Correction of chlorophyll-defective male-sterile winter oilseed rape (Brassica napus) through organelle exchange: Characterization of the chlorophyll deficiency

Jarl, C. I., Ljungberg, U. K. and Bornman, C. H. 1988. Correction of chlorophyll-defective male-sterile winter oilseed rape ( Brassica napus ) through organelle exchange: Characterization of the chlorophyll deficiency. - Physiol. Plant. 72: 505–510.
As is known, the introduction of male-sterile Raphanus sativus L. cytoplasm into Brassica napus L. results in male-sterile oilseed rape plants, which display a temperature-related chlorophyll defect. The influences of temperature and irradiance on this defect were investigated. Compared to a line of normal (green phenotype) male-fertile oilseed rape, the male-sterile line had reduced chlorophyll content, fewer chloroplasts per cell, an altered ultrastructure of the chloroplasts and reduced activities of both photosystems, although the relative amounts of the photosystems and the chlorophyll a/b ratio were similar. The lower activity of the photosystems is explained by a decreased functional antennae size and a reduced efficiency in the interactions between the nuclear-encoded light-harvesting proteins and the reaction centres coded for by the plastome. Some thylakoid polypeptides differed in proportion between the male-fertile line with green phenotype and the male-sterile line with chlorotic phenotype. Characters, in which the two lines exhibited differences, are ascribed to difficulties in molecular communication between the oilseed rape nucleus and the radish cytoplasm, which are combined in the deficient male-sterile line.     

Measurement of light within thin plant tissues with fiber optic microprobes

Vogelmann, T. C., Knapp, A. K., McClean, T. M. and Smith, W. K. 1988. Measurement of light within thin plant tissues with fiber optic microprobes. - Physiol. Plant. 72: 623–630.
The measurement of light with fiber optic microprobes has been extended to thin (200–300 μm) plant tissue samples. To test the method, light measurements were made in thin aqueous films and paradermal sections from 10-day-old etiolated Cucurbita pepo L. cv. Fordhook cotyledons. The measurements obtained were highly reproducible. Paradermal sections of spongy mesophyll that were irradiated with collimated light scattered light more effectively than the palisade layer of intact cotyledons. These results demonstrate that different plant tissues have different light scattering characteristics. The successful extension of the fiber optic microprobe technique to thin systems makes it possible to examine the optical properties of different cell layers within leaves and other plant organs.     

Hypertrophy without increased isometric strength after weight training

Eight men (20-23 years) weight trained 3 days.week-1 for 19 weeks. Training sessions consisted of six sets of a leg press exercise (simultaneous hip and knee extension and ankle plantar flexion) on a weight machine, the last three sets with the heaviest weight that could be used for 7-20 repetitions. In comparison to a control group (n = 6) only the trained group increased (P less than 0.01) weight lifting performance (heaviest weight lifted for one repetition, 29%), and left and right knee extensor cross-sectional area (CAT scanning and computerized planimetry, 11%, P less than 0.05). In contrast, training caused no increase in maximal voluntary isometric knee extension strength, electrically evoked knee extensor peak twitch torque, and knee extensor motor unit activation (interpolated twitch method). These data indicate that a moderate but significant amount of hypertrophy induced by weight training does not necessarily increase performance in an isometric strength task different from the training task but involving the same muscle group. The failure of evoked twitch torque to increase despite hypertrophy may further indicate that moderate hypertrophy in the early stage of strength training may not necessarily cause an increase in intrinsic muscle force generating capacity.     

Canopy photosynthetic production in a Japanese larch stand. I. Seasonal and vertical changes of leaf characteristics along the light gradient in a canopy

In an 18 year old Japanese larch stand, leaf characteristics such as area, weight, gross photosynthetic rate and respiration rate were studied in order to obtain basic information on estimating canopy photosynthesis and respiration. The leaf growth courses in area and weight from bud opening were approximated by simple logistic curves. The growth coefficient for the area growth curve was 0.155–0.175 day⁻¹, while that for the weight growth was 0.112–0.117 day⁻¹. The larger growth coefficient in area growth caused the seasonal change in specific leaf area (SLA) that increased after bud opening to its peak early in May at almost 300 cm² g⁻¹ and then decreased until it leveled off at about 140 cm²g⁻¹. The change inSLA indicates the possibility that leaf area growth precedes leaf thickness growth. The relationship between the coefficientsa andb of the gross photosynthetic rate (p)-light flux density (1) curve (p=bI/(1+aI)) and the mean relative light flux density (I′/I ₀) at each canopy height were approximated by hyperbolic formulae:a=A/(I′/I ₀)+B andb=C/(I′/I ₀)+D. Leaf respiration rate was also increased with increasingI′/I ₀. Seasonal change of gross photosynthetic rate and leaf respiration rate were related to mean air temperature through linear regression on semilogarithmic co-ordinates.     

