoscope

Background

Flexible video bronchoscopes, in particular the Olympus BF Type 3C160, are commonly used in pediatric respiratory medicine. There is no data on the magnification and distortion effects of these bronchoscopes yet important clinical decisions are made from the images. The aim of this study was to systematically describe the magnification and distortion of flexible bronchoscope images taken at various distances from the object.

Methods

Using images of known objects and processing these by digital video and computer programs both magnification and distortion scales were derived.

Results

Magnification changes as a linear function between 100 mm (×1) and 10 mm (×9.55) and then as an exponential function between 10 mm and 3 mm (×40) from the object. Magnification depends on the axis of orientation of the object to the optic axis or geometrical axis of the bronchoscope. Magnification also varies across the field of view with the central magnification being 39% greater than at the periphery of the field of view at 15 mm from the object. However, in the paediatric situation the diameter of the orifices is usually less than 10 mm and thus this limits the exposure to these peripheral limits of magnification reduction. Intraclass correlations for measurements and repeatability studies between instruments are very high, r = 0.96. Distortion occurs as both barrel and geometric types but both types are heterogeneous across the field of view. Distortion of geometric type ranges up to 30% at 3 mm from the object but may be as low as 5% depending on the position of the object in relation to the optic axis.

Conclusion

We conclude that the optimal working distance range is between 40 and 10 mm from the object. However the clinician should be cognisant of both variations in magnification and distortion in clinical judgements.