Effects of source-sink relations on photosynthetic acclimation to elevated CO2

Abstract. While photosynthesis of C₃ plants is stimulated by an increase in the atmospheric CO₂ concentration, photosynthetic capacity is often reduced after long-term exposure to elevated CO₂. This reduction appears to be brought about by end product inhibition, resulting from an imbalance in the supply and demand of carbohydrates. A review of the literature revealed that the reduction of photosynthetic capacity in elevated CO₂ was most pronounced when the increased supply of carbohydrates was combined with small sink size. The volume of pots in which plants were grown affected the sink size by restricting root growth. While plants grown in small pots had a reduced photosynthetic capacity, plants grown in the field showed no reduction or an increase in this capacity. Pot volume also determined the effect of elevated CO₂ on the root/shoot ratio: the root/shoot ratio increased when root growth was not restricted and decreased in plants grown in small pots. The data presented in this paper suggest that plants growing in the field will maintain a high photosynthetic capacity as the atmospheric CO₂ level continues to rise.     

Antibiotic production by the marine photosynthetic bacterium Chromatium purpuratum NKPB 031704: localization of activity to the chromatophores

Abstract Over 200 strains of marine purple photosynthetic bacteria were isolated. Two strains showed antibiotic activity towards Saccharomyces cerevisiae and were tentatively identified as Chromatium purpuratum . Crude antibiotic, prepared by solvent extraction, showed a broad antimicrobial spectrum. The highest activity was found in the chromatophore fraction. Chromatographic separation of purified light harvesting complex from one strain, NKPB 031704, showed the presence of two separate pigmented compounds which were responsible for antimicrobial activity. Our findings reveal the unexpected ability of photosynthetic bacteria to produce broad spectrum antibiotics. In addition, this is the first example of intracellular localization of antibiotic activity in a marine bacterium.     

Membrane and cytoplasmic resistivity properties of normal and sickle red blood cells

The cytoplasmic resistivities and membrane breakdown potentials of normal (AA), sickle-cell-trait (AS), and sickle (SS) red blood cells have been measured by the biophysical methodology of resistive pulse spectroscopy over a range of osmolalities. At isotonicity, the average membrane breakdown potentials are virtually identical for the three types of cells occurring at about 1150 V/cm. Average isotonic cytoplasmic resistivities are somewhat higher for the SS cells (166.7±7.49 ohm-cm) compared to the AA (147.6±1.98 ohm-cm) or AS cells (148.7±1.79 ohm-cm). As medium osmolality is varied, the differences in resistive properties become enlarged, especially at very low and very high osmolalities. At high osmolalities, both types of sickle cells show a large increase in internal resistivity compared to the normals; at low osmolality, the SS samples exhibit a distinctly different membrane breakdown characteristic, decreasing in this parameter, whereas the other two groups increase. Of the 15 SS samples tested, three displayed much higher cytoplasmic resistivities at isotonicity: 218.2±5.25 ohm-cm, compared to an average of 153.5±3.46 ohm-cm for the other 12. The relationship between these high resistivities and the subfraction of irreversibly sickled cells in the sample is discussed.     

光合能量代谢对C_3植物光呼吸的调节作用

C_3植物光呼吸与光合作用关系受光合能量代谢状况的调节。在外界无CO_2和照光条件下,贮藏性光合产物经某种转化途径能“回迁”光合与光呼吸碳循环并显著地受到光合能量代谢的影响。在无CO_2或低CO_2浓度、高光强条件下,此碳素“回迁”过程对协调光合能量代谢与光合碳素代谢平衡,可能起重要作用。     

Comparison of glucokinase in C3H/He and C58 mice that differ in their hepatic activity

Partially purified preparations of the hepatic glucokinase from C3H/He and C58 inbred mice have been used to explore the molecular basis for the observed twofold difference in activity between the strains. The single codominant gene that appears to regulate activity, the alleles of which are designated Gk^a and Gk^b, respectively, for the two strains, could represent a structural gene change. This now seems unlikely because the mouse enzyme, although showing small differences from rat glucokinase, appeared to be identical in the two strains with respect to thermal stability, electrophoretic mobility in agarose gels, and kinetic properties such as the apparent K _m values for MgATP^2– and glucose and the unique cooperative interaction with the latter substrate. The enzymes also reacted identically in a range of immunological tests (double-diffusion, immunoelectrophoresis, immune precipitation and immune inhibition assays) and ELISA immune inhibition assays indicated that the twofold difference in activity was due to a similar difference in antigenically active enzyme. Genetic control over the physiologically significant regulation of enzyme amount is therefore probable.This work has been supported in part by a grant from the British Diabetic Association and a Training Studentship to PAJ from the Medical Research Council (U.K.